HANDBOOK ON OVERHEAD LINE CONSTRUCTION HANDBOOK ON OVERHEAD LINE CONSTRUCTION COMPILED BY THE SUB-COMMITTEE ON OVERHEAD LINE CONSTRUCTION NATIONAL ELECTRIC LIGHT ASSOCIATION Sub-Committee THOMAS SPROULE, Chairman PAUL SPENCER R. D. COOMBS W. T. OVIATT FARLEY OSGOOD J. E. KEARNS N. '. ^UNK, Secretary PRESENTED AT THE THIRTY-SEVENTH CONVENTION NATIONAL ELECTRIC LIGHT ASSOCIATION HELD AT PHILADELPHIA, PENNSYLVANIA JUNE 1-5, 1914 VA3 Copyright, 1914 National Electric Light Association FRANKLIN PRINTING COMPANY PHILADELPHIA PUBLISHED BY ORDER OF THE National Electric Light Association NEW YORK CITY OFFICERS JOSEPH B. McCALL President Philadelphia, Pa. JOHN A. BRITTON Vice President, San Francisco, Cal. HOLTON H. SCOTT Vice President, New York E. W. LLOYD Vice President, Chicago, 111. E. C. DEAL Vice President, Augusta, Ga. T. COMMERFORD MARTIN Secretary, New York S. A. SEW ALL Assistant to Secretary, New York W. F. WELLS Treasurer, Brooklyn, N. Y. H. BILLINGS Asst. Sec'y and Treas., New York EVERETT W. BURDETT General Counsel, Boston, Mass. GEORGE W. ELLIOTT Master of Transp'tion, New York EXECUTIVE COMMITTEE JOSEPH B. McCALL H. C. ABELL HENRY G. BRADLEE JOHN A. BRITTON E. C. DEAL CHARLES L. EDGAR W. C. L. EGLIN A. C. EINSTEIN H. L. BLEECKER President Northwest Association DUNCAN T. CAMPBELL President Pennsylvania Section R. E. LEE President Iowa Electrical Association W. F. GORENFLO President Mississippi Section H. A. HOLDREGE President Nebraska Section H. W. PECK President Eastern New York Section C. E. GROESBECK E. W. LLOYD R. S. ORR W. N. RYERSON HOLTON H. SCOTT FRANK M. TAIT ARTHUR WILLIAMS T. W. PETERS . President Southeastern Section C. W. ROGERS President New Hampshire Section H. C. STERLING President Michigan Section D. R. STREET President Canadian Association C. C. WELLS President New England Section W. W. FREEMAN Chairman Hydro- Electric Section T. I. JONES, Chairman Commercial Section 297667 TABLE OF CONTENTS Section Page 1. An Abridged Dictionary of Electrical Words, Terms and Phrases 1 Logarithmic Tables, Trigonometric Tables. Deci- mal Equivalent Tables, Tables of Circumferences and Areas of Circles, Units and Conversion Tables. 2. Distribution and Transmission Line Supports 107 3. Conductors and Wire Tables 171 4. Cross- Arms, Pins and Pole Line Hardware 263 5. Insulators 285 6. Transformers and Induction Regulators. Lightning Phe- nomena in Connection with Electric Circuits, Protective Apparatus, Grounding, Etc 315 7. Systems of Distribution and Transmission, Electrical Cal- culations 'j 435 8. Mechanical Calculations of Transmission and Distribution Lines '. 519 9. Preservative Treatment of Poles and Cross- Arms 561 1 0. Primary and Secondary Line Construction *. 675 1.1. Meteorological Data, General Data and Rules for Re- suscitation from Electric Shock . . . 750 Preface THE purpose of this Handbook is the presentation, in one volume, of descriptions of the methods and the materials employed in overhead line construction, and a tabulation of the^necessary formulae for the electrical and mechanical solutions of various transmission and distribution problems. While many handbooks hitherto have been prepared covering these various branches of engineering, this, we believe, is the first attempt made to compile a work strictly on overhead line construction. Literature on the subject is comparatively scarce and that which is available is distributed through a great number of publications. It has therefore been felt by almost all who have taken an active interest in overhead line construction that a handbook would be extremely useful. The preparation of this book has involved the collection of the available data and selection from these data what were most essential. It is not the intention, and it must not be so considered, that this is a handbook of rules and regulations ; or that an attempt has been made to create standards or write specifications. It is rather a collection of useful informa- tion, which should prove of material assistance to all those engaged in the construction or maintenance of overhead lines for light and power purposes. The authorship of such specifications as have been included is specially noted. The formulae used have been taken from authoritative sources, and while the Sub-Committee is not responsible for them, it believes they will be found of service. It must be expected there will be found omissions of matter which should have been added; and material may be included which later may prove of little value. It is Preface hoped, however, that users of this Handbook will assist future committees by offering suggestions, additions or corrections for use in later editions. In the treatment of apparatus, efforts have been made to describe the various types at present on the market. It has been necessary to quote extensively from manu- facturers' literature; and, in illustrating types of devices, to select those marketed by a limited number of manu- facturers. This is not intended either as an endorsement of such apparatus, or as a condemnation of apparatus not illustrated or described. In the majority of cases, selections were made because of the availability of the information. The compilation of the data for this Handbook has been carried out by the secretary of the Sub-Committee, Mr. N. E. Funk, of The Philadelphia Electric Company, to whom belongs the greatest share of credit for what has been accomplished in the preparation of this work. Mr. Funk was detailed by that Company to devote all of his time to this subject, under the direction of the Chairman of the Sub-Committee, who desires to take this opportunity to express his appreciation of the amount of thought and judgment given to the work. We also wish to acknowledge the assistance which we have received wherever asked, and especially to Professor Charles F. Marvin, Chief, Professor William J. Humphreys and Mr. George S. Bliss, all of the United States Weather Bureau, who have cooperated in the compilation of the chapter on " Meteorology," which is the first attempt ever made to tabulate such data for publication in a handbook. The Section on the "Preservative Treatment of Poles and Cross-Arms" is a reprint of the 1910 and 1911 Re- ports of the National Electric Light Association Committee appointed to consider this subject. These reports have viii Preface been combined by Mr. W. K. Vanderpoel, of the Public Service Electric Company, whose efforts^ are gratefully acknowledged. The available information on "Pole Timber Logging and Pole Timber Defects" is meager; much of the data that are included has been secured through the coopera- tion of Mr. O. T. Swan, of the Forestry Service, U. S. Bureau of Agriculture, and Mr. F. L. Rhodes, of the American Telephone and Telegraph Company, and this also is gratefully acknowledged. The ready cooperation of the various manufacturers, who contributed for publication much valuable information many photographs and cuts, is hereby acknowledged. Grateful acknowledgment is also made particularly to Mr. J. C. Parker, of the Rochester Railway and Light Company Mr F L Rhodes of the American Telephone and Telegraph Company, Mr. S. M. Viele, of the Pennsyl- vania Railroad Company, Mr. J. E. Kearns, of the General Electric Company, Mr. R. D. Coombs, of R. D. Coombs and Company, Mr. E. G. Reed, of the Westinghouse Electric Company and also to Mr. W. C. L. Eglin, Mr. George Ross Green, Mr. Horace P. Liversidge, Mr. Charles Penrose, Mr. J. V. Matthews, Mr. W. L. Robertson, Mr. Alexander Wilson, 3rd and Mr. Robert A. Hentz, all of The Philadelphia Electric Company; and to rep- resentatives of the many manufacturing companies for their assistance in checking over the various parts of the Handbook. In the first edition of any handbook embracing so large a subject, errors undoubtedly will be made. These will be corrected in future editions and we would ask our readers to send all criticisms to the secretary of the Asso- ciation so that they can be referred to those responsible for the revision of the Handbook. In this connection, Preface consideration should be given to the broadening of the scope of the Handbook, and to the question as to whether it should include transmission line construction, under- ground construction, maintenance and methods of keeping accurate records of outdoor apparatus, etc. These and other important questions must receive the attention of future committees, and it will be extremely helpful to these committees to obtain the advice and assistance of the membership at large. In conclusion, we desire to express our appreciation to the present officers and Executive Committee of the National Electric Light Association, particularly to its president, Mr. Joseph B. McCall, through whose personal efforts the preparation and publication of the Handbook have been made possible. It is our earnest hope that this Handbook may prove of service to the industry; this has been the controlling thought throughout its preparation. SUB-COMMITTEE ON HANDBOOK THOMAS SPROULE, Chairman PHILADELPHIA, JUNE 1 , 1914 X SECTION 1 AN ABRIDGED DICTIONARY OF ELECTRICAL WORDS, TERMS AND PHRASES TABLES INCLUDING LOGARITHMIC TABLES, TRIGONO- METRIC TABLES, DECIMAL EQUIVALENT TABLES, TABLES OF CIRCUMFERENCES AND AREAS OF CIRCLES, UNITS AND CONVERSION TABLES A. A. C. An abbreviation for alternating current. ABSOLUTE TEMPERATURE. That temperature which is reckoned from the absolute zero, -273 C. or -459 F. ADMITTANCE. The reciprocal of the impedance in an alter- nating-current circuit. The apparent conductance of an alternating- current circuit or conductor. AERIAL CABLE. An insulated cable protected by a metallic sheath and suspended from a messenger cable which is usually grounded. AERIAL CONDUCTOR. An overhead conductor. AGEING OF TRANSFORMER CORE. Increase in the hys- teretic coefficient in the iron of a transformer core during its com- mercial operation, from its continued magnetic reversals at com- paratively high temperature. AIR-CORE TRANSFORMER. A transformer which is void of a core other than that of air. AIR-GAP. In a magnetic circuit, any gap or opening containing air only. AIR-PATH. The path a disruptive discharge takes through the air. AIR-RELUCTANCE. The reluctance of that portion of a mag- netic circuit which consists of air. ALTERNATION. An oscillation of an electric or magnetic wave from a zero to a maximum value and back to zero again, a half of a cycle. (See cycle.) ALTERNATING CURRENT is a current which alternates regu- larly in direction. Unless distinctly otherwise specified, the term "alternating current" refers to a periodic current with successive half waves of the same shape and area. An alternating current equals the electromotive force divided by the impedance, or E E z VR 2 +X 2 E 1 = This expression may be solved by complex quantities or vectorially. I 3] I Sec. 1 : * * V : tirCTlONARY -(-A) Z =*. vRM- XS, Impedance 01 circuit R= ' 'Ohmic resistance 'of circuit X = Reactance of circuit in Ohms = ( &L -^ L = Coefficient of self-induction in henrys C = Capacity of the circuit in farads 6> = 27rf, angular velocity, where f = the number of cycles per second or frequency. ALTERNATING CURRENT POWER. The power expended in an alternating current circuit at any given instant in the cycle is equal to the product of the voltage and current at that instant. When the voltage and current reverse at the same instant, this product is always positive, and if their wave forms are alike, the power expended is a maximum, and is equal to the product of the effective values of voltage and current. Such voltages and currents are in phase. When the term "power expended in an alternating current circuit" is used, the average value during one cycle is ordi- narily meant. ALTERNATION, PERIODICITY OF. The time required for the current to pass through one cycle. When any particular periodic- ity or frequency is spoken of, as for example, 250 alternations per second, 125 complete periods or cycles per second are meant. ALUMINUM. A soft, ductile, malleable metal of white color approaching silver, but with a bluish cast. Does not readily oxidize. Melts at a low temperature. Cannot readily be welded, or brazed or soldered. Very electro-positive, and is eaten away in presence of salts and other metals. Atomic weight 27.1. Specific gravity 2.6 to 2.7. The lightest of all useful metal c next to mag- nesium. Expands greatly with increasing temperature. For equal conductivity, aluminum has about one-half the weight of copper. Tenacity about one-third that of wrought-iron. AMERICAN WIRE GAUGE. The name generally given to the Brown and Sharpe wire gauge, in which the large wire No. 0000, has a diameter of 0.46", the wire No. 36, 0.005", and all other diameters are in geometrical progression. It will be seen upon examining a wire table that an increase of three in the wire number corresponds to doubling the resistance and halving the cross-section and weight. Also, that an increase of ten in the wire number increases the resistance ten times and di- minishes the cross-section and weight to one-tenth their original values. The American Steel and Wire gauge is used almost universally in this country for steel and iron wires. The Birmingham gauge is used largely in England as their stand- ard, and in this country for steel wires and for other wires not used especially for electrical purposes. [4] DICTIONARY Sec. 1 AMPERE. The practical unit of electric current. A rate of flow of electricity transmitting one coulomb per second. The current of electricity which would pass through a circuit whose resistance is one ohm, under an electromotive force of one volt. A current of such a strength as will deposit 1.118 milligrammes of silver per second from a specifically prepared solution of silver nitrate. The value of the ampere as adopted by the International Congress of 1893, at Chicago is equal to the one-tenth of a unit of current in the C.G.S. system of electric-magnetic units and represented with sufficient accuracy for practical purposes, by the unvarying current, which, when passed through a solution of nitrate of silver in water, in accordance with certain specifications, deposits silver at the rate of 0.001118 of a gramme-per-second. AMPERE HOUR. A unit of electrical quantity equal to the quantity of electricity conveyed by one ampere flowing for one hour. A quantity of electricity equal to 3600 coulombs. AMPERE SECOND. A unit of electric quantity equal to the quantity of electricity conveyed by one ampere flowing for one second. A coulomb. AMPERE TURN. A unit of magneto-motive force equal to that produced by one ampere flowing around a single turn of wire. AMPLITUDE OF VIBRATION OF WAVE. The extent of a movement measured from the starting point or position of equilib- rium. The maximum voltage of a sine wave. ANCHOR LOG. A log buried in the ground and serving as an anchor for a pole guy. ANGLE OF LAG OR LEAD OF CURRENT. An angle whose tangent is equal to the ratio of the reactive to the ohmic resistance in a circuit; whose cosine is equal to the ohmic resistance divided by the impedance of a circuit; whose cosine is the ratio of the real to the apparent power in an alternating current circuit or the angle by which the current lags behind or leads the e.m.f. ANGULAR VELOCITY. The velocity of a point moving rel- atively to a centre of rotation or to some selected point, and usually measured in degrees per second, or in radians per second. In a sinusoidal current circuit the product of 6.2832 and the frequency of the current. APPARENT EFFICIENCY. The volt-ampere efficiency or the ratio of volt-ampere output to volt-ampere input. In apparatus in which a phase displacement is inherent to their operation, apparent efficiency should be understood as the ratio of net power output to volt-ampere input. APPARENT POWER. In an alternating current circuit the product obtained by multiplying the mean effective value of the [5] Sec. 1 DICTIONARY e.m.f . by the mean effective value of the current, such as read directly from a volt-meter and ammeter. p 7T = apparent power. When the power-factor is unity the apparent power in volt-amperes is equal to watts. APPARENT OR EQUIVALENT RESISTANCE. Represents a counter e.m.f. which is in exact phase opposition with the current, i. e., in phase with the I R drop. These counter e.m.f. 's may be generated in motors or in transformers. Losses in the magnetic circuit such as hysteresis and secondary losses such as eddy currents may also be considered as forming part of the apparent resistance loss. ARMOR OF CABLE. The protecting sheathing or metallic covering of a submarine or other electric cable. ASBESTOS. A hydrous silicate of magnesia, i. e., silicate of magnesia combined with water. A fire-proofing material some- times used by itself or in connection with other material for insulating purposes. AUTOMATIC CIRCUIT-BREAKER. A device for automatically opening a circuit when the current passing through it is excessive. AUTOMATIC SWITCH. A switch which is automatically opened or closed on the occurrence of certain predetermined events. AUTO-TRANSFORMER. A one-coil transformer consisting of a choking coil connected across a pair of alternating-current mains, and so arranged that a current or pressure differing from that supplied by the mains can be obtained from it by tapping the coil at different points. Called also a compensator. A transformer in which a part of the primary winding is used as the secondary wind- ing, or conversely. AXIS OF CO-ORDINATES. A vertical and a horizontal line, usually intersecting each other at right angles, and called respectively the axes of ordinates and abscissas, from which the ordinates and abscissas are measured. B. B. & S. G. An abbreviation for Brown and Sharpe's Wire Gauge. B. W. G. An abbreviation for Birmingham Wire Gauge. BALANCED CIRCUIT. A circuit which has been so erected and adjusted as to be free from mutual inductive disturbances from neighboring circuits. BALANCED LOAD O SYSTEM. Any system is said to be balanced when all conditions of each of the circuits of a polyphase, or n-wire, system are alike and numerically equal. [6] DICTIONARY Sec. 1 BARROW-REEL. A reel supported on a barrow for convenience in paying out an overhead conductor during its installation. BEG-OHMS. One billion ohms, or one thousand megohms. BICRO. A prefix for one-billionth, one thousand millionth. BIGHT OF CABLE. A single loop or bend of cable. BIMETALLIC WIRE. A compound wire consisting of a steel core and a copper envelope. BLOWING A FUSE. The fusion or volatilization of a fuse wire or safety strip by the current passing through it. BLOWING POINT OF FUSE. The current strength at which a fuse blows or melts. BRAIDED WIRE. A wire covered with a braiding of insulating material. BRANCH CIRCUITS. Additional circuits provided at points of a circuit where the current branches or divides, part of the current flowing through the branch, and the remainder flowing through the original circuit. A shunt circuit. BRANCH CUT-OUT. A safety fuse or cut-out, inserted between a pair of branch wires and the mains supplying them. BREAKING DOWN OF INSULATION. The failure of an insulating material, as evidenced by the disruptive passage of an electric discharge through it. BRITANNIA JOINT. A joint in which the ends of the wires are laid side by side bound together, and subsequently soldered. BRONZE. An alloy of copper and tin. BRUSH AND SPRAY DISCHARGE. A streaming form of high potential discharge possessing the appearance of a spray of silvery white sparks, or of a branch of thin silvery sheets around a powerful brush. Obtained by increasing the frequency of the alternations. BRUSH DISCHARGE. The faintly luminous discharge which takes place from a positive charged pointed conductor. BUNCHED CABLE. A cable containing more than a single wire or conductor. c. C. An abbreviation for Centigrade. C. A symbol used for capacity. Farad. The defining equation is C = -^~ hi The same symbol is often used for current. [7] Sec. 1 DICTIONARY c.c. An abbreviation for cubic centimeter, the C.G.S. unit of volume. cm. An abbreviation for centimeter, the C.G.S. unit of length. C. G. S. UNITS. An abbreviation for centimeter, gram, second units. The metric system of units for measuring length, mass and time. CABLE. A stranded conductor (single-conductor cable); or a combination of conductors insulated from one another (multiple- conductor cable). CABLE CASING. The metallic sheathing of a cable. CABLE CORE. The hemp or steel center of an aerial electrical cable to enlarge the cross section of the cable or to carry the me- chanical strain of the conductors. CABLE DUPLEX. Two insulated single-conductor cables twisted together. CABLE GRIP. The grip provided for holding the end of an under- ground cable while it is being drawn into a duct. CABLE HOUSE. A hut provided for securing and protecting the end of a cable. CABLE, SUBMARINE. A cable designed for use under water. CABLE VAULT. A vault provided in a building where cables enter from underground conduits and where the cables are opened and connected to fusible plugs or safety catches. CALORIE. A heat unit. The quantity of heat required to raise 1 gramme of water 1 centigrade. CAP WIRE. An overhead wire carried on the summit of a pole, as distinguished from an overhead wire carried on a crossarm. CAPACITY, ELECTROSTATIC. The quantity of electricity which must be imparted to a given body or conductor as a charge, in order to raise its potential a certain amount. (See Potential Electric.) The electrostatic capacity of a conductor is not unlike the capa- city of a vessel filled with a liquid or gas. A certain quantity of liquid will fill a given vessel to a level dependent on the size or capacity of the vessel. In the same manner a given quantity of electricity will produce, in a conductor or condenser a certain dif- ference of electric level, or difference of potential, dependent on the electrical capacity of the conductor or condenser. In the same manner, the smaller the capacity of a conductor, the smaller is the charge required to raise it to a given potential, or the higher the potential a given charge will raise it. The capacity C, of a conductor or condenser, is therefore directly proportional to the charge Q, and inversely proportional to the potential E; or, [8] DICTIONARY Sec. 1 C _Q C -~E~ from which we obtain Q =CE. The quantity of electricity required to charge a conductor or condenser to a given potential is equal to the capacity of the con- ductor or condenser multiplied by the potential through which it is raised. CAPACITY, ELECTROSTATIC, UNIT OF. The farad. Such a capacity of a conductor or condenser that an electromotive force of one volt will charge it with a quantity of electricity equal to one coulomb. CAPACITY OF CABLE. The quantity of electricity required to raise a given length of cable to a given potential, divided by the potential. The ability of a conducting wire or cable to permit a certain quantity of electricity to be passed into it before acquiring a certain potential. CAPACITY OF LINE. The ability of a line to act as a condenser, and, therefore, like it, to possess capacity. CAPACITY REACTANCE. The property by which a counter e.m.f. is produced when an e.m.f. is impressed across the terminals of two conducting surfaces separated by a dielectric. CARBON. An elementary substance which occurs naturally in three distinct allotropic forms: graphite, charcoal and the diamond. CARRYING CAPACITY. The maximum current strength that any conductor can safely transmit. CATENARY CURVE. The curve described by the sagging of a wire, under its own weight, when stretched between two points of support. CENTIGRAMME. The hundredth of a gramme; or, 0.1543 grain avoirdupois. CENTIMETER. The hundredth of a metre; or 0.3937 inch. CENTIMETER-GRAMME-SECOND SYSTEM. A system based on the centimeter as the unit length, the gramme as the unit of mass, and the second as the unit of time. CENTER OF DISTRIBUTION. Is the point from which the electrical energy must be supplied to use a minimum weight of conducting material. CHARACTERISTIC CURVE. A diagram in which a curve is employed to represent the relation of certain varying values. A curve indicating the characteristic properties of a dynamo-electric machine under various phases of operation. A curve indicating the electromotive force of a generator, as a variable dependent on the excitation. Sec. 1 DICTIONARY CHARGE, ELECTRIC. The quantity of electricity that exists on the surface of an insulated electrified conductor. CHOKE COIL. A reactance used in alternating current circuits for the adjustment of voltage and power factor; and also to impede high frequency oscillations such as lightning discharges in both direct current and alternating current circuits. CIRCUIT BREAKER. Any device for opening or breaking a circuit. CIRCUIT, ELECTRIC. The path in which electricity circulates or passes from a given point, around or through a conducting path, back again to its starting point. All simple circuits consist of the following parts, viz : (1) Of an electric source which may be a voltaic battery, a thermo- pile, a dynamo-electric machine, or any other means for pro- ducing electricity. (2) Of leads or conductors for carrying the electricity out from the source, through whatever apparatus is placed in the line, and back again to the source. (3) Various electro-receptive devices, such as electro-magnets, electrolytic baths,, electric motors, electric heaters, etc., through which passes the current by which they are actuated or operated. CIRCUIT MULTIPLE. A circuit in which a number of separate sources or separate electro-receptive devices or both, each have one of their poles connected to a single lead or conductor and their other poles connected to another single lead or conductor. CIRCUIT, OPEN. A broken circuit. A circuit, the conducting continuity of which is broken. CIRCUIT, PARALLEL. A name sometimes applied to circuits connected in multiple. CIRCUIT, SERIES. A circuit in which the separate sources or the separate electro-receptive devices, or both, are so placed that the current produced in each, or passing through each, passes suc- cessively through the entire circuit from the first to the last. CIRCULAR MIL. A unit of area employed in measuring the cross-section of wires, equal, approximately, to 0.7854 square mils. The area of a circle one mil in diameter. CLOCKWISE MOTION. A rotary motion whose direction is the same as that of the hands of a clock, looking at the lace. COEFFICIENT OF EXPANSIpN. The coefficient of linear expansion of a solid is the increase in length of unit length when the temperature is raised from 32 to 33 degrees Fah. or from to 1 degree Cent. The coefficient of cubical expansion is the increase in volume of a [10] DICTIONARY Sec. 1 body when its temperature is raised from 32 to 33 degrees Fah. or from to 1 degree Cent., divided by its original volume. COEFFICIENT OF HYSTERESIS. The work expended hys- teretically in a cubic-centimetre of iron, or other magnetic substance, in a single cycle, at unit magnetic flux density. The coefficient which multiplied by the volume of iron, the frequency of alternation, and the 1 .6th power of the maximum flux density gives the hysteretic power loss. COEFFICIENT OF INDUCTANCE. A constant quantity such that, when multiplied by the cunent strength passing through any coil or circuit, will numerically represent the flux linkage with that coil or circuit due to that current. A term sometimes used for coefficient of self-induction. The ratio of the counter e.m.f. of self-induction in a coil or circuit to the time-rate-of-change of the inducing current. COEFFICIENT OF MUTUAL INDUCTANCE. The ratio of the electromotive force induced in a circuit to the rate-of-change of the inducing current in a magnetically associated circuit. The ratio of the total flux-linkage with a circuit proceeding from an associated inducing circuit, to the strength of current flowing in the latter. COEFFICIENT OF SELF-INDUCTANCE. Self-inductance. The ratio in any circuit of the flux induced by and linked with a current, to the strength of that current. The ratio in any circuit of the e.m.f. of self-induction to the rate-of-change of the current. COME ALONG. A small portable vise capable of ready attachment to an aerial line or cable, and used to pull the wire to its proper tension. COMMON RETURN. A return conductor common to several circuits. COMPENSATOR. An auto-transformer. COMPLETE WAVE. Two successive alternations or a double alternation of a periodically-alternating quantity. A cycle. COMPONENTS OF IMPEDANCE. The energy component or effective resistance and the wattless component or effective react- ance. COMPOSITE WIRE. A wire provided with a steel core and an external copper sheath, possessing sufficient tensile strength to enable it to be used in long spans without excessive sagging. A bimetallic wire. COMPOUND. An asphaltic composition employed in the sheath- ing of submarine cables. A term often applied to insulating ma- terials. CONCENTRIC CABLE. A cable provided with both a leading and return conductor insulated from each other, and forming re- [11] Sec. 1 DICTIONARY spectively the central core or conductor, and the enclosing tubular conductor. A cable having concentric conductors. CONDENSANCE. Capacity reactance. CONDENSER. A device composed of two or more conducting bodies separated by a dielectric. CONDENSER CAPACITY. The capacity of a condenser. (See Capacity.) CONDUCTANCE. A word sometimes used in place of conduct- ing power. The reciprocal of resistance. In a continuous-current circuit the ratio of the current strength to the e.m.f. ; in an alter- nating current circuit the quantity by which the e. m. f . is multiplied to give the component of the current in phase with the e. m. f . CONDUCTIVITY, ELECTRIC. The reciprocal of electric resistivity. The conductance of a substance referred to unit dimen- sions. CONDUCTOR. Any substance which will permit the so-called passage of an electric current. A substance which possesses the ability of determining the direction in which electric energy shall pass through the ether in the dielectric surrounding it. CONNECTING SLEEVE. A metallic sleeve employed as a con- nector for readily joining the ends of two or more wires. CONNECTION, MULTIPLE. Such a connection of a number of separate electric sources, or electro-receptive devices, or circuits, that all the positive terminals are connected to one main or positive conductor, and all the negative terminals are connected to one main or negative conductor. CONNECTIpN, SERIES. The connection of a number of separate electric sources, or electro-receptive devices, or circuits, so that the current passes successively from the first to the last in the circuit . CONSTANT. A quantity used in a formula, the value of which remains the same, regardless of the value of the other quantities used in the formula. CONSTANT CURRENT. A current maintained at a constant effective value in a circuit is known as a constant current. This maj be either alternating or direct current. CONSTANT-CURRENT TRANSFORMER. A transformer which is intended to raise or reduce a current strength in a given constant ratio. A transformer designed to maintain a constant strength of current in its secondary circuit, despite changes of load. CONSTANT-POTENTIAL CIRCUIT. A circuit whose potential is maintained approximately constant. A multiple-arc or parallel connected circuit. [ 12] DICTIONARY Sec. 1 CONTINUOUS CURRENT. An electric current which flows in one and the same direction. A steady or non-pulsating direct current. CONVECTION CURRENTS. Currents produced by the bodily carrying forward of static charges in convection streams. CONVECTIVE DISCHARGE. The discharge which occurs from the points of a highly charged conductor, through the electrostatic repulsion of similarly charged air particles, which thus carry off minute charges. CO-PERIODIC. Possessing the same periodicity. CO-PHASE. Coincidence in phase of co-periodic motions. Such a phase relation between two periodic but non-co-periodic quantities as tends to increase the amplitude of the motion. COPPER, Cu. Atomic weight 63.2, specific gravity 8.81 to 8.95. Fuses at about 1930 F. Distinguished from all other metals by its reddish color. Very ductile and malleable and its tenacity is next to iron. Tensile strength 20,000 to 30,000 Ibs. per square inch. Heat conductivity 73.6% of that of silver and superior to that of other metals. Expands 0.0051 of its volume bv heating from 32 to 212 F. COPPER LOSS. The total loss of energy produced by the pass- age of a current through the copper wire of a dynamo, motor, or conducting system generally. The loss of energy due to the re- sistance of the conductor to the passage of the current. This loss is equal to the resistance of the conductor times the square of the effective current flowing in the conductor. CORE, LAMINATION OF. Structural subdivisions of the cores of magnets, transformers, or similar apparatus, in order to prevent heating and subsequent loss of energy from the production of local eddy or Foucault currents. These laminations are obtained by forming the cores of sheets, rods, plates, or wires of iron insulated from one another. CORE LOSSES. The hysteresis and the Foucault or eddy- current losses of the core of a dynamo, motor or transformer. CORONA. The name given to a brush discharge surrounding aerial conductors which carry high potential. The discharge is red violet in color, gives a hissing sound and is probably intermittent in character. COSINE. One of the trigonometrical functions. The ratio of the base to the hypothenuse of a right-angled triangle in which the hypo- thenuse is the radius vector, and the angle between the base and hypothenuse the angle whose cosine is considered. [ 13] Sec. 1 DICTIONARY COTANGENT. The ratio of the adjacent side to the opposite side of an angle of a right triangle. Cotangent 6 = tangent Q COULOMB. The practical unit of electric quantity. Such a quantity of electricity as would pass in one second through a circuit conveying one ampere. The quantity of electricity contained in a condenser of one farad capacity, when subjected to the e.m.f. of one volt. The value of the coulomb as adopted by the International Elec- trical Congress of 1893, at Chicago. The quantity of electricity equal to that transferred through a circuit by a current of one International ampere in one second. The quantity of electricity which if concentrated at a point and placed at one centimeter from an exactly similar quantity will repel the latter with a force of one dyne. COUNTER-ELECTROMOTIVE FORCE. An opposite or re- verse electromotive force which tends to set up a current in the opposite direction to that actually produced by a source. COUNTER-ELECTROMOTIVE FORCE OF INDUCTION. The counter-electromotive force of self or mutual induction. COUPLE. In mechanics, two equal and parallel, but oppositely directed forces, not acting in the same line, and tending to produce rotation. CROSS ARM. A horizontal beam attached to a pole for the support of the insulators of electric light, or other electric wires. CROSS, ELECTRIC. A connection, generally metallic, acci- dentally established between two conducting lines. A defect in an electric circuit, caused by two wires coming into contact by crossing each other. CURRENT DISTRIBUTION. The density of electric currents in the various parts of a conducting mass or net work. CURRENT DETERMINATION FROM WATTAGE. The rated current may be determined as follows: If W = rating in watts, or apparent watts, if the power-factor be other than 100 per cent, and E = full-load terminal voltage, the rated current per terminal is: W I = -=7- in continuous current, or single-phase apparatus El T in three-phase apparatus V3-E W I = 2^ in two-phase four wire apparatus. CURRENT, ELECTRIC. The quantity of electricity per second which passes through any conductor or circuit, when the flow is [14] DICTIONARY Sec. 1 uniform. The rate at which a quantity of electricity flows or passes through a circuit. ^ The ratio, expressed in terms of electric quantity per second, existing between the electromotive force causing a current and the resistance which opposes it. The unit of current, or the ampere, is equal to one coulomb per second. (See Ampere, and Coulomb.) The word current must not be confounded with the mere act of flowing; electric current signifies rate of flow, and always supposes an electromotive force to produce the current, and a resistance to oppose it. The electric current is assumed to flow out from the positive terminal of a source, through the circuit and back into the source at the negative terminal It is assumed to flow into the positive terminal of an electro receptive device such as a lamp, motor, or storage battery, and out of its negative terminal; or, in other words, the positive pole of the source is always connected to the positive terminal of the electro-receptive device. The current that flows or passes in any circuit is, in the case of a constant current, equal to the electromotive force, or difference of potential, divided by the resistance, as: D. C, A. C. T B T E = R I = Z The flow of an electric current may vary in any manner whatsoever. A current which continues flowing in the same direction no matter how its strength may vary, is called a direct current. If the strength of such a current is constant, it is called a continuous current. A regular varying continuous current is called a pulsatory current. A current which alternately flows in opposite directions, no matter how its strength may vary, is called an alternating current. This may be periodic or non-periodic. CURRENT, FOUCAULT. A name sometimes applied to eddy currents, especially in armature cores. CURRENT, POLYPHASE, is the general term applied to any system of more than a single phase. CURRENT RUSH. The initial flow of electricity that occurs when a transformer, transmission line or other electrical apparatus is switched on or connected to an electric circuit. CURRENT, SIMPLE PERIODIC. A current, the flow of which is variable both in strength and duration, but recurring at definite intervals. A flow of current passing any section of a conductor that may be represented by a simple harmonic curve. CURRENT STRENGTH. In a direct-current circuit the quo- tient of the total electromotive force divided by the total resistance. The time-rate-of-flow in a circuit expressed in amperes, or coulombs [ 15 ] Sec. 1 DICTIONARY per second. In an alternating current the quotient of the total electromotive force divided by the impedance. CUT-OUT. A device for removing an electro-receptive device or loop from the circuit. A safety fuse. CUT-OUT-BLOCK. A block containing a fuse wire or safety catch. CUT-OUT-SWITCH. A short-circuiting switch by means of which an arc-light or series loop is cut out from its feeding circuit. CYCLEi One complete set of positive and negative values of 3n alternating current. D. D. C. An abbreviation for direct current. D. P. SWITCH. An abbreviation for double-pole switch. DEAD MAN. A support for raising a pole and supporting it in place while securing it in the ground. DELTA-CONNECTION. The connection of circuits employed in a delta three phase system. DELTA THREE PHASE SYSTEM. A three phase system in which the terminal connections resemble the Greek letter delta, or a triangle. DEMAND. Demand is a load specified, contracted for or used, expressed in terms of power as kilowatts or horse-power. DEMAND FACTOR. Unless otherwise specified, demand factor is the maximum connected kilowatts of capacity divided into the actual kilowatts of demand, and expressed in terms of percent. DENSITY. Mass of unit volume, compactness. DENSITY OF CURRENT. The quantity of current that passes per-unit-of-area of cross-section in any part of a circuit. DENSITY OF FIELD. The quantity of magnetic flux that passes through any field per-unit-of-area of cross-section. DIELECTRIC. Any substance which permits electrostatic in- duction to take place through its mass. The substance which separates the opposite coatings of a con- denser is called the dielectric. All dielectrics are non-conductors. All non-conductors or insulators are dielectrics, but their dielectric power is not exactly proportional to their non-conducting power. Substances differ greatly in the degree or extent to which they permit induction to take place through or across them. A dielectric may be regarded as pervious to rapidly reversed periodic currents, but opaque to continuous currents. There is, however, some conduction of continuous currents. [16] DICTIONARY Sec. 1 DIELECTRIC CAPACITY. A term employed in the same sense as specific inductive capacity. DIELECTRIC HYSTERESIS. A variety of molecular friction, analogous to magnetic hysteresis, produced in a dielectric under charges of electrostatic stress. That property of a dielectric by virtue of which energy is consumed in reversals of electrification. DIELECTRIC RESISTANCE. The resistance which a dielectric offers to strains produced by electrification. The resistance of a dielectric to displacement currents. DIELECTRIC STRAIN. The strained condition of the glass or other dielectric of a condenser produced by the charging of the con- denser. The deformation of a dielectric under the influence of an electro-magnetic stress. DIPPING. An electro-metallurgical process whereby a thin coating or deposit of metal is obtained on the surface of another metal by dipping it in a solution of a readily decomposable metallic salt. Cleansing surfaces for electric-plating by immersing them in various acid liquors. DISCHARGE. The equalization of the difference of potential between the terminals of a condenser or source, on then* connection by a conductor. The removal of a charge from a conductor by connecting the conductor to the earth or to another conductor. The removal of a charge from an insulated conductor by means of a stream of electrified air particles. DISRUPTIVE DISCHARGE. A sudden and more or less com- plete discharge that takes place across an intervening non-conductor or dielectric. DISRUPTIVE STRENGTH OF DIELECTRIC. The strain a dielectric is capable of bearing without suffering disruption, or with- out permitting a disruptive discharge to pass through it. DISSIPATION OF ENERGY. The expenditure or loss of avail- able energy. DISTRIBUTED CAPACITY. The capacity of a circuit con- sidered as distributed over its entire length, so that the circuit may be considered as shunted by an infinite number of infinitely small condensers, placed infinitely near together, as distinguished from localized capacity, in which the capacity is distributed in definite aggregations. DISTRIBUTED INDUCTANCE. Inductance distributed through the entire length of a circuit or portion thereof, as distinguished from inductance interposed in a circuit in bulk at some one or more points. DISTRIBUTING CENTER. (See Center of Distribution.) [17] Sec. 1 DICTIONARY DISTRIBUTING MAINS. The mains employed in a feeder system of parallel distribution. DIVERSITY FACTOR. A diversity factor is used to express the relation between the simultaneous demand of all individual con- sumers and the sum of the maximum demands made by these con- sumers; the sum of the maximum demands of the consumers for one year, no matter at what time they occurred, divided into the simul- taneous greatest demand of these consumers for a like period, when expressed in percent will give the diversity factor. DRAW VISE. A device employed in stringing overhead wires. A portable vise for holding and drawing up an overhead wire. DROP. A word frequently used for drop of potential, pressure, or electromotive force. The fall of potential which takes place in an active conductor by reason of its resistance, or impedance. DROP OF POTENTIAL. The fall of potential, equal in any part of a circuit to the product of the current strength and the resistance, or impedance of that part of the circuit. DROP OF VOLTAGE. The drop or difference of potential of any part of a circuit. DUPLEX CABLE. A cable containing two separate conductors placed parallel to each other. DUPLEX WIRE. An insulated conductor containing two sepa- rately insulated parallel wires. DYNAMIC ELECTRICITY. A term sometimes employed for the phenomena of the transfer of electric energy, in contradistinction to static electricity. DYNE. The C.G.S. unit of force. The force which in one second can impart a velocity of one centimeter-per-second to a mass of one gramme. E. e. h. p. An abbreviation for electrical horse-power, e. m. f. An abbreviation for electromotive force. - e. m. f . OF SELF-INDUCTION. The e.m.f . generated in a loop oi wire during the change of magnetic flux due to the current flowing therein. EARTH CIRCUIT. A circuit in which the ground or earth forms part of the conducting path. EARTH CURRENTS. Electric currents flowing through the earth, caused by the difference of potential of its different parts. EASEMENT. A permit obtained from the owner of a property for the erection of poles or attachments for aerial lines. [18] DICTIONARY Sec. 1 EDDY CURRENTS. (See Foucault currents.) EFFECTIVE ELECTROMOTIVE FORCE. The difference be- tween the direct and the counter e.m.f. The square root of the mean square of the instantaneous values of a varying electromotive force. The value which is equivalent to a constant electromotive force. EFFECTIVE REACTANCE. In an alternating-current circuit, the ratio of the wattless component of an electromotive force to the total current. EFFECTIVE RESISTANCE. In an alternating-current circuit, the ratio between the energy component of an electromotive force and the total current. EFFICIENCY. The efficiency of an apparatus is the ratio of its output to its input. The output and input may be in terms of watt- hours, watts, volt-amperes, amperes, or any other quantity of interest, thus respectively defining energy efficiency, power efficiency, ap- parent-power efficiency, current efficiency, etc. Unless otherwise specified, however, the term efficiency is ordinarily assumed to refer to power efficiency. When the input and output are expressed in terms of the same unit, the efficiency is a numerical ration, otherwise it is a physical dimensional quantity. ELASTIC LIMIT. This may be defined as that point at which the deformation ceases to be proportional to the stresses, or, the point at which the rate of stretch or other deformations begin to increase. It is also defined as the point at which permanent set becomes visible. ELECTRIFICATION. The production of an electric charge. ELECTRO-CHEMISTRY. That branch of electric science which treats of electric combinations and decompositions effected by the electric current. The science which treats of the relation between the laws of electricity and chemistry. ELECTRO-MAGNETIC UNITS. A system of C.G.S. units employed in electro-magnetic measurements. Units based on the attraction and repulsions capable of being exerted between two unit magnetic poles at unit distance apart, or between a unit magnetic pole and a unit electric current. ELECTRO-METALLURGY. That branch of electric science which relates to the electric reduction or treatment of metals. Electro-metallurgical processes effected by the agency o^ electricity. Electro-plating or electro-typing. ELECTRO-NEGATIVE. In such a state as regards electricity as to be repelled by bodies negatively electrified, and attracted by [19] Sec. 1 DICTIONARY those positively electrified. The ions or radicals which appear at the anode or positive electrode of a decomposition cell. ELECTRO-NEGATIVE IONS. The negative ions, or groups of atoms or radicals, which appear at the anode or positive terminal of a decomposition cell. The anions. ELECTRO-PLATING. The process of covering any conducting surface with a metal, by the aid of an electric current. ELECTRO-POSITIVE. In such a state, as regards an electric charge, as to be attracted by a body negatively electrified, and repelled by a body positively electrified. The ions or radicals which appear at the cathode or negative electrode of a decomposition cell. ELECTRO-POSITIVE IONS. The cations or groups of atoms or radicals which appear at the cathode of a decomposition cell. ELECTROLYSIS. Chemical decomposition effected by means of an electric current. The decomposition of the molecule of an electrolyte into its ions or radicals. Electrolytic decomposition. ELECTROLYTE. Any compound liquid which is separable into its constituent ions or radicals by the passage of electricity through it. ELECTROLYTIC CELL. A cell or vessel containing an electro- lyte in which electrolysis is carried on. A plating cell or vat. ELECTROSTATIC CAPACITY. (See Capacity Electrostatic.) ELECTROSTATIC DISCHARGE. A term sometimes employed for a disruptive discharge. ELECTROSTATIC FIELD. The region of stress existing about an electrified body due to its electric potential. ELECTROSTATIC FORCE. The force of attraction or repulsion exerted between two electrified bodies due to their potentials. ELECTROSTATIC INDUCTION. The induction of an electric charge produced in a conductor brought into an electrostatic field. ELECTROSTATIC LINES OF FORCE. Lines of force produced in the neighborhood of a charged body, by the presence of the charge. Lines extending in the direction in which the force of electrostatic attraction or repulsion acts. ELECTROSTATIC POTENTIAL. The power of doing electric work possessed by a unit quantity of electricity residing on the surface of an insulated body. That property in space by virtue of which work is done when an electric charge is moved therein. ELECTROSTATIC UNITS. Units based on the attractions or repulsions of two unit charges of electricity at unit distance apart. ENERGY. The power of doing work. [20] DICTIONARY Sec. 1 ENERGY COMPONENT OF E.M.F. In an alternating current circuit the component of e.m.f. which is in phase with the current. In an alternating current circuit, the product of the current and the effective resistance. ENERGY COMPONENT OF CURRENT. In an alternating current circuit the component of current which is in phase with the impressed e.m.f. In an alternating current, the product of the e.m.f. and the effective conductance. ENERGY, ELECTRIC. The power which electricity possesses of doing work. EQUALIZER FEEDER. A feeder whose principal purpose is to equalize the pressure between the ends of two or more other feeders, as distinguished from supplying current to feeding points. EQUIPOTENTIAL. Of, or pertaining to an equality of potential. EQUIVALENT RESISTANCE. A single resistance which may replace a number of resistances in a circuit without altering the current traversing it. Such a resistance in a simple-harmonic-current circuit as would permit energy to be absorbed, with the same ef- fective current strength, at the same rate as an actual resistance in a complex-harmonic-current circuit. ERG. The C.G.S. unit of work, or the work done when unit C. G. S. force is overcome through unit C. G. S. distance. The work accomplished when a body is moved through a distance of one centimeter with the force of one dyne. A dyne-centimeter. F. FAHRENHEIT THERMOMETRIC SCALE. The thermometric scale in which the length of the thermometer tube, between the melting point of ice and the boiling point of water, is divided into 180 equal parts or degrees. FARAD. The practical unit of electric capacity. Such a capacity of a conductor or condenser that one coulomb of electricity is re- quired to produce therein a difference of potential of one volt. FATIGUE OF IRON OR STEEL, MAGNETIC. The change of magnetic hysteresis loss with time. Ageing of magnetic material. FEED. To supply with an electric current. To move or regulate one or both of the carbon electrodes in an arc-lamp. FEEDER. An electric circuit, used to supply power to a station or service, as distinguished from circuits confined to a single station. FEEDER DISTRIBUTION. A feeder-and-main system of dis- tribution. [21] Sec. 1 DICTIONARY FEEDING POINT. A point of connection between a feeder and the mains. A feeding center. FIELD, ELECTROSTATIC. (See Electrostatic Field.) FIELD, MAGNETIC. The region of stress existing around the poles of a magnet or a magnetized body, with reference to its effect upon a unit magnetic charge. Also the field around a conductor due to a current flowing in it. FOOT-POUND. A unit of work. The amount of work required to raise one pound vertically through a distance of one foot. FOOT-POUND-PER-SECOND. A rate of doing work equal to the expenditure of one foot-pound of energy per second. FOUCAULT OR EDDY CURRENTS. It was observed a num- ber of years before Faraday's discovery of induced currents, that, a vibrating magnetic needle quickly came to rest when near or over a copper plate. Arago had in 1824 also shown that a magnetic needle suspended over a rotating copper disk rotates with the disk. Both FIG. 1. Foucault Currents Generated in Disk by Arago's Rotation. FIG. 2. Another Form of Arago's Experiment. the damping of the needle and Arago's disk experiment were ex- plained by Faraday as phenomena of electro-magnetic induction. The relative motion of the magnet and the disk induces an e.m.f. in the metal disk. The current thus generated circulates in the disk, producing a magnetic action, which by Lenz's law tends to hold the magnet at rest relative to the disk or plate. Electric currents, thus induced and circulating in a metallic mass, are called eddy currents or Foucault currents. The energy of such currents is dissipated in heat. The iron cores of armatures of dynamo machines and transformers are always laminated so as to offer resistance to the formation of such currents, and thus to stop the heat losses (Figs. 1 and 2). FREQUENCY. The number of cycles or periods per second. [22] DICTIONARY Sec. 1 FUNDAMENTAL FREQUENCY. The nominal or lowest frequency of a complex harmonic electromotive force, flux or current. FUSE BLOCK. A block containing a safety fuse, or fuses. FUSE BOX. A box containing a safety fuse. A box containing fuse wires. FUSE, ELECTRIC. A conductor designed to melt or fuse at a certain value of current and time and by so doing to rupture the circuit. FUSE LINKS. Strips or plates of fusible metal in the form of links employed for safety fuses. FUSING CURRENT. A term sometimes applied to the current which causes a fuse to melt. G. g. An abbreviation or symbol for the gravitation constant, or the force with which the earth acts upon unit mass at any locality. An abbreviation proposed for gramme, the unit of mass in physical investigations. GAINS. The spaces cut in poles for the support and placing of the cross arms. GALVANIZING. Covering iron with an adherent coating of zinc by dipping it in a bath of molten metal. GAUSS. The name proposed in 1894 by the American Institute of Electrical Engineers for the C.G.S. unit of magnetic flux density. A unit of intensity of magnetic flux, equal to one C.G.S. unit of magnetic flux per-square-centimeter of area of normal cross-section. A name proposed for the C.G.S. unit of magnetic potential or mag- netomotive force by the British Association in 1895. GILBERT. A name proposed for the C.G.S. unit of magneto- motive force. A unit of magnetomotive force equal to that produced bv - of one ampere-turn. That value of magnetic force which 1.25oo will establish one line or one maxwell per centimeter cube of air. GLOBE STRAIN-INSULATORS. Insulators provided for the support of the strain wires in an overhead system. GRADIENT, ELECTRIC. The rapidity of increase or decrease of the strength of an electromotive force. The vector space-rate of descent of electric potential at any point. GRAPHITE. Graphite is used for rendering surfaces to be elec- tro-plated, electrically conducting, and also for the brushes of dyna- mos and motors. For the latter purpose it possesses the additional advantage of decreasing the friction by means of its marked lubri- cating properties. [ 23 ] Sec. 1 DICTIONARY GROUND. A general term for the earth when employed as a return conductor. A term for the connection of a conductor to the earth. GROUND CIRCUIT. A circuit in which the ground forms part of the path through which the current passes. GROUND, EFFECT OF. On the neutral point of three-phase, three-wire systems. Consider a general case. A lightning stroke disables some apparatus so that inductive reactance is introduced in the accidental ground. Before the accident there was a perfectly balanced system, where the neutral, or ground potential, is symmetrical in reference to the line conductors and governed A I 13 FIG. 3. FIG. 4. FIG. 5. entirely by the ground capacities represented in Fig. 3, as three con- densers. If, now, one line is grounded through an impedance, the neutral will be displaced along line AB. The conditions are then : First. Ground made by infinite reactance. (No Ground.) We have then X = - and e 2 = when is the voltage from one wire to the neutral of a balance system and e 2 is the voltage from the neutral of the balanced system to a point midway between the other two wires and X is the condensive reactance; that is, in Fig. 4 the neutral lies at O, and the ground is symmetrical in reference to the three lines. Second, when e 2 = 0, and ei=e (shown in Fig. 5). In this case the neutral lies midway between the other two con- ductors and its potential difference -to ground is .87e. Third, when ei and e 2 both become infinite, under such condition, the system would be subjected to infinite potential. The third con- dition arises if one line is grounded by a reactance of | of the con- densive reactance, the system then being subjected to very great stresses, even at normal frequency. GROUND-RETURN. A general term used to indicate the use of the ground or earth for part of an electric circuit. The earth or ground which forms part of the return path of an electric circuit. [24] DICTIONARY \ A "\ 560 V/ = 10% 5th, = 2. 22i% 3 r d, = 180 5% 5th, = 180 3. 15% 3rd, = 180 10% 5th, = 4. 15% 3rd, = 10% 5th, < = 180 [30] DICTIONARY Sec. 1 changes to a second peak, giving ultimately a flat-top or even double- peaked wave with sharp zero. The intermediate positions represent what is called a saw-tooth wave. The quintuple harmonic causes a flat-topped or even double- peaked wave with flat zero. With increasing phase displacement, the wave becomes of the type called saw-tooth wave also. The flat zero rises and becomes a third peak, while of the two former peaks, one rises, the other decreases, and the wave gradually changes to a triple-peaked wave with one main peak, and a sharp zero. As seen, with the triple harmonic, flat-top or double-peak coin- cides with sharp zero, while the quintuple harmonic flat-top or double-peak coincides with flat zero. Sharp peak coincides with flat zero in the triple, with sharp zero in the quintuple harmonic. With the triple harmonic, the saw-tooth shape appearing in case of a phase difference between the funda- mental and harmonic, is single, while with the quintuple harmonic it is double. Thus in general, from simple inspection of the wave shape, the existence of these first harmonics can be discovered. Some char- acteristic shapes are shown in Fig. 13. HEAT. A form of energy. A vibratory motion impressed on the molecules of matter by the action of any form of energy. A wave motion impressed on the universal ether by the action of some form of energy. HEAT UNIT. The quantity of heat required to raise a unit mass of water through one degree of the thermometric scale the cal- orie. There are a number of different heat units. The most im- portant are: The British Heat Unit, or Thermal Unit, or the amount of heat required to raise 1 pound of water 1 degree Fahr. This unit repre- sents an amount of work equal to 772 foot-pounds. The Calorie, or the amount of heat required to raise the tempera- ture of one gramme of water 1 degree C. The Joule, or the quantity of heat developed in one second by the passage of a current of one ampere through a resistance of one ohm. 1 joule equals .2407 calories. 1 foot-pound equals 1.356 joules. HENRY. The practical unit of self-induction. An earth-quad- rant or 10 9 centimeters. The value of the henry as adopted by the International Electrical Congress of 1893, at Chicago. The value of the induction in a circuit, when the electromotive force induced in the circuit in one International volt, and the inducing current varies at the rate of one ampere per second. HIGH FREQUENCY. This term is used to some extent as de- nning high commercial frequencies such as 133 cycles per second. The term should rather be used to define frequencies much higher [31] Sec. 1 DICTIONARY than those in commercial use; i. e., frequencies produced by light- ning discharges, arcing grounds, etc. HIGH POTENTIAL CURRENT. A term loosely applied for a current produced by high electromotive forces. HIGH POTENTIAL INSULATOR. An insulator suitable for use on high potential circuits. HIGH TENSION CIRCUIT. A circuit employed in connection with high electric pressures. HORSE-POWER. A commercial unit of power, or rate-of-doing- work. A rate-of-doing-work equal to 33,000 pounds raised one foot- per-minute, or 550 pounds raised one fpot-per-second. A rate-of- doing-work equal to 4.562 kilograms raised one meter per minute. HORSE-POWER, ELECTRIC. Such a rate-of -doing electrical work as is equal to 746 watts, or 746 volt-coulombs per second. HORSE-POWER-HOUR. A unit of work equal to the work done by one horse-power acting for an hour. 1,980,000 foot-pounds. HYDRO-ELECTRIC SYSTEM. An electric system with gen- erators driven by water-power. HYSTERESIS. A lagging behind of magnetization relatively to magnetizing force. Apparent molecular friction due to magnetic change of stress. A retardization of the magnetizing or demagnet- izing effects as regards the causes which produce them. That qual- ity of a para-magnetic substance by virtue of which energy is dissi- pated on the reversal of its magnetization. HYSTERESIS COEFFICIENT. The hysteretic coefficient. The energy dissipated in a cubic centimeter of magnetic material by a single cyclic reversal of. unit magnetic density. HYSTERETIC CYCLE. A cycle of complete magnetization and reversal. HYSTERETIC LAG. The lag in the magnetization of a trans- former due to hysteresis. I. I. An abbreviation for the amount of current. I. H. P. An abbreviation for indicated horse-power. I. 2 R LOSS. The loss of power in any circuit equal to the square of the current in amperes by the resistance in ohms. IMPEDANCE COILS. A term sometimes applied to choking coils, reactance coils, or economy coil. IMPEDANCE. That quantity which when multiplied with the total current in amperes will give the impressed e.m.f. in volts. [32] DICTIONARY Sec. 1 IMPRESSED ELECTROMOTIVE FORCE. The electromotive force brought to act in any circuit to produce a current therein. In an alternating-current circuit, the electromotive force due to an impressed source, in contradistinction to the effective electromotive force, or that which is active in producing current, or the electro- motive forces due to, or opposed to, self or mutual induction. An applied e.m.f. as distinguished from a resultant, or wattless e.m.f. INDIA RUBBER. A resinous substance obtained from the milky juices of a tropical tree. INDUCED CURRENT. When by any means whatever the total number of lines of force passing through any circuit is changed, an electric current is produced in that circuit. Such a current is called an induced current. INDUCED ELECTROMOTIVE FORCES, e.m.f.'s set up by electro-dynamic induction. INDUCED M. M. F. Any magnetomotive force produced by induction. The aligned or structural magnetomotive force as dis- tinguished from the prime magnetomotive force. INDUCTANCE. That property, in virtue of which a finite elec- tromotive force impressed on a circuit does not immediately gen- erate the full current due to the resistance of the circuit, and which, when the electromotive force is withdrawn, requires a finite time for the current strength to fall to its zero value. A property, by virtue of which the passage of an electric current is necessarily accompanied by the absorption of electric energy in producing a magnetic field. A constant quantity in a circuit at rest, and devoid of iron, depend- ing only upon its geometrical arrangement, and usually expressed in henrys, or in centimeters. INDUCTANCE COIL. An impedance, reactance, or choking coil. A coil placed in a circuit, for the purpose of preventing an impulsive current-rush in that circuit, by means of the counter-electromotive force developed in the coil on being magnetized. INDUCTION. The property by which one body having electrical or magnetic polarity causes or induces it, in another body or another part of its own body without direct contact. INDUCTION, MAGNETIC. The production of magnetism in a magnetizable substance by bringing it into a magnetic field. INDUCTION, MUTUAL. Induction produced by two neighbor- ing circuits on each other by the mutual interaction of their magnetic fields. INDUCTION, SELF. (See Self Induction.) INDUCTIVE CIRCUITS. Circuits containing certain types of apparatus and known as inductive circuits have the property of storing up a part of the energy supplied to the circuits during a 2 [33] Sec. 1 DICTIONARY part of each cycle, and restoring this energy to the source during the remainder of the cycle. This causes the reversal of current to take place at an earlier or a later instant that the reversal of yoltage, the current being known then as a lagging current. During the time when energy is being delivered to the circuit, the product of voltage and current is positive ; that is, the voltage and the current have the same sign. When either voltage or current is reversed with respect to the other so that this product is negative, power is being returned, by the circuit to the source, and is then reckoned as a negative. The net value of the energy delivered to the circuit per cycle is equal to the difference between the positive and the nega- tive values of energy in the two periods above referred to. The average value of the power for a given value of voltage and current is then less than the product of the voltage and the current (the volt- amperes) and may have any value between the value of the volt- amperes and zero. INDUCTIVE CIRCUIT. Any circuit in which induction occurs. INDUCTIVE REACTANCE. Reactance due to self induction as distinguished from reactance due to a condenser. IN-PUT. The power absorbed by any machine in causing it to perform a certain amount of work. INSTANTANEOUS PEAK. The highest value reached by the quantity under consideration as measured by some device which indicated high actual value of the quantity at every moment. INSULATE. To so cover or protect a body as to prevent elec- tricity from being conducted to or removed from it. INSULATED WIRES. Wires provided with insulating coverings or coatings. INSULATING JOINT. A joint in an insulating material or covering in which the continuity of the insulating material is in- sured. INSULATING VARNISH. An electric varnish formed of any good insulating material. INSULATION RESISTANCE. The resistance existing between a conductor and the earth or between two conductors in a circuit through insulating materials lying between them. A term applied to the resistance of the insulating material of a covered wire or con- ductor to an impressed voltage tending to produce a leakage of current. INSULATOR, ELECTRIC. A body or substance which offers such resistance to the passage of electric current that it is used to prevent the passage of current. Any device employed for insulating a wire or other body. [34] DICTIONARY Sec. 1 INSULATOR PIN. The device by which an insulator is attached to a bracket, cross-arm, or support. IRON-CORE-LOSS. The hysteretic and Foucault losses due to the presence of an iron core. J. JOULE. A volt coulomb or unit of electric energy or work. The amount of electric work required to raise the potential of one coul- omb of electricity one volt. Ten million ergs. The value of the joule as adopted by the International Electrical Congress of 1893, at Chicago. A value equal to 10 7 units of work of the C.G.S. system and represented with sufficient accuracy for practical purposes by the energy expended in one second by one ampere in one International ohm. JOULE'S LAW OF HEATING. In any given conductor the heat developed by an electric current in any given time varies di- rectly as the square of the current, and as the resistance, that is, the heat varies as I 2 R. Also since the total heat varies as the time, the total heat is PR T or, if expressed in calories PR^T 4.2 JUMPER. A temporary shunt or short circuit put around a source, lamp or receptive device on a series-connected circuit, to enable it to be readily removed or repaired. K. kg. An abbreviation for kilogramme, a practical unit of mass. kgm. An abbreviation for kilogramme meter, a practical unit of the moment of a couple or of work. kv-a. An abbreviation for kilo volt-ampere. KAOLIN. A variety of white clay sometimes employed for in- sulating purposes. KILO. A prefix for one thousand times. KILOVOLT. One thousand volts. KILO VOLT- AMPERE. A kilo volt-ampere is 1000 volt-amperes. A volt-ampere is the product of an ampere times a volt. Its energy equivalent may be one kilowatt or zero, depending upon the phase relation between the current and voltage. KILOWATT. One thousand watts. [ 35 ] Sec. 1 DICTIONARY KILOWATT-HOUR. The amount of work equal to that per- formed by one kilowatt maintained steadily for one hour. An amount of work equal to 3,600,000 joules. KNIFE-SWITCH. A switch which is opened or closed by the motion of a knife contact between parallel contact plates. A knife- edge switch or knife switch. L. LAGGING CURRENT. A periodic current lagging behind the impressed electromotive force which produces it. LAMINATED CORE. An iron core that has been sub-divided in planes parallel to its magnetic flux-paths, in order to avoid the injurious production of Foucault or eddy currents. LAMINATION. The sub-division of an iron core into lamina. LEAD. A very malleable and ductile metal of low tenacity and high specific gravity. Tensile strength 1600 to 2400 pounds per square inch. Elasticity very low, and the metal flows under a very slight strain. Lead dissolves to some extent in pure water, but water containing carbonates or sulphates forms over it a film of in- soluble salt which prevents further action. Atomic weight 206.9. Specific gravity 11.07 to 11.44. Melts at about 625 F.; softens and becomes pasty at 617 F. LEAD-ENCASED CABLE. A cable provided with a sheathing or coating of lead on its external surface. LEADING CURRENT. An alternating current wave or com- ponent, in advance of the electromotive force producing it. LEAKAGE REACTANCE. That portion of the reactance of any induction apparatus which is due to stray flux. LEG OF CIRCUIT. A branch of a bifurcated or divided circuit. A loop or offset in a series circuit. LENZ'S LAW. In all cases of induction the direction of the in- duced current is such as to oppose the motion which produces it. LIGHTNING ARRESTER. A device by means of which the apparatus placed in any electric circuit is protected from the de- structive effects of a flash or discharge of lightning. LIGHTNING ROD. A rod, strap, wire or stranded cable, of good conducting material, placed on the outside of a house or other struc- ture, in order to protect it from the effects of a lightning discharge. LINES OF FORCE. Lines of magnetization. LINES OF MAGNETIZATION. A term sometimes applied for lines of magnetic induction. A term sometimes applied to those [36] DICTIONARY Sec. 1 portions of the lines of magnetic force which lie within the mag- netized substance. LIVE WIRE. A wire through which current is passing. A wire connected with an electric pressure or source. LOAD. The work thrown on any machine. LOAD-FACTOR. The fraction expressed in percent obtained by dividing the average load over any given period of time by the maximum load during the same period of time. LOGARITHM. The exponent, or the power to which it is neces- sary to raise a fixed number called the base, in order to produce a given number. LOOP TEST. A localization test for a fault in a loop of two wires, or in a complete metallic circuit. LOW-POTENTIAL SYSTEM. In the National Electric Code a system having a pressure less than 550 and more than 10 volts. M. m. A symbol for strength of magnetic pole. m. An abbreviation for meter, a practical unit of length. M, m. An abbreviation for mass. mm. An abbreviation for millimeter. m.m.f. An abbreviation for magnetomotive force. MAGNETIC FATIGUE. (See Fatigue of Iron and Steel, Mag- netic.) MAGNETIC FIELD. (See Field Magnetic.) MAGNETIC FLUX. The streamings that issue from and return to the poles of a magnet. The total number of lines of magnetic force in any magnetic field. The magnetic flow that passes through any magnetic circuit. MAGNETIC FLUX-PATHS. Paths taken by magnetic flux in any magnetic circuit. MAGNETIC FORCE. The force which causes the attractions and repulsions of magnetic poles. MAGNETIC INTENSITY. Magnetic flux-density. The quan- tity of magnetic flux per-unit-of-area of normal cross-section. MAGNETIC SATURATION. The maximum magnetization which can be imparted to a magnetic substance. The condition of iron or other magnetic substance, when its intensity of magnetiza- [37] Sec. 1 DICTIONARY tion is so great that it fails to be further magnetized by any mag- netizing force, however great. MAGNETIC UNITS. Units based on the force exerted between magnet poles. Units employed in dealing with magnets and mag- netic phenomena. The magnetic system of C.G.S. electromagnetic units, as distinguished from the electrostatic system. MAGNETIZING FORCE. The force at any point with which a unit magnetic pole would be acted on. MAINS. In a parallel system of distribution the conductors carrying the main current, and to which translating devices are con- nected. MASS. Quantity of matter contained in a body. MAXIMUM DEMAND. The maximum demand is the maxi- mum load specified, contracted for or used, expressed in terms of power as kilowatts or horse-power. MAXWELL. The unit of magnetic flux. MEAN CURRENT. The time average of a current strength. In an alternating-current circuit, the time average of a current strength without regard to sign or direction. MEAN ELECTROMOTIVE FORCE. The average electro- motive force. In an alternating-current circuit the time average of the e.m.f. without regard to sign or direction. MECHANICAL EQUIVALENT OF HEAT. The amount of mechanical energy converted into heat that would be required to raise the temperature of a unit mass of water one degree of the thermometric scale. The quantity of energy mechanically equival- ent to one heat unit. (See Heat Unit.) MEGOHM. One million ohms. MESSENGER ROPE. In cable-work a rope drive f9r operating a drum or winch at a distance. A rope supporting guide sheaves. MHO. The unit of conductance. Such a conductance as is equal to the reciprocal of one ohm. A unit of electric conductance of the value of 10 9 absolute units. MICA. A refractory mineral substance employed as an insulator. A double silicate of alumina or magnesia and potash or soda. MICROFARAD. One-millionth of a farad. MICROMETER WIRE-GAUGE. A sensitive form of wire gauge, usually constructed with a fine thread screw, having a graduated head for close measurements of wire diameters. MICROHM. The millionth of an ohm. [38] DICTIONARY Sec. 1 MIL. A unit of length used in measuring the diameter of wires equal to the one-thousandth of an inch. MIL-FOOT. A resistance standard consisting of a foot of wire, or other conducting material, one mil in diameter. A standard of comparison of resistivity or conductivity of wires. MILLI-AMPERE. The thousandth of an ampere. MILLI-HENRY. A thousandth part of a henry. MILLI-VOLT. The thousandth of a volt. MODULUS OF ELASTICITY. The ratio of the simple stress required to produce a small elongation or compression in a rod of unit area of normal cross-section, to the proportionate change of length produced. MOISTURE-PROOF INSULATION. A type of insulation which is not strictly water-proof, but which is capable of being immersed for a short time without suffering serious loss of insulation. MULTIPLE CIRCUIT. (See Circuit Multiple.) MULTIPLE-SERIES CIRCUIT. A circuit in which a number of separate sources, or receptive devices, or both, are connected in a number of separate groups in series, and these separate groups sub- sequently connected in multiple. MUTUAL INDUCTION. (See Induction, Mutual.) N. N. Used to designate the number of turns of a conductor in electro-magnetic equations or calculations. Also used to indicate the number of revolutions per minute (R.P.M.). n. An abbreviation for a number. NEGATIVE CONDUCTOR. The conductor connected to the negative terminal of an electric source. NEGATIVE FEEDERS. The feeders connecting the negative mains with the negative poles of the generators. NEUTRAL CONDUCTOR. The middle wire in a three wire "Edison system." The wire from the common point of connection of the phases in four wire, three phase and five wire, two phase systems. NEUTRAL FEEDER. In a three-wire system, a feeder connected with the neutral bus-bar. NON-CONDUCTOR. Any substance whose conductivity is low, or whose electric resistance is great. [ 39 ] Sec. 1 DICTIONARY NON-INDUCTIVE RESISTANCE. A resistance devoid of self- induction. NORMAL CURRENT. The current strength at which a system or apparatus is designed to be operated. o. Q An abbreviation for ohm, the practical unit of resistance, w A symbol sometimes employed for angular velocity. OERSTED. The name used for the C.G.S. unit of magnetic reluctance. The reluctance offered to the passage of magnetic flux by a cubic centimetre of air when measured between parallel faces. OHM. The practical unit of electric resistance. Such a re- sistance as would limit the flow of electricity under an electromotive force of one volt, to a- current of one ampere, or one-coulomb-per- second. The value of the ohm as adopted by the International Electrical Congress of 1893, at Chicago, is a value of the ohm equal to 10 9 units of resistance of the C.G.S. system of electro-magnetic units, and represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice, 14.4521 grammes in mass, of a constant cross-sectional area, and of the length of 106.3 centimeters. OHMIC DROP. The drop in pressure due to the ohmic resist- ance. OHMIC RESISTANCE. The true resistance of a conductor due to its dimensions and conductivity, as distinguished from the spuri- ous resistance produced by counter-electromotive force. A re- sistance such as would be measurable in ohms by the usual methods of continuous-current measurement. OHM'S LAW. The law of non-varying current strength in a circuit not subject to variation. The strength of a continuous cur- rent is directly proportional to the difference of potential or electro- motive force in the circuit and inversely proportional to the resist- ance of the circuit, i. e., is equal to the quotient arising from dividing the electromotive force by the resistance. Ohm's law is expressed algebraically thus: E E I= ~R~ ; or E=IR ; or R= T~ If the electromotive force is given in volts, and the resistance in ohms, the formula will give the current strength directly in amperes. The current in amperes is equal to the electromotive force in volts divided by the resistance in ohms. The electromotive force in volts is equal to the product of the cur- rent in amperes and the resistance in ohms. [40] DICTIONARY Sec. 1 The resistance in ohms is equal to the electromotive force in volts divided by the current in amperes. OPEN CIRCUIT. A broken circuit, or a circuit whose conduct- ing continuity is broken. OSCILLATORY CURRENT. A current which oscillates or per- forms periodic vibrations usually of diminishing amplitude. OVERHEAD CONDUCTOR. An aerial conductor. P. PAGE EFFECT. Faint sounds produced when a piece of iron is rapidly magnetized and demagnetized. PAPER CABLE. A paper-insulated cable. A cable in which paper is the solid insulator employed. PARAFFINE. A solid hydro-carbon possessing high insulating powers. PARALLEL CIRCUIT. A term sometimes used for multiple circuit. PEAK-LOAD. The highest average load carried for any specified period. NOTE. The term may be preceded by the qualifying terms "hourly," " daily," "monthly," "yearly," etc. PEAK. The highest load carried for any specified period. PERCENTAGE CONDUCTIVITY OF WIRE. The conductiv- ity of a wire in terms of the conductivity of pure copper. The con- ductivity of a particular copper wire compared with the conductivity of a standard wire of the same dimensions. The conductivity of a wire referred to Matthiessen's standard of conductivity for copper. PERIODIC FUNCTION. A periodic function is one which re- pea.ts itself after a definite time or period. If any number of simple sine functions of the same period be added, the resultant sum will be a simple sine function of the same period. This is shown in Fig. 14 for the addition of two simple sine functions or sine waves, and it is evident that, if true for the addition of two, it is true for the addition of any number of simple sine functions. "An example of the addition of two simple sine functions of the same period is shown in Fig. 15. The resultant curve, represented by the heavy line, is likewise a sine curve. PERIODICITY. The number of periods executed per second by a periodically alternating quantity. The number of cycles executed in unit time by an alternating current. The frequency of an alter- nating current. PERMITTANCE. Electrostatic capacity. The capability of a condenser or dielectric to hold a charge. [41] Sec. 1 DICTIONARY PETTICOAT INSULATOR. An insulator provided with a deep internal groove, around its lower extremity or stalk. A line wire FIG. 14. Summation of Two Simple Sine Waves to Form a Resultant Sine Wave. vertical insulator provided with an insulating inverted cup having a form resembling a petticoat. 360 FIG. 15. Diagram showing the Formation of a Resultant Sine Wave from Two Simple Sine Waves. PHASE. The distance, usually in angular measure, of the base of any ordinate of an alternating wave from any chosen point on the time axis, is called the phase of this ordinate with respect to this [42] DICTIONARY Sec. 1 point. In the case of a sinusoidal alternating quantity the phase at any instant may be represented by the corresponding position of a line or vector revolving about a point with such an angular velocity (oj=27rf) that its projection at each instant upon a convenient reference line is proportional to the value of the quantity at that instant. PHASE ANGLE. In alternating current systems two or more currents or e.m.f.'s which do not come to their maximum values at the same instant are said to be out of phase, or to have a phase dif- ference, and the angle between the vectors which represent these currents or e.m.f.'s is called a phase angle. If it is measured for- ward, in the direction of rotation, the angle is called the angle of FIG. 16. Diagram showing the Phase Angles between Three Distinct e.m.f.'s. and their Vector Representations. lead, and if measured against the direction the angle is called the angle of lag. (Fig. 16.) PHASE DIFFERENCE: LEAD and LAG. When corresponding cyclic values of two sinusoidal alternating quantities of the same fre- auency occur at different instants, the two quantities are said to iffer in phase by the angle between their nearest corresponding values, e.g., their nearest ascending zeros or positive maxima. That quantity whose maximum value occurs first in time is said to lead the other, and the latter is said to lag behind the former. PINS. Wooden or steel pegs for supporting pole line insulators. PLANE VECTOR. A quantity which possesses not only magni- tude but also direction in a single plane. [43] Sec. 1 DICTIONARY PLATINUM. A heavy refractory and not readily oxydizable metal of a tin-white color. PLUMBAGO. An allotropic modification of carbon. POLE GUYS. A guy employed for stiffening a pole. POLE STEPS. Steps permanently fastened to a wood or iron pole to facilitate climbing. POLYPHASE. Possessing more than a single phase. POLYPHASE CIRCUITS. The circuits employed in polyphase - current distribution. POLYPHASE CURRENTS. Currents differing in phase from one another by a definite amount, and suitable for the operation of polyphase motors or similar apparatus. PpLYPHASE TRANSFORMER. A transformer suitable for use in connection with polyphase circuits. POLYPHASE TRANSMISSION. Transmission of power by means of polyphase currents. PORCELAIN. A variety of insulating substance, made from clay. POSITIVE WIRE. The wire connected with the positive pole of a source. POTENTIAL, ELECTRIC. The power of doing electric work. ' Electric level. POTENTIAL ENERGY. Stored energy. Capability of doing work. Energy, possessing the power or potency of doing work but not actually performing such work. POWER. Rate-of-doing-work, expressible in watts, joules-per- second, foot pounds-per-hour, etc. POWER CIRCUITS. Circuits employed for the electric trans- mission of power. POWER-FACTOR. The ratio of the power (cyclic average) to the volt-amperes. In the case of sinusoidal current and voltage the power-factor is equal to the cosine of the difference in phase between them. PRIMARY. That winding of a transformer which directly re- ceives power. The term is to be preceded, in the case of transform- ers, by the words "high voltage" or "low voltage." PRIMARY COIL OF TRANSFORMER. That coil of an in- duction coil or transformer on which the primary electromotive force is impressed. The coil which receives energy prior to trans- formation. DICTIONARY Sec. 1 PRIMARY CURRENTS. Currents flowing in a primary circuit, as distinguished from currents flowing in a secondary circuit. PRIMARY ELECTROMOTIVE FORCE. The electromotive force applied to the primary coil of a transformer. PULSATING CURRENT is a current which pulsates regularly in magnitude. As ordinarily employed, the term refers to unidirec- tional current. Q. QUADRATURE. A term applied to express the fact that one simple-harmonic quantity lags 90 behind another. QUANTITY, ELECTRIC. The amount of electricity present in any current or charge. QUARTER PHASE. A term implying the supplying of power through two circuits. The vector angle of this voltage is 90 degrees. This term is used at times instead of the term "two-phase." QUARTER-PHASE SYSTEM. A two-phase system of alter- nating-current distribution employing two currents dephased by a quarter period. R. r.m.s. A term sometimes used for the square root of the mean square of the current. The effective current or voltage. RADIAN. A unit angle. An angle whose circular arc is equal in length to its radius; or, approximately 57 17' 45". RADIAN-PER SECOND. A unit of angular velocity of a rotat- ing body. RATIO OF TRANSFORMATION. The ratio between the elec- tromotive force produced at the secondary terminals of an induction coil or transformer, and the electromotive force impressed on the primary terminals. REACTANCE, INDUCTIVE. The inductance of a coil or circuit multiplied by the angular velocity of the sinusoidal current passing through it, or expressed by the formula X = 2-n- f L = coL, where co = 2irf, f is the frequency in cycles per second, and L is the coefficient of self-induction. A quantity whose square added to the square of the resistance gives the square of the impedance, in a simple harmonic current cir- cuit. REACTANCE FACTOR. The ratio of the reactance of a coil, or circuit, to its ohmic resistance. REACTIVE DROP. The drop in a circuit or conductor due to its reactance as distinguished from the drop due to its ohmic re- sistance. [45] Sec. 1 DICTIONARY REACTIVE ELECTROMOTIVE FORCE. In an alternating current circuit, that component of the electromotive force that is in quadrature with the current and is employed in balancing the counter e.m.f. of inductance. REACTIVE FACTOR. The ratio of the wattless volt-amperes to the total volt-amperes. REGULATION. The regulation of a machine or apparatus in regard to some characteristic quantity, such as current or terminal voltage, is the ratio of deviation of that quantity from its normal value at rated-load to the normal rated-load value. Sometimes called inherent regulation. RELUCTANCE. A term applied to magnetic resistance. In a magnetic circuit the ratio of the m.m.f. to the total magnetic flux. RELUCTIVITY. The specific magnetic resistance of a medium. RESIDUAL MAGNETISM. The magnetism remaining in a core of an electromagnet on the opening of the magnetizing circuit. The small amount of magnetism retained by soft iron when removed from any magnetic field. RESIN. A general term applied to a variety of dried juices of vegetable origin. RESISTANCE. The quality of an electrical conductor by virtue of which it opposes an electric current. The unit of resistance is the ohm. Resistance is that attribute of a conductor or of a circuit which determines the strength of the electric current that can be sent through the conductor or the circuit, on which a constant difference of potential is maintained, as shown by Ohm's law. The resistance of a given conductor is always constant at the same temperature, irrespective of the strength of current flowing through it or the elec- tromotive force of the current, and the resistance of a given con- ductor increases as the length of the conductor increases; that is, the resistance of a conductor is directly proportional to its length. Also the resistance of a conductor varies inversely as its sectional area, or the resistance of a conductor of circular cross section is inversely proportional to the square of its diameter. The combined resistance of several resistances in parallel may be found by taking the reciprocal of the sum of the reciprocals of the individual resistances of the branch circuits. This law follows from the law of conductance, which states that the combined conductance of a parallel branch circuit is equal to the sum of the conductances of the branches, and since the resistance is equal to the reciprocal of the conductance, the reciprocal law holds true, as above stated. RESISTIVITY. The specific resistance of a substance referred to the resistance of a cube of unit volume. Specific resistance, or the inverse of specific conductivity. [46] DICTIONARY Sec. 1 RESONANCE. In a circuit containing both inductance and capacity, the neutralization or annulment of inductance-reactance by capacity-reactance, whereby the impedance of the circuit or branch is reduced to the ohmic resistance. In an alternating-cur- rent circuit, the attunement of a circuit, containing a condenser to the same natural undamped frequency of oscillation as the fre- quency of impressed e.m.f. whereby the circuit responds to this frequency more than to any other. In an alternating current cir- cuit, the annulment of inductance-reactance by capacity-reactance, whereby the impedance of the circuit is not only reduced to its ohmic resistance, but its current is in phase with its impressed e.m.f. RESULTANT MAGNETIC FIELD. A single magnetic field produced by two or more co-existing magnetic fields. RIGHT-HANDED ROTATION. A direction of rotation which is the same as that of the hands of a watch, when one looks directly at the face of the watch. Negative rotation. ROOT-MEAN-SQUARE or EFFECTIVE VALUE. The square root of the mean of the squares of the instantaneous values for one complete cycle. It is usually abbreviated r.m.s. Unless otherwise specified the numerical value of an alternating current (or e.m.f.) refers to its r.m.s. value. The r.m.s. value of a sinusoidal wave is equal to its maximum value divided by \ r z. s. S.W.G. An abbreviation for Stubb's wire gauge. SADDLE BRACKET. A bracket holding an insulator and fast- ened to the top of a pole. SAFETY FUSE. A wire, bar, plate or strip of readily fusible metal, capable of conducting, without fusing, the current ordinarily employed on the circuit, but which fuses and thus automatically breaks the circuit on the passage of an abnormally strong current. SAG OF CONDUCTOR OR LINE WIRE. The dip of an aerial wire or conductor, between two adjacent supports, due to its weight. SECONDARY AMPERE-TURNS. Ampere-turns in the second- ary of a transformer or induction coil. SECONDARY. That portion of a transformer which receives power by induction. The term is to be preceded by the same words as in the case of "primary." SECONDARY COIL OF TRANSFORMER. The coil of a trans- former into which energy is transferred from the primary line and primary coil by induction. SECONDARY CURRENTS. The currents produced in the secondary of a transformer. The currents produced by secondary batteries. Currents in any secondary circuit. 147] Sec. 1 DICTIONARY SECONDARY RESISTANCE. The resistance of a secondary coil or circuit. SECONDARY WINDING is that winding of a transformer which receives power from the primary by induction. NOTE: The terms "High-tension winding" and "Low-tension winding" are suitable for distinguishing between the windings of a transformer where the relations of the apparatus to the source of power are not involved. SELF-INDUCTION. (See Induction, Self.) SERIES CIRCUIT. (See Circuit, Series.) SERIES DISTRIBUTION. A distribution of electric energy in which the receptive devices are placed one after another in succes- sion upon a single conductor, extending throughout the entire cir- cuit from pole to pole. SERIES-MULTIPLE CIRCUIT. A compound circuit in which a number of separate sources, or separate electro-receptive devices, or both, are connected in a number of separate groups in multiple, and these separate groups subsequently connected in series. SERVICE WIRES. The wires which lead into a building and which are connected to the supply mains or supply circuits. The wires through which service is given to a consumer. Delivery wires. SHELLAC. A resinous substance obtained from the roots and branches of certain tropical plants, which possesses high insulating powers, and high specific inductive capacity. SHORT CIRCUIT. A shunt or by-path of negligible or com- paratively small resistance, placed around any part of an electric circuit through which so much of the current passes as to virtually cut out the parts of the circuit to which it acts as a shunt. An accidental direct connection between the mains or main terminals of a dynamo or system producing a heavy overload of current. SIMPLE HARMONIC ELECTROMOTIVE FpRCE. An electro- motive force whose value varies directly as the sine or cosine of the angle which its rotating vector makes with a fixed axis. SINE. One of the trigonometrical functions. The ratio of the vertical leg of a right-angle triangle to the hypotenuse, in which the hypotenuse is the radius vector, and the angle between the base and the hypotenuse the angle whose sine is considered. SINE LAW. A law of magnitude defined by the sines of angles. A magnitude which follows the sines of successive angles. SINGLE-PHASE. A term characterizing a circuit energized by a single alternating e.m.f. Such a circuit is usually supplied through two wires. The currents in these two wires counted positively out- wards from the source, differ in phase by 180 degrees or half a cycle. [48] DICTIONARY Sec. 1 SINGLE-POLE CUT-OUT. A cut-out by means of which the circuit is broken or cut in one of the two leads only. SINUSOIDAL ALTERNATING ELECTROMOTIVE FORCES. Alternating electromotive forces whose variations in strength are correctly represented by a sinusoidal curve. SINUSOIDAL CURVE. A curve of sines. A curve which to rectangular co-ordinates has an ordinate at each point proportionate to the sine of an angle proportionate to the abscissa. SKIN EFFECT. The tendency of rapidly alternating currents to avoid the central portions of solid conductors and flow, for the greater part, through the superficial portions. SLEEVE JOINT. A junction of the ends of conducting wires obtained by passing them through tubes, and subsequently twisting and soldering. SOFT DRAWN COPPER WIRE. Copper wire that is softened by annealing after being drawn. SPECIFIC CONDUCTIVITY. The particular conductivity of a substance for electricity. Conductivity with reference to Matth- iessen's standard conductivity. SPECIFIC INDUCTIVE CAPACITY. The ability of a dielectric to permit induction to take place through its mass as compared with the ability possessed by a vacuous space of the same dimensions, under precisely the same conditions. The relative power of bodies for transmitting electrostatic stresses and strains, analogous to permeability in metals. The ratio of the capacity of a condenser whose coatings are separated by a dielectric of a given substance, to the capacity of a similar condenser, whose plates are separated by a vacuum. SPECIFIC RESISTANCE. The particular resistance a substance offers to the passage of electricity through it, compared with the resistance of some standard substance. In absolute measurements, the resistance in absolute units between opposed faces of a centi- metre cube of a given substance. In the practical system, the above resistance in ohms. SPELTER. A name sometimes given to commercial zinc. (See Zinc.) SPLICING SLEEVE. A tube of conducting material employed for covering a splice in a conducting wire. SPLIT PHASE. A difference produced between the phases of two or more alternating currents into which a uniphase alternating current has divided. SQUARE MIL. A unit of area employed in measuring the areas of cross-section of wires, equal to .000001 square inch. A unit of area equal to 1.2732 circular mils. [49] Sec. 1 DICTIONARY STAR THREE-PHASE SYSTEM. A system in which all three phase windings are connected together at a common point or neutral point, and the three free ends connected to the circuit. STATIC DISCHARGE. A name sometimes given to a disruptive discharge. STATIC ELECTRICITY. A term applied to electricity produced by friction. STEP-DOWN TRANSFORMER. A transformer in which a small current of comparatively great difference of potential is con- verted into a large current of comparatively small difference of potential. STEP-UP TRANSFORMER. A transformer in which a large current of comparatively small difference of potential is converted into a small current of comparatively great difference of potential. STRAIN. Any change of size or shape, any deformation. STRAIN INSULATOR. An insulator used for the double pur- pose of taking the mechanical strain at a bend or at the end of a conductor, and also insulating the same electrically. STRANDED CONDUCTOR. A conductor formed of a number of smaller interlaced or twisted conductors, either for the purpose of reducing self-induction, or eddy currents, or for increasing its flexibility. STRAY CURRENTS. A term sometimes used for eddy currents. Also currents that leave their normal or proper path such as earth currents of ground return feeders. STRAY FIELD. Leakage magnetic flux. That portion of a magnetic field which does not pass through an armature or other magneto-receptive device. STRENGTH OF CURRENT. (See Current Strength.) STRESS. Any action between two bodies that causes a strain, or deformation. SUPPLY MAINS. A term sometimes applied to the mains in a system of incandescent light or power distribution. SURFACE DENSITY. The quantity of electricity-per-unit-of- area at any point on a charged surface. SURGING DISCHARGE. A discharge accompanied by electric surgings. An oscillatory discharge. SURGINGS, ELECTRIC. Electric oscillations set up in a con- ductor that is undergoing rapid discharging, or in neighboring con- ductors that are being rapidly charged and discharged. Electric oscillations, direct or induced. SYNCHRONISM. Unison of frequencies in alternating-current systems or apparatus. Generally, the co-periodicity and co-phase [50] DICTIONARY Sec. 1 of two periodically recurring events. The coincidence in cyclic recurrence of two or more periodic variables, without regard to amplitude. SYNCHRONO SCOPE. A synchronizing device which, in ad- dition to indicating synchronism, shows whether the machine is synchronized fast or slow. T. TANGENT. The tangent of any angle may be found by con- structing a right triangle in which the angle or its supplement is one of the acute angles of the triangle. By dividing the opposite side of the triangle by the adjacent side, the tangent of the angle is obtained. Also Sine0 Tangent = TAP. A conductor attached as a shunt to a larger conductor. A derived circuit for carrying off a share of the main current. FIG. 17. Relation of the Waves of Current, or e.m.f.'s., in a Three-phase System. TEMPERATURE. State of matter in respect to heat. TEMPERATURE COEFFICIENT. A coefficient of variation in a quantity, per degree of change in temperature. The coefficient by which a change of temperature must be multiplied in order to arrive at the change in a quantity due to the change of temperature. TERMINAL VOLTAGE. The voltage between the poles at the source of the e. m. f . THREE-PHASE. A term characterizing the combination of three circuits energized by alternating e.m.f.'s. which differ in phase by one-third of a cycle; i. e., 120 degrees. (Fig. 17.) [51] Sec. 1 DICTIONARY THREE-PHASE TRANSFORMER. A transformer constructed for changing the ratios of voltages and currents of a three-phase system. THREE-PHASE TRANSMISSION. Transmission by means of three-phase currents. THREE-WIRE CIRCUIT. A circuit employed in a three-wire system. A three-wire two phase system. A three-wire three phase system. THREE-WIRE MAINS. The mains employed in a three-wire system of distribution. THREE- WIRE SYSTEM. A system of electric distribution for lamps or other multiple-connected translating devices, in which three conductors are employed in connection with two dynamos, or parts of transformers connected in series, the central or neutral conductor being connected to the junction of this apparatus, and the two othe conductors to the remaining free terminal of each. TIE- WIRE. Binding wire of an insulator. Wire which binds an overhead wire to the groove of its insulator. TIME-CONSTANT OF CIRCUIT. The time in which a current will fall in a circuit when the e.m.f. is suddenly removed, in a ratio whose Naperian logarithm is unity. The ratio of the inductance of a circuit to its resistance. TIME SWITCH. A switch arranged to open or close a circuit at a certain time or after the lapse of a certain time. TRANSFORMER. A stationary piece of apparatus for trans- forming, by electro-magnetic induction, power from one circuit to another, or for changing, through such transformation, the values of the electromotive force or current. TRANSFORMER-BALANCER. An auto-transformer for divid ing a voltage in constant proportions, and usually into two equal portions. TRANSFORMER STAMPINGS. Sheet steel stampings of such shape as is suitable for building up the laminated core of a trans- former. TRANSMISSION CIRCUIT, ELECTRIC. The circuit em- ployed to receive the apparatus necessary in any transfer of electric energy from the generators to the receptive devices. In alternating- current constant-potential transmission circuits the following average voltages are in general use: 6,600, 11,000, 22,000, 33,000, 44,000, 66,000, 88,000, 110,000. TRANSMISSION, ELECTRIC. The transference of energy from one point to another by means of electric currents. [52] DICTIONARY Sec. 1 TRANSPOSING. A device for avoiding the bad effects of mutual induction by alternately crossing equal lengths of consecutive sections of the line. TRIPLE PETTICOAT INSULATOR. An aerial line insulator having three discs or petticoats. TWO-PHASE. A term characterizing the combination of two circuits energizing by alternating e.m.f.'s. which differ in phase by a quarter of a cycle; i. e., 90 degrees. (Fig. 18.) TWO-WIRE MAINS. A name for the mains employed in the ordinary system of multiple distribution, as distinguished from a three-wire main, or that used in a three-wire system. V. VECTOR DIAGRAM. A diagram representing the relations of vector quantities. VECTOR QUANTITY. A quantity possessing both direction and magnitude. VECTOR SUM. The geometrical sum of two or more vector quantities. Thus, in Fig. 16 by completing the parallelogram formed FIG. 18. Relation of the Waves of Current, or e.m.f's., in a Two-phase System. by the vectors coLI and RI, and drawing the diagonal, the vector E is obtained, which is the vector sum of wLI and RI. In practice, these vectors are drawn free-hand and the resultants calculated by means of the geometrical laws. (Fig. 19.) Example. It is intended to find the value of e.m.f. between two E wires, across each of which to the neutral is maintained an e.m.f. -^r. It is known that these two e.m.f.'s. differ 90 degrees. In Fig. 19, [53] Sec. 1 DICTIONARY which is a right angle triangle, OB = v / OA 2 +AB 2 or E VOLT. The practical unit of electromotive force. Such an electromotive force as is induced in a conductor which cuts lines of magnetic flux at the rate of 100,000,000 per second. Such an electromotive force as would cause a current of one ampere to flow against a resistance of one ohm. Such an electromotive force as B FIG. 19. Vector Diagram fpr Calculating the Vector Sum of Two e.m.f.'s. in Ninety-degree Phase Relation. would charge a condenser of the capacity of one farad with a quantity of electricity equal to one coulomb. 10 8 absolute electro-magnetic units of electromotive force. The value of the volt as adopted by the International Electrical Congress of 1893, at Chicago, is an electromotive force which is 1000 represented with sufficient accuracy for practical use by ?7o7 of the electromotive force between the poles or electrodes of the voltaic cell known as Clark's cell, at a temperature of 15 Cent, when pre- pared in accordance with certain specifications. VOLT AMPERE. The product of one volt times one ampere. [54] DICTIONARY Sec. 1 W. w-hr. An abbreviation for watt-hour, a practical unit of electric energy. WATT. A unit of electric power. A volt ampere at unity power- factor. The power developed when 44.25 foot-pounds of work are done in a minute, or 0.7375 foot-pound of work is done in a second. The value of the watt as adopted by the International Electrical Congress of 1893, at Chicago, is a value equal to 10 7 units of activity in the C.G.S. system, and equal to the work done at the rate of one joule-per-second. WATT-HOUR. A unit of electric work. A term employed to indicate the expenditure of an electric power of one watt for an hour. WATTLESS COMPONENT OF CURRENT. In an alternating- current circuit, that component of the current which is in quadrature with the impressed e.m.f. and which, therefore, takes from or gives no energy to the circuit. In an alternating-current circuit the product of the e.m.f. and the effective susceptance. WATTLESS COMPONENT OF ELECTROMOTIVE FORCE. In an alternating-current circuit, that component of the e.m.f. which is in quadrature with the current strength, and, therefore does not work on the current. In an alternating-current circuit the product of the current and the effective reactance. WAVE, ELECTRIC. An electric periodic disturbance. WEATHER-PROOF INSULATION. A trade-name for a charac- ter of insulation consisting of one or more layers of braided material soaked in an insulating compound. WEATHER-PROOF WIRE. A wire provided with weather- proof insulation. WIRE. A slender rod or filament of drawn metal. WORK. When a force acts on a body the product of the force by the distance through which it acts in the direction of the force is called the work performed by the force. Thus, when a force applied to a heavy body raises it a certain vertical distance, work is per- formed by the force, the amount of the work being the product of the force and the distance of ascent; and when a horizontal force draws a body horizontally the work is the product of the force and the horizontal distance. The unit of work is the work done by the unit force in acting through unit distance. When the dyne is taken as unit of force and the cm. as unit of length, the unit of work is that performed by a dyne acting through a cm. and is called an erg. Since this is a very small unit, a multiple of it, namely 10,000,000 ergs, is frequently used and is called a joule. In practical mechanical work the unit of time is always one minute, and the unit which measures the work performed in a given [55] Sec. 1 DICTIONARY time is the foot-pound per minute. This unit is called the unit of mechanical power. Power is, therefore, rate of doing work, and hence the power exerted can always be determined by dividing the work done in foot-pounds by the time in minutes required to do it. In practical electrical work the unit of time is the second, and the unit which measures the work performed in a given time is the joule per second. This unit is called the unit of electrical power, and has been named the watt. The equation or formula expressing the power exerted in any electrical circuit is determined as follows: The electrical power is expressed by watts = joules per second, but joules = volt-coulombs, and hence joules per second = volt-coulombs per second. There- fore also, watts = volt-coulombs per second. Now, coulombs per second = amperes. Inserting this value above, watts = volts X am- peres, or W = EI. When the power is to be expressed by the current and resistance, the formula is obtained as follows: According to formula W=EI. According to Ohm's law, E=IR. Substituting this value of E=IR in the formula W=EI, we have When the power is to be expressed by the electromotive force and resistance, the formula is obtained as follows: According to formula E W =EI. According to Ohm's law, I = ~>~ . Substituting this value E ' R For alternating current Y. Y-CONNECTOR. A connector resembling the letter Y in shape for joining a conductor to two branch wires. Y-CURRENT. The current between any wire of a three-phase system and the neutral point. z. ZINC, Zn. Atomic weight 65. Specific gravity 7.14. Melts at 780 F. Volatilizes and burns in the air when melted, with bluish- white fumes of zinc oxide. It is ductile and malleable but to a much less extent than copper, and its tenacity, about 5000 to 6000 [56] DICTIONARY Sec. 1 Ibs. per square inch, is about one-tenth that of wrought iron. It is practically non-corrosive in the atmosphere, a thin film of car- bonate of zinc forming upon it. Cubical expansion between 32 and 212 F., 0.0088. Specific heat .096. Electric conductivity 29, heat conductivity 36, silver being 100. Its principal uses are for coat- ing iron surfaces, called "galvanizing," and for making brass and other alloys. ZINC PLATING. Electro-plating with zinc. Galvanizing. THE GREEK ALPHABET. Name Large Small Commonly used to designate alpha . . A a angles, coefficients. beta . . . B ft angles, coefficients. gamma delta . . r A 7 8 specific gravity, density, variation. epsilon . E base of hyperbolic logarithms. zeta . . . Z r co-ordinates, coefficients. eta H i? hysteresis (Steinmetz) coefficient, efficiency theta . . e angular phase displacement. iota . . . I i kappa . K K dielectric constant. lambda A \ conductivity. mu .... M M permeability. mi .... N V reluctivity. xi H t output coefficient. omicron O o pi . . n 7T circ jmf erence -T- diameter. *1L rho .... p P resistivity. sigma. . 2 (T (cap.), summation; leakage coefficient. tau .... T T time-phase displacement. upsilon T V .. phi .... <*> flux. chi . . . . X X psi * * angular velocity in time. omega . 12 CO (small), angular velocity in space. [57] TABLE No. 1 COMMON LOGARITHMS OF NUMBERS Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 100-129 N 2 3 4 5 6 7 8 9 D 100 00000 043 087 130 173 217 260 303 346 389 43 101 432 475 518 561 604 647 689 732 775 817 43 102 86 903 945 988 *o 30 *072 *115 *157 * L99 *242 42 103 01284 326 368 410 452 494 536 578 620 662 42 104 70 3 745 787 828 8 70 912 953 995 * 336 *078 42 105 02119 160 202 243 284 325 366 407 449 490 41 106 531 572 612 653 694 735 776 816 857 898 41 107 93 8 979 *019 *050 *1 00 *141 *181 *222 * 252 *302 40 108 03342 383 423 463 503 543 583 623 663 703 40 109 743 782 822 8S2 902 941 981 *021 *060 *100 40 110 04139 179 218 258 297 336 376 415 454 493 39 111 532 571 610 650 689 727 766 805 844 883 39 112 92 2 961 999 *038 *c 77 *11S *154 *192 * 231 *269 39 113 05308 346 385 423 461 500 538 576 614 652 38 114 69 729 767 805 a 43 881 918 956 934 *032 38 115 06070 108 145 183 221 258 296 333 371 408 38 116 446 483 521 558 595 633 670 707 744 781 37 117 81 9 856 893 930 9 67 *004 *041 *078 * 115 *151 37 118 07188 225 262 298 335 372 408 445 482 518 37 119 555 591 628 664 700 737 773 809 846 882 36 120 918 954 990 *027 *063 *099 *135 *171 *207 *243 36 121 08279 314 350 386 422 458 493 529 585 600 36 122 636 672 707 743 778 814 849 884 920 955 35 123 99 1 *026 *061 *096 *1 32 *16-! *202 *237 * 272 *307 35 124 09342 377 412 447 482 517 552 587 621 656 35 125 691 726 760 795 830 864 899 934 968 *003 35 126 10037 072 106 140 175 209 243 278 312 346 34 127 38 415 449 483 5 17 551 585 619 553 687 34 128 721 755 789 823 857 890 924 958 992 *025 34 129 11059 093 126 160 193 227 261 294 327 361 34 PP 44 43 42 41 40 39 38 37 3G j 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 2 8.8 8.6 8.4 8.2 8.0 7.8 7.6 7.4 7.2 3 13.2 12.9 12.6 12.3 12.0 11.7 11.4 11.1 10.8 4 17.6 17.2 16.8 16.4 16.0 15.6 15.2 14.8 14.4 5 22.0 21.5 21.0 20.5 20.0 19.5 19.0 18.5 18.0 6 26.4 25.8 25.2 24.6 24.0 23.4 22.8 22.2 21.6 7 30.8 30.1 29.4 28.7 28.0 27.3 26.6 25.9 25.2 8 35.2 34.4 33.6 32.8 32.0 31.2 30.4 29.6 28.8 9 39.6 38.7 37.8 36.9 36.0 35.1 34.2 33.3 32.4 f 60] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 130-159 N 1 2 3 4 5 6 7 8 9 D 130 11394 428 461 494 528 561 594 628 661 694 33 131 727 760 793 826 860 893 926 959 992 *024 33 132 12057 090 123 156 189 222 254 287 320 352 33 133 38! 418 450 483 51 6 548 581 613 6 46 678 33 134 710 743 775 808 840 872 905 937 969 *001 32 135 13033 066 098 130 162 194 226 258 290 322 32 136 354 386 418 450 481 513 545 577 609 640 32 137 672 704 735 767 799 830 862 893 925 956 32 138 981 I *019 *051 *082 *11 4 *145 *176 *208 *2 39 *270 31 139 14301 333 364 395 426 457 489 520 551 582 31 140 613 644 675 706 737 768 799 829 860 891 31 141 922 953 983 *014 *045 *076 *106 *137 *168 *198 31 142 15229 259 290 320 351 381 412 442 473 503 31 143 tn 1 564 594 625 65 5 685 715 746 1 76 806 30 144 836 866 897 927 957 987 *017 *047 *077 *107 30 145 16137 167 197 227 256 286 316 346 3 76 406 30 146 435 465 495 524 554 584 613 643 673 702 30 147 732 761 791 820 850 879 909 938 967 997 29 148 1702( 056 085 114 14 3 173 202 231 2 60 289 29 149 319 348 377 406 435 464 493 522 551 580 29 150 609 638 667 696 725 754 782 811 840 869 29 151 898 926 955 984 *013 *041 *070 *099 *127 *156 29 152 18184 213 241 270 298 327 355 384 412 441 29 153 46 ) 498 526 554 58 3 611 639 667 C 96 724 28 154 752 780 808 837 865 893 921 949 977 *005 28 155 19033 061 089 117 145 173 201 229 257 285 28 156 312 340 368 396 424 451 479 507 535 562 28 157 590 618 645 673 700 728 756 783 811 838 28 158 86( 5 893 921 948 91 6 *003 *030 *058 *( 85 *112 27 159 20140 167 194 222 249 276 303 330 358 385 27 PP 35 34 33 32 31 30 29 28 27 1 3.5 3.4 3.3 3.2 3.1 3.0 2.9 2.8 2.7 2 7.0 6.8 6.6 6.4 6.2 6.0 5.8 5.6 5.4 3 10.5 10.2 9.9 9.6 9.3 9.0 8.7 8.4 8.1 4 14.0 13.6 13.2 12.8 12.4 12.0 11.6 11.2 10.8 5 17.5 17.0 16.5 16.0 15.5 15.0 14.5 14.0 13.5 6 21.0 29.4 19.8 19.2 18.6 18.0 17.4 16.8 162 7 24.5 23.8 23.1 22.4 21.7 21.0 20.3 19.6 18.9 8 28.0 27.2 25.4 25.6 21.8 24.0 23.2 22.4 216 9 31.5 3D.6 23.7 23.8 27.9 27.0 26.1 25.2 24.3 [61] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 160-189 N' 1 2 3 4 5 6 7 8 9 D 160 20412 439 466 493 520 548 575 602 629 656 27 161 683 710 737 763 790 817 844 871 898 925 27 162 952 978 *005 *032 *059 *085 *112 *139 *165 *192 27 163 21219 245 272 299 325 352 378 405 431 458 27 164 484 5 LI 537 J >S4 590 617 643 669 696 722 26 165 748 775 801 827 854 880 906 932 953 985 26 166 22011 037 063 089 115 141 167 194 220 246 26 167 272 2 )8 324 : (50 376 401 427 453 479 505 26 168 531 557 583 608 634 660 686 712 737 763 26 169 789 814 840 866 891 917 943 968 994 *019 26 170 23045 070 096 121 147 172 198 223 249 274 25 171 300 325 350 376 401 426 452 477 502 528 25 172 553 5 16 603 ( 29 654 679 704 729 754 779 25 173 805 830 855 i 80 905 930 955 980 *005 *030 25 174 24 055 02 JO 105 3 30 155 180 204 229 254 279 25 175 304 329 353 378 403 428 452 477 502 527 25 176 551 576 601 625 650 674 699 724 748 773 25 177 797 82 2 846 I 71 895 920 944 969 993 *018 25 178 25042 066 091 115 139 164 188 212 237 261 24 179 285 310 334 358 382 406 431 455 479 503 24 180 527 551 575 600 624 648 672 696 720 744 24 181 768 792 816 840 864 888 912 925 959 983 24 182 26007 031 055 079 102 126 150 174 198 221 24 183 245 269 293 316 340 364 387 411 435 458 24 184 482 5C 5 529 5 53 576 600 623 647 670 694 24 185 717 741 764 788 811 834 858 881 905 928 23 186 951 975 998 *021 *045 *088 *091 *114 *138 *161 23 187 27 184 207 231 254 277 300 323 346 370 393 23 188 416 439 462 485 508 531 554 577 600 623 23 189 646 669 692 715 738 761 784 807 830 852 23 PP 27 26 25 24 23 22 1 2.7 2.6 2.5 2.4 2.3 2.2 2 5.4 5.2 50 4.8 4.6 4.4 3 8.1 7.8 7.5 7.2 6.9 6.6 4 10.8 10.4 10.0 9.6 9.2 8.8 5 13.5 13.0 12.5 12.0 11.5 11.0 6 16.2 15.6 15.0 14.4 13.8 13.2 7 18.9 18.2 17.5 16.8 16.1 15.4 8 21.6 20.8 20.0 19.2 18.4 17.6 9 24.3 23.4 22.5 21.6 20.7 19.8 [62] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 190-229 N 1 2 3 4 5 6 7 8 9 D 190 875 898 921 944 967 989 *012 *035 *058 *081 23 191 28103 126 149 171 194 217 240 262 285 307 23 192 3*0 353 375 398 421 443 466 488 511 533 23 193 556 578 601 623 . 646 6*8 691 713 735 758 22 194 780 803 825 847 870 892 914 937 959 981 22 195 29003 026 048 070 092 115 137 159 181 203 22 196 226 248 270 292 314 336 358 380 403 425 22 197 447 469 491 513 535 557 579 601 623 645 22 198 667 688 710 732 754 776 798 820 842 863 22 199 885 907 929 951 973 994 *016 *035 *060 *081 22 200 30103 125 146 168 190 211 233 255 276 298 22 201 320 341 363 384 406 428 449 471 492 514 22 202 535 557 578 600 621 643 664 685 707 728 21 203 750 771 792 814 835 856 878 899 920 942 21 204 963 984 *006 *027 *048 *069 *091 *112 *133 *154 21 205 31175 197 218 239 260 281 302 323 345 366 21 206 387 408 429 450 471 492 513 534 555 576 21 207 597 618 639 660 681 702 723 744 765 785 21 208 806 827 848 869 890 911 931 952 973 994 21 209 32015 035 056 077 098 118 139 160 181 201 21 210 222 243 263 284 305 325 346 366 387 408 21 211 428 449 469 490 510 531 552 572 593 613 20 212 634 654 675 695 715 736 756 777 797 818 20 213 838 858 879 899 919 940 960 980 *001 *021 20 214 33041 062 082 102 122 143 163 183 203 224 20 215 244 264 284 304 325 345 365 385 405 425 20 216 445 465 486 506 526 546 566 586 606 626 20 217 646 666 686 706 726 746 766 786 806 826 20 218 846 866 885 905 925 945 965 985 *005 *025 20 219 34044 064 084 104 124 143 163 183 203 223 20 220 242 262 282 301 321 341 361 380 400 420 20 221 439 459 479 498 518 537 557 577 596 616 19 222 635 655 674 694 713 733 753 772 792 811 19 223 830 850 869 889 908 928 947 967 986 *005 19 224 35025 044 064 083 102 122 141 160 180 199 19 225 218 238 257 276 295 315 334 353 372 392 19 226 411 430 449 468 488 507 526 545 564 583 19 227 603 622 641 660 679 698 717 736 755 774 19 228 793 813 832 851 870 889 908 927 946 965 19 229 984 *003 *021 *040 *059 *078 *097 *116 *135 *154 19 N 1 2 3 4 5 6 7 8 9 D [ 63] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 230-269 N 1 2 3 4 5 6 7 8 9 D 230 36173 192 211 229 248 267 286 305 324 342 19 231 361 380 399 418 436 455 474 493 511 530 19 232 549 568 5X6 605 624 642 661 680 698 717 19 233 736 754 773 791 810 829 847 866 884 903 19 234 922 940 959 977 996 *014 *033 *051 *070 *088 18 235 37107 125 144 162 181 199 218 236 254 273 18 236 291 310 328 346 365 383 401 420 438 457 18 237 475 493 511 530 548 566 585 603 621 639 18 238 658 676 694 712 731 749 767 785 803 822 18 239 840 858 876 894 912 931 949 967 985 *003 18 240 38021 039 057 075 093 112 130 148 166 184 18 241 202 220 238 256 274 292 310 328 346 364 18 242 3*2 399 417 435 453 471 489 507 525 543 18 243 561 578 596 614 632 650 668 686 703 721 18 244 739 757 775 792 810 828 846 863 881 899 18 245 917 934 952 970 987 *005 *023 *041 *058 *076 18 246 39094 111 129 146 164 182 199 217 235 252 18 247 270 287 305 322 340 358 375 393 410 428 18 248 445 463 480 498 515 533 550 568 585 602 18 249 620 637 655 672 690 707 724 742 759 777 17 250 794 811 829 846 863 881 898 915 933 950 17 251 967 985 *002 *019 *037 *054 *071 *088 *106 *123 17 252 40140 157 175 192 209 226 243 261 278 295 17 253 312 329 346 364 381 398 415 432 449 466 17 254 483 500 518 535 552 569 586 603 620 637 17 255 654 671 688 705 722 739 756 773 790 807 17 256 824 841 858 875 892 909 926 943 960 976 17 257 993 *010 *027 *044 *061 *078 *095 *111 *128 *145 17 258 41162 179 196 212 229 246 263 280 296 313 17 259 330 347 363 380 397 414 430 447 464 481 17 260 497 514 531 547 564 581 597 614 631 647 17 261 664 681 697 714 731 747 764 780 797 814 17 262 830 847 863 880 896 913 929 946 963 979 16 263 996 *012 *029 *045 *062 *078 *095 *111 *127 *144 16 264 42160 177 193 210 226 243 259 275 292 308 16 265 325 341 357 374 390 406 423 439 455 472 16 266 488 504 521 537 553 570 586 602 619 635 16 267 651 667 684 700 716 732 749 765 781 797 16 268 813 830 846 862 878 894 911 927 943 959 16 269 975 991 *008 *024 *040 *056 *072 *088 *104 *120 16 N 1 2 3 4 5 6 7 8 9 D [ 64] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 270-309 N 1 2 3 4 5 6 7 8 9 D 270 43136 152 169 185 201 217 233 249 265 281 16 271 297 313 329 345 361 377 393 409 425 441 16 272 457 473 489 505 521 537 553 569 584 600 16 273 616 632 648 664 680 696 712 727 743 759 16 274 775 791 807 823 838 854 870 886 902 917 16 275 933 949 965 981 996 *012 *028 *044 *059 *075 16 276 44091 107 122 138 154 170 185 201 217 232 16 277 248 264 279 295 311 326 342 358 373 389 16 278 404 420 436 451 467 483 498 514 529 545 16 279 560 576 592 607 623 638 654 669 685 700 16 280 716 731 747 762 778 793 809 824 840 855 15 281 871 886 902 917 932 948 963 979 994 *010 15 282 45025 040 056 071 086 102 117 133 148 163 15 283 179 194 209 225 240 255 271 286 301 317 15 284 332 347 362 278 393 408 423 439 454 469 15 285 484 500 515 530 545 561 576 591 606 621 15 286 637 652 667 682 697 712 728 743 758 773 15 287 788 803 818 834 849 864 879 894 909 924 15 288 939 954 969 984 *000 *015 *030 *045 *060 *075 15 289 46090 105 120 135 150 165 180 195 210 225 15 290 240 255 270 285 300 315 330 345 359 374 15 291 389 404 419 434 449 464 479 494 509 523 15 292 538 553 568 5R3 598 613 627 642 657 672 15 293 687 702 716 731 746 761 776 790 805 820 15 294 835 850 864 879 894 909 923 938 953 967 15 295 982 997 *012 *026 *041 *056 *070 *085 *100 *114 15 296 47129 144 159 173 188 202 217 232 246 261 15 297 276 290 305 319 334 349 363 378 392 407 15 298 422 436 451 465 480 494 509 524 538 553 15 299 567 582 596 611 625 640 654 669 683 698 15 300 712 727 741 756 770 784 799 813 828 842 14 301 857 871 885 900 914 929 943 958 ' 972 986 14 302 48001 015 029 044 058 073 087 101 116 130 14 303 144 159 173 187 202 216 230 244 259 273 14 304 287 302 316 330 344 359 373 287 401 416 14 305 430 444 458 473 487 501 515 530 544 558 14 306 572 586 601 615 629 643 657 671 686 700 14 307 714 728 742 756 770 785 799 813 827 841 14 308 855 869 883 897 911 926 940 954 968 982 14 309 996 *010 *024 *038 *052 *066 *080 *094 *108 *122 14 N O 1 2 3 4 5 6 7 8 9 D [ 65 ] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 310-349 N O 1 2 3 4 5 6 7 8 9 D 310 49136 150 164 178 192 206 220 234 248 262 14 311 276 290 304 318 332 346 360 374 388 402 14 312 415 429 443 457 471 485 499 513 527 541 14 313 554 568 582 596 610 624 638 651 665 679 14 314 693 707 721 734 748 762 776 790 803 817 14 315 831 845 859 872 886 900 914 927 941 955 14 316 969 982 996 *010 *024 *037 *051 *065 *079 *092 14 317 50106 120 133 147 161 174 188 202 215 229 14 318 243 256 270 284 297 311 325 338 352 365 14 319 379 393 406 420 433 447 461 474 488 501 14 320 515 529 542 556 569 583 596 610 623 637 14 321 651 664 678 691 705 718 732 745 759 772 14 322 786 799 813 826 840 853 866 880 893 907 13 323 920 934 947 961 974 987 *001 *014 *028 *041 13 324 51055 068 081 095 108 121 135 148 162 175 13 325 188 202 215 228 242 255 268 282 295 308 13 326 322 335 348 362 375 388 402 415 428 441 13 327 455 468 481 495 508 521 534 548 561 574 13 328 587 601 614 627 640 654 667 680 693 706 13 329 720 733 746 759 772 786 799 812 825 838 13 330 851 865 878 891 904 917 930 943 957 970 13 331 983 996 *009 *022 *035 *048 *061 *075 *088 *101 13 332 52114 127 140 153 166 179 192 205 218 231 13 333 244 257 270 284 297 310 323 336 349 362 13 334 375 388 401 414 427 440 453 466 479 492 13 335 504 517 530 543 556 569 582 595 608 621 13 336 634 647 660 673 686 699 711 724 737 750 13 337 763 776 789 802 815 827 840 853 866 879 13 338 892 905 917 930 943 956 969 982 994 *007 13 339 53020 033 046 058 071 084 097 110 122 135 13 340 148 161 173 186 199 212 224 237 250 263 13 341 275 288 301 314 326 339 352 364 377 390 13 342 403 415 428 441 453 466 479 491 504 517 13 343 529 542 555 567 580 593 605 618 631 643 13 344 656 668 681 694 706 719 732 744 757 769 13 345 782 794 807 820 832 845 857 870 882 895 13 346 908 920 933 945 958 970 983 995 *008 *020 13 347 54033 045 058 070 083 095 108 120 133 145 13 348 158 170 183 195 208 220 233 245 258 270 12 349 283 295 307 320 332 345 357 370 382 394 12 N O 1 2 3 4 5 6 7 8 9 D [ 66 ] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 350-389 N 1 2 3 4 5 6 7 8 9 D 350 407 419 432 444 456 469 481 494 506 518 12 351 531 543 555 568 580 593 605 617 630 642 12 352 654 667 679 691 704 716 728 741 753 765 12 353 777 790 802 814 827 839 851 864 876 888 12 354 900 913 925 937 949 962 974 986 998 *011 12 355 55023 035 047 060 072 084 096 108 121 133 12 356 145 157 169 182 194 206 218 230 242 255 12 357 267 279 291 303 315 328 340 352 364 376 12 358 388 400 413 425 437 449 461 473 485 497 12 359 509 522 534 546 558 570 582 594 606 618 12 360 630 642 654 666 678 691 703 715 727 739 12 361 751 763 775 787 799 811 823 835 847 859 12 362 871 883 895 907 919 931 943 955 967 979 12 363 991 *003 *015 *027 *038 *050 *062 *074 *086 *098 12 364 56110 122 134 146 158 170 182 194 205 217 12 365 229 241 253 265 277 289 301 312 324 336 12 366 348 360 372 384 396 407 419 431 443 455 12 367 467 478 490 502 514 526 538 549 561 573 12 368 535 597 608 620 632 644 656 667 579 691 12 369 703 714 726 738 750 761 773 785 797 808 12 370 820 832 844 855 867 879 891 902 914 926 12 371 937 949 961 972 984 996 *008 *019 *031 *043 12 372 57054 066 078 089 101 113 124 13 S 148 159 12 373 171 183 194 206 217 229 241 252 264 276 12 374 287 299 310 322 334 345 357 363 380 392 12 375 403 415 426 438 449 461 473 481 496 507 12 376 519 530 542 553 565 576 588 60) 611 623 12 377 634 646 657 669 680 692 703 715 726 738 11 378 749 761 772 784 795 807 818 830 841 852 11 379 864 875 887 898 910 921 933 944 955 967 11 380 978 990 *001 *013 *024 *035 *047 *058 *070 *081 11 381 58092 104 115 127 138 149 161 172 '184 195 11 382 206 218 229 240 252 263 274 286 297 309 11 383 320 331 343 354 365 377 388 399 410 422 11 384 433 444 456 467 478 490 501 512 524 535 11 385 546 557 569 580 591 602 614 625 636 647 11 386 659 670 681 692 704 715 726 737 749 760 11 387 771 782 794 805 816 827 838 850 861 872 11 388 883 894 906 917 928 939 950 961 973 984 11 389 995 *006 *017 *028 *040 *051 *062 *073 *084 *095 11 N O 1 2 3 4 5 6 7 8 9 D [ 67] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 390-429 N O 1 2 3 4 5 6 7 8 9 D 390 59106 118 129 140 151 162 173 184 195 207 11 391 218 229 240 251 262 273 284 295 306 318 11 392 329 340 351 362 373 384 395 406 417 428 11 393 439 450 461 472 483 494 506 517 528 539 11 394 550 561 572 583 594 605 616 627 638 649 11 395 660 671 682 693 704 715 726 737 748 759 11 396 770 780 791 802 813 824 835 846 857 868 11 397 879 890 901 912 923 934 945 956 966 977 11 398 988 999 *010 *021 *032 *043 *054 *065 *076 *086 11 399 60097 108 119 130 141 152 163 173 184 195 11 400 206 217 228 239 249 260 271 282 293 304 11 401 314 325 336 347 358 369 379 390 401 412 11 402 423 433 444 455 466 477 487 498 509 520 11 403 531 541 552 563 574 584 595 606 617 627 11 404 638 649 660 670 681 692 703 713 724 735 11 405 746 756 767 778 788 799 810 821 831 842 11 406 853 863 874 885 895 906 917 927 938 949 11 407 959 970 981 991 *002 *013 *023 *034 *045 *055 11 408 61066 077 087 098 109 119 130 140 151 162 11 409 172 183 194 204 215 225 236 247 257 268 11 410 278 289 300 310 321 331 342 352 363 374 11 411 384 395 405 416 426 437 448 458 469 479 11 412 490 500 511 521 532 542 553 563 574 584 11 413 595 606 616 627 637 648 658 669 679 690 11 414 700 711 721 731 742 752 763 773 784 794 10 415 805 815 826 836 847 857 868 878 888 899 10 416 909 920 930 941 951 962 972 982 993 *003 10 417 62014 024 034 045 055 066 076 086 097 107 10 418 118 128 138 149 159 170 180 190 201 211 10 419 221 232 242 252 263 273 284 294 304 315 10 420 325 335 346 356 366 377 387 397 408 418 10 421 428 439 449 459 469 480 490 500 511 521 10 422 531 542 552 562 572 583 593 603 613 624 10 423 634 644 655 665 675 685 696 706 716 726 10 424 737 747 757 767 778 788 798 808 818 829 10 425 839 849 859 870 880 890 900 910 921 931 10 426 941 951 961 972 982 932 *002 *012 *022 *033 10 427 63043 052 063 073 083 094 104 114 124 134 10 428 144 155 165 175 185 195 205 215 225 236 10 429 246 256 266 276 286 296 306 317 327 337 10 N O 1 2 3 4 5 6 7 8 9 D [ 68] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 430-469 N 1 2 3 4 5 6 7 8 . 9 D 430 347 357 367 377 387 397 407 417 428 438 10 431 448 458 468 478 488 498 508 518 528 538 10 432 548 558 568 579 589 599 609 619 629 639 10 433 649 659 669 679 689 699 709 719 729 739 10 434 749 759 769 779 789 799 809 819 829 839 10 435 849 859 869 879 889 899 9Q9 919 929 939 10 436 949 959 969 979 988 998 *008 *018 *028 *038 10 437 64048 058 068 078 088 098 108 118 128 137 10 438 147 157 167 177 187 197 207 217 227 237 10 439 246 256 266 276 286 296 306 316 326 335 10 440 345 355 365 275 285 395 404 414 424 434 10 441 444 454 464 473 483 493 503 513 523 532 10 442 542 552 562 572 582 591 601 611 621 631 10 443 640 650 660 670 680 689 699 709 719 729 10 444 738 748 758 768 777 787 797 807 816 826 10 445 836 846 855 865 875 885 895 904 914 924 10 446 933 943 953 963 972 982 992 *002 *011 *021 10 447 65031 040 050 060 070 079 089 099 108 118 10 448 128 137 147 157 167 176 186 196 205 215 10 449 225 234 244 254 263 273 283 292 302 312 10 450 321 331 341 350 360 369 379 389 398 408 10 451 418 427 437 447 456 466 475 485 495 504 10 452 514 523 533 543 552 562 571 581 591 600 10 453 610 619 629 639 648 658 667 677 686 696 10 454 706 715 725 734 744 753 763 772 782 792 9 455 801 811 820 830 839 849 858 868 877 887 9 456 896 906 916 925 935 944 954 963 973 982 9 457 992 *001 *011 *020 *030 *039 *049 *058 *068 *077 9 458 66087 096 106 115 124 134 143 153 162 172 9 459 181 191 200 210 219 229 238 247 257 266 9 460 276 285 295 304 314 323 332 342 351 361 9 461 370 380 389 398 408 417 427 436 445 455 9 ' 462 464 474 483 492 502 511 521 530 539 549 9 463 558 567 577 586 596 605 614 624 633 642 9 464 652 661 671 680 689 699 708 717 727 736 9 465 745 755 764 773 783 792 801 811 820 829 9 466 839 848 857 867 876 885 894 904 913 922 9 467 932 941 950 960 969 978 987 997 *006 *015 9 468 67025 034 043 052 062 071 080 089 099 108 9 469 117 127 136 145 154 164 173 182 191 201 9 N 1 2 3 4 5 6 7 8 9 D [ 69] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 470-509 N i 2 3 4 5 6 7 8 9 D 470 210 219 228 237 247 256 265 274 284 293 9 471 302 311 321 330 339 348 357 367 376 385 9 472 394 403 413 422 431 440 449 459 468 477 9 473 486 495 504 514 523 532 541 550 560 569 9 474 578 587 596 605 614 624 633 642 651 660 9 475 669 679 688 697 706 715 724 733 742 752 9 476 761 770 779 788 797 806 815 825 834 843 9 477 852 861 870 879 888 897 906 916 925 934 9 478 943 952 961 970 979 988 997 *006 *015 *024 9 479 68034 043 052 061 070 079 088 097 106 115 9 480 124 133 142 151 160 169 178 187 196 205 9 481 215 224 233 242 251 260 269 278 287 296 9 482 305 314 323 332 341 350 359 368 377 386 9 483 395 404 413 422 431 440 449 458 467 476 9 484 485 494 502 511 520 529 538 547 556 565 9 485 574 583 592 601 610 619 628 637 646 655 9 486 664 673 681 690 699 708 717 726 735 744 9 487 753 762 771 780 789 797 806 815 824 833 9 488 842 851 860 869 878 886 895 904 913 922 9 489 931 940 949 958 966 975 984 993 *002 *011 9 490 69020 028 037 046 055 064 073 082 090 099 9 491 108 117 126 135 144 152 161 170 179 188 492 197 205 214 223 232 241 249 258 267 276 493 285 294 302 311 320 329 338 346 355 364 494 373 381 390 399 408 417 425 434 443 452 495 461 469 478 487 496 504 513 522 531 539 496 548 557 566 574 583 592 601 609 618 627 497 636 644 653 662 671 679 688 697 705 714 498 723 732 740 749 758 767 775 784 793 801 9 499 810 819 827 836 845 854 862 871 880 888 9 500 897 906 914 923 932 940 949 958 966 975 9 501 984 992 *001 *010 *018 *027 *036 *044 *053 *062 9 502 70070 079 088 096 105 114 122 131 140 148 9 503 157 165 174 183 191 200 209 217 226 234 9 504 243 252 260 269 278 286 295 303 312 321 9 505 329 338 346 355 364 372 381 389 398 406 9 506 415 424 432 441 449 458 467 475 484 492 9 507 501 509 518 526 535 544 552 561 5*9 578 9 508 586 595 603 612 621 629 638 646 655 663 9 509 672 680 689 697 706 714 723 731 740 749 9 N o 1 2 3 4 5 6 7 8 9 D [ 70 ] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 510-549 N 1 2 3 4 5 6 7 8 9 D 510 757 766 774 783 791 800 808 817 825 834 9 511 842 851 859 868 876 885 893 902 910 919 9 512 927 935 944 952 961 969 978 986 995 *003 9 513 71012 020 029 037 046 054 063 071 079 088 8 514 096 105 113 122 130 139 147 155 164 172 8 515 181 189 198 206 214 223 231 240 248 257 8 516 265 273 282 290 299 307 315 324 332 341 8 517 349 357 366 374 383 391 399 408 416 425 8 518 433 441 450 458 466 475 483 492 500 508 8 519 517 525 533 542 550 559 567 575 584 592 8 520 600 609 617 625 634 642 650 659 667 675 8 521 684 692 700 709 717 725 734 742 750 759 8 522 767 775 784 792 800 809 817 825 834 842 8 523 850 858 867 875 883 892 900 908 917 925 8 524 933 941 950 958 966 975 983 991 999 *008 8 525 72016 024 032 041 049 057 066 074 082 090 8 526 099 107 115 123 132 140 148 156 165 173 8 527 181 189 198 206 214 222 230 239 247 255 8 528 263 272 280 288 296 304 313 321 329 337 8 529 346 354 362 370 378 387 395 403 411 419 8 530 428 436 444 452 460 469 477 485 493 501 8 531 509 518 526 534 542 550 558 567 575 583 8 532 591 599 607 616 624 632 640 648 656 665 8 533 673 681 689 697 705 713 722 730 738 746 8 534 754 762 770 779 787 795 803 811 819 827 8 535 835 843 852 860 868 876 884 892 900 908 8 536 916 925 933 941 949 957 965 973 981 989 8 537 997 *006 *014 *022 *030 *038 *046 *054 *062 *070 8 538 73078 086 094 102 111 119 127 135 143 151 8 539 159 167 175 183 191 199 207 215 223 231 8 540 239 247 255 263 272 280 288 296 304 312 8 541 320 328 336 344 352 360 368 376 384 392 8 542 400 408 416 424 432 440 448 456 464 472 8 543 480 488 496 504 512 520 528 536 544 552 8 544 560 568 576 584 592 600 608 616 624 632 8 545 640 648 656 664 672 679 687 695 703 711 8 546 719 727 735 743 751 759 767 775 783 791 8 547 799 807 815 823 830 838 846 854 862 870 8 548 878 886 894 902 910 918 926 933 941 949 8 549 957 965 973 981 989 997 *OQ5 *013 *020 *028 8 N O 1 2 3 4 5 6 7 8 9 D I 71 ] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 550-589 N i 2 3 4 5 6 7 8 9 D 550 74036 044 052 060 068 076 084 092 099 107 8 551 115 123 131 139 147 155 162 170 178 186 8 552 194 202 210 218 225 223 241 249 257 265 8 553 273 280 288 296 304 312 320 327 335 343 8 554 351 359 367 374 382 390 398 406 414 421 8 555 429 437 445 453 461 468 476 484 492 500 8 556 507 515 523 531 539 547 554 562 570 578 8 557 5*6 593 601 609 617 624 632 640 648 656 8 558 6*3 671 679 687 695 702 710 718 726 733 8 559 741 749 757 764 772 780 788 796 803 811 8 560 819 827 834 842 850 858 865 873 881 889 8 561 896 904 912 920 927 935 943 950 958 966 8 562 974 981 989 997 *095 *012 *020 *028 *035 *043 8 563 75051 059 066 074 082 089 097 105 113 120 8 564 128 136 143 151 159 166 174 182 189 197 8 565 205 213 220 228 236 243 251 259 266 274 8 566 282 289 297 305 312 320 328 335 343 351 8 567 358 366 374 381 389 397 404 312 420 427 8 568 435 442 450 458 465 473 481 488 496 504 8 569 511 519 526 534 542 549 557 565 572 580 8 570 587 595 603 610 618 626 633 641 648 656 8 571 664 671 679 686 694 702 709 717 724 732 8 572 740 747 755 762 770 778 785 793 800 808 8 573 815 823 831 838 846 853 8S1 868 876 884 8 574 891 899 906 914 921 929 937 944 952 959 8 575 967 974 982 989 997 *005 *012 *020 *027 *035 8 576 76042 050 057 065 072 080 087 095 103 110 8 577 118 125 133 140 148 155 163 170 178 185 8 578 193 200 208 215 223 230 238 245 253 260 8 579 268 275 283 290 298 305 313 320 328 335 8 580 343 350 358 365 373 380 388 395 403 410 8 581 418 425 433 440 448 455 462 470 477 485 7 582 492 500 507 515 522 530 537 545 552 559 7 583 567 574 582 589 597 604 612 619 626 634 7 54 641 649 658 664 671 678 686 693 701 708 7 585 716 723 730 738 745 753 760 768 775 782 7 586 790 797 805 812 819 827 834 842 849 856 7 587 864 871 879 886 893 901 908 916 923 930 7 588 938 945 953 960 967 975 982 989 997 *004 7 589 77012 019 026 034 041 048 056 063 070 078 7 N 1 2 3 4 5 6 7 8 9 D [ 72 ] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 590-629 N 1 2 3 4 5 6 7 8 9 D 590 085 093 100 107 115 122 129 137 144 151 7 591 159 166 173 181 188 195 203 210 217 225 7 592 232 240 247 254 262 269 276 283 291 298 7 593 305 313 320 327 335 342 349 357 364 371 7 594 379 386 393 401 408 415 422 430 437 444 7 595 452 459 466 474 481 488 495 503 510 517 7 596 525 532 539 546 554 561 568 576 583 590 7 597 597 605 612 619 627 634 641 648 656 663 7 598 670 677 685 692 699 706 714 721 728 735 7 599 743 750 757 764 772 779 786 793 801 808 7 600 815 822 830 837 844 851 859 866 873 880 7 601 887 895 902 909 916 924 931 938 945 952 7 602 960 967 974 981 988 996 *003 *010 *017 *025 7 603 78032 039 046 053 061 068 075 082 089 097 7 604 104 111 118 125 132 140 147 154 161 168 605 176 183 190 197 204 211 219 226 233 240 606 247 254 262 269 276 283 290 297 305 312 607 319 326 333 340 347 355 362 369 376 383 608 390 398 405 412 419 426 433 440 447 455 609 462 469 476 483 490 497 504 512 519 526 610 533 540 547 554 561 569 576 583 590 597 7 611 604 611 618 625 633 640 647 654 661 668 7 612 675 682 689 696 704 711 718 725 732 739 7 613 746 753 760 767 774 781 789 796 803 810 7 614 817 824 831 838 845 852 859 866 873 880 7 615 888 895 902 909 916 923 930 937 944 951 7 616 958 965 972 979 986 993 *000 *007 *C14 *021 7 617 79029 036 043 050 057 064 071 078 085 092 7 618 099 106 113 120 127 134 141 148 155 162 7 619 169 176 183 190 197 204 211 218 225 232 7 620 239 246 253 260 267 274 281 288 295 302 7 621 309 316 323 330 337 344 351 358 365 372 7 622 379 386 393 400 407 414 421 428 435 442 7 623 449 456 463 470 477 484 491 498 505 511 7 6?4 518 525 532 539 546 553 560 567 574 581 7 625 588 595 602 609 616 623 630 637 644 650 7 626 657 664 671 678 685 692 699 706 713 720 7 627 727 734 741 748 754 761 768 775 782 789 7 628 796 803 810 817 824 831 837 844 851 858 7 629 865 872 879 886 893 900 906 913 920 927 7 N 1 2 3 4 5 6 7 8 9 D [73] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 630-669 N O 1 - 2 3 4 5 6 7 8 9 D 630 934 941 948 955 962 969 975 982 989 996 7 631 80003 010 017 024 030 037 044 051 058 065 7 632 072 079 085 092 099 106 113 120 127 134 7 633 140 147 154 161 168 175 182 188 195 202 7 634 209 216 223 229 236 243 250 257 264 271 7 635 277 284 291 298 305 312 318 325 332 339 7 636 346 353 359 366 373 380 387 393 400 407 7 637 414 421 428 434 441 448 455 462 468 475 7 638 482 489 496 502 509 516 523 530 536 543 7 639 550 557 564 570 577 584 591 598 604 611 7 640 618 625 632 638 645 652 659 665 672 679 7 641 686 693 699 706 713 720 726 733 740 747 7 642 754 760 767 774 781 787 794 801 808 814 7 643 821 828 835 841 848 855 862 868 875 882 7 644 889 895 902 909 916 922 929 936 943 949 7 645 956 963 969 976 983 990 996 *003 *010 *017 7 646 81023 030 037 043 050 057 064 070 077 084 7 647 090 097 104 111 117 124 131 137 144 151 7 648 158 164 171 178 184 191 198 204 211 218 7 649 224 231 238 245 251 258 265 271 278 285 7 650 291 298 305 311 318 325 331 338 345 351 7 651 358 365 371 378 385 391 398 405 411 418 7 652 425 431 438 445 451 458 465 471 478 485 7 653 491 498 505 511 518 525 531 538 544 551 7 654 558 564 571 578 584- 591 598 604 611 617 7 655 624 631 637 644 651 657 664 671 677 684 7 656 690 697 704 710 717 723 730 T37 743 750 7 657 757 763 770 776 783 790 796 803 809 816 7 658 823 829 836 842 849 856 862 869 875 882 7 659 889 895 902 908 915 921 928 935 941 948 7 660 954 961 968 974 981 987 994 *000 *007 *014 7 661 82020 027 033 040 046 053 060 066 073 079 7 662 086 092 099 105 112 119 125 132 138 145 7 663 151 158 164 171 178 184 191 197 204 210 7 664 217 223 230 236 243 249 256 263 269 276 7 665 282 289 295 302 308 315 321 328 334 341 7 666 347 354 360 367 373 380 387 393 400 406 7 667 413 419 426 432 439 445 452 458 465 471 7 668 478 484 491 497 504 510 517 523 530 536 7 669 543 549 556 562 569 575 582 588 595 601 7 N O 1 2 3 4 5 6 7 8 9 D [74] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 670-709 N 1 2 3 4 5 6 7 8 9 D 670 607 614 620 627 633 640 646 653 659 666 7 671 672 672 737 679 743 685 750 692 756 698 763 705 769 711 776 718 782 at 730 795 6 6 673 802 808 814 821 827 834 840 847 853 860 6 674 866 872 879 885 892 898 905 911 918 924 6 675 930 937 943 950 956 963 969 975 982 988 6 676 995 *001 *008 *014 *020 *027 *033 *040 *046 *052 6 677 83059 065 072 078 085 091 097 104 110 117 6 678 123 129 136 142 149 155 161 168 174 181 6 679. 187 193 200 206 213 219 225 232 238 245 6 680 251 257 264 270 276 283 289 296 302 308 6 681 315 321 327 334 340 347 353 359 366 372 6 682 378 385 391 398 404 410 417 423 429 436 6 683 442 448 455 461 467 474 480 487 493 499 6 684 506 512 518 525 531 537 544 550 556 563 6 685 569 575 582 588 594 601 607 613 620 626 6 686 632 639 645 651 658 664 670 677 683 689 6 687 696 702 708 715 721 727 734 740 746 753 6 688 759 765 771 778 784 790 797 803 809 816 6 689 822 823 835 841 847 853 860 866 872 879 6 690 885 891 897 904 910 916 923 929 935 942 6 691 948 954 960 967 973 979 985 992 998 *004 6 692 84011 017 023 029 036 042 048 055 061 067 6 693 073 080 086 092 098 105 111 117 123 130 6 694 136 142 148 155 161 167 173 180 186 192 6 695 198 205 211 217 223 230 236 242 248 255 6 696 261 267 273 280 286 292 298 305 311 317 6 697 323 330 336 342 348 354 361 367 373 379 6 698 386 392 398 404 410 417 423 429 435 442 6 699 448 454 460 466 473 479 485 491 497 504 6 700 510 516 522 528 535 541 547 553 559 566 6 701 572 578 584 590 597 603 609 615 621 628 702 634 640 646 652 658 665 671 677 683 689 703 696 702 708 714 720 726 733 739 745 751 704 757 763 770 776 782 788 794 800 807 813 705 819 825 831 837 844 850 856 862 868 874 706 880 887 893 899 905 911 917 924 930 936 6 707 942 948 954 960 967 973 979 985 991 997 6 708 85003 009 016 022 028 034 040 046 052 058 6 709 065 071 077 083 089 095 101 107 114 120 6 N 1 2 3 4 5 6 7 8 9 D [75] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 710-749 N 1 2 3 4 5 6 7 8 9 D 710 126 132 138 144 150 156 163 169 175 181 6 711 187 193 199 205 211 217 224 230 236 242 6 712 248 254 260 266 272 278 285 291 297 303 6 713 309 315 321 327 333 339 345 352 358 364 6 714 370 376 382 388 394 400 406 412 418 425 6 715 431 437 443 449 455 461 467 473 479 485 6 716 491 497 503 509 516 522 528 534 540 546 6 717 552 558 564 570 576 582 588 594 600 606 6 718 612 618 625 631 637 643 649 655 661 667 6 719 673 679 685 691 697 703 709 715 721 727 6 720 733 739 745 751 757 763 769 775 781 788 6 721 794 800 806 812 818 824 830 836 842 848 6 722 854 860 866 872 878 884 890 896 902 908 6 723 914 920 926 932 938 944 950 956 962 968 6 724 974 980 986 992 998 *004 *010 *016 *022 *028 6 725 86034 040 046 052 058 064 070 076 082 088 6 726 094 100 106 112 118 124 130 136 141 147 6 727 153 159 165 171 177 183 189 195 201 207 6 728 213 219 225 231 237 243 249 255 261 267 6 729 273 279 285 291 297 303 308 314 320 326 6 730 332 338 344 350 356 362 368 374 380 386 6 731 392 398 404 410 415 421 427 433 439 445 6 732 451 457 463 469 475 481 487 493 499 504 733 510 516 522 528 534 540 546 552 558 564 6 734 570 576 581 587 593 599 605 611 617 623 6 735 629 635 641 646 652 658 664 670 676 682 6 736 688 694 700 705 711 717 723 729 735 741 737 747 753 759 764 770 776 782 788 794 800 738 806 812 817 823 829 835 841 847 853 859 739 864 870 876 882 888 894 900 906 911 917 740 923 929 935 941 947 953 958 964 970 976 741 982 938 994 999 *005 *011 *017 *023 *029 *035 742 87040 046 052 058 064 070 075 081 087 093 743 099 105 111 116 122 128 134 140 146 151 744 157 163 169 175 181 186 192 198 204 210 745 216 221 227 233 239 245 251 256 262 268 746' 274 280 286 291 297 303 309 315 320 326 747 332 338 344 349 355 361 367 373 379 384 748 390 396 402 408 413 419 425 431 437 442 749 448 454 460 466 471 477 483 489 495 500 N 1 2 3 4 5 6 7 8 9 D [76] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 750-789 N 1 2 3 4 5 6 7 8 9 D 750 506 512 518 523 529 535 541 547 552 558 6 751 564 570 576 581 587 593 599 604 610 616 6 752 622 628 633 639 645 651 656 662 668 674 6 753 679 685 691 697 703 708 714 720 726 731 6 754 737 743 749 754 760 766 772 777 783 789 6 755 795 800 806 812 818 823 829 835 841 846 6 756 852 858 864 869 875 881 887 892 898 904 6 757 910 915 921 927 933 938 944 950 955 961 6 758 967 973 978 984 990 996 *001 *007 *013 *018 6 759 88024 030 036 041 047 053 058 064 070 076 6 760 081 087 093 098 104 110 116 121 127 133 6 761 138 144 150 156 161 167 173 178 184 190 6 762 195 201 207 213 218 224 230 235 241 247 6 763 252 258 264 270 275 281 287 292 298 304 6 764 309 315 321 326 332 338 343 349 355 360 6 765 366 372 377 383 389 395 400 406 412 417 6 766 423 429 434 440 446 451 457 463 468 474 6 767 480 485 491 497 502 508 513 519 525 530 6 768 536 542 547 553 559 564 570 576 581 587 6 769 593 598 604 610 615 621 627 632 638 643 6 770 649 655 660 666 672 677 683 689 694 700 6 771 705 711 717 722 728 734 739 745 750 756 6 772 762 767 773 779 784 790 795 801 807 812 6 773 818 824 829 835 840 846 852 857 863 868 6 774 874 880 885 891 897 902 908 913 919 925 6 775 930 936 041 947 953 958 964 969 975 981 6 776 986 992 997 *003 *009 *014 *020 *025 *031 *037 6 777 89042 048 053 059 064 070 076 081 087 092 6 778 098 104 109 115 120 126 131 137 143 148 6 779 154 159 165 170 176 182 187 193 198 204 6 780 209 215 221 226 232 237 243 248 254 260 6 781 265 271 276 282 287 293 298 304 310 315 6 782 321 326 332 337 343 348 354 350 365 371 6 783 376 382 387 393 398 404 409 415 421 426 6 784 432 437 443 448 454 459 465 470 476 481 6 785 487 492 498 504 509 515 520 526 531 537 6 786 542 548 553 559 564 570 575 581 586 592 6 787 597 603 609 614 620 625 631 636 642 647 6 788 653 658 664 669 675 680 686 691 697 702 6 789 708 713 719 724 730 735 741 746 752 757 6 N 1 2 3 4 5 6 7 8 9 D [77] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 790-829 N 1 2 3 4 5 6 7 8 9 D 790 763 768 774 779 785 790 796 801 807 812 5 791 818 823 829 834 840 845 851 856 862 867 5 792 873 878 883 889 894 900 905 911 916 922 5 793 927 933 938 944 949 955 960 966 971 977 5 794 982 988 993 998 *004 *009 *015 *020 *026 *031 5 795 90037 042 048 053 059 064 069 075 080 086 5 796 091 097 102 108 113 119 124 129 135 140 5 797 146 151 157 162 168 173 179 184 189 195 5 798 200 206 211 217 222 227 233 238 244 249 5 799 255 260 266 271 276 282 287 293 298 304 5 800 309 314 320 325 331 336 342 347 352 358 5 801 363 369 374 380 385 390 396 401 407 412 5 802 417 423 428 434 439 445 450 455 461 466 5 803 472 477 482 488 493 499 504 509 515 520 5 804 526 531 536 542 547 553 558 563 569 574 5 805 580 585 590 596 601 607 612 617 623 628 5 806 634 639 644 650 655 660 666 671 677 682 5 807 687 693 698 703 709 714 720 725 730 736 5 808 741 747 752 757 763 768 773 779 784 789 5 809 795 800 806 811 816 822 827 832 838 843 5 810 849 854 859 865 870 875 881 886 891 897 5 811 902 907 913 918 924 929 934 940 945 950 5 812 956 961 966 972 977 982 988 993 998 *004 5 813 91009 014 020 025 030 036 041 046 052 057 5 814 062 068 073 078 084 089 094 100 105 110 5 815 116 121 126 132 137 142 148 153 158 164 5 816 169 174 180 185 190 196 201 206 212 217 5 817 222 228 233 238 243 249 254 259 265 270 5 818 275 281 286 291 297 302 307 312 318 323 5 819 328 334 339 344 350 355 360 365 371 376 5 820 381 387 392 397 403 408 413 418 424 429 5 821 434 440 445 450 455 461 466 471 477 482 5 822 487 492 498 503 508 514 519 524 529 535 5 823 540 545 551 556 561 566 572 577 582 587 5 824 593 598 603 609 614 619 624 630 635 640 5 825 645 651 656 661 666 672 677 682 687 693 5 826 698 703 709 714 719 724 730 735 740 745 5 827 751 756 761 766 772 777 782 787 793 798 5 828 803 808 814 819 824 829 834 840 845 850 5 829 855 861 866 871 876 882 887 892 897 903 5 N 1 2 3 4 5 5 7 8 9 D [78] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 830-869 N O 1 2 3 4 5 6 7 8 9 D 830 908 913 918 924 929 934 939 944 950 955 5 831 960 965 971 976 981 986 991 997 *002 *007 5 832 92012 018 023 028 033 038 044 049 054 059 5 833 065 070 075 080 085 091 096 101 106 111 5 834 117 122 127 132 137 143 148 153 158 163 5 835 169 174 479 184 189 195 200 205 210 215 5 836 221 226 231 236 241 247 252 257 262 267 5 837 273 278 283 288 293 298 304 309 314 319 5 838 324 330 335 340 345 350 355 361 366 371 5 839 376 381 387 392 397 402 407 412 418 423 5 840 428 433 438 443 449 454 459 464 469 474 5 841 480 485 490 495 500 505 511 516 521 526 5 842 531 536 542 547 552 557 562 567 572 578 5 843 583 588 593 598 603 609 614 619 624 629 5 844 634 639 645 650 655 660 665 670 675 681 5 845 686 691 696 701 706 711 716 722 727 732 5 846 737 742 747 752 758 763 768 773 778 783 5 847 788 793 799 804 809 814 819 824 829 834 5 848 840 845 850 855 860 865 870 875 881 886 5 849 891 896 901 906 911 916 921 927 932 937 5 850 942 947 952 957 962 967 973 978 983 988 5 851 993 998 *003 -008 *013 *018 *024 *029 *034 *039 5 852 93044 049 054 059 064 069 075 080 085 090 5 853 095 100 105 110 115 120 125 131 136 141 5 854 146 151 156 161 166 171 176 181 186 192 5 855 197 202 207 212 217 222 227 232 237 242 5 856 247 252 258 263 268 273 278 283 288 293 5 857 298 303 308 313 318 323 328 334 339 344 5 858 349 354 359 364 369 374 379 384 389 394 5 859 399 404 409 414 420 425 430 435 440 445 5 860 450 455 460 465 470 475 480 485 490 495 5 861 500 505 510 515 520 526 531 536 541 546 5 862 551 556 561 566 571 576 581 586 591 596 5 863 601 606 611 616 621 626 631 636 641 646 5 864 651 656 661 666 671 676 682 687 692 697 5 865 702 707 712 717 722 727 732 737 742 747 5 866 752 757 762 767 772 777 782 787 792 797 5 867 802 807 812 817 822 827 832 837 842 847 5 868 852 857 862 867 872 877 882 887 892 897 5 869 902 907 912 917 922 927 932 937 942 947 5 N 1 2 3 4 5 6 7 8 9 D [79] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 870-909 N 1 2 3 4 5 6 7 8 9 D 870 952 957 962 967 972 977 982 987 992 997 5 871 94002 007 012 017 022 027 032 037 042 047 5 872 052 057 062 067 072 077 082 086 091 096 5 873 101 106 111 116 121 126 131 136 141 146 5 874 151 15S 161 166 171 176 181 186 191 196 5 875 201 206 211 216 221 226 231 236 240 245 5 876 250 255 260 265 270 275 280 285 290 295 5 877 300 305 310 315 320 325 330 335 340 345 5 878 349 354 359 364 369 374 379 384 389 394 5 879 399 404 409 414 419 424 429 433 438 443 5 880 448 453 458 463 468 473 478 483 488 493 881 498 503 507 512 517 522 527 532 537 542 5 882 547 552 557 562 567 571 576 581 586 591 5 883 596 601 606 611 616 621 626 630 635 640 5 884 645 650 655 660 665 670 675 680 685 689 5 885 694 699 704 709 714 719 724 729 734 738 5 886 743 748 753 758 763 768 773 778 783 787 5 887 792 797 802 807 812 817 822 827 832 836 5 888 841 846 851 856 861 866 871 876 880 885 5 889 890 895 900 905 910 915 919 924 929 934 5 890 939 944 949 954 959 963 968 973 978 983 5 891 988 993 998 *002 *007 *012 *017 *022 *027 *032 5 892 95036 041 046 051 056 061 066 071 075 080 6 893 085 090 095 100 105 109 114 119 124 129 5 894 134 139 143 148 153 158 163 168 173 177 5 895 182 187 192 197 202 207 211 216 221 226 5 896 231 236 240 245 250 255 260 265 270 274 5 897 279 284' 289 294 299 303 308 313 318 323 5 898 328 332 337 342 347 352 357 361 366 371 5 899 376 381 386 390 395 400 405 410 415 419 5 900 424 429 434 439 444 448 453 458 463 468 5 901 472 477 482 487 492 497 501 506 511 516 5 902 521 525 530 535 540 545 550 554 559 564 5 903 569 574 578 583 588 593 598 602 607 612 5 904 617 622 626 631 636 641 646 650 655 660 5 905 665 670 674 679 684 689 694 698 703 708 6 906 713 718 722 727 732 737 742 746 751 756 5 907 761 766 770 775 780 785 789 794 799 804 5 908 809 813 818 823 828 832 837 842 847 852 5 909 856 861 866 871 875 880 885 890 895 899 5 N 1 2 3 4 5 6 7 8 9 D [80] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 910-949 N 2 3 4 5 6 7 & 9 D 910 904 909 914 918 923 928 933 938 942 947 5 911 952 957 961 966 971 976 980 985 990 995 912 999 *004 *009 *014 *019 *023 *028 *033 *038 *042 913 96047 052 057 061 066 071 076 080 085 090 914 095 099 104 109 114 118 123 128 133 137 915 142 147 152 156 161 166 171 175 180 185 916 190 194 199 204 209 213 218 223 227 232 5 917 237 242 246 251 256 261 265 270 275 280 5 918 284 289 294 298 303 308 313 317 322 327 5 919 332 336 341 346 350 355 360 365 369 374 5 920 379 384 388 393 398 402 407 412 417 421 5 921 426 431 435 440 445 450 454 459 464 468 5 922 473 478 483 487 492 497 501 506 511 515 5 923 520 525 530 534 539 544 548 553 558 562 5 924 567 572 577 581 586 591 595 600 605 609 5 925 614 619 624 628 633 638 642 647 652 656 5 926 661 666 670 675 680 685 689 694 699 703 5 927 708 713 717 722 727 731 736 741 745 750 5 928 755 759 764 769 774 778 783 788 792 797 5 929 802 806 811 816 820 825 830 834 839 844 5 930 848 853 858 862 867 872 876 881 886 890 5 931 895 900 904 909 914 918 923 928 932 937 5 932 942 946 951 956 960 965 970 974 979 984 5 933 988 993 997 *002 *007 *011 *016 *021 *025 *030 5 934 97035 039 044 049 053 058 063 067 072 077 5 935 081 086 090 095 100 104 109 114 118 123 5 936 128 132 137 142 146 151 155 160 165 169 5 937 174 179 183 188 192 197 202 206 211 216 5 938 220 225 230 234 239 243 248 253 257 262 5 939 267 271 276 280 285 290 294 299 304 308 5 940 313 317 322 327 331 336 340 345 350 354 5 941 359 364 368 373 377 382 387 391 396 400 5 942 405 410 414 419 424 428 433 437 442 447 5 943 451 456 460 465 470 474 479 483 488 493 5 944 497 502 506 511 516 520 525 529 534 539 5 945 543 548 552 557 562 566 571 575 580 585 5 946 589 594 598 603 607 612 617 621 626 630 5 947 635 640 644 649 653 658 663 667 672 676 5 948 681 685 690 695 699 704 708 713 717 722 5 949 727 731 736 740 745 749 754 759 763 768 5 N 1 2 3 4 5 6 7 8 9 D [81] Sec. 1 COMMON LOGARITHMS COMMON LOGARITHMS OF NUMBERS. 95O-989 N 1 2 3 4 5 6 7 8 9 D 950 772 777 782 786 791 795 800 804 809 813 5 .951 818 823 827 832 836 841 845 850 855 859 5 952 864 868 873 877 882 886 891 896 900 905 5 953 909 914 918 923 928 932 937 941 946 950 5 954 955 959 964 968 973 978 982 987 991 996 5 955 98000 005 009 014 019 023 028 032 037 041 5 956 046 050 055 059 064 068 073 078 082 087 5 957 091 096 100 105 109 114 118 123 127 132 5 958 137 141 146 150 155 159 164 168 173 177 5 959 182 186 191 195 200 204 209 214 218 223 5 960 227 232 236 241 245 250 254 259 263 268 5 961 272 277 281 286 290 295 299 304 308 313 5 962 318 322 327 331 336 340 345 349 354 358 5 963 363 367 372 376 381 385 390 394 399 403 5 964 408 412 417 421 426 430 435 439 444 448 5 965 453 457 462 466 471 475 480 484 489 493 4 966 498 502 507 511 516 520 525 529 534 538 4 967 543 547 552 556 561 565 570 574 579 583 4 968 588 592 597 601 605 610 614 619 623 628 4 969 632 637 641 646 650 655 659 664 668 673 4 970 677 682 686 691 695 700 704 709 713 717 4 971 722 726 731 735 740 744 749 753 758 762 4 972 767 771 776 780 784 789 793 798 802 807 4 973 811 816 820 825 829 834 838 843 847 851 4 974 856 860 865 869 874 878 883 887 892 896 4 975 900 905 909 914 918 923 927 932 936 941 4 976 945 949 954 958 963 967 972 976 981 985 4 977 989 994 998 *003 *007 *012 *016 *021 *025 *029 4 978 99034 038 043 047 052 056 061 065 069 074 4 979 078 083 087 092 096 100 105 109 114 118 4 980 123 127 131 136 140 145 149 154 158 162 4 981 167 171 176 180 185 189 193 198 202 207 4 982 211 216 220 224 229 233 238 242 247 251 4 983 255 260 264 269 273 277 282 286 291 295 4 984 300 304 308 313 317 322 326 330 335 339 4 985 344 348 352 357 361 366 370 374 379 383 4 986 388 392 396 401 405 410 414 419 423 427 4 987 432 436 441 445 449 454 458 463 467 471 4 988 476 480 484 489 493 498 502 506 511 515 4 989 . 520 524 528 533 537 542 546 550 555 559 4 N 1 2 3 4 5 6 7 8 9 D [ 82 ] COMMON LOGARITHMS Sec. 1 COMMON LOGARITHMS OF NUMBERS. 990-999 990 991 992 993 994 995 996 997 998 999 564 607 651 695 870 913 957 568 612 656 699 743 787 830 874 917 961 572 616 660 704 747 791 835 878 922 965 577 621 664 752 795 839 926 970 581 625 669 712 756 800 843 887 930 974 585 629 673 717 760 804 848 891 935 978 590 634 677 721 765 808 852 896 939 594 682 726 769 813 856 900 944 987 599 642 686 730 774 817 861 904 948 991 603 647 691 734 778 822 865 909 952 996 [83] TABLE 2 NATURAL TRIGONOMETRIC FUNCTIONS Sec. 1 NATURAL TRIGONOMETRIC FUNCTIONS FOUR-PLACE VALUES OF TRIGONOMETRIC FUNCTIONS. o / N. Sin. N. Tan. N. Cot. N. Cos. 00 .0000 .0000 00 1.0000 00 90 10 .0029 .0029 343.77 1.0000 50 20 .0058 .0058 171.89 1.0000 40 30 .0087 .0087 114.59 1.0000 30 40 .0116 .0116 85.940 .9999 20 50 .0145 .0145 68.750 .9999 10 1 00 .0175 .0175 57.290 .9998 00 89 10 .0204 .0204 49.104 .9998 50 20 .0233 .0233 42.964 .9997 40 30 .0262 .0262 38.188 .9997 30 40 .0291 .0291 34.368 .9996 20 50 .0320 .0320 31.242 .9995 10 2 00 .0349 .0349 28.636 .9994 00 88 10 .0378 .0378 26.432 .9993 50 20 .0407 .0407 24.542 .9992 40 30 .0436 .0437 22.904 .9990 30 40 .0465 .0466 21.470 .9989 20 50 .0494 .0495 20.206 .9988 10 3 00 .0523 .0524 19.081 .9986 00 87 10 .0552 .0553 18.075 .9985 50 20 .0581 .0582 17.169 .9983 40 30 .0610 .0612 16.350 .9981 30 40 .0640 .0641 15.605 .9980 20 50 .0669 .0670 14.924 .9978 10 4 00 .0698 .0699 14.301 .9976 00 86 10 .0727 .0729 13.727 .9974 50 20 .0756 .0758 13.197 .9971 40 30 .0785 .0787 12.706 .9969 30 40 .0814 .0816 12.251 .9967 20 50 .0843 .0846 11.826 .9964 10 5 00 .0872 .0875 11.430 .9962 00 85 10 .0901 . .0904 11.059 .9959 50 20 .0929 .0934 10.712 .9957 40 30 .0958 .0963 10.385 .9954 30 40 .0987 .0992 10.078 .9951 20 50 .1016 .1022 9.7882 .9948 10 6 00 .1045 .1051 9.5144 .9945 00 84 10 .1074 .1080 9.2553 .9942 50 20 .1103 .1110 9.0098 .9939 40 30 .1132 .1139 8.7769 .9936 30 40 .1161 .1169 8.5555 .9932 20 50 .1190 .1198 8.3450 .9929 10 7 00 .1219 .1228 8.1443 .9925 00 83 10 .1248 .1257 7.9530 .9922 50 20 .1276 .1287 7.7704 .9918 40 30 .1305 .1317 7.5958 .9914 30 40 .1334 .1346 7.4287 .9911 20 50 .1363 .1376 7.2687 .9907 10 N. Coa. N. Cot. N. Tan. N. Sin. / o [ 86] NATURAL TRIGONOMETRIC FUNCTIONS Sec. 1 FOUR-PLACE VALUES OF TRIGONOMETRIC FUNCTIONS. / N. Sin. N. Tan. N. Cot. N. Cos. 8 00 .1392 .1405 7.1154 .9903 00 82 10 .1421 .1435 6.9682 .9899 50 20 .1449 .1465 6.8269 .9894 40 30 .1478 .1495 6.6912 .9890 30 40 .1507 .1524 6.5606 .9886 20 50 .1536 .1554 6.4348 .9881 10 9 00 .1564 .1584 6.3138 .9877 00 81 10 .1593 .1614 6.1970 .9872 50 20 .1622 .1644 6.0844 .9868 40 30 .1650 .1673 5.9758 .9863 30 40 .1679 .1703 5.8708 .9858 20 50 .1708 .1733 5.7694 .9853 10 10 00 .1736 .1763 5.6713 .9848 00 80 10 .1765 .1793 5.5764 .9843 50 20 .1794 .1823 5.4845 .9838 40 30 .1822 .1853 5.3955 .9833 30 40 .1851 .1883 5.3093 .9827 20 50 .1880 .1914 5.2257 .9822 10 11 00 .1908 .1944 5.1446 .9816 00 79 10 .1937 .1974 5.0658 .9811 50 20 .1965 .2004 4.9894 .9805 40 30 .1994 .2035 4.9152 .9799 30 40 .2022 .2065 4.8430 .9793 20 50 .2051 .2095 4.7729 .9787 10 12 00 .2079 .2126 4.7046 .9781 00 78 10 .2108 .2156 4.6382 .9775 50 20 .2136 .2186 4.5736 .9769 40 30 .2164 .2217 4.5107 .9763 30 40 .2193 .2247 4.4494 .9757 20 50 .2221 .2278 4.3897 .9750 10 13 00 .2250 .2309 4.3315 .9744 00 77 10 .2278 .2339 4.2747 .9737 50 20 .2306 .2370 4.2193 .9730 40 30 .2334 .2401 4.1653 .9724 30 40 .2363 .2432 4.1126 .9717 20 50 .2391 .2462 4.0611 .9710 10 14 00 .2419 .2493 4.0108 .9703 00 76 10 .2447 .2524 3.9617 .9696 50 20 .2476 .2555 3.9136 .9689 40 30 .2504 .2586 3.8667 .9681 30 40 .2532 .2617 3.8208 .9674 20 50 .2560 .2648 3.7760 .9667 10 15 00 .2588 .2679 3.7321 .9659 00 75 10 .2616 .2711 3.6891 .9652 50 20 .2644 .2742 3.6470 .9644 40 30 .2672 .2773 3.6059 .9636 30 40 .2700 .2805 3.5656 .9628 20 50 .2728 .2836 3.5261 .9621 10 N. Cos. N. Cot. N. Tan. N. Sin. > o [ 87 ] Sec. 1 NATURAL TRIGONOMETRIC FUNCTIONS FOUR-PLACE VALUES OF TRIGONOMETRIC FUNCTIONS. / N. Sin. N. Tan. N. Cot. N. Cos. 16 00 .2756 .2867 3.4874 .9613 00 74 10 .2784 .2899 3.4495 .9605 50 20 .2812 .2931 3.4124 .95% 40 30 .2840 .2962 3.3759 .9588 30 40 .2868 .2994 3.3402 .9580 20 50 .2896 .3026 3.3052 .9572 10 17 00 .2924 .3057 3.2709 .9563 00 73 10 .2952 .3089 3.2371 .9555 50 20 .2979 .3121 3.2041 .9546 40 30 .3007 .3153 3.1716 .9537 30 40 .3035 .3185 3.1397 .9528 20 50 .3062 .3217 3.1084 .9520 10 18 00 .3090 .3249 3.0777 .9511 00 72 10 .3118 .3281 3.0475 .9502 50 20 .3145 .3314 3.0178 .9492 40 30 .3173 .3346 2.9887 .9483 30 40 .3201 .3378 2.9600 .9474 20 50 .3228 .3411 2.9319 .9465 10 19 00 .3256 .3443 2.9042 .9455 00 71 10 .3283 .3476 2.8770 .9446 50 20 .3311 .3508 2.8502 .9436 40 30 .3338 .3541 2.8239 .9426 30 40 .3365 .3574 2.7980 .9417 20 50 .3393 .3607 2.7725 .9407 10 20 00 .3420 .3640 2.7475 .9397 00 70 10 .3448 .3673 2.7228 .9387 50 20 .3475 .3706 2.6985 .9377 40 30 .3502 .3739 2.6746 .9367 30 40 .3529 .3772 2.6511 .9356 20 50 .3557 .3805 2.6279 .9346 10 21 00 .3584 .3839 2.6051 .9336 00 69 10 .3611 .3872 2.5826 .9325 50 20 .3638 .3906 2.5605 .9315 40 30 .3665 .3939 2.5386 .9304 30 40 .3692 .3973 2.5172 .9293 20 50 .3719 .4006 2.4960 .9283 10 22 00 .3746 .4040 2.4751 .9272 00 68 10 .3773 .4074 2.4545 .9261 50 20 .3800 .4108 2.4342 .9250 40 30 .3827 .4142 2.4142 .9239 30 40 .3854 .4176 2.3945 .9228 20 50 .3881 .4210 2.3750 .9216 10 23 00 .3907 .4245 2.3559 .9205 00 67 10 .3934 .4279 2.3369 .9194 50 20 .3961 .4314 2.3183 .9182 40 30 .3987 .4348 2.2998 .9171 30 40 .4014 .4383 2.2817 .9159 20 50 .4041 .4417 2.2637 .9147 10 N. Cos. N. Cot. N. Tan. N. Sin. > o [88] NATURAL TRIGONOMETRIC FUNCTIONS Sec. 1 FOUR-PLACE VALUES OF TRIGONOMETRIC FUNCTIONS. / N. Sin. N. Tan. N. Cot. N. Cos. 24 00 .4067 .4452 2.2460 .9135 00 66 10 .4094 .4487 2.2286 .9124 50 20 .4120 .4522 2.2113 .9112 40 30 .4147 .4557 2.1943 .9100 30 40 .4173 .4592 2.1775 .9088 20 50 .4200 .4628 2.1609 . .9075 10 25 00 .4226 .4663 2.1445 .9063 00 65 10 .4253 .4699 2.1283 .9051 50 20 .4279 .4734 2.1123 .9038 40 30 .4305 .4770 2.0965 .9026 30 40 .4331 .4806 2.0809 .9013 20 50 .4358 .4841 2.0655 .9001 10 26 00 .4384 .4877 2.0503 .8988 00 64 10 .4410 .4913 2.0353 .8975 50 20 .4436 .4950 2.0204 .8962 40 30 .4462 .4986 2.0057 .8949 30 40 .4488 .5022 1.9912 .8936 20 50 .4514 .5059 1.9768 .8923 10 27 00 .4540 .5095 1.9626 .8910 00 63 10 .4566 .5132 1.9486 .8897 50 20 .4592 .5169 1.9347 .8884 40 30 .4617 .5206 1.9210 .8870 30 40 .4643 .5243 1.9074 .8857 20 50 .4669 .5280 1.8940 .8843 10 28 00 .4695 .5317 1.8807 .8829 00 62 10 .4720 .5354 1.8676 .8816 50 20 .4746 .5392 1.8546 .8802 40 30 .4772 .5430 1.8418 .8788 30 40 .4797 .5467 1.8291 .8774 20 50 .4823 .5505 1.8165 .8760 10 29 00 .4848 .5543 1.8040 .8746 00 61 10 .4874 .5581 1.7917 .8732 50 20 .4899 .5619 1.7796 .8718 40 30 .4924 .5658 1.7675 .8704 30 40 .4950 .5696 1.7556 .8689 20 50 .4975 .5735 1.7437 8675 10 30 00 .5000 .5774 1.7321 .8660 00 60 10 .5025 .5812 1.7205 .8646 50 20 .5050 .5851 1.7090 .8631 40 30 .5075 .5890 1.6977 .8616 30 40 .5100 .5930 1.6864 .8601 20 50 .5252 .5969 1.6753 .8587 10 31 00 .5150 .6009 1.6643 .8572 00 59 10 .5175 .6048 1.6534 .8557 50 20 .5200 .6088 1.6426 .8542 40 30 .5225 .6128 1.6319 .8526 30 40 .5250 .6168 1.6212 .8511 20 50 .5275 .6208 1.6107 .8496 10 N. Cos. N. Cot. N. Tan. N. Sin. / o [ 89 ] Sec. 1 NATURAL TRIGONOMETRIC FUNCTIONS FOUR-PLACE VALUES OF TRIGONOMETRIC FUNCTIONS. o / N. Sin. N. Tan. N. Cot. N. Cos. 32 00 .5299 .6249 1.6003 .8480 00 58 10 .5324 .6289 1.5900 .8465 50 20 .5348 .6330 1.5798 .8450 40 30 .5373 .6371 1.5697 .8434 30 40 .5398 .6412 1-5597 .8418 20 50 .5422 .6453 1.5497 .8403 10 33 00 .5446 .6494 1.5399 .8387 00 57 10 .5471 .6536 1.5301 .8371 50 20 .5495 .6577 1.5204 .8355 40 30 .5519 .6619 1.5108 .8339 30 40 .5544 .6661 1.5013 .8323 20 50 .5568 .6703 1.4919 .8307 10 34 00 .5592 .6745 1.4826 .8290 00 56 10 .5616 .6787 1.4733 .8274 50 20 .5640 .6830 1.4641 .8358 40 30 .5664 .6873 1.4550 .8241 30 40 .5688 .6916 1.4460 .8225 20 50 .5712 .6959 1.4370 .8208 10 35 00 .5736 .7002 1.4281 .8192 00 55 10 .5760 .7046 1.4193 .8175 50 20 .5783 .7089 1.4106 .8158 40 30 .5807 .7133 1.4019 .8141 30 40 .5831 .7177 1.3934 .8124 20 50 .5854 .7221 1.3848 .8107 10 36 00 .5878 .7265 1.3764 .8090 00 54 10 .5901 .7310 1.3680 .8073 50 20 .5925 .7355 1.3597 .8056 40 30 .5948 .7400 1.3514 .8039 30 40 .5972 .7445 1.3432 .8021 20 50 .5995 .7490 1.3351 .8004 10 37 00 .6018 .7536 1.3270 .7986 00 53 10 .6041 .7581 1.3190 .7969 50 20 .6065 .7627 1.3111 .7951 40 30 .6088 .7673 1.3032 .7934 30 40 .6111 .7720 1.2954 .7916 20 50 .6134 .7766 1.2876 .7898 10 38 00 .6157 .7813 1.2799 .7880 00 52 10 .6180 .7860 1.2723 .7862 50 20 .6202 .7907 1.2647 .7844 40 30 .6225 .7954 1.2572 .7826 30 40 .6248 .8002 1.2497 .7808 20 50 .6271 .8050 1.2423 .7790 10 39 00 .6293 .8098 1.2349 .7771 00 51 10 .6316 .8146 1.2276 .7753 50 20 .6338 .8195 1.2203 .7735 40 30 .6361 .8243 1.2131 .7716 30 40 .6383 .8292 1.2059 .7698 20 50 .6406 .8342 1.1988 .7679 10 N. Cos. N. Cot. N. Tan. N. Sin. / o [90] NATURAL TRIGONOMETRIC FUNCTIONS Sec. 1 FOUR-PLACE VALUES OF TRIGONOMETRIC FUNCTIONS. o / N. Sin. N. Tan. N. Cot. N. Cos. 40 00 .6428 .8391 1.1918 .7660 00 50 10 .6450 .8441 1.1847 .7642 50 20 .6472 .8491 1.1778 .7623 40 30 .6494 .8541 1.1708 .7604 30 40 .6517 .8591 1.1640 .7585 20 50 .6539 .8642 1.1571 .7566 10 41 00 .6561 .8693 1.1504 .7547 00 49 10 .6583 .8744 1.1436 .7528 50 20 .6604 .8796 1.1369 .7509 40 30 .6626 .8847 1.1308 .7490 30 40 .6648 .8899 1.1237 .7470 20 50 .6670 .8952 1.1171 .7451 10 42 00 .6691 .9004 1.1106 .7431 00 48 10 .6713 .9057 1.1041 .7412 50 20 .6734 .9110 1.0977 .7392 40 30 .6756 .9163 1.0913 .7373 30 40 .6777 .9217 1.0850 .7353 20 50 .6799 .9271 1.0786 .7333 10 43 00 .6820 .9325 1.0724 .7314 00 47 10 .6841 .9380 1.0661 .7294 50 20 .6862 .9435 1.0599 .7274 40 30 .6884 .9490 1.0538 .7254 30 40 .6905 .9545 1.0477 .7234 20 50 .6926 .9601 1.0416 .7214 10 44 00 .6947 .9657 1.0355 .7193 00 46 10 .6967 .9713 1.0295 .7173 50 20 .6988 .9770 1.0235 .7153 40 30 .7009 .9827 1.0176 .7133 30 40 .7030 .9884 1.0117 .7112 20 50 .7050 .9942 1.0058 .7092 10 45 00 .7071 1.0000 1.0000 .7071 00 45 N. Cos. N. Cot. N. Tan. N. Sin. / o [ 91 ] TABLE No. 3 DECIMAL EQUIVALENTS AND CIRCUMFERENCES AND AREAS OF CIRCLES DECIMAL EQUIVALENTS OF 64ths The decimal fractions printed in large type give the exact value of the corresponding fraction to the fourth decimal place. A given decimal fraction is rarely exactly equal to any of these values, and the numbers in small type show which common fraction is nearest to the given decimal. Thus, lay off the fraction 0.1330 in 64ths. The nearest decimal fractions are 0.1250 and 0.1406. The value of any fraction in small type is the mean of the two adjacent fractions. In this instance the mean fraction is 0.1328, and as 0.1330 is greater than this, 0.1406 or / will be chosen. In the same manner the nearest 64ths corresponding to the decimal fractions 0.3670 and 0.8979 are found to be f f and ||, respectively. Frac- tion. Decimal. Frac- tion. Decimal. Frac- tion. Decimal. Frac- tion. Decimal. e J 4 .0078 .0156 U .2656 U .5078 .5156 U j0 A 0235 .0313 A I2813 17 5235 .5313 II .7813 .0391 .2891 5391 .7891 B 3 f .0469 H .2969 1! .5469 II .7969 0547 3047 5547 .8047 A .0625 A .3125 I 9 5 .5625 U .8125 .0703 3203 573 .820.5 et .0781 ti .3281 it .5781 11 .8281 .0860 .3360 .5860 .8360 a 3 " .0938 tt .3438 II .5938 5 .8438 .1016 35i6 .6016 .8516 A .1094 U .3594 If .6094 II .8594 .1172 .3672 .6172 .8672 i .1250 1 .S750 1 .6250 .8750 A 1328 .1406 If fgol II .6328 .6406 i! .8828 .8906 A 1485 .1563 U '.4063 H .6485 .6563 ii .898 s .9063 ii .1641 .1719 II .4141 .4219 U .6641 .6719 .9141 .9219 .1797 4297 .6797 .9297 TS .1875 TB .4375 U .6875 B .9375 H 1953 .2031 IS 4453 .4531 ti 6953 .7031 Ii 9453 .9531 .2110 .4610 .7110 .9610 3 7 5 .2188 Si .4688 H .7188 31 .9688 .2266 .4766 .7266 .9766 41 .2344 U .4844 i? .7344 If .9844 .2422 .4922 7422 .9922 i .2500 .5000 2 .7500 1 1.0000 2578 .5078 7578 [ 94] CIRCUMFERENCES AND AREAS Sec. 1 CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. Circum. Area. Diam. Circum. Area. j .0491 .0982 .1963 .3927 .0002 .0008 .0031 .0123 4f 4j *| 4j 13.7445 14 1372 14.5299 14.9226 15.0330 15.9043 16.8002 17.7206 A .5890 .7854 .9817 1.1781 .0276 .0491 .0767 .1104 4J 5 5| 51 15.3153 15.70&0 16.1UU7 16.4934 18.6555 19.6350 20.6290 21.6476 $ 1.3744 1.5708 1.7671 1.9635 .1503 .1963 .2485 .3068 5| 5* 5| 5| 16.8861 17.2788 17.6715 18.0642 22.6907 23.7583 24.8505 25.9673 1,5 f 2.1598 2.3562 2.5525 2.7489 .3712 .4418 .5185 .6013 51 6 N 61 18.4569 18.8496 19.2423 19.6350 27.1036 28.2744 29.4648 30.6797 i .> l 1 " !! 2.9452 3.1416 3.5343 3.9270 .6903 .7854 .9940 1.2272 6 6 6 6 20.0277 20.4204 20.8131 21.2058 31.9191 33.1831 34.4717 35.7848 If l 11 4.3197 4.7124 5.1051 5.4978 - 1.4849 1.7671 2.0739 2.4053 61 ?! 21.5985 21.9912 22.3839 22.7766 37.1224 38.4846 39.8713 41.2826 H 2 2* 2i 5.8905 6.2832 6.6759 7.0686 2.7612 3.1416 3.5466 3.9761 71 7 7i 23.1693 23.5620 23.9547 24.3474 42.7184 44.1787 45.6636 47.1731 2 2 2 2 7.4613 7.8540 8.2467 8.6394 4.4301 4.9087 5.4119 5.9396 71 8 8* 81 24.7401 25.1328 25.5255 25.9182 48.7071 50.2656 51.8487 53.4563 I s 3| 3* 9.0321 9.4248 9.8175 10.2102 6.4918 7.0686 7.6699 8.2958 8f 1 l! 26.3109 26.7036 27.0963 27.4890 55.0884 56.7451 58.4264 60.1322 3 3 3 3! 10.6029 10.9956 11.3883 11.7810 8.9462 9.6211 10.3206 11.0447 S 1 9| 91 27.8817 28.2744 28.6671 29.0598 61.8625 63.6174 65.3968 67.2008 I 1 4 4 12.1737 12.5664 12.9591 13.3518 11.7933 12.5664 13.3641 14.1863 9| 9J 9| 91 29.4525 29.8452 30.2379 30.6306 69.0293 70.8823 72.7599 74.6621 [95] Sec. 1 CIRCUMFERENCES AND AREAS CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. Circum. Area. Diam. Circum. Area. 1 31.0233 31.4160 31.8087 32.2014 76.589 78.540 80.516 82.516 15f 15k 15| 48.3021 48.6948 49.0875 49.4802 185.661 188.692 191.748 194.828 oooo 32.5941 32.9868 33.3795 33.7722 84.541 86.590 88.664 90.763 15 16 16 16 \ 49.8729 50.2656 50.6583 51.0510 197 933 201.062 204.216 207.395 10 11 11 11 i : ; 34.1649 34.5576 34.9503 35.3430 92.886 95.033 97.205 99.402 16| 16f 16f 51.4437 51.8364 52.2291 52.6218 210.598 213.825 217.077 220.354 11 11 11 11 35.7357 36.1284 36.5211 36.9138 101.623 103.869 106.139 108.434 I? 17 17 i 53.0145 53.4072 53.7999 54.1926 223.655 226.981 230.331 233.706 HI 12 12* 121 37.3065 37.6992 38.0919 38.4846 110.754 113.098 115.466 117.859 17 17 17 17 54.5853 54.9780 55.3707 55.7634 237.105 240.529 243.977 247.450 to to to tc ' 38.8773 39.2700 39.6627 40.0554 120.277 122.719 125.185 127.677 18* 18f 181 56.1561 56.5488 56.9415 57.3342 250948 254.470 258.016 261.587 oowcoto \ 40.4481 40.8408 41.2335 41.6262 130.192 132.733 135.297 137.887 18 18 18 18 57.7269 58.1196 58.5123 58.9050 265.183 268.803 272.448 276.117 co co co co 42.0189 42.4116 42.8043 43.1970 140.501 143.139 145.802 148.490 181 19 m 191 59.2977 59.6904 60.0831 60.4758 279.811 283.529 287.272 291.040 13J 14 14J 43.5897 43.9824 44.3751 44.7678 151.202 153.938 156.700 159.485 19 19 19 : 60.8685 61.26t2 61.6539 62.0466 294.832 298.648 302.489 306.355 14 14 14 14 45.1605 45.5532 45 9459 46.3386 162.296 165.130 167.990 170.874 191 20 20| 201 62.4393 62.8320 63.2247 63.6174 310.245 314.160 318.099 322.063 15 15 15 " 46.7313 47.1240 47.5167 47.9094 173.782 176.715 179.673 182.655 20S 20* 20 20 . 1 ." 64.0101 64.4028 64.7955 65.1882 326.051 330.064 334.102 338.164 [ 96] CIRCUMFERENCES AND AREAS Sec. 1 CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. Circum. Area. Diam. Circum. Area. 201 21 2U m 65.5809 65 9736 66.3663 66.7590 342.250 346.361 350.497 354.657 26| 26 264 261 82.8597 83.2524 83.6451 84.0378 546.356 551547 556.763 562.003 21| 21* 21f 21| 67.1517 67.5444 67.9371 68.3298 358.842 363.051 367.285 371543 261 27 27 i 27* 84.4305 84.8232 85.2159 85.6086 567.267 572.557 577.870 583.209 21f 22 22k 22i 687225 69.1152 69.5079 69.9006 375826 380.134 384.466 388.822 27| 21h 27| 27| 86.0013 86.3940 86 7867 87.1794 588.571 593.959 599.371 604.807 22f 22 1 22| 221 70.2933 70.6860 71.0787 71.4714 393.203 397.609 402.038 406.494 271 28 281 28* 87.5721 87.9648 88.3575 88.7502 610.268 615.754 621.264 626.798 221 23 23| 23* 71.8641 72.2568 72.6495 73.0422 410.973 415.477 420.004 424.558 28f 28^ 28f 28| 89.1429 89.5356 89.9283 90.3210 632.357 637.941 643.549 649.182 23f 23^ 23| 231 73.4349 73.8276 74.2203 74.6130 429.135 433.737 438.364 443.015 281 29 29J 29* 90.7137 91.1064 91.4991 91.8918 654.840 660.521 666.228 671.959 231 24 24 i 241 75.0057 75.3984 75.7911 76.1838 447.690 452.390 457.115 461.864 29f 29| 29f 29f 92.2845 92.6772 93.0699 93.4626 677.714 683.494 689.299 695.128 24| 24| 24f 241 76.5765 76.9692 77.3619 77.7546 466.638 471.436 476.259 481.107 291 30 30| 30* 93.8553 94.2480 94.6407 95.0334 700.982 706.860 712.763 718.690 241 25 25| 25i 78.1473 78.5400 78.9327 79.3254 485.979 490.875 495.796 500.742 ISf 30f 301 95.4261 95.8188 96.2115 96.6042 724.642 730.618 738.619 742.645 25f 25i 25| 25| 79.7181 80.1108 80.5035 80.8962 505.712 510.706 515.726 520.769 301 31 3H 31i 96.9969 97.38% 97.7823 98.1750 748.695 754.769 760.869 766.992 251 26 26J 26* 81.2889 81.6816 82.0743 82.4670 525.838 530.930 536.048 541.190 31f 314- 31f 311 98.5677 98.9604 99.3531 99.7458 773.140 779.313 785.510 791.732 [97] Sec. 1 CIRCUMFERENCES AND AREAS CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. Circum Area. Diam. Circum. Area. 311 32 321 100.1385 100.5312 100.9239 101.3166 797.979 804.250 810.545 816.865 37| 37f 37| 117.417 117.810 118.203 118.595 1,097.118 ,104.469 ,111.844 ,119.244 32 32 32 32 101.7093 102.1020 102.4947 102.8874 823.210 829.579 835.972 842.391 38* 381 381 118.988 119.381 119.773 120.166 .126.669 ,134.118 1,141.591 1,149.089 321 33 331 103.280 103.673 104.065 104.458 848.833 855.301 861.792 868.309 38f 381 38f 88| 120.559 120.952 121.344 121.737 1,156.612 1,164.159 1,171.731 1,179.327 33 33 33 33 104.851 105.244 105.636 106.029 874.850 881.415 888.005 894.620 381 39 391 39i 122.130 122.522 122.915 123.308 1,186.948 1,194.593 1,202.263 1,209.958 33 34 34 34 \ 106.422 106 814 107.207 107.600 901.259 907 922 914.611 921.323 39f 391 39 f 39f 123.700 124.093 124.486 124.879 1,217.677 1,225.420 1,233.188 1,240.981 34 34 34 34 107.992 108.385 108.778 109.171 928.061 934.822 941.609 948.420 391 40 401 401 125.271 125.664 126.057 126.449 1,248.798 1,256.640 1,264.510 1,272.400 341 35 351 35i 109.563 109.956 110.349 110.741 955.255 962.115 969.000 975.909 40| i 126.842 127.235 127.627 128.020 1,280.310 1,288.250 1,296.220 1,304.210 35 35 35 35 111.134 111.527 111.919 112.312 982.842 989.800 996.783 1,003.790 401 41 411 411 128.413 128.806 129.198 129.591 1,312.220 1,320.260 1,328.320 1,336.410 35i 36 36 36 f 112.705 113.098 113.490 113.883 1,010.822 1,017.878 1,024.960 1,032.065 41 |}f 129.984 130.376 130.769 131.162 1,344.520 1,352.660 1,360.820 1,369.000 36 36 36 36 114.276 114.668 115.061 115.454 1,039.195 1,046.349 1,053.528 1,060.732 411 42 421 421 131.554 131.947 132.340 132733 1,377.210 1,385.450 1,393.700 1,401.990 36 37 37 37 \ -- 115.846 116.239 116.632 117.025 1,067.960 1,075.213 1,082.490 1,089.792 42f 421 42f 42| 133.125 133.518 133.911 134.303 1,410.300 1,418.630 1,426.990 1,435.370 t 98 ] CIRCUMFERENCES AND AREAS Sec. 1 CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. Circum. Area. Diam. Circum. Area. 421 134,696 1,443.770 46 146.084 1,698.23 43 43| 135.089 135.481 1,452.200 1,460.660 46 46 146.477 146.870 1,707.37 1,716.54 431 135.874 1,469.140 46 147.262 1,725.73 43f 136.267 1,477.640 47 147.655 1,734.95 43* 136.660 1,486.170 47 148.048 1,744.19 434 137.052 1,494.730 47 148.441 1,753.45 43| 137.445 1,503.300 47| 148.833 1,762.74 431 137.838 1,511.910 47* 149.226 1,772.06 44 138.230 1,520.530 47 149.619 1,781.40 44 i 138.623 1.529.190 47 150.011 1,790.76 44 i 139.016 1,537.860 47 150.404 1,800.15 44 f 139.408 1,546.56 48 150.797 1,809.56 44* 139.801 1,555.29 48| 151.189 1,819.00 44 f 140.194 1,564.04 48 151.582 1,828.46 44f 140.587 1,572.81 48 151.975 1,837.95 441 140.979 1,581.61 48 i 152.368 1,847.46 45 141.372 1,590.43 48 .. 152.760 1,856.99 45i 141.765 1,599.28 48- : 153.153 1,866.55 45* 142.157 1,608.16 481 153.546 1,876.14 45J 142.550 1,617.05 49 153.938 1,885.75 45* 142.943 1,625.97 49 j 154.331 1.895.38 45| 143.335 1,634.92 49 154.724 1,905.04 45f 143.728 1,643.89 48 155.116 1,914.72 451 144.121 1,652.89 49 155.509 1,924.43 46 144.514 1,661.91 49 155.902 1.934.16 46J 144.906 1,670.95 49 156.295 1,943.91 46J 145.299 1,680.02 49 156.687 1,953.69 40| 145.692 1,689.11 50 157.080 1,963.50 FUNDAMENTAL UNITS, MENSURATION, CONVERSION FACTORS AND METRIC UNITS FUNDAMENTAL UNITS The electrical units are derived from the following mechanical units: The centimeter, the unit of length. The gramme, the unit of mass. The second, the unit of time. The centimeter equals 0.3937 of an inch, or one thousand-millionth part of a quadrant of the earth. The gramme is equal to 15.432 grains, the mass of a cubic centi- meter of water at 4 C. The second is the time of one swing of the pendulum, making 86,464.09 swings per day, or the 1-86400 part of a mean solar day. MENSURATION Circumference of circle whose diameter is 1 =ir = 3. 14159265. Circumference of any circle = diameter Xir. Area of any circle = (radius) 2 Xir, or (diameter) 2 X 0.7854. Surface of sphere = (diameter) 2 XTT, or = circumference X diameter. Volume of sphere = (diameter) 3 X0.5236, or = surface Xi diameter. Area of an ellipse = long diameter X short diameter X 0.7854. 7^ = 9.8696; TT* = 1.772454; = 0.7854. A = 0.31831; logx =0.4971499. Basis of natural log r = 2.7183, log e = 0.43429. Modulus of natural logarithm M = j ( ~ = 2.3026. 144 Ib. per sq. foot. 51.7116 mm. of mercury. 1 Ib. per sq. inch 2.30665 feet of water. 0.072 ton (short) per sq. foot. 0.0680415 atmosphere. ' One mile = 320 rod = 1760 yards = 5280 feet = 63,360 inches. One fathom = 6 feet; 1 knot = 6080 feet. 1728 cubic inches = 1 cubic foot. 231 cubic inches = 1 liquid gallon = 0.134 cubic foot. 1 pound avoirdupois = 7000 grains = 453.6 grammes. The angle of which the arc is equal to the radius, a Radian 57.2958. PHYSICAL DATA The equivalent of one B.t.u. of heat = 778 foot-pounds. The equivalent of one calorie of heat = 426 kg-m. = 3.968 B. t.u. One cubic foot of water weighs 62.355 pounds at 62 F. [ 102] CONVERSION FACTORS Sec. 1 One cubic foot of air weighs 0.0807 pound at 32 F. and one atmosphere. One cubic foot of hydrogen weighs 0.00557 pound. One foot-pound = 1.3562 X 10 7 ergs. One horse-power hour = 33,000 X 60 foot-pounds. One horse-power = 33,000 foot-pounds per min. = 550 foot-pounds per second = 746 watts = 2545 B.t.u. per hour. Acceleration of gravity (g) = 32.2 feet per second. = 980 mm. per second. One atmosphere = 14.7 pounds per square inch. = 2116 pounds per square foot. = 760 mm. of mercury. Velocity of sound at cent, in dry air = 332.4 meters per sec. = 1091 feet per sec. Velocity of light in vacuum = 299,853 km. per sec. = 186,325 miles per sec. Specific heat of air at constant pressure = 0.237. A column of water 2.3 feet high corresponds to a pressure of 1 pound per square inch. Coefficient of expansion of gases = ?fg = 0.00367. Latent heat of water = 79. 24. Latent heat of steam = 535. 9. CENTIGRADE DEGREES. To convert into the corresponding one in Fahrenheit degrees, multiply by 9 A and add 32. To convert it into the one in Reaumur degrees multiply by Vs. To convert It into the one on the Absolute scale, add 273. FAHRENHEIT DEGREES. To convert into the one in Centigrade degrees, subtract 32 and then multiply by 6 / 9 , being careful about the signs when the reading is below the melting point of ice. To convert it into the one in Reaumur degrees, subtract 32 and multiply by 4 / 9 . To convert it into the one on the Absolute scale, subtract 32, then multiply by 5 A and add 273; or multiply by 5, add 2297, and divide by 9. ELECTRICAL DATA {=unit of electric power = h. p.X746. = current X volts X power factor. = foot pounds per sec. -f- 1.355. Joules, W = work done = watts X seconds. 3412 B.t.u. 2,654,536 foot-pounds. 1 kw. hour = 3.53 pounds water evaporated at 212 F. 22.8 pounds water raised from 62 to 212 F. 0.235 pounds carbon oxidized at 100 per cent. eff. METRIC WEIGHTS AND MEASURES Linear 1 meter = 39.3704 inches = 3.281 feet =1.094 yards. Centimeter (1-100 meter) = 0.3937 inch. [ 103 ] Sec. 1 METRIC UNITS 1 millimeter (mm.) = 0.03937 inch = 39.37 mils. 1 inch = 25.3997 millimeters = 0.083 foot = 2.54 centimeters. 1 kilometer = 1,000 meters or 3,281 feet = 0.6213 mile. For the purpose of memory, a meter may be considered as 3 feet 3H inches. Surface Measures Centare (1 square meter) = 1,550 square inches = 10.764 square feet. Are (100 square meters) = 119.6 square yards. 1 square centimeter = 0.155 square inch = 197,300 circular mils. 1 square millimeter = 0.00155 square inch = 1973 circular mils. 1 square inch = 6.451 square centimeters = 0.0069 square foot. 1 square foot = 929.03 square centimeters = 0.0929 square meter. Weights Milligram (1-1000 gram) = 0.0154 grain. Centigram (1-100 gram) = 0.1543 grain. Decigram (1-10 gram) = 1.5432 grains. Gram = 15.432 grains. Decagram (10 grams) = 0.3527 ounce. Hectogram (100 grams) = 3. 5274 ounces. Kilogram (1,000 grams) =2.2046 pounds. Myriagram (10,000 grams) = 22.046 pounds. Quintal (100,000 grams) = 220.46 pounds. Millier or tonne ton (1,000,000 grams) = 2,204.6 pounds. Volumes Milliliter (1-1000 liter) = 0.061 cubic inch. Centiliter (1-JOO liter) = 0.6102 cubic inch. Deciliter (1-10 liter) = 6. 1023 cubic inches. Liter = 1,000 cu. cm. = 61. 023 cubic inches. Hectoliter (100 liters) = 2.838 bushels. Kiloliter (1,000 liters) = 1,308 cubic yards. Liquid Measures Milliliter (1-1000) =0.0338 fluid ounce. Centiliter (1-100 liter) = 0.338 fluid ounce. Deciliter (1-10 liter) =0.845 gill. Liter = 0.908 quart = 0.2642 gallon. Decaliter (10 liters) = 2.6418 gallons. Hectoliter (100 liters) = 26.418 gallons. Kiloliter (1,000 liters) =264.18 gallons. [ 104 ] BIBLIOGRAPHY Sec. 1 BIBLIOGRAPHY Electrical Meterman's Handbook. American Institute of Electrical Engineers. Publications of Various Wire Manufacturers. Standard Handbook for Electrical Engineers. Foster's Electrical Engineer's Pocketbook. [105] SECTION 2 DISTRIBUTION AND TRANSMISSION LINE SUPPORTS SECTION 2 DISTRIBUTION AND TRANSMISSION LINE SUPPORTS TABLE OF CONTENTS ARTICLE Wood Poles General 1 White Cedar or Arbor Vitae 2 Chestnut 3 Western Red Cedar 4 Loblolly Pine Poles 5 Western Yellow Pine 6 Lodgepole Pine Poles 7 Pole Defects 8 Butt Rot 9 Heart Rot 10 Season Checks 11 Wind Shakes and Ring Shakes 12 Ring Rot 13 Cat Faces 14 Pole Specifications General 15 Specifications for Chestnut Poles 16 Specifications for Eastern White Cedar Poles 17 Specifications for Western White Cedar, Red Cedar, Western Cedar, Idaho Cedar 18 Specifications for Sawed Redwood Poles 19 Specification for Yellow Pine Poles 20 Specifications for Creosoted Yellow Pine Poles 21 Concrete Poles General 22 Steel Reinforcing 23 Concrete Mixture 24 Molding Pole 25 Hollow Concrete Poles 26 Steel Poles and Towers 27 Patented Steel Poles 28 Tubular Steel Poles 29 Structural Steel Poles and Towers 30 Flexible Towers 31 Outdoor Substations , ... 32 [109] WOOD POLES 1. General. Wood poles comprise a large majority of the poles in use upon which are strung aerial conductors. Approximately 82 percent of the wood poles in use in this country are either cedar or chestnut. Cedar represents about 62 percent and chestnut about 20 percent of the total. The remaining 18 percent include poles manufactured from every specie of timber.* It is customary to purchase poles under specifications which usually provide for their dimensions, etc.; but, in general, the logging of the poles is entirely neglected. Inasmuch as it is the practice of a number of companies to purchase poles on the stump the following data on logging have been compiled, covering a few of the more important species, also the more important defects usually found in timber are described. LOGGING 2. White Cedar or Arbor Vitae. Northern white cedar or arbor vitae is a common swamp tree in the northeastern and lake states and in Canada. It is extensively used for poles as it grows to the required form and size, and also combines the desired strength, lightness and durability. Since the growth of this species is so slow, careful logging methods will not bring about reproduction that will benefit the present logger, the method of getting out white cedar poles is determined only by the mechanical and topographical problems involved. The summer and winter are undoubtedly the best seasons in which to work in swamps and as woods labor is most available in winter this would seem to be the better of the two. Further because of the advantages of hauling on sleds, the late fall and winter offer the best conditions for cutting, skidding and hauling, and these opera- tions are therefore usually carried on at that time. Stumps should not be cut low; and at least above the characteristic crook near the ground. Poles cut and peeled during the late fall and winter and skidded in a single layer well off the ground should be held until the first of May before shipping, thus insuring a decrease in freight weight more than equal to the expense of holding. Poles so held will also gain in strength and durability. Green arbor vitae poles lose the larger portion of their moisture from the sapwood. This sapwood is very thin, consequently, the loss begins immediately after exposure to favorable seasoning in- fluence, and a large percent of the moisture is lost during sixty days of fair weather. Spring and early summer offer the best conditions for maximum seasoning in the shortest time. Checking during seasoning, if not serious, lias no particular effect on the strength of the pole and is of little assistance in the absorption * U. S. Government Statistics. [1111 Sec. 2 WOOD POLES of preservatives. The greatest checking occurs in the spring and summer cut poles. If arbor vitae poles are properly seasoned, the sapwood can be thoroughly impregnated with creosote in the open tank. Fall and winter cut poles, if properly skidded, should be in satisfactory condition for impregnation by the following June. If skidded several layers deep, as is the usual custom, they will probably have to be seasoned for a longer period. 3. Chestnut. The chestnut-bearing states are as follows: New Hampshire, Vermont, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Ohio, Maryland, Delaware, Virginia, West Virginia, Kentucky, Tennessee and North Carolina. The best chestnut poles are cut from trees grown in coves, on lower slopes, and in level country on deep, well-drained, loamy soil. It has been found that trees grown on high elevations have a larger FIG. 20. Butt Rot in Eastern White Cedar Pole. Right^ hand section was cut 5 feet from Butt. Middle section was cut 10 feet from* Butt. Left hand section shows remainder of the pole. taper than trees grown on lower levels. A considerable difference has been found where the elevation varies as little as 150 feet. The exact relation between the inherent specific gravity of the wood and the strength of the pole is not definitely known. It is estimated, however, that the strength varies directly with the specific gravity. Chestnut timber can be divided into two general classes seed- grown and sprout-grown. The method of production of seed-grown trees is self-evident. Sprout-grown trees are trees that grow from the stumps of live timber which has been cut down. Such poles have a much more rapid growth; it is estimated that a tree of suffi- cient size from which to cut a 30 foot pole will mature when grown from a stump ten years sooner than a tree grown from seed. The average age of a sprout-grown tree from which a 30-f t. pole can be cut is forty years, and of those grown from seed to a similar size, fifty years. [112] WOOD POLES Sec. 2 In cutting chestnut-trees it is most important to consider the time at which the timber should be cut and the method of cutting. Un- doubtedly the best season is the late fall and winter. This is due to the fact that most vigorous sprouts originate from winter-cut stumps. The cost of logging is least. The season is not conducive to the danger of an attack of fungi. The poles season persistently and have the advantage of a gradual rise in temperature as their moisture contents gradually decrease. The slow drying rate does not result in serious checking; hence the poles are stronger. The spring and summer months are the most unfavorable months FIG. 21. Frequency of Butt Rot in Eastern White Cedar Poles. in which to cut timber, as it dries very rapidly, causing large season checks, which may seriously decrease the strength of the pole. If trees are cut in summer, the stumps are practically killed, and few, if any, sprouts will originate from them. Summer cutting should, therefore, be discouraged. Moreover, trees cut at this season are subjected to decay and their strength may be materially affected thereby. In cutting chestnut-trees, consideration should be given to cutting ; the stumps will sprout. This is accomplished in such a manner that [113] Sec. 2 WOOD POLES by cutting the tree as near the ground as possible and giving the cut a decided pitch, in order to avoid butt rot in the sprout-grown poles. The height at which the pole is cut materially affects its taper. If the tree is cut low the basal swelling of the tree will be included in the pole, which, where the tree has been cut one (1) foot above the ground, increases the taper in circumference as much as five inches over its circumference if cut four (4) feet above the ground. The practice of dragging poles over the ground for long distances should be discouraged because the outer layers of wood are sheared off and the strength of the poles is lessened. Further, a pole in this FIG. 22. Butt Rot in Eastern White Cedar Poles. condition is more susceptible to decay because of the crevices caused thereby which will hold water and spores. The tops of trees remaining after poles are cut should be utilized for cordwood, as this increases the gross value of the timber. 4. Western Red Cedar. The regions from which the largest pro- duction of western red cedar poles are secured are situated in the panhandle of the State of Idaho, or Puget Sound, in the vicinity of Bellingham and Everett, Washington and along the lower Columbia River. Some poles are logged in the Grays Harbor region of the State of Washington. The northern portion of the State of Idaho produces more poles [114] WOOD POLES Sec. 2 than any similar region in the United States. West Coast poles are logged and marketed on Puget Sound. Poles obtained from the lower Columbia River are heavier butted and weigh more than those from either of the above mentioned regions. The taper and other properties of Columbia River poles compare favorably with those secured from other regions, but Columbia River poles are generally free from butt rot, which is not so true of Idaho cedar poles. The logging and piling of cedar poles is generally carried on in advance of the logging of saw timber, the pole company taking the small timber before the fellers of saw timber advance in the woods. FIG. 23. Hollow Knot indicating Heart Rot in Eastern White Cedar Pole. This is an important item of conservation, since in ordinary logging operations where pole timber is not removed it is destroyed by breakage in felling the larger trees. Poles are generally removed from the woods by horse team, usually to storage yards or to the logging railroad of the logging company, over which they are trans- ported to storage yards or connecting railroad transportation. In Idaho and on Puget Sound many poles are cut by ranchers in the clearing of land and are finally marketed through pole companies. Poles are always peeled on the ground immediately after felling [115] Sec. 2 WOOD POLES or in the pole yard close by. As a rule the pole cutter works alone, felling the timber, slashing the branches and peeling. Pole dealers contend that winter cut poles are more durable and are stronger than summer cut poles because the sap is down in the winter, the moisture content is less and the poles check less in drying. However, when the sap is down, poles are harder to peel. Users pre- fer winter cut poles and generally order such. The pole cutting season in Idaho extends from May 1st to December 1st and often throughout the year. On Puget Sound poles are cut at any time during the year, preferably, however, during the winter season in FIG. 24. Butt Rot in Chestnut Pole. order to meet the demands of the trade for winter cut poles. The season of cutting affects the rate of drying and the resulting checking, but otherwise offers no convenience to the cutter or dealer. On Puget Sound it is customary to store poles for water shipments in fresh water booms -in the rivers a short distance from the Sound. This fresh water storage insures against the attack of teredo and other salt water borers. In the Inland Empire the poles, after being peeled, are yarded and stored on the ground for seasoning or they are boomed in the Inland lakes or rivers. Ground storage is often [116] WOOD POLES Sec. 2 practiced in the Puget Sound region, if, as is the exception, the poles are for rail distribution. Poles for cargo shipments on Puget Sound are gathered from the fresh water booms and are built into cribs in the salt water. Cribs are built in tiers and contain from 200 to 300 poles sorted for length and top diameter. Each tier is laid at right angles to the one below and the crib generally contains five or six tiers of poles. In loading for water shipments, these cribs are towed to the side of the vessel and the poles are loaded direct. Poles cannot be stored in the salt water on Puget Sound for a long period because of the attack of the teredo. During the months of August and September thirty days' storage will show the beginning of teredo attack, while during the winter and spring seasons they will not be .active for from four to six months. It is also claimed that the teredo is much more active on mud flats than on gravel bottoms. Therefore, when storage grounds are in salt water, the FIG. 25. Heart Rot in Chestnut Pole. grounds should be carefully selected and the poles loaded as soon as possible after storage. It is noticeable that specifications for cedar poles generally provide that the poles be cut from live, growing cedar timber. This excludes the use of insect or fire-killed pole timber. If fire- killed poles are cut before decay or insect attack begins, they are not necessarily inferior unless the" killing fire injured the wood of the tree in a visible manner. Fire-killed poles may generally be con- sidered more durable and more economical to handle as they season before cutting. Furthermore, in cases where the bark has fallen, some of the food substances in the sapwood which nourish destruc- tive fungous agencies are leached out by rains, and decay is retarded. Unless large cracks or checks develop, it is doubtful if the fire-killed timber is materially weaker than green cut timber. Many fire- killed or dead cedar poles are accepted under specifications requiring green cut poles, the inspectors being unable to distinguish them. Such poles have been used in the same line with green cut poles and have given equal satisfaction. There is no well defined reason for [117] Sec. 2 WOOD POLES excluding dead poles from specifications, provided they are sound and show no detrimental defects, such as insect workings, decay of serious checking. Checking, in fact, is liable to be more severe in green logged, air seasoned poles than in fire-killed poles, provided the bark of the fire-killed poles was not directly destroyed by the killing fire. 5. Loblolly Pine Poles. Loblolly pine is a probable important future source of poles because of the depletion of the northern white cedar stand and because of the destruction of chestnut forests by the bark disease. Generally speaking loblolly pine is not as good a pole timber as northern white cedar or chestnut, as it is likely to be FIG. 26. Checks and Butt Rot in Eastern White Cedar Pole. very knotty and trees of pole form are not so common in pine stands as they are in chestnut and cedar stands. Trees suitable for poles will be found more often in medium open old field stands. The more open stands will have trees that are very knotty while dense stands are likely to produce trees compara- tively small at the butt and of little taper. It is advisable to cut loblolly pine poles in the later fall or winter in order to allow as much seasoning as possible before spring, for the reason that spring cut poles are very liable to decay during seasoning owing to the un- evaporated water they contain. Loblolly pine poles should be given a preservative treatment before using and before such treatment [118] WOOD POLES Sec. 2 they should be placed on high skids with space between all poles, and seasoned for several months or else artificially seasoned. 6. Western Yellow Pine. In certain parts of the states of Cali- fornia, Nevada, Utah, Wyoming, Colorado, Arizona and New Mexico, it may be advisable for pole using companies to use a local timber rather than bring in western red cedar poles by rail. Through- out this region there is a great deal of western yellow pine. Such timber will furnish poles which will give good~service if treated. The following statements are conclusions from an investigation in California. Poles of western yellow pine should be cut from hill- grown timber rather than from valley-grown timber. FIG. 27. Ring Shakes in Chestnut Pcrte. Hill-grown timber grows under dryer conditions and on poorer soil; hence it grows much more slowly. It grows remarkably straight and free from limbs. It has a uniform taper, which is less p r onounced and better adapted to poles than valley grown timber. This particular kind of timber is finer grained, stronger and contains much more heart wood. Valley Grown Timber is more liable to knottiness, it is badly shaped, rarely shows any heartwood and usually grows so rapidly that the annular rings do not hang together. Valley grown timber also has a very coarse grain and if grown in the open, has a large taper and many small limbs. The bole in such timber forms a spool-like shape between each tree's growth or whorl or limbs, [ H9 ] Sec. 2 WOOD POLES making a knotty and badly appearing pole. The butt is apt to be oversize and of irregular shape. Where such timber grows closely together it often has many limbs well toward the ground but these limbs are smaller and there are no spool-like depressions between the whorls. Such timber makes good poles. FIG. 28. Butt Rot and Ring Shakes in Eastern White Cedar Pole. FIG. 29. Ring Rot in Chestnut Pole. [120] WOOD POLES Sec. 2 Western yellow pine has a short life below ground. As a pole timber it will serve but two or three years untreated and if set green will show decided decay in one year. Otherwise, it is satisfactory. The decay-resisting power can be controlled by the use of preserv- atives which the timber takes successfully. All yellow pine poles should be treated with a preservative before use. The poles should be well seasoned before treatment and are best treated during the second summer after cutting. The poles should not be lumbered during the summer for the reason that case hardening, due to rapid drying, causes summercut poles to resist the entrance of preservatives to a marked degree. Poles may be cut at any other season but preferable during the [121] Sec. 2 WOOD POLES autumn, after September, as the fall-cut poles absorb the preserv- ative far more readily than poles cut during any other season. 7. Lodgepole Pine Poles. In the Rocky Mountain and Coast Ranges there are at present abundant stands of lodgepole pine which after treatment make very satisfactory poles. It is not naturally durable in contact with the ground, but it takes treatment readily and even with the additional cost of treatment the pine pole is comparatively cheap. In many regions outside the region where cedar grows, the pine may be made to last longer than untreated cedar. Poles should be cut from fairly dense stands in order to avoid the knottiness in open grown trees and the small slender poles FIG. 31. Ant Eaten Butt in Eastern White Cedar Pole. grown in very thick stands. As in the case of other species, lodge- pole pine poles should be thoroughly seasoned before treatment. Forest fires have killed many stands of lodgepole pine and on many such areas the timber remains entirely sound for many years after the fire. Such timber is thoroughly seasoned and therefore ready for treatment as soon as cut. When both sound dead timber and live timber are available for poles which are to be treated, the sound dead timber is usually preferable as it is already seasoned. The prejudice in many regions against the use of dead timber is based on the mistaken assumption that there is some inherent difference in wood that has been seasoned on the stump and wood that has been cut when green. [ 122 ] WOOD POLES Sec. 2 8. Pole Defects. The natural defects, some of which, are found in all kinds of timber make theoretical calculations of strength very uncertain. It is of utmost importance that all poles be subjected to a most careful inspection, in order that a reasonably uniform product will be secured. The defects which may occur in all kinds of timber are more or less similar. The principal ones are as follows: (a) Butt Rot (Art. 9) (b) Heart Rot (Art. 10) (c) Season Checks (Art. 11) (d) Wind shakes, Ring shakes, etc. (Art. 12) (e) Ring Rot (Art. 13) (f) Cat Faces (Art. 14) 9. Butt Rot (Figs. 20, 21, 22 and 24) is more prevalent in some species of timber than in others. When appearing in chestnut poles it is usually found in sprout grown trees and is generally the FIG. 32. Ant Eaten Butt in Eastern White Cedar Pole. result of careless cutting of the original tree. The rot should be confined to a small proportional part of the cross-section of the butt. It should not extend into the pole a very great distance and never to above what will be the ground line. 10. Heart Rot (Figs. 23 arid 25) is usually evidenced by small defective knots which show rot. It is extremely important that such knots be carefully examined. Fig. 25 shows an apparently perfectly sound chestnut pole. A few small knots about 0.5 inches in diameter indicated evidence of heart rot. The pole was cut into and decided heart rot was found existing for about 15 feet of the pole's length. 11. Season Checks (Fig. 26) are due mostly to the rate at which the pole is seasoned. The more rapid the seasoning, the more [ 123 ] Sec. 2 WOOD POLES extensive the checks. In general, they may be said to decrease the strength of the pole. The greater their number, or the larger their size, the weaker the pole. 12. Wind Shakes and Ring Shakes. (Figs. 27 and 28.) Wind shakes and ring shakes are caused by wind strains in the standing tree or by careless felling. Such defects may seriously damage the pole. Defects which are incipient in green poles sometimes extend until they form a split anywhere from 1 to 9 feet long. The extent of such defects should be carefully examined, in order that the strength of accepted poles will not be materially reduced. 13. Ring Rot. (Fig. 29.) takes the form of a ring and is usually in evidence at the butt of the pole. When such rot exists, it should FIG. 33. Ant Eaten Butt in Chestnut Pole. not be extensive in character and should not extend into the pole for too great a distance. 14. Cat Faces (Figs. 30A and B) are the result of an injury to a tree over which the bark never heals. The wood at this point dries out and is not covered, except at the edges of a wound, by new wood or bark and therefore becomes dead wood. Sometimes there is also a swelling at this point. It is exposed to fungus, insect attack, and weathering, and therefore, after a pole has been cut and peeled, the [ 124] WOOD POLES Sec. 2 cat face shows as a weathered place, which it may not be possible to eliminate by shaving. However, if no decay has started in the cat face, the pole should not be rejected. If any decay, which has started, can be shaved off and down into sound wood without materially decreasing the pole diameter at this point, the pole should not be rejected. A pole that shows bright sap just after shaving with one or more cat faces, will, after it has seasoned a year or more, present practically the same appearance all over. POLE SPECIFICATIONS: 15. General. The preparation of specifications covering all kinds of timber would be extremely lengthy. Therefore, detail specifica- tions are given for the more generally used timbers only. The selection of the proper kind of timber, from which poles should be manufactured, is governed entirely by the locality in which they are to be used. Any available timber may be used provided it develops sufficient mechanical strength. The theoretical strength of a pole is dependent on the diameter of the butt, the modulus of rupture of the timber, and the taper. The natural defects found in all kinds of timber makes it necessary that they be subjected to very careful inspection, in order that incipient rot, bad knots, etc. do not decrease their strength to a dangerous degree. The theoretical calculation of the strength of a wood pole (Sec. 8, Art. 18) develops the following important facts. A pole will break where its diameter is 1.5 times the diameter at which the load is applied. (The critical diameter.) When the taper of a pole, with a given top diameter, is uniform and of such a value that the ground line diameter is greater than the critical diameter, the strength of the pole is constant and independent of its height; when the height of such a pole is reduced until its diameter at the ground line is less than the critical diameter, the strength will vary, depending upon its height and its diameter at the ground line. When the diameter at the ground line is greater than the critical diameter, a certain decrease in ground line diameter, due to rot, may occur without decreasing the strength of the pole; this amount of decrease is dependent only on the taper of the pole. From the above, it follows that pole specifications should be such that the greatest possible taper will be secured, and if the kind of timber is such that small tapers are natural the butt diameter should be the controlling factor. Where larger tapers are natural the butt and top diameters must be considered. 16. SPECIFICATIONS FOR CHESTNUT POLES.* To determine the character of poles to be used, pole lines may be divided into the three following classes : Class "A": for heavy transmission lines or heavy distribution lines. * National Electric Light Association Specification. -,-- [125] Sec. 2 WOOD POLES Class "B": for light transmission lines or ordinary distribution lines. Class "C": for very light distribution lines or light secondary lines. The purchasing company is to have the right to make such in- spections of the poles as it may desire. The inspector of the pur- chasing company shall have the power to reject any pole which is defective in any respect. Inspection, however, shall not relieve the manufacturer from furnishing perfect poles. Any imperfect poles which may be discovered before their final acceptance shall be replaced immediately upon the requirement of the purchasing company, notwithstanding that the defects may have been overlooked by the inspector. If the requirements of these specifications are not fulfilled when the poles are offered for final acceptance, not only shall the purchasing company have the right to reject the poles, but the expense of inspection of such defective poles shall be borne by the manufacturer. All poles shall be subject to inspection by the purchasing company, either in the woods, where the trees are felled, or at any point of shipment or destination. Any pole failing to meet all the require- ments of these specifications may be rejected. All poles shall be of the best quality live white chestnut, squared at both ends, reasonably straight, well proportioned from butt to top, peeled and with knots trimmed close. The dimensions of poles shall be according to the following table, DIMENSIONS OF POLES IN INCHES. CLASSES. Length of A B C Poles. Top. 6' from Butt. Top. 6' from Butt. Top. 6' from Butt. 25 20 30 30 24 40 22 36 20 33 35 24 43 22 40 20 36 40 24 45 22 43 20 40 45 24 48 22 47 20 43 50 24 51 22 50 20 46 55 22 54 22 53 20 49 60 22 57 22 56 65 22 60 22 59 70 22 63 22 62 75 22 66 22 65 80 22 70 22 69 85 22 73 22 72 90 22 76 22 75 [ 126] WOOD POLES Sec. 2 the "Top" measurements being the circumference at the top of the pole, and the "Butt" measurement being the circumference six feet (6' 0") from the butt. 17. SPECIFICATIONS FOR EASTERN WHITE CEDAR POLES.* The material desired under these specifications consists of poles of the best quality of either seasoned or live green cedar of the di- mensions hereinafter specified. Seasoned poles shall have preference over green poles provided they have not been held for seasoning long enough to have developed any of the timber defects hereinafter referred to. All poles shall be reasonably straight, well proportioned from butt to top, shall have both ends squared, the bark peeled and all knots and limbs closely trimmed. Dimensions The dimensions of the poles shall be in accordance with the fol- lowing table, the "top" measurement being the circumference at the top of the pole and the "butt" measurement the circumference six (6) feet from the butt. MINIMUM DIMENSIONS OF POLES IN INCHES (CIR- CUMFERENCE) Length Poles. (Feet.) CLASSES. A B C Top. 6' from Butt. Top. 6' from Butt. Top. 6' from Butt. 25 30 35 40 45 50 55 60 24 24 24 24 24 24 24 40 43 47 50 53 56 59 22 22 22 22 22 22 22 22 32 36 38 43 47 50 53 56 it 18 18 18 18 j 18, ! 30 33 36 40 43 46 49 When the dimension at the butt is not given the poles shall be reasonably well proportioned throughout their entire length. The dimension requirement at the six (6) foot mark shall be rigidly followed in all cases. Class, A, B, and C Poles may have top cir- * National Electric Light Association Specification. [ 127] Sec. 2 WOOD POLES cumference not more than one half ( l /$) inch less than those shown in the preceding table. No pole shall be over six (6) inches longer or three (3) inches shorter than the length for which it is accepted; if any pole be more than six inches longer than is required it shall be cut back. Quality of Timber Dead Poles. The wood of a dead pole is grayish in color. The Eresence of a black line on the edge of the sapwood (as seen on the utt) also shows that a pole is dead. No dead poles, and no poles having dead streaks covering more than one quarter of their surface shall be accepted under these specifications. Poles having dead streaks covering less than one quarter of their surface shall have a circumference greater than otherwise required. The increase in the circumference shall be sufficient to afford a cross-sectional area of sound wood equivalent to that of sound poles of the same class. Fire Killed or River Poles. No dark red or copper colored poles, which when scraped do not show good live timber shall be accepted under these specifications. Twisted, Checked or Cracked Poles. No poles having more than one complete twist for every twenty (20) feet in length, no cracked poles containing large season checks shall be accepted under these specifications. "Cat Faces." No poles having "cat Faces," unless they are small and perfectly sound and the poles have an increased diameter at the "cat face," and no poles having "cat faces" near the six (6) foot mark or within ten (10) feet of their tops, shall be accepted under these specifications. Shaved Poles. No shaved poles shall be accepted under these specifications. Miscellaneous Defects. No poles containing sap rot, evidence of internal rot as disclosed by a careful examination of all black knots, hollow knots, woodpecker holes, or plugged holes; and no poles showing evidences of having been eaten by ants, worms or grubs shall be accepted under these specifications, except that poles containing worm or grub marks below the six (6) foot mark will be accepted. Crooked Poles. No poles having a short crook or bend, a crook or bend in two planes or a reverse curve shall be accepted under these specifications. The amount of sweep, measured between the six foot mark and the top of the pole, that may be present in poles acceptable under these specifications, is shown in the following table: 35 foot poles shall not have a sweep over 10)^ inches. 40 foot poles shall not have a sweep over 12 inches. 45 foot poles shall not have a sweep over 9 inches. 50 foot poles shall not have a sweep over 10 inches. 55 foot poles shall not have a sweep over 11 inches. 60 foot poles shall not have a sweep over 12 inches. [ 128] WOOD POLES Sec. 2 Defective Tops. Poles having tops of the required dimensions must have sound tops. Poles having tops one (1) inch or more above the requirements in circumference may have one (1) pipe rot not more than one-half (J^) inch in diameter. Poles with double tops or double hearts shall be free from rot where the two parts or hearts join. Defective Butts. No poles containing ring rot (rot in the form of a complete or partial ring) shall be accepted under these specifications. Poles having hollow hearts may be accepted under the conditions shown in the following table: Add to Butt Requirements Average Diameter of of of of Rot. 25 and 30 35, 40 and 45 50, 55, 60 and 65 foot Poles. foot Poles. foot Poles. 2 inches Nothing Nothing Nothing 3 inches 1 inch Nothing Nothing 4 inches 2 inches Nothing Nothing 5 inches 3 inches 1 inch Nothing 6 inches 4 inches 2 inches 1 inch 7 inches Reject 4 inches 2 inches 8 inches Reject 6 inches 3 inches 9 inches Reject Reject 4 inches 10 inches 11 inches Reject Reject Reject Reject 5 inches 7 inches 12 inches Reject Reject 9 inches 13 inches Reject Reject Reject Scattered rot, unless it is near the outside of the pole may be estimated as being the same as heart rot of equal area. "Wind Shakes." Poles with cup shakes (Checks in the form of rings) which also have heart or star checks may be considered as equal to poles having hollow hearts of the average diameter of the cup shakes. Inspection. All poles shall be subject to inspection by the purchaser's representative, either in the woods where the trees are felled, or at any point of shipment, or destination. Each pole thus inspected shall be marked according to its length and class with a marking hammer, by the purchaser's representative. All poles fail- ing to meet these specifications shall be rejected. 18. SPECIFICATIONS FOR WESTERN WHITE CEDAR, RED CEDAR, WESTERN CEDAR, IDAHO CEDAR.* General. The material desired under these specifications consists of poles and guy stubs of the best quality of either seasoned or live green * American Telephone & Telegraph Co. Specification. 5 [ 129 ] Sec. 2 WOOD POLES cedar of the dimensions hereinafter specified. The poles covered by these specifications are of Western White Cedar, otherwise known as red cedar, western cedar, or Idaho cedar. Seasoned poles shall have preference over green poles provided they have not been held for seasoning long enough to have developed any of the timber defects hereinafter referred to. All poles shall be reasonably straight, well proportioned from butt to top, shall have both ends squared, sound tops, the bark peeled, and all knots and limbs closely trimmed. Dimensions. The dimensions of the poles shall be in accordance with the fol- lowing table, the "top" measurement being the circumference at the top of the pole and the "butt" measurement, the circumference six (6) feet from the butt. The dimensions given are the minimum allowable circumferences at the point specified for measurement and are not intended to preclude the acceptance of poles of larger di- mensions. When the dimension at the butt is not given, the poles shall be reasonably well proportioned throughout their entire length. No pole shall be over six (6) inches longer or three (3) inches shorter than the length for which it is accepted. If any pole is more than six (6) inches longer than is required it shall be cut back. MINIMUM DIMENSIONS OF POLES IN INCHES. Length of Poles. (Feet.) CLASSES. A B C (Minimum Top circumference 28) Circumference 6 feet from Butt (Minimum Top Circumference 25) Circumference 6 feet from Butt (Minimum Top Circumference 22) Circumference 6 feet from Butt 20 22 25 30 35 40 45 50 55 60 65 30 32 34 37 40 43 45 47 49 52 54 28 30 31 34 36 38 40 42 44 46 48 26 27 28 30 32 34 36 38 40 41 43 [ 130] WOOD POLES Sec. 2 Quality of Timber Dead Poles. No dead poles and no poles having dead streaks covering more than one quarter of their surface shall be accepted under these specifications. Poles having dead streaks covering less than one-quarter of their surface shall have a circumference greater that otherwise required. The increase in the circumference shall be sufficient to afford a cross sectional area of sound wood equivalent to that of sound poles of the same class. Twisted, Checked or Cracked Poles. No poles having more than one complete twist for every twenty (20) feet in length, no cracked poles, and no poles containing large season checks, shall be accepted under these specifications. Crooked Poles. No poles having a short crook or bend, a crook or bend in two planes, or a reverse crook or bend shall be accepted under these specifications. The amount of sweep measured between the six (6) foot mark and the top of the pole, shall not exceed one (1) inch to every six (6) feet in length. "Cat Faces." No poles having "cat faces" unless they are small and perfectly sound, and the poles have an increased diameter at the "cat face," and no poles having "cat faces" near the six (6) foot mark, or within ten (10) feet of their tops shall be accepted under these specifications. Shaved Poles. No shaved poles shall be accepted under these specifications. Wind Shakes. No poles shall have cup shakes (checks in the form of rings) containing heart or star shakes which enclose more than ten (10) percent of the area of the butt. ' Butt Rot. No poles shall have butt rot covering in excess of ten (10) percent of the total area of the butt. The butt rot, if pres- ent, must be located close to the center in order that the pole may be accepted. Knots. Large knots, if sound and trimmed close shall not be considered a defect. No poles shall contain hollow or rotten knots. Miscellaneous Defects. No poles containing sap rot, wood- pecker holes or plugged holes, and no poles showing evidences of having been eaten by worms, ants, or grubs shall be accepted under these specifications. 19. SPECIFICATIONS FOR SAWED REDWOOD POLES* General. The material desired under these specifications consists of poles of redwood (Sequois Sempervirens) sawed to shape as here- inafter set forth. Quality of Timber and Workmanship. All poles shall be of sound Number One Common Redwood ; they should be reasonably straight and well sawn. * American Telegraph & Telephone Co. Specification. [131] Sec. 2 WOOD POLES Dimensions. The dimensions of the poles shall be in accordance with the following table: A B Length in Feet. Top. Butt. Top. Butt. 24 6' x6' 6" 6" 4 x 6' 4' x 6" 25 7' x7' 10" 10" 6 x 6' 9' x9" 30 7' x7' 11" 11" 6 x6' 10' x 10" 35 T x7' 12" 12" 6 x 6' 11' x 11" 40 r x7' 13" 13" 6 xfi' 12' x 12" 45 T x7' 14" 14" 6 x 6' 13' x 13" 50 r x 7' 15" 15^" 6 x6' 14' x 14" The sectional dimensions of the sawn poles shall not be more than one-quarter (24) of an inch under or three quarters (%) of an inch over the dimensions specified in the above table. No pole shall be more than three inches longer or shorter than the lengths required in the above table. Sap wood. No pole shall have sapwood covering more than four (4) percent of the area of all the surfaces. No pole shall have sapwood for a distance of more than eight (8) feet from the top. No sapwood shall be deeper than one (1) inch at any point. Plugged Holes. No poles shall contain plugged holes. Cracked Poles. No pole shall contain cracks transverse to the length of the pole. Checked Poles. No pole shall contain large season checks. Wind Shakes. No pole shall contain wind shakes including in excess of ten (10) percent of the area of the butt. Knots. No pole shall contain loose, hollow, or rotten knots, black or red knots shall be carefully examined for internal rot. In 4" x 6" poles sound knots with a diameter smaller than one (1) inch may be present in any number. No 4" x 6" pole shall be accepted which contains more than one sound knot in each five superficial feet having a diameter of one (1) inch or more, or which contains any knots with a diameter greater than one and one half (\y 2 ) inch. In all other sizes of poles covered by these specifications sound knots with a diameter smaller than one and one half (1 1 A) inches may be present in any number. No pole shall be accepted which contains more than one sound knot in each five superficial feet having a diameter of one and one half (1^) inches or more, or which contains any knots of a diameter greater than two and one-half (23/0 inches. NOTE: Where diameters are specified in connection with knots the knot shall be rated on the basis of its average diam- eter. I 132] WOOD POLES Sec. 2 20. SPECIFICATION FOR YELLOW PINE POLES* Quality of Timber. All poles shall be cut from the best quality of live, straight grained, unbled, long leaf yellow pine. The butt end shall be squared and the top end pointed to an angle of 45 degrees. The poles shall be sawed octagonal in shape and shall be dressed, with the heart running parallel to the line of the pole. The timber shall be free of decayed or loose knots or clusters of small knots. * Classification and Dimensions. Poles shall be classified accord- ing to their butt dimensions into two classes, to be known as Class "A" poles and Class "B" poles, with dimensions for the respective classes as specified in the following table. Where "top" measure- ment is specified it shall be the diameter at the top of the pole and where "butt" measurement is specified it shall be at the dia- meter of the butt end of the pole. Inspection and Rejection. All poles shall be subject to inspection by the purchaser's representative, either in the woods where the trees are felled, or at any point of shipment, or destination. Each pole thus inspected shall be marked according to its length and class with a marking hammer, by the purchaser's representative. All poles failing to meet these specifications shall be rejected. DIMENSIONS OF POLES IN INCHES (DIAMETER) Length of Poles. (Feet.) CLASSES. A B Top. Butt End. Top. Butt End. 30 8 11 7 10 35 8 12 7 11 40 8 13 7 12 45 8 14 7 12 50 8 15 7 13 55 8 16 7 14 60 8 17 65 8 18 * National Electric Light Association Specification. [ 133 ] Sec. 2 WOOD POLES 21. SPECIFICATIONS FOR CREOSOTED YELLOW PINE POLES.* These specifications are for Class A, B and C poles of Southern Yellow Pine treated with Dead Oil of Coal Tar. Quality of Poles. All poles shall be sound southern yellow pine (longleaf, shortleaf, or loblolly yellow pine,) squared at the butt, reasonably straight, well proportioned from butt to top, peeled and with knots trimmed close. All pales shall be free from large or decayed knots. All poles shall be cut from live timber. It is desired that all poles be well air seasoned before treatment and such poles shall be treated in accordance with the requirements for treating seasoned timber contained in the "Specifications for Creosoting Timber" referred to in Section 9. The poles shall not be held for seasoning, however, up to the point where local experi- ence shows that sap-wood decay would begin. Unseasoned poles shall be treated in accordance with the requirements for treating unseasoned timber contained in the above mentioned specifications. All poles shall be sufficiently free from adhering "inner bark" before treatment to permit the penetration of the oil. If the "inner bark" is not satisfactorily removed when the pole is peeled, the pole shall either be shaved, or be allowed to season until the "inner bark" cracks and tends to peel off of the surface of the pole. Dimensions. The dimensions of the poles shall not be less than those given in the following table: DIMENSIONS OF POLES IN INCHES (CIRCUMFERENCE). Class A Class B Class C Length of Poles (Feet.) 6' from Butt. 6' from Butt. 6' from Butt. 25 33 30 28H 30 35 32 3fli 2 35 38 34 32 40 40 36 34 45 42H 38 36 50 44H 40 38 55 47 42H 40 60 49 44^ 42 65 51 47 44 70 53 49 46 75 55 51 80 57 No class A poles having a top circumference of less than 22 inches will be accepted. * American Telephone & Telegraph Co. Specification. [ 134] CONCRETE POLES Sec. 2 No class B poles having a top circumference of less than 20 inches will be accepted. No class C poles having a top circumference of less than 18 inches will be accepted. Framing of Poles. Before the poles are subjected to the creosoting process they shall be framed, unless otherwise ordered, in the fol- lowing manner and as shown in drawing No. . The tops of all poles shall be roofed at an angle of ninety (90) degrees. All class A poles shall have eight (8) gains, all class B poles shall have four (4) gains and all class C poles shall have two (2) gains. The gains shall be located on the side of the pole with the greatest curvature, and on the convex side of the curve. The faces of all gains shall be parallel. Each gain shall be four and one-half (4 J/0 inches wide and one-half (Yi) inch deep, spaced twenty-four (24) inches on centers. The center of the top gain shall be twelve (12) inches from the apex of the gable. A twenty-one thirty-second (f|) inch hole shall be bored through the pole at the center of each gain perpendicular to the plane of the gain. Inspection. The quantity of dead oil of coal tar forced into the poles shall be determined by tank measurements, and by observing the depth of penetration of the oil into the pole. In the case of poles having a growth of sapwood not less than one and one-half (1J/6) inches in thickness, the depth of penetration shall be not less than one and one-half (1^2) inches. In the case of poles having a growth of sapwood less than one and one-half (1J^) inches in thick- ness, the dead oil or coal tar shall penetrate through the sapwood and into the heartwood. Depth of penetration shall be determined by boring the pole with a one (1) inch auger. The right is reserved to bore, for this purpose, two holes at random about the circumference, one hole (5) five feet from the butt and one hole ten (10) feet from the top. After inspection each bore hole shall be first filled with hot dead oil of coal tar, and then with a close fitting creosoted wooden plug. The rejection of any pole on the score of insufficient penetration shall not preclude its being retreated and again offered for in- spection. REINFORCED CONCRETE POLES. 22. General. Reinforced Concrete poles are divided into two general classes, the solid and the hollow type; the latter type serves a two fold purpose of decreasing the weight of the pole and providing a means for making connections through the pole from aerial lines to underground cable. The solid type has been used to the greatest extent in the United States, the probable reason being that this type is more easily made. In the casting of concrete poles horizontal forms are generally employed, although in several instances poles have been cast in position in vertical forms. The forms for casting poles (the types of which, are illustrated in [ 135 ] Sec. 2 CONCRETE POLES Figs. 34 and 35), generally consist of tapered troughs of wood or steel of the desired form, so constructed that the sides can be removed after the concrete has set. The general requirements, of a form for concrete poles, are the same as for any other kind of concrete work where the forms are to be used repeatedly. The material should be such that there will be no warping and the construction should be such that there will be no leakage when using sloppy concrete, no bulging of the sides when filled, and that it will be sufficiently rigid to retain its shape with ordinary handling. In general, a square, octagonal, circular or other cross-section may be used, but it is desirable as a matter of appearance, since sharp corners are difficult to make and subject to accident, that all such corners be chamfered or rounded. The minimum diameter, or width, at the top may be made 5 or 6 inches for small poles, and increased as required for the strength and appearance of long poles, or poles carrying a heavy line. In any case, care should be exercised, in determining the taper and reinforcement, that no weak section occurs at some distance above the ground-level. 23. Steel Reinforcing (Fig. 36.) When steel is embedded in well- made concrete its preservation is perfect, and the life of a reinforced monolith is practically indefinite. If designed and built with the same attention now given other materials, reinforced concrete poles should attain the necessary strength and give satisfactory service. The present practice differs rather widely as to the most economical or most desirable distribution of reinforcement. It is now generally conceded, in reinforced concrete work, that the finer the distribu- tion of metal, the greater the homogenity and strength of the con- struction. However, in the case of poles where the concrete is deposited within narrow forms, other conditions partly modify or control the distribution. In construction, such as concrete poles or other work, in which there is a relatively large and important amount of reinforcing, great care must be exercised to thoroughly tamp or puddle the con- crete as it is deposited, in order to prevent pockets, and to insure every lineal inch of metal having a firm adherence to the concrete. In such structures, the increase in stress in the reinforcement must be very rapid, and the additions of stress are dependent upon the efficiency of the connection between the steel and the concrete. Mechanical bond or deformed bars, i. e. twisted squares or bars with various projections in their surfaces are superior to smooth bars for work in which high stresses must be developed in short lengths. Rods may often be bent into hooks or clamped together to advantage. Reinforcing metal may be either medium grade steel with an ultimate strength of 60,000 to 70,000 pounds per square inch and an elastic limit of 30,000 to 40,000 pounds per square inch and capable of being bent cold about its own diameter, or it may be high carbon steel with an ultimate strength of 80,000 to 100,000 pounds per square inch, and an elastic limit of 40,000 to 60,000 pounds per [ 136] CONCRETE POLES Sec. 2 square inch, and capable of being bent cold about a radius equal to four times the diameter of the rod. Since the elastic limits of these two grades of material are quite different, they will have a very marked effect upon the design and there will be no similarity between two poles of the same dimensions and reinforcement in which different grade rods are used. Owing to the fact that in a [137] Sec. 2 CONCRETE POLES [ 138] CONCRETE POLES Sec. 2 pole the stresses in the reinforcement must change rapidly in amount with every lineal foot of the pole, it is most essential, at least for high strength poles, to use mechanical bond or twisted bars. It is also necessary to provide diagonal or spiral reinforcing when poles are to be subjected to torsion, although the close spacing of horizontal ties will be of assistance. The horizontal ties are needed primarily to restrain the rods from local buckling with consequent spalling off of concrete. The rods should be tied to the horizontal straps or other secondary system at each intersection, in order to assist in developing bond stress. In view of the character of service to FIG. 36. Steel reinforcement for solid concrete pole and cross-arm. which horizontal bands or spacers are subjected, the use of cast rings or bands is inadvisable. 24. Concrete Mixture. The most commonly used mixture is 1:2:4 Portland Cement, sand, and broken stone or gravel. It should be mixed wet, using carefully selected materials and tamped or churned to eliminate air-bubbles, obtain a good surface, and thorough contact with the reinforcement. Such a mixture when well made has an average compressive strength of about 900 pounds per square inch in seven days, 2400 pounds per square inch in one month, 3100 pounds pel square inch in three months and 4400 pounds per square inch in six months. If conditions make it desirable to [ 139 1 Sec. 2 CONCRETE POLES use high working stresses, a month or more should elapse before new poles undergo severe tests. 25. Molding Pole. The bolt holes and step bolt sockets must be cast in place during the concreting. Hardwood blocks may be used for step bolts, although a cast or spiral socket is preferable. No attempt should be made to remove the forms until the concrete has obtained a good set, and care must be exercised to prevent injury FIG. 37. Illustrating flexibility of concrete poles. to the surfaces during such removal. The forms should be kept covered during setting, particularly when exposed to direct sunlight in hot weather, and the concrete pole should be well sprinkled and kept under canvass for some days after the forms have been removed. A freshly made concrete pole cannot be handled or rolled with im- punity until it has become.well set. Further, the subsequent han- dling, particularly of long poles, must be done with care, and is pref- [ 140 ] CONCRETE POLES Sec. 2 erably done by slings attached at two separate points. Plastering the surface of poles to remove pockets or to produce a finished surface is particularly objectionable. The former should be avoided by proper workmanship, and the latter is unnecessary since a very fine surface can readily be produced by rubbing. If we may judge by the kind of handling which concrete poles successfully withstand, it would seem entirely probable that con- crete poles, if properly reinforced, will survive any shocks incident to ordinary service. When subjected to any overload or accidental shock, a timber pole will bend and in some cases survive; but failure, when it does occur, is usually complete, and the pole falls. FIG. 38. Hollow concrete poles manufactured by the Centrifugal Process. Concrete poles on the contrary, while without the elasticity of timber, do not fall by breaking off, but are held by the reinforcement from falling to the ground. Tests also show that a reasonable amount of bending (sufficient for the balancing of stresses in the wires) can occur without apparent injury to the pole. (Fig. 37.) 26. Hollow Concrete Poles have been used quite extensively in Europe. Their manufacture is usually a machine process, there being two general methods employed. The first method is the centrifugal. (Fig. 38.) This process consists in manufacturing poles in revolving forms by centrifugal force. A wet mixture of rich concrete is placed in a tubular form, inside which the reinforcement metal has been fastened, and revolved at high speed. It is claimed that the centrifugal [141] Sec. 2 CONCRETE POLES action forces the concrete to an even thickness against the reinforce- ment, the operation taking place in a warm room and occupying but a few minutes. These hollow poles when set have the butts filled with stones to the ground line. In the second method an interior form or mandrel is used instead of an exterior shell as in the centrifugal process, and after fitting the steel reinforcement on this, a fairly dry mixture of concrete is mechanically plastered, on the revolving mandrel in a narrow con- tinuous belt, by means of a combination of conveyor and wrapping of canvas under tension, wound spirally the length of the pole. It is claimed that both this and the centrifugal process have given very satisfactory results in Europe. FIG. 39. Hand-made hollow concrete pole (collapsible core.) Hollow concrete poles have been made by hand in this country, in which the core is made collapsible and is removed as soon as the concrete has set sufficiently to bear its own weight. (Fig. 39.) Another method consists in molding poles in forms similar to those used for solid poles. When the mold is about orie-third poured, a hollow, conical galvanized iron core is inserted in the mold and the remainder of the concrete and reinforcement is put in place. The core is wrapped loosely with a spiral of building paper, which facilitates the removal of the core after the concrete has set. The poles are constructed in a horizontal position and reinforced with four, six and eight bars, as desired. The top of the mold is left op?n for pouring the concrete and when it is filled the concrete is tamped down and troweled off smooth. [142] CONCRETE POLES Sec. 2 [143] Sec. 2 CONCRETE POLES When the form is filled, the concrete is allowed to set for several hours; the core is then partially removed and the pole is allowed to set from twenty-four to forty-eight hours longer. The pole is cured by wetting it thoroughly each day for twenty-five to thirty days. It is an established fact that satisfactory concrete poles can be made and are now in service. The only consideration would seem FIG. 43. Steel pole 30 feet high. to be that of mechanical efficiency and actual cost. The question of mechanical efficiency is in reality combined with that of cost. Concrete poles have been built at a low original cost, but with an equally low mechanical efficiency, while others have been built at excessive cost and excessive strength. Neither extreme is good engineering or good economics. The successful concrete pole must be one that has a strength at least comparable with a Class "A" STEEL POLES Sec. 2 wood pole, the cost of which, including maintenance, replacement, etc. when considered for a term of years, will be not more than that of an equally satisfactory wood pole. FIG. 44. Double circuit three-phase 60,000 volt steel pole. 27. STEEL POLES AND TOWERS Steel poles and towers may be divided into five general classes: (a) Patented Poles. (Art. 28.) (b) Tubular Steel Poles. (Art, 29.) (c) Latticed Structural Steel Poles. (Art, 30.) (d) Structural Steel Towers. (Art. 31.) (e) Flexible Frames. (Art. 32.) [145] Sec. 2 STEEL POLES iii SSSS5 05 W M CO COM 10 W h-l tf m SSSsS 3 [146] STEEL POLES Sec. 2 28. Patented Steel Poles are manufactured by a number of companies and can be secured in various heights. The design varies considerably out the manufacturers of such poles furnish data on their strength, from which data calculations can be made, enabling the computation of safe working loads. 29. Tubular Steel Poles are standardized by steel tube manu- facturers. Their use is confined chiefly to trolley construction and FIG. 45. Single circuit three-phase 30,000 volt steel pole. FIG. 46. Guyed Bteel pole, 13,200 volts. to supports for street lighting units. Such poles are made of two, three, four or more different lengths of standard or special steel tubing of various sizes and it is advisable, when ordering such poles, to confine the selection to standard sections, for in such standard poles the length of the various sections have been selected so that their manufacture results in a minimum waste of material. [1471 Sec. 2 STEEL POLES Table No. 5, on page 143, has been compiled from data pub- lished by a manufacturer and gives the extreme weights (light and heavy) and the respective strength of standard tubular steel poles of the two, three and four section type in lengths of from 22 feet to 40 feet. 30. Structural Steel Poles and Towers are in general specially designed for the particular conditions of the line in question. FIG. 47. Double circuft three-phase steel pole. FIG. 48. Single circuit three-phase steel pole. Their design is so diversified and is dependent on such a variety of conditions that the subject cannot be covered in detail, also such poles are usually purchased through designing engineers, and, there- fore, only the important features of design will be discussed. If a given line is to be designed in a logical manner and with a minimum of cut and try methods, an assumption of the various [148] STEEL POLES Sec. 2 loads and the /desired factors of safety must be made. Such assump- tions will enable the designer to mentally predetermine, to some extent, the general nature of the supports, or at least to narrow the field of choice. These assumptions are based primarily on the weight of the con- ductor plus the assumed ice and wind load, in addition to which it Fie. 49. Double circuit narrow base flexible steel frame three-phase 60,000 volts. FIG. 50. Double circuit narrow base flexible steel frame three-phase 44,000 volts. is sometimes specified that the structure must care for one or more broken wires under the assumed loaded conditions. In some instances the test loads -which sample towers or poles must withstand are specified. Unfortunately for the entire success of this procedure the test load is very rarely an accurate representa- tion of the possible maximum, nor is the condition of the test struc- ture similar to that of many of the structures as installed. Test [149] Sec. 2 STEEL POLES loads are almost always applied regularly and slowly; and in many cases uneccentrically. The test structure will have at least a fairly good foundation and be composed of members free from incipient bends or other effects of mishandling. It would also be very well bolted together and plumbed with greater accuracy than the average line structure. In general, it may be said that an expert structural Fia. 51. Single circuit three-phase steel "A" frame 60,000 volts. ' FIG. 52. Single circuit three-phase steel "A" frame 60,000 volts. assembler should be able to obtain test loads quite noticeably in excess of the presumptive average strength of the finally erected structures. It would seem, moreover, that the period of usefulness of this practice is past, and that competent designers should be able to produce structures having an actual strength much nearer their predetermined strength, than the actual loads will be to the assumed loads. [150] STEEL POLES Sec. 2 The failure of a steel pole or tower will almost invariably be due to the buckling of a main compression member and this may or may not be superinduced by inefficient bracing. Owing to the possible application of the load from the opposite side of the structure, line supports must have the same main compression section at each corner, regardless of the tension stress. The compression stress per FIG. 53. Double circuit three-phase steel "A" frame 35,000 volts. square .inch in the main legs is, therefore, the first and most im- portant determination. A secondary condition to be borne in mind during the foregoing calculations is that the selected section must be of a size suitable for the connection of the desired bracing. A long slender member is not well adapted to take compression and it has been customary in other work to limit the relation of the length to the radius of gyration. In transmission line construc- [ 151] Sec. 2 STEEL POLES tion very much higher values of this ratio have been used than are generally permitted in other work. It is probably not necessary to adhere to the low limits of building construction, but it is equally prob- able that in some cases heretofore, too much latitude has been taken. Inasmuch as the strength of the main leg members of the pole FIG. 54. Double circuit three-phase steel "A" frames. or tower, as well as most of the bracing, is predicated upon their strength as compression members, the most important requirement of a specification next to the broken wire condition, is the formula for compression members known as the column formula. Unfortunately, the many column formulae in existence are stated in terms of safe working unit stresses, which renders them, unless [152] STEEL POLES Sec. 2 \ [153] Sec. 2 STEEL POLES their factor of safety is known, almost valueless to the inexpert transmission line designer. This is due to the fact that in general, in transmission line construction, it is the ultimate or breaking strength that is to be determined in order that a specified factor of safety may be applied thereto. In pole and tower design, the compression members are simple in FIG. 56. Single circuit three-phase steel tower 50 feet high for 66,000 volts. FIG. 57. Double circuit three-phase steel tower, 50 feet high, for 66,000 volts. type, usually single angles with relatively large ratios of the un- supported length to the radius of gyration i. e. ;. Failure occurs when such members buckle, as the structure becomes distorted and useless, though it may not fall to the ground. It is readily apparent that any incipient bends in such columns will very markedly affect the theoretical compressive strength. In addition, it is quite pos- sible to select sections such as 4" x 4" x J" angles, or example, whose theoretical strength exceeds their actual strength. This s [154] STEEL POLES Sec. 2 due to the fact that in such large thin sections, failure may start by the local buckling of the legs of the angle. The function of lacing is to stiffen the connected members by reducing the unsupported length of the compression section and also to transmit shearing stresses. If the shear is relatively large, the limiting condition may be the number of rivets connecting the FIG. 5S. Double circuit steel corner tower, 40 feet high. lattice to the main section, otherwise it will be the stiffness of the lattice bar itself; that is, the lattice is a compression member whose strength depends upon its ratio of stiffness or 7. Since the minimum radius of gyration, of a flat section or bar is much smaller than that of an angle, the unsupported length of the former must be less. Again flat lacing is more subject to accidental injury than angle lacing because a slight bend in the direction of the thickness may [155] Sec. 2 STEEL POLES easily occur and make the theoretical compressive strength neg- ligible. When double lacing is used, some reduction in effective length may be assumed as provided by the connection at the intersection. In the case of flat lacing, however, it is not proper to assume the FIG. 59. Double circuit steel tower, 40 feet high. effective length as the distance from the end hole to the intersection. Owing to the larger value of the radius of gyration of an angle sec- tion, as compared with a flat section, the former allows a consider- able increase in the width of the main members with less material in the lacing. Apart from the avoidance of excessive inclinations, the available angle section may depend upon the size of the bolt needed to transmit stress, or if the lacing is turned in, on the per- missible end and edge distances. [ 156 ] STEEL POLES Sec. 2 The bracing of secondary members, if they are not liable to accidental injury or torsion, may properly be allowed larger ratios than that of main compression members which, from their position, may be subject to both. The horizontal flanges of horizontal or inclined angles should FIG. 60. Double circuit steel corner towers. always be turned up, as this position drains and drys quickly and does not collect dirt or hold water. Similar reasoning will prohibit the use of any closed pockets or semi-closed pockets anywhere in [157] Sec. 2 STEEL POLES the structure, as they are certain to become clogged with refuse and filled with water. Since moisture is a necessary condition of all decay and corrosion, rapid and thorough drainage are prime req- uisites of a good design whether the material be timber or steel. One bolt connections should be prohibited in the main bracing system of wide base towers, except possibly for the connection of FIG. 61. Single circuit steel anchor tower at corner, 150,000 volts. such secondary members as sub-panel struts, whose sole function is to reduce the unsupported length of another member. Square latticed structural steel poles may be of any width from the true narrow base poles used along curb lines to the wide base poles which are in reality towers. There is no fixed dividing line [158] STEEL POLES Sec. 2 between a pole and a tower, unless it be that of strength and rigidity, or possibly the use of widths which preclude shop riveting and ship- ment assembled. The greater number of the structual steel poles used are square in cross-section, one angle at each corner, and are assembled and riveted before shipment. In the case of long poles, it will frequently be found advantageous to ship in two sections and bolt them together in the field. There is no reasonable objection to the use of such field bolts, provided a splice is used of sufficient length and strength. The splice angle can be made an interior splice, with the root of the angle ground to fit the fillet of the main legs and thus be comparatively unobstrusive in the final appearance of the pole. Several types of poles are in use, the most common being those with a regular taper or those with parallel legs. Parabolic slopes have been used and they present a very graceful appearance under favorable conditions, although the rapid increase in width for longer poles may result in an inconvenient spread at the ground line. The design of square latticed poles resolves itself into a determina- tion of the stresses at the ground line or rather in the first panel above ground. This statement is based upon the assumption that owing to the adoption of greater top widths than in wood poles, the upper portion of the pole has an excess width as compared with the lowest panel. It is further predicated upon there being no attempt made to seriously reduce the sections of the material in the upper half. In the case of parabolic slopes, stress determinations must be made at various heights since the widths presumably follow, more or less closely, the changes in bending moment and the weakest section may be anywhere. Owing to the more rigid form of the frame, the breaking strength per unit of area in a pole will exceed that in a wide base tower. Again, since the main legs have little inclination, the web system is compelled to carry the shearing stresses, which in a tower are partly carried by the main legs. For these reasons, the web or lattice is more often limited by the strength required than in the bracing of a wide tower. The shearing stress must, therefore, be computed and the lattice and its connection to the main legs be designed accordingly. Single flat lacing should not be used except for small stresses and in narrow widths, since, as previously stated, its strength is low and it is subject to injury. Double flat lacing is appliable to greater stresses and widths, but is often not as economical as angle lacing. In any case the strength of the pole depends upon the unit strength of the weakest unsupported length, which is usually the lowest panel, but may be the entire pole if the width is small and the height great. That is, the ^ of the entire cross-section of the pole may be greater than that of an individual panel. The char- acter and spacing of the lattice will determine to a large extent the amount of support afforded by it to the main leg angles at the panel joints. When the lacing connects to both faces of the pole at the [159] Sec. 2 STEEL POLES elevation, the unsupported length of main leg is the distance between panel joints. If, however, the lacing is staggered, so that the support is in one direction only at each panel point, the unsupported length of main leg is somewhere between a half and a whole panel length. 31. Flexible Towers. Assuming that a reasonable amount of skill has been employed in the selection of spans, heights and main FIG. 62. Steel tower at river crossing. section, the most important provisions for an adequate A frame line are the installation of an overhead ground wire and substantial foundations. The ground wire, which should be of considerable strength, may properly be given a little less sag that the conductors, thus acting as a continuous head guy, the usefulness of which can hardly be overestimated. In fact, it is extremely difficult to string [160] STEEL POLES Sec. 2 the power cables unless there is a ground wire in place to steady the frame. The conditions which promote buckling are not very clearly understood, or rather their limits are not definitely known. If the main channels are assumed to be of absolutely identical material and the base of the foundation is firm and unyielding, some degree FIG. 63. Double circuit three-phase steel corner tower, 50 feet high, for 66,000 volts. of difference in the latteral support at the ground line, or of the rigidity of the bracing connections, may allow sufficient deflection to start the buckling. As the failure is a compressive failure in a relatively long column, any measures which restrain such a column from moving sideways at any point will be of effective service. Thus a comparatively long stiff connection of the bracing to the 6 [ 161 ] Sec. 2 STEEL POLES main legs is useful as it stiffens this column locally. Such connec- tions, therefore, should never be of less than two rivets and pref- erably of not less than 6" in length. Further, the diagonal braces should not have any slack and, if made of rods or adjustable members, should be tightened as near equally as possible. FIG. 64. River crossing steel tower, 169 feet high. The present tendency is toward the use of galvanized ground stub angles, whether the superstructure is painted or galvanized and with either concrete or earth back filling. Galvanizing such mem- bers is a relatively inexpensive operation and they can be painted over the galvanizing at the ground line. No reduction of section on account of the protective coating should be made in the ground stubs. [162] STEEL POLES Sec. 2 Typical structural steel poles, towers and flexible frames are illustrated in Figs. 43 to 65. 32. Outdoor Substations. Outdoor transformer and switching substations vary in design from the simple transformer supported FIG. 65. Double circuit river crossing, three-phase, 66,000 volts, 2,000 feet span on wood poles to the more complex steel structures supporting switches and transformers of large capacity. A number of types are illustrated in Figs. 66 to 76. [163] Sec. 2 SUB-STATIONS FIG. 66. Outdoor sub-station, three-phase 3-2000 kv-a transformers, 101,100 volts to 13,200 volts, 60 cycles. FIG. 67. Outdoor sub-station, three-phase, 33,000 volts, illustrating air- break switches and lightning protection devices. [ 164] SUB-STATIONS Sec. 2 FIG. 68. Outdoor sub-station, three-phase, 150,000 volts to 33,000 volts, 60 cycles. FIG. 69. Outdoor sectionalizing and branch tower, three-phase, 66,000 volts. [165] Sec. 2 SUB-STATIONS g SUB-STATIONS Sec. 2 [167] Sec. 2 SUB-STATIONS [ 168 ] SUB-STATIONS Sec. 2 FIG. 76. Steel outdoor sub-station for 33,000 volts. 1, 2 and 3 are jib cranes for handling transformers A, B, and C, respectively. BIBLIOGRAPHY. United States Government Reports. N. E. L. A. Publications. Electrical World. Current News, Philadelphia Electric Company. American Telephone and Telegraph Company. Transmission Line Construction, Lundquist. Publications of Various Manufacturers. [169] SECTION 3 CONDUCTORS AND WIRE TABLES SECTION 3 CONDUCTORS AND WIRE TABLES TABLE OF CONTENTS Production and Refining of Conductor Material Copper ores and their reduction 1 Aluminum ores and their reduction 2 Iron and steel ores and their reduction 3 Copper Clad Wire 4 Manufacture of Wire Working Ingots 5 Wire Drawing 6 Weatherproofing 7 Rubber Insulation 8 Application of Rubber Compound 9 Vulcanizing 10 Protection of Insulation 11 Physical Characteristics 12 Tables 6 to 10 inclusive. Units of Resistance 13 Table 11. Specific Resistance 14 Specific Conductivity 15 Percentage Conductivity 16 Matthiessen's Standard of Conductivity 17 Table 12. Specific Resistance, Relative Resistance and Relative Conduc- tivity of Conductors, 18 Table 13. Temperature Coefticient 19 Table 14. Table 15. Table 16. American Steel and Wire Gauge 20 Brown and Sharpe Gauge 21 Birmingham Gauge 22 [173] Sec. 3 CONDUCTORS AND WIRE TABLES ARTICLE Comparison of Wire Gauges 23 Table 17. Law of the Brown and Sharpe Gauge 24 Table 18. Wire Strands 25 Table 19. Illustrations of Bare Wire, Strand and Cable 26 Heating Effects of Current 27 Table 20. Table 21. Fig. 77. Table 22. Table 23. Table 24. Effective Resistance 28 Table 25. Figs. 78-81 inclusive. Explanation Guy Wire 29 Table 26. Extra Galvanized Special Strands 30 Table 27. Table 28. Copper, Aluminum, Copper Clad and Iron Wire Tables Total Pounds Pull Required to Break Wire Solid wire Table 29. Stranded wire Table 30. Diameters of Wires, Bare and T.B.W. Solid wire Table 31. Stranded wire Table 32. Weights of Wires, Bare and T.B.W. Solid wire Table 33. Stranded wire Table 34. Resistance of Wires Solid wire Table 35. Stranded wire Table 36. Self-inductance Solid wire Table 37. Stranded wire Table 38. [174] CONDUCTORS AND WIRE TABLES Sec. 3 Capacity ARTICLE Solid wire Table 39. Stranded wire Table 40. Inductive Reactance Solid wire, 25 cycles Table 41. Solid wire, 60 cycles Table 42. Solid wire, 100 cycles Table 43. Stranded wire, 25 cycles Table 44. Stranded wire, 60 cycles Table 45. Stranded wire, 100 cycles Table 46. Charging Current Solid wire, 25 cycles Table 47. Solid wire, 60 cycles Table 48. Solid wire, 100 cycles Table 49. Stranded wire, 25 cycles Table 50. Stranded wire, 60 cycles Table 51. Stranded wire, 100 cycles Table 52. Stranded Aluminum Wire Equal in Conductivity to Copper Table 53. Correction for Internal Inductance of Copper Clad Wire 31 Figs. 84-87 inclusive. Average Track Resistance Table 54. Specifications Specifications for Galvanized Steel Strand 32 Specifications for Copper Wire and Cables with Weather Proof Insulation 33 Specifications for Bare Hard Drawn Copper Wire and Strand 34 Specifications for Hard Drawn Copper Clad Steel Wire 35 Specifications for Aluminum Wires and Cables, Weatherproof Insulation 36 Specifications for Bare Aluminum Wire 37 Specifications for Rubber Insulated Tree Wire Braided 38 Specifications for Circular Loom Covered Tree Wire . . 39 [175] CONDUCTORS AND WIRE TABLES In the section following, data are compiled on conductors and conductor material, in which some general information is given on the production and refining of the conductor material and also a brief description of wire drawing and insulating. These data have been collected with the cooperation of various wire manufacturers. A comparison of the diameters, weights, strengths, etc., of the various sizes of wire, as produced by different manufacturers, indicated certain discrepancies and therefore, it was necessary to confine the data on any particular wire material to that furnished by one manufacturer. These discrepancies were slight, however, and the tables given herein will be found sufficiently accurate to apply to any standard product which may be purchased. The tables have been compiled in a form thought to be most con- ducive to rapid calculation and contain only such wire sizes as are considered standard. PRODUCTION AND REFINING OF CONDUCTOR MATERIALS 1. Copper. Copper ores occur in many and various forms in widely distributed localities. In the United States there are three localities in which the copper mineralization is of considerable magni- tude. Approximately 95 percent of the total copper ore of the country is mined in the Lake Superior, Rocky and Sierra Nevada Mountain regions. The copper bearing rocks in the Lake district are very distinctly stratified beds of trap, sandstone and conglomerates which rise at an angle of about 45 degrees from the horizontal sandstone which forms the basin of Lake Superior. One peninsula extending into the Lake has developed copper in profitable amounts, almost chem- ically pure. The amount of copper in the ore as mined averages about 3 per- cent, the balance being rock, which is intimately mixed with the metal. The ore is first subjected to a mechanical process whereby the metal is concentrated into a small bulk and the rock rejected. "Lake" copper is so pure that final melting without refining is practicable. The deposits in the Rocky Mountains and in the Sierra Nevadas show all phases of formation from the original unaltered sulphide deposits to the most highly altered oxides and carbonates. A Sulphide ore is an ore in which copper appears in chemical combination with sulphur and in some cases is first roasted or heated so that the sulphur is burned off, leaving the copper and iron, which is usually present, in an oxidized or burned form. In another process the raw unroasted ore is thrown into a furnace, the sulphur itself burned and made to smelt the mass, producing, on account of its chemical nature, a highly impure, yet very valuable, compound [177] Sec. 3 CONDUCTORS AND WIRE TABLES with iron and sulphur, called matte. This matte, which is about half copper, is poured from the furnace into a converter and the iron and sulphur are burned out, by blowing through great volumes of air. The result of this operation is blister copper, so called, on ac- count of the blistered appearance of the surface caused by the quantities of gases absorbed by the metal. If copper ore occurs in an oxidized or carbonate form, or roasted ore is used, a blast furnace is also utilized for the reduction. Oxi- dized or sulphide ores are also often mixed and the matte is blown. Blister copper contains about 99 percent of copper, which is not, however, pure enough for use as a conductor material. If a suffi- cient amount of precious metal is contained in it, the electrolytic refining process is used, by which method the blister copper is dis- solved and the chemically pure copper separated from the impurities and other metals. The blister copper or electrolytic copper is then charged iAto a refining furnace and melted by means of a very pure fuel. The furnace is a simple bowl shaped hearth, covered and provided with doors for skimming and stirring. After the metal is quickly melted and the last traces of sulphur have been removed by combination with the oxygen from the flame, the process known as rabbling or flapping is begun. This is a violent agitation of the metal through one of the side doors, by means of small rabbles or pokers. During the flapping, samples are frequently taken in a hemispherical mould about an inch in diameter. When the set or appearance of the solidified metal in this mould indicates that sufficient work has been done upon it, the surplus oxygen is removed in order to prevent extreme brittleness and the lack of conductivity incident to an over- oxidized metal. This is done by poling the bath. A large stick of green hardwood is introduced into the bath, which burns and the metal is violently agitated by the gas driven off. The surface of the bath is covered with charcoal to prevent further oxidation, and samples are very frequently taken. This is continued until the test piece shows tough pitch or the removal of the excess of oxygen, and that the metal is in its toughest condition. This tough pitch con- dition is essential for the requirements of rolling and wire drawing, as copper in this state possesses the highest degree of conductivity and is of an extremely tough and ductile nature. The metal is then poured into ingot-moulds or wire bars, in which form it goes to the wire manufacturer. 2. Aluminum. Although aluminum is a component part of a very large portion of the earth's crust, forming an essential part of all granites, gneisses, clays and other very numerous and complex silicates, there are very few natural compounds of aluminum which are suitable for use as ores for the production of the pure metal. The only compound at present used, from which aluminum is pro- duced, is bauxite, which is hydrated aluminum oxide with oxides of iron, silicon and titanium as impurities. Ordinary clays are so high in silicon that the separation of the aluminum from the silicon is [178] CONDUCTORS AND WIRE TABLES Sec. 3 extremely difficult. More or less extensive deposits of bauxite are found in Arkansas, Georgia, France, Ireland and in a few other places. Before bauxite can be subjected to the smelting process, it must be refined and purified to remove from it the last possible trace of silicon, iron and titanium, water and other impurities, which may be present in it as mined. Since there is no method available for the further purification of aluminum when once it has been obtained in the metallic state, its purity depends almost entirely upon the purity of the ore used. The bauxite is .therefore put through an elaborate chemical process, as a result of which it is delivered to the ore reduction plants in the form of practically chemically pure aluminum oxide, or alumina. This pure alumina is then subjected to the smelting or reduction process, which is purely electrochemical in its nature. This is carried on in large rectangular iron tanks or pots, which are thickly lined with carbon which also serves as one electrode for the very heavy electric current required. The other electrode consists of a group of cylindrical carbons suspended above and serving to lead the current into the tank or pot. The details of the reduction process vary slightly at different plants, but fundamentally the processes are all the same and con- sist of the electrolytic decomposition of alumina. The alumina so electrolysed is first dissolved in a flux or fused bath of a suitable aluminum salt, which is maintained in a molten condition by the joulean heat of the current passing through the pot. The alumina (aluminum oxide) thus carried in solution is broken up into metallic aluminum and oxygen. The metallic aluminum, which collects at the bottom of the pots, is tapped off at stated intervals and the oxygen combines with the carbon electrode forming carbon dioxide. In order to produce aluminum of a purity sufficient for electrical conductor purposes, only the purest ore can be used and at all stages of the process great care must be exercised to avoid the introduction of impurities into the metal. The extra pure metal so obtained, after being analyzed and classified according to purity, is sent to the smelting furnaces, where it is carefully melted in large open hearth furnaces and cast into wire bars, in which form it goes to the wire manufacturer. 3. Iron and Steel. The distribution of iron ores follows in a gen- eral way those of copper statistics showing that the states of Michi- gan, Wisconsin and Minnesota produce about 80 percent of the total ore mined in the United States. The southern states, Alabama, the Virginias, Tennessee, Ken- tucky, Georgia, Maryland and North Carolina contribute about 12 percent of the country's supply. The balance is distributed quite widely along the Atlantic Coast range, the Mississippi Valley and Rocky Mountains. Practically all of the ores commercially utilized are in an oxide or carbonate combination so that a simple heating to the reducing [ 179 ] Sec. 3 CONDUCTORS AND WIRE TABLES point of the ore in contact with a proper reducing material is sufficient to bring about the first step in the process. The ore, as mined, consists of two main constituents, the valuable material which contains the iron and quantities of rock and other materials from which the metallic part must be separated. The ore is charged, as a whole, into the furnace and the proper mixing with non-metallic substances relied upon to form the final products which are easily fusible, and from which the liquid iron will separate itself by reason of its greater specific gravity. The flux as these additions are called, is usually limestone, as the gangue is usually of a silicious nature. The ore, fuel, and fluxes are charged into a blast furnace, which is a cylindrical stack 80 to 100 feet high and about 20 feet in diameter at its largest point, having suitable arrangements near its base for blowing in great volumes of air. The fuel used is coke, which heats the charge to its melting point and at the same time frees the iron from its chemical bonds in the ore. The earthy portions of the ore unite with the limestone, forming a waste product known as slag. The carbon in the coke combines with the oxygen in the oxide of iron, thus separating the metallic iron from the ore. The metal from these furnaces is called Pig Iron and is employed mainly in this shape as a stepping stone toward other products. Pig Iron is coarse-grained, brittle and full of impurities, which must be removed. This is done by several processes in one of which the pig is mixed with steel scrap of a highly selected grade and the molten mass subjected for several hours to the purifying action of an intensely hot flame, by which the various impurities are elimi- nated. The metal is then poured into iron moulds, which shape it into ingots. The ingots are taken out of the moulds as soon as the outside has firmly solidified and are plunged in a deep, white hot pit, where they are kept until their temperature is uniform throughout. After this they are sent to the wire manufacturer. 4. Copper Clad. Copper clad wire is composed of a steel core around which is formed a copper sheath, varying in thickness in accordance with the grade of wire, which sheath is practically welded to the steel core. In one process of the manufacture of such wire, a steel billet, of a suitable composition for wire making, is carefully pickled and washed, then heated to a given temperature and lowered into a furnace con- taining molten copper, at a very high temperature, where it is allowed to remain until an alloy forms on the billet's surface. The billet is then inserted in a mould of such a diameter that a space remains around the billet into which space chemically pure molten copper is poured. This is allowed to set; the billet is then rolled to wire rod which is put through the ordinary process of wire draw- In another process there is first formed a two-metal or composite ingot by inserting a bar of high grade steel of suitable length and uniform cross section into and in close contact with a seamless [ 180 ] CONDUCTORS AND WIRE TABLES Sec. 3 copper tube of high conductivity and physical qualities, and of equal length and exactly finished thickness, the diameter of the core and thickness of the copper being accurately predetermined in order to give the proper proportion of each metal in the finished product. The two-metal ingot thus formed is then placed in a heating furnace and there brought to a temperature suitable for welding. While still hot, and with both copper and steel in a plastic or pasty condi- tion, they are taken to the rolls and there the two metals are welded together. MANUFACTURE OF WIRE 5. Working Ingots. The treatment of copper, aluminum, copper clad or steel is practically the same. The material is received in approximately the same size and length, is heated and then passed through a rolling mill, reducing the size and finally producing a rod which may be a quarter of an inch in diameter and nearly a quarter of a mile in length. Up to this point the metal has been handled hot, but during the processes of wire drawing it is worked in the cold state. 6. Wire Drawing consists briefly in pulling the wire through tapering holes in iron or steel plates, reducing its diameter and in- creasing its length with each draft until the wire has undergone a sufficient number of drafts and consequent reductions to bring it to the proper diameter. When the finer sizes of wire are to be produced, the total reduction cannot be made in one series of drafts, as the wire must be treated at intervals to relieve the strains produced by the cold working. This treatment, called annealing, consists in heating the metal uniformly to a sufficiently high temperature to remove the internal molecular strains and to make the metal once more soft and ductile. This may be repeated many times before the necessary amount of reduction has been attained. The finest sizes of magnet wire are produced by drawing through holes drilled in diamonds. 7. Weatherproof Insulation. In the manufacture of triple braided weatherproof wire, the wires are covered by three closely and evenly woven braids of strong fibrous material after which they are placed in a hot bath of weatherproof insulating compound. They remain in this bath until the fibrous insulation is completely and thoroughly saturated. After thoroughly drying, the wire receives a dressing of mineral wax and the surface is then thoroughly finished and polished. 8. Rubber Insulation. There are various grades of crude rubber usually known under the name of the country or seaport from which they come, such as "Para," "Ceylon," etc. Rubber for insulation purposes must be free from impurities, such as bark and sand. This cleansing is done by passing the crude rubber several times between corrugated steel rolls, revolving at different speeds and under a constant stream of water. Thus the [181] Sec. 3 CONDUCTORS AND WIRE TABLES rubber is washed and cleansed from such impurities and is delivered in a sheet ready to be dried. Crude rubber is affected by changes in temperature, hardening with cold and softening and losing its shape with heat. In such an uncured state it readily oxidizes and is particularly susceptible to the action of certain solvents. To obtain the properties needed in the insulation of a wire, the rubber must be compounded with other materials and then vulcanized. Compounding consists of mixing the rubber with other substances, chiefly powdered minerals, including a small percentage of sulphur. After the rubber has been warmed to a plastic condition in the heated mixing rolls, which are smooth and run at different speeds, the compounding ingredients are added to the rubber and the whole is thoroughly kneaded together by the action of the mixing rolls, until the resulting compound is homogeneous in nature and of suit- able physical condition. 9. Application of the Rubber Compound. Two different methods are commonly in use for applying rubber insulation to wires. In one, a machine similar in action to a lead press is used. The rubber is forced by a revolving worm into a closed chamber at high pressure, at the same time being heated to a soft and plastic state by a steam jacket. The wire enters this same chamber through a nozzle of its own diameter, and leaves it from a nozzle having the diameter of the intended insulation. The wire thus comes out with a seamless coating of rubber insulation. In the other method of application, the rubber is sheeted on a calender having heavy smooth rolls and the sheets thus made are cut into narrow strips, the width and thickness of which depends upon the size of the wire to be insulated and the number of covers to be used. In this method the wire is passed between one or more pairs of grooved rolls running tangent to each other. As the wire enters each pair of rolls, one or more strips of rubber enter at the same time and the grooves fold a uniform thickness of rubber about the wire, the edges meeting in a continuous seam. All surplus rubber is cut off by the rolls at the seams. These seams being made between two pieces of the same unvulcanized cohesive stock under very great pressure, become invisible in the finished wire and can be determined only by a ridge along the insulation. In the process of vulcanizing, the rubber at the seams is kneaded together so that the insulation at this point is as dense and homo- geneous as at any other part of the insulation. 10. Vulcanizing. To vulcanize rubber compounds they are subjected to temperatures somewhat above the melting point of sulphur, which temperatures are usually obtained by use of steam under pressure. This operation causes the sulphur in the compound to unite chemically with the rubber and other ingredients of the compound, with the results that the rubber is no longer plastic, but becomes firm, elastic, strong, less susceptible to heat and cold, to the action of the air and less readily affected at ordinary tempera- tures, by the usual solvents of unvulcanized rubber. Its chemical [ 182 ] CONDUCTORS AND WIRE TABLES Sec. 3 and mechanical properties depend considerably on the time and the temperature of vulcanization and on the amount of sulphur used. 11. Protection of Rubber Insulation. Rubber insulation for aerial work should be protected by a winding of tape, or by a braid, or a tape and one or more braids. The tape used consists of a good grade of cloth filled with a high class rubber compound. The braiding consists of a strong cotton yarn, knitted tightly and evenly about the insulation by a machine resembling a stocking machine. The braid is then saturated with a black weatherproof compound, which is waxed and polished. 12. PHYSICAL CHARACTERISTICS. The average physical characteristics of copper, aluminum, copper clad, steel and iron wire are given in Tables 6 to 10 inclusive. While copper clad is a com- pound wire consisting of copper and steel, it will be noted that its characteristics differ from both those of copper and steel. The physical characteristics of compound stranded cables, such as copper steel core and aluminum steel core cables have not been included, since the relative proportions of the compounding vary to such an extent with the mechanical and electrical conditions to be obtained by such compounding, that such cables are practically a special product. [ 183 ] Sec. 3 CONDUCTORS AND WIRE TABLES TABLE 6 COPPER WIRE Physical constants of commercial wire. Average values Annealed Hard Percent Conductivity (Matthiessen's Standard 100) Specific Gravity 99-102 8.89 .320 .003027 28,000 32-34,000 12,000,000 .0000171 .0000095 1100 2012 176 8.7 1.594 .6276 9.59 10.36 50,600 96-99 8.94 .322 .003049 30-35,000 50-67,000 16,000,000 .0000171 .0000095 1100 2012 176 8.7 1.626 .6401 9.78 10.57 51,600 Pounds in 1 cubic inch Pounds per 1000 ft per circular mil Elastic Limit in Ibs Ibs. Ultimate Strength ' Modulus of elasticity ^ =~~ y m.Xsq. in. ' Coefficient of Linear Expansion per C Coefficient of Linear Expansion per F Melting Point in C Melting Point in F Specific Heat (watt-seconds to heat 1 Ib. 1 C.) Thermal Conductivity (watts through cu. in., Resistance: Michroms per centimeter cube C Microhms per inch cube C Ohms per mil-foot C Ohms per mil-foot 20 C Cir. Mils 54,600 Cir. Mils 55,700 Pounds per mile ohm C. Cir. Mils 810 875 .0042 .00233 Cir. Mils 830 896 .0042 .00233 Pounds per mile ohm 20 C. ... Temperature Coefficient per F L184] CONDUCTORS AND WIRE TABLES Sec. 3 TABLE 7 ALUMINUM WIRE Physical constants of commercial wire. Average values Aluminum Wire Percent Conductivity (Matthiessen's Standard 100) 61 Specific Gravity 2.68 Pounds in 1 cubic inch .0967 Pounds per 1000 ft. per circular mil .000920 Elastic Limit 14000-16000 Ibs Ultimate Strength - ^ 23000-27000 Ib. Xin. Modulus of elasticity - n Xg ^ 9,000,000 Coefficient of Linear Expansion per C .0000231 Coefficient of Linear Expansion per F .0000128 Melting Point in C 657 Melting Point in F 1215 Specific Heat (watt-seconds to heat 1 Ib. 1 C.) 412 Thermal Conductivity (watts through cu. in., temperature gradient 1 C. at 100 C.) 3.85 Resistance: Microhms per centimeter cube C 2.612 Microhms per inch cube C 1.028 Ohms per mil-foot C 15.72 Ohms per mil-foot 20 C 16.97 AAACA Resistance per mile C Cir. Mils QQCCA Resistance per mile 20 C Cir. Mils Pounds per mile ohm C 403.5 Pounds per mile ohm 20 C 435.6 Temperature Coefficient per C .0039 Temperature Coefficient per F .0022 [185] Sec. 3 CONDUCTORS AND WIRE TABLES TABLE 8 COPPER CLAD WIRI Physical constants of commercial wire. I Average values 30% 40% Percent Conductivity (Matthiessen's Standard 100) Specific Gravity 29M% 8.25 39% 8.25 Pounds in 1 cubic inch .298 .298 0.00281 0.00281 Ultimate Strength =-~ 60,000 100,000 19 000 000 21 000 000 .000012 .000012 .0000067 .0000067 Melting Point in C. Melting Point in F Specific Heat (watt-seconds to heat 1 Ib. 1 C.) Thermal Conductivity (watts through cu. in., temperature gradient 1 C.) Resistance : Microhms per centimeter cube C Microhms per inch cube C Ohms per mil-foot 20 C 35.5 26.6 Resistance per mile C Resistance per mile 20 C 187,000 140,000 Cir. Mils Cir. Mils Pounds per mile ohm 20 C 2,775 2,075 Temperature Coefficient per C, from C .0044 Temperature Coefficient per F, from 32 F .0024 [ 186] CONDUCTORS AND WIRE TABLES Sec. 3 TABLE 9 STEEL WIRE Physical constants of commercial wire. Average values Siemens's Martin High Strength Extra High Strength Percent Conductivity (Matthiessen's Standard 100) 8.7 7.85 .283 .002671 38000 75,000 29,000,000 .0000118 .00000662 1360 2480 18.10 7.13 108.8 119.7 574,000 7.85 .283 69000 125,000 29,000,000 18.47 7.27 llf.3 122.5 588,000 7.85 .283 112000 187,000 29,000,000 18.88 7.43 113.7 125.0 600,000 Specific Gravity Pounds in 1 cubic inch Pounds per 1000 ft. per circular mil . . . Elastic Limit Ibs. *. 8q ' m ib.Xin. Coefficient of Linear Expansion per C. Coefficient of Linear Expansion per F. Melting Point in C. Melting Point in F Specific Heat (watt-seconds to heat 1 Ib. 1 C.) Thermal Conductivity (watts through cu. in., temperature gradient 1 C.) . Resistance : Microhms per centimeter cube C. . Microhms per inch cube C. Ohms per mil-foot C. Ohms per mil-foot 20 C. Cir. Mils 632,000 Cir. Mils 647,000 Cir. Mils Pounds per mile ohm C Cir. Mils 8090 8900 .00501 .00278 Cir. Mils 8270 9100 .00501 .00278 Cir. Mils 8450 9300 .00501 .00278 Pounds per mile ohm 20 C Temperature Coefficient per C Temperature Coefficient per F [ 187 ] Sec. 3 CONDUCTORS AND WIRE TABLES TABLE 10 IRON WIRE Physical constants of commercial wire. Average values B. B. E. B. B. Percent Conductivity (Matthiessen's Standard 100) Specific Gravity 19.99 7.77 16.8 7.77 Pounds in 1 cubic inch .282 .282 Pounds per 1000 ft. per circular mil .00265 .002652 Elastic Limit 30,000 Ibs. 61 000 55 000 so. in. Ib.Xin. 26 000 000 Modulus uf elasticity in x sq- in> .000012 .000012 Coefficient of Linear Expansion per F .0000067 .00000673 Melting Point in C 1635 Melting Point in F 2975 Specific Heat (watt-seconds to heat 1 Ib. 1 C.) Thermal Conductivity (watts through cu. in., 209 1.39 Resistance : 11.3 9.5 4.45 3.74 68.0 57.2 Ohms per mil-foot 20 C 74.80 62.92 Resistance per mile C 358,000 302,000 Cir. Mils 395,000 Cir. Mils 332,000 Pounds per mile ohm C. Cir. Mils 5,000 Cir. Mils 4,270 5,500 4,700 Temperature Coefficient per C .... .005 .005 .00278 .00278 [ 188 ] CONDUCTORS AND WIRE TABLES Sec. 3 13. UNITS OF RESISTANCE. The unit of resistance now universally used is the International Ohm. The following table gives the value and relation of the principal practical units of resistance which existed prior to the establishment of the International Units. (Table 11.) TABLE 11 Unit Interna- tional Ohm B. A. Ohm Legal Ohm 1884 Siemens's Ohm International Ohm 1 1.0136 1.0028 1 0630 B. A. Ohm 0.9866 1. 0.9894 1 0488 Legal Ohm 0.9972 1.0107 1. 1 0600 0.9407 9535 9434 1 To reduce British Association ohms to international ohms divide by 1.0136, or multiply by 0.9866; and to reduce legal ohms to international ohms, divide by 1.0028, or multiply by 0.9972, etc. 14. SPECIFIC RESISTANCE: Let L = length of conductor. A = cross section of the conductor. R = resistance of the conductor. p = specific resistance of the conductor. or R A A If "L" is measured in centimeters and " A" in square centimeters, P is the resistance of a centimeter cube of the conductor. If "L" is measured in inches and "A" in square inches, p is the resistance of an inch cube of the conductor. In telegraph and telephone practice, specific resistance is sometimes expressed as the "weight per mile-ohm," which is the weight in pounds of a conductor one mile long having a resistance of one ohm. Another common way of expressing specific resistance is in terms of "ohms per mil-foot," i. e., the resistance of a round wire one foot long and 0.001 inch in diameter; L is then measured in feet and A in circular mils. Microhms per inch cube =0.3937 X microhms per centimeter cube. Pounds per mile-ohm times specific gravity =57.07 X microhms per centimeter cube. Ohms per mil-foot " =6.015 X microhms per centimeter cube. [ 189] Sec. 3 CONDUCTORS AND WIRE TABLES 15. SPECIFIC CONDUCTIVITY is the reciprocal of specific resistance. If c = specific conductivity c = cA _L_ RA 1 16. By RELATIVE OR PERCENTAGE CONDUCTIVITY of a sample is meant 100 times the ratio of the conductivity of the sample at standard temperature, to the conductivity of a conductor of the same dimensions made of the standard material and at standard temperature. If p is the specific resistance of the sample at stand- ard temperature, and p a is the specific resistance of the standard at standard temperature, then Percentage conductivity = 100 In comparing different materials, the specific resistance should always be determined at the standard temperature, which is usually taken as Centigrade. If it is inconvenient to measure the resist- ance of the sample at the standard temperature, this may be cal- culated provided the temperature coefficient a of the sample is known, i. e. pt po ~l+at where pt is the specific resistance at temperature t. 17. MATTHIESSEN'S STANDARD CONDUCTIVITY is the commercial standard of conductivity and is the conductivity of a copper wire having the following properties at a temperature of 0C: Specific gravity 8.89. Length 1 meter. Weight 1 gram. Resistance 141729 ohms. Specific resistance 1.594 microhms per cubic centimeter. Relative conductivity 100%. TABLE 12 MATTHIESSEN'S STANDARD Equivalent length of a square mm. mercury column. B. A. units. Legal ohms. Interna- tional ohms. 104.8 cms. 106.0 cms. 106.3 cms. Resistance at C. of Mat- thiessen's Standard Meter-gram soft copper Meter-millimeter soft copper . Cubic centimeter soft copper . Mil-foot soft copper 143 65 .020 57 .000 001 616 9.72 .142 06 .020 35 .000 001 598 9.612 .141 73 .0203 .000 001 594 9.59 [ 190 ] CONDUCTORS AND WIRE TABLES Sec. 3 18. SPECIFIC RESISTANCE, RELATIVE RESISTANCE, AND RELATIVE CONDUCTIVITY OF CONDUCTORS. TABLE 13 Referred to Matthiessen's Standard Metals: Resistance in Microhms atOC Relative Resistance Percent Relative Conductivity Percent Centimeter Cube Inch Cube Silver annealed Copper, annealed .... Copper (Matthiessen's Standard) . Gold (99.9% pure) Aluminum (99% pure) Zino Platinum, annealed . . . Iron 1.47 1.55 1.594 2.20 2.58 5.75 8.98 9.07 12.3 13.1 20.4 35.2 94.3 130. 2400-42,000 about 4000 6 x IQio .579 .610 .6276 .865 1.01 2.26 3.53 3.57 4.85 5.16 8.04 13.9 37.1 51.2 950-16,700 about 1590 2.38 x 10' 92.5 975 100 138 161 362 565 570 778 828 1280 2210 5930 8220 108.2 102.6 100.0 12.5 62.1 27.6 17.7 17.6 12.9 12.1 7.82 4.53 1.69 1.22 Nickel Tin . . Lead Antimony Mercury Bismuth Carbon (graphite) .... Carbon (arc light) .... Selenium GENERAL Liquids at 18 C. Ohms per Centimeter Cube Ohms per Inch Cube Pure Water 2650 30 4.86 1.37 9.18 1.29 21.4 1050 11.8 1.93 .544 3.64 .512 8.54 Sea Water Sulphuric acid, 5% . . . Sulphuric acid, 30% . . Sulphuric acid, 80% . . Nitric acid, 30% Zinc sulphate, 24% . . 19. TEMPERATURE COEFFICIENT. The resistance of a conductor varies with the temperature of the conductor. Let Ro = Resistance at R = Resistance at t ThenR =R (l+at). a is called the temperature coefficient of the conductor. 100 a is the percentage change in resistance per degree ^change in tem- perature. The following values of the temperature coefficient have been found for temperatures measured in degrees Centigrade and in degrees Fahrenheit. The coefficients vary considerably with the purity of the conductor. (Table 15.) [191] Sec. 3 CONDUCTORS AND WIRE TABLES TABLE 14 TEMPERATURE COEFFICIENTS Table of temperature variations in the resistance of pure soft copper according to Matthiessen's standard and formulae. g.i rt * Matthiessen meter-gram standard o O resistance. 5 ll a 2 . g.sl j3 |61 111 *H o3 B. A. Legal Interna- tional M VM 0>T3 6fl pH fa 1 units. ohms. ohms. i. 0. 0.143 65 0.142 06 0.141 73 1 1.003 876 0.001 680 1 0.144 21 0.142 61 0.142 28 2 1.007 764 0.003 358 8 0.144 77 0.143 17 0.142 83 3 1.011 66 0.005 036 2 0.145 33 0.143 72 0.143 38 4 1.015 58 0.006 712 1 0.145 89 0.144 27 0.143 94 5 1.019 5 0.008 386 4 0.146 45 0.144 83 0.144 49 6 1.023 43 0.010 059 3 0.147 02 0.145 39 0.145 05 7 1.027 38 0.011 730 7 0.147 59 0.145 95 0.145 61 8 1.031 34 0.013 400 3 0.148 15 0.146 51 0.146 17 9 1.035 31 0.015 068 3 0.148 73 0.147 08 0.146 73 10 1.039 29 0.016 734 6 0.149 3 0.147 64 0.147 S 11 1.043 28 0.018 399 3 0.149 87 0.148 21 0.147 86 12 1.047 28 0.020 062 1 0.150 45 0.148 78 0.148 43 13 1.051 29 0.021 723 0.151 02 0.149 35 0.149 14 1.055 32 0.023 382 1 0.151 6 0.149 92 0.149 57 15 1.059 35 0.025 039 0.152 18 0.150 49 0.150 14 16 1.063 39 0.026 694 0.152 77 0.151 07 0.150 71 17 1.067 45 0.028 348 0.15334 0.151 64 0.151 29 18 1.071 52 0.029 999 0.153 93 0.152 22 0.151 86 19 1.075 59 0.031 648 0.154 51 0.152 8 0.152 44 20 1.079 68 0.033 294 0.155 1 0.153 38 0.153 02 21 1.083 78 0.034 939 0.155 69 0.153 96 0.153 6 22 1.087 88 0.036 581 0.156 28 0.154 55 0.154 18 23 1.092 0.038 222 0.156 87 0.155 13 0.154 77 24 1.096 12 0.039 859 0.157 46 0.155 72 0.155 35 25 1.100 26 0.041 494 0.158 06 0.15631 0.155 94 26 1.104 4 0.043 127 0.158 65 0.156 89 0.156 53 27 1.108 56 0.044 758 0.159 25 0.157 48 0.157 11 28 1.112 72 0.046 385 0.159 85 0.158 08 0.157 7 29 1.116 89 0.048 Oil 0.160 44 0.158 67 0.1583 30 1.121 07 0.049 633 0.161 05 0.159 26 0.158 89 40 1.163 32 0.065 699 0.167 11 0.165 26 0.164 88 50 1.206 25 0.081 436 0.173 28 0.171 36 0.17095 60 1.249 65 0.096 787 0.179 52 0.177 53 0.177 11 70 1.293 27 0.111 687 0.185 78 0.183 72 0.183 29 80 1.336 81 0.126 069 0.192 04 0.189 91 0.189 46 90 1.379 95 0.139 863 0.198 23 0.196 04 0.195 58 100 1.422 31 0.152 995 0.204 32 0.202 06 0.201 58 [ 192] CONDUCTORS AND WIRE TABLES Sec. 3 TABLE 15 TEMPERATURE COEFFICIENTS Pure Metals Centigrade a Fahrenheit a Silver, annealed 0.00400 0.00428 0.00377 0.00423 0.00406 0.00247 0.00625 0.0062 0.00440 0.00411 0.00389 0.00072 0.00354 0.00222 0.00242 0.00210 0.00235 0.00226 0.00137 0.00347 0.00345 0.00245 0.00228 0.00216 0.00044 0.00197 Copper, annealed Gold (99 9%) Aluminum (99%) Zinc Platinum, annealed Nickel Tin. . Lead Antimony Mercury Matthiessen's formula for soft copper wire R = Ro (1 + .003871 + .00000597t 2 ) . The wire used by Matthiessen was as pure as could be obtained at the time (1860), but in reality contained considerable impurities; the above formula, therefore, is not generally applicable. Later experiments have shown that for all practical work the above equation for copper wire may be written R =R (1 + .0042t) for t in C. TEMPERATURE COEFFICIENT OF COPPER A. I. E. E. The fundamental relation between the rise of temperature and the increase of resistance of copper may be expressed thus: Rt = Rt 1 (l+a tl [t-t 1 ]) where Rt is the resistance at any temperature t deg. Cent. ; R^ is the resistance at any " initial temperature" (or " temperature of ref- erence") ti deg. cent.; and at x is the temperature coefficient from and at the initial temperature ti deg. cent. Obviously the tem- perature coefficient is different for different initial temperatures, and this variation is shown in the horizontal rows of Table 16. ^ Further- more, it has been shown that the temperature coefficient is different for different conductivities, and that the temperature coefficient is substantially proportional to the conductivity. The results of this simple law are shown by the vertical columns of Table 16. 7 [ 193 ] Sec. 3 CONDUCTORS AND WIRE TABLES TABLE 16 TEMPERATURE COEFFICIENTS OF COPPER FOR DIFFERENT INITIAL TEMPERATURES AND DIFFERENT CONDUCTIVITIES Ohms per meter- gram at 20 deg. Cent. Per cent con- duc- tivity ao ais 0,20 0-25 aso 0.50 -T "Inferred absolute zero" 0.16108 0.15940 0.15776 0.15727 15614 0.15557 0.153022 95 96 97 97.3 98 99 100 101 0.00405 0.00409 0.00414 0.00415 0.00418 0.00423 0.00428 0.00432 0.00381 0.00386 0.00390 0.00391 0.00394 0.00398 0.00402 0.00406 0.00374 0.00378 0.00382 0.00383 0.00386 0.00390 0.00394 0.00367 0.00371 0.00375 0.00376 0.00379 0.00383 0.00386 0.00390 0.00361 0.00364 00368 0.00369 0.00372 0.00375 0.00379 0.00383 0.00336 0.00340 0.00343 0.00344 0.00346 0.00349 0.00352 0.00355 -247.2 -244.4 -241.7 -240.9 -239.0 -236.4 -233.8 -231.3 0.15151 0.00398 The quantity ( T) given in the last column of Table 16 is the calculated temperature on the Centigrade scale at which copper of the particular conductivity concerned would have zero electrical re- sistance provided the temperature coefficient between deg. Cent, and 100 deg. Cent, applied continuously down to the absolute zero. The usefulness of this "inferred absolute zero temperature of resistance" in calculating temperature rise is evident from the following formula: Rt ~ Rt i rr-i-t ^ t ti = (l-t-ti; Ivtj The presentation of the above table is intended to emphasize the desirability of determining the temperature coefficient rather than assuming it. Actual experimental determination is facilitated by the proportional relation between the temperature coefficient and the conductivity; a measurement of either quantity gives both. However, if a temperature coefficient must be assumed, the best value to take for average commercial annealed copper wire is that given in Table 16 for 100 percent conductivity, viz., a = 0.00428, 020 =0.00394, a 25 = 0.00386 This is the value recommended for wire wound on instruments and machines, since they are generally wound with annealed wire, and experiments have shown that the distortions due to the winding of the wire do not appreciably affect the temperature coefficient. If a value must be assumed for hard-drawn copper wire, the value recommended is that given in Table 16 for 97.3 percent conductivity viz., a =0.00415, a 20 =0.00383, o 25 =0.00376 The temperature coefficients in Fahrenheit degrees are given by dividing any a above by 1.8. Thus, the 20 deg. Cent, or 68 deg. Fahr. temperature coefficient for copper of 100 percent conductivity is 0.00394 per deg. Cent., or 0.00219 per deg. Fahr. [ 194] CONDUCTORS AND WIRE TABLES WIRE GAUGES Sec. 3 20. AMERICAN STEEL AND WIRE GAUGE is generally used in America for iron and steel wire. 21. BROWN AND SHARPE GAUGE is the standard gauge used for wires for electrical purposes, (iron and steel wire excepted). 22. BIRMINGHAM GAUGE is used largely in England and also in this country for wires (excepting iron wire) other than those made especially for electrical purposes. 23. COMPARISON OF WIRE GAUGES. The sizes of wires are ordinarily expressed by an arbitrary series of numbers. Unfortu- nately there are several independent numbering methods, so that it is alwa} r s necessary to specify the method or wire gauge used. Table 17 gives the numbers and diameters in decimal parts of an inch for the various wire gauges used in this country and Eng- land. TABLE 17 COMPARATIVE SIZES WIRE GAUGE IN DECIMALS OF AN INCH No. of Wire American Steel & American Standard Birming- ham or British Imperial Old English or French. Gauge. Wire (B. & S.) Stubs'. Standard. London. 0000000 .4900 .500 000000 .4615 .58000 .464 00000 .4305 .51650 .500 .432 0000 .3938 .46000 .454 .400 .4540 000 .3625 .40964 .425 .372 .4250 00 .3310 .36480 .380 .348 .3800 .3065 .32486 .340 .324 .3400 1 .2830 .28930 .300 .300 .3000 .0325 2 .2625 .25763 .284 .276 .2840 .040 3 .2437 .22942 .259 .252 .2590 .050 4 .2253 .20431 .238 .232 .2380 .0625 5 .2070 .18194 .220 .212 .2200 .068 6 .1920 .16202 .203 .192 .2030 .083 7 .1770 .14428 .180 .176 .1800 .097 8 .1620 .12849 .165 .160 .1650 .110 9 .1483 .11443 .148 .144 .1480 .120 10 .1350 .10189 .134 .128 .1340 .135 11 .1205 .09074 .120 .116 .1200 .149 12 .1055 .08081 .109 .104 .1090 .162 13 .0915 .07196 .095 .092 .0950 .172 14 .0800 .06408 .083 .080 .0830 .185 15 .0720 .05706 .072 .072 .0720 .197 16 .0625 .05082 .065 .064 .0650 .212 17 .0540 .04525 .058 .056 .0580 .225 18 0475 .04030 .049 .048 .0490 .238 19 .0410 .03589 .042 .040 .0400 .250 20 .0348 .03196 .035 .036 .0350 .263 [ 195] Sec. 3 CONDUCTORS AND WIRE TABLES 24. LAW OF THE BROWN AND SHARPE GAUGE. The diameters of wires of the B. and S. gauge are obtained from the geometric series in which No. 0000=0.4600 inch and No. 36 = .005 TABLE 18 DIAMETER AND CROSS-SECTION AREA SOLID WIRE Brown & Sharpe Gauge Diameter of Wire Cross-sectional Area In Inches In Millimeters Circular Mils (d 2 ) d=. 001 Inch Square Inch (d x .7854) Square Millimeter 0000 000 00 .4600 .4096 .3648 .3250 11.683 10.404 9.266 8.255 211600. 167772. 133079. 105625. .166190 .131770 .104520 .082958 107.219 85.011 67.432 53.521 1 2 3 4 .2893 .2576 .2294 .2043 7.348 6.543 5.827 5.189 83694. 66358. 52624. 41738. .065733 .052117 .041331 .032781 42.408 33.624 26.665 2*. 149 5 6 7 8 .1819 .1620 .1443 .1285 4.620 4.115 3.665 3.264 33088. 26244. 20822. 16512. .025987 .020612 .016354 .912969 16.766 13.298 10.550 8.3666 9 10 11 12 .1144 .1019 .0907 .0808 2.906 2.588 2.304 2.052 13087. 10384. 8226.5 6528.6 .010279 .0081553 .0064611 .0051276 6.6313 5.2614 4.1684 3.3081 13 14 15 16 .0720 .0641 .0571 .0508 1.829 1.628 1.450 1.290 5184.0 4108.8 3260.4 2580.6 .0040715 .0032271 .0025607 .0020268 2.6267 2.0819 1.6520 1.307 x 17 18 19 20 .0453 .0403 0359 .0320 1.151 1.024 .9119 .8128 2052.1 1624.1 1288.8 1024.0 .0016117 .0012756 .0010122 .00080425 1.0398 .82294 .65304 .51887 inch, the nearest fourth significant figure being retained in the areas and diameters so deduced. Brown and Sharpe tables are derived from the following formulae: Let n=gauge number (0000= -3;000= -2;00= -1). d = diameter of wire in inches. Cir. mils = area in circular mils. r = resistance in ohms per 1000 ft. at 20 C. w = weight in pounds per 1000 ft. [ 196] CONDUCTORS AND WIRE TABLES Sec. 3 Then 0.3249 ~1.123 n 105,500 r = 0.09811 Xl.261n 319.5 A useful approximate formula for resistance per 1000 feet at about 20 C. is as follows; r = 0.!X(2)| ((2)* = 1.26; (2)* = 1.59.) From this it is seen that an increase of 3 in the wire number corresponds to doubling the resistance and halving the cross section and weight. Also, that an increase of 10 in the wire number in- creases the resistance 10 times and diminishes the cross section and weight to Yio their original value. 25. WIRE STRANDS. Wires larger than No. 0000 B. and S. are seldom made solid, but are built up of a number of small wires into a strand. The group of wires is called a "strand"; the term "wire" being reserved for the individual wires of the strand. Strands are usually built up of wires of such a size that the cross section of the metal in the strand is the same as the cross section of a solid wire having the same gauge number. If n= number of concentric layers around one central strand, Al 3 (n 2 -f-n)-f-l metal area then 7^~-r~^r~ = ratio of - rp- r-j available area The number of wires that will strand will be3n (n+1) +1. TABLE 19 WIRE STRANDS Number of Strands Metal area available area 1 7 19 37 61 91 1.000 .778 .760 .755 ..,..: .753 ' .752 [ 197 ] Sec. 3 CONDUCTORS AND WIRE TABLES 26. ILLUSTRATIONS OF BARE WIRE, STRAND AND CABLE BARE WIRE STRAND Full Sizes of Wire B. AS. Gauge Concentric Strand, 37 Wires 10 11 12 13 14 15 16 [198] CONDUCTORS AND WIRE TABLES Sec. 3 TABLE 20 CURRENTS FUSING EFFECTS OF CURRENTS Table giving the diameters of wires of various materials which will be fused by a current of given strength Current in amperes Diameters in inches. 1 O Aluminum Platinum German Silver Platinoid 1 a jb I 1 3 1 2 3 4 5 0.002 1 0.003 4 0.004 4 0.005 3 0.006 2 0.002 6 0.004 1 0.005 4 0.006 5 0.007 6 0.003 3 0.005 3 0.007 0.008 4 0.009 8 0.003 3 0.005 3 0.006 9 0.008 4 0.009 7 0.003 5 0.005 6 0.007 4 0.008 9 0.010 4 0.004 7 0.007 4 0.009 7 0.011 7 0.013 6 0.007 2 0.011 3 0.014 9 0.018 1 0.021 0.008 3 0.013 2 0.017 3 0.021 0.024 3 0.008 1 0.012 8 0.016 8 0.020 3 0.0236 10 15 20 25 30 0.009 8 0.012 9 0.015 6 0.018 1 0.020 5 0.012 0.015 8 0.019 1 0.022 2 0.025 0.015 5 0.020 3 0.024 6 0.028 6 0.032 3 0.015 4 0.020 2 0.024 5 0.028 4 0.032 0.016 4 0.021 5 0.026 1 0.030 3 0.034 2 0.021 6 0.028 3 0.034 3 0.039 8 0.045 0.033 4 0.043 7 0.052 9 0.061 4 0.069 4 0.038 6 0.050 6 0.061 3 0.071 1 0.080 3 0.037 5 0.049 1 0.059 5 0.069 0.077 9 35 40 45 50 60 0.022 7 0.024 8 0.026 8 0.028 8 0.032 5 0.027 7 0.030 3 0.032 8 0.035 2 0.039 7 0.035 8 0.039 1 0.0423 0.045 4 0.051 3 0.035 6 0.038 8 0.042 0.045 0.050 9 0.037 9 0.0414 0.044 8 0.048 0.054 2 0.0498 0.0545 0.058 9 0.063 2 0.071 4 0.076 9 0.084 0.090 9 0.097 5 0.110 1 0.089 0.0973 0.105 2 0.112 9 0.127 5 0.086 4 0.0944 0.102 1 0.109 5 0.123 7 70 80 90 100 120 0.036 0.039 4 0.042 6 0.045 7 0.051 6 0.044 0.048 1 0.052 0.055 8 0.063 0.056 8 0.062 1 0.067 2 0.072 0.081 4 0.056 4 0.061 6 0.066 7 0.071 5 0.080 8 0.0601 0.065 7 0.071 1 0.076 2 0.086 1 0.079 1 0.086 4 0.093 5 0.100 3 0.113 3 0.122 0.133 4 0.144 3 0.154 8 0.174 8 0.141 3 0.154 4 0.167 1 0.179 2 0.202 4 0.137 1 0.149 9 0.162 1 0.173 9 0.196 4 140 160 180 200 225 0.057 2 0.062 5 0.067 6 0.072 5 0.078 4 0.0698 0.076 3 0.082 6 0.088 6 0.095 8 0.090 2 0.098 6 0.1066 0.114 4 0.123 7 0.089 5 0.097 8 0.105 8 0.113 5 0.122 8 0.095 4 0.104 3 0.112 8 0.121 0.130 9 0.125 5 0.137 2 0.148 4 0.159 2 0.172 2 0.193 7 0.211 8 0.229 1 0.245 7 0.265 8 0.224 3 0.245 2 0.265 2 0.284 5 0.307 7 0.217 6 0.237 9 0.257 3 0.276 0.298 6 250 275 300 0.084 1 0.089 7 0.095 0.102 8 0.109 5 0.116 1 0.132 7 0.141 4 0.149 8 0.131 7 0.140 4 0.148 7 0.140 4 0.149 7 0.158 6 0.184 8 0.196 9 0.208 6 0.285 1 0.303 8 0.322 0.330 1 0.351 8 0.372 8 0.320 3 0.341 7 0.361 7 [ 199 ] Sec. 3 CONDUCTORS AND WIRE TABLES 27. HEATING EFFECTS OF CURRENT. If a continuous current of electricity flows through any conductor, a certain definite portion of the electrical energy supplied to the conductor will be required to overcome its resistance and transmit the current between any two points in the conductor. This energy of transmission, as it is called, is never lost, but is transformed into heat energy. Heat will be developed whenever any electric current flows through any conductor, or part of conductor, the amount of heat being directly proportional to the resistance of the conductor and to the square of the current flowing. The amount of heat measured in calories will equal II = 0.24 PR t Where H represents calories of heat produced I current in amperes R resistance of conductor in ohms, t " time in seconds that the current flows. If heat be developed in the conductor faster than it can be dissi- pated from the surface by radiation and convection the temperature will rise. The allowable safe temperature rise is one of the limiting features of the current carrying capacity of any conductor. Since the rate at which heat will be dissipated from any conductor will depend upon many conditions, such as its size and structure, the kind and amount of insulation, if any, and its location with respect to other bodies, it is not possible to give any general definite rule for carrying capacity that will be true for all conditions. The fol- lowing empirical formula will give approximate values for the cur- rent I flowing through a solid conductor, or through each conductor of a multiple conductor cable which will cause a rise in temperature of t degrees C. I = C In this, d represents the diameter of the bare wire or strand in inches, K is the resistance per mil-foot of the wire at allowable elevated temperature t taken from the curves given in Fig. 77 and C is a constant having the following values for different con- ditions. TABLE 21 Location and Kind of Conductor Values of Con- / d 8 stant C in Expression of CA/ *j Solid Conductor Stranded Conductor Bare overhead wires out of doors ..... 1250 660 530 1100 610 490 Single conductor rubber covered cable in still air [ 200 ] CONDUCTORS AND WIRE TABLES Sec. 3 The heat radiating surface of any conductor varies as the diameter of the conductor, Awhile the current carrying capacity, depending on the number of circular mils, will vary as the square of the diameter. In consequence, the current density in large conductors will be less FIG. 77. Resistance per Mil-Foot of Pure Copper at Various Temperatures and I d Conductivities. Values of K in expression y* A/* "K than in small conductors for an equal temperature rise. It has been found impracticable on this account to use insulated conductors larger than 2,000,000 c. m., except in special cases. [201] Sec. 3 CONDUCTORS AND WIRE TABLES TABLE 22 HEATING EFFECTS OF CURRENTS Bare copper in still air Rise in temperature, degrees Centigrade. 10 20 40 80 I 4! i 4J V c3 j I 4 1 ,M J i M a /, X v~ / / I/ I I /^ /o \ 1 7 // I // 1 // X 1 / / / / / x ^r / / ' / ? 1 / ' / / f J 111/ // ML Sflt *6 4 / // // *7 // 'I '/* *ONUSOU ,^ p 1^1 CO H 5 J cjj g t 9 1! S 9 8 A w cc^ g 5 CO " : : j 1 u us c- t- u O l 8 2 "8 J3 03 s s |*| us us us * 11 D 51 H 02 1 t> s 1 2 e 1 S S 02 r4 ^ * 1 [214] CONDUCTORS AND WIRE TABLES Sec. 3 i c CJ j C w PQ fi W . ' ' ' 2J2sI 2HC S2^ 55S SSS SSsS w *-tC s 400*4*Ot***4tTHO)t-tOiO^COC v 4iHiH^H 1 S PQ : : : 2553^2^5*^^ ^^^* *"* s * : : fi ^ o 3 1 3 ( 8 o | WM 3 c f } H-I cr 1 H3 H CQ C^ PH H w CO * -;' . ' < 3 3 iig is! Ss3 sal asS 2s^ sss sss M CS C4 TH TH TH rH CL Drawn 0) t~ <4< ** P) cs -^ i o t- es to oe o S * 10 t- M E-COT-I eoteiA 3 co c* m M Pi 1 i c Q ooooooooo 00.0 ooo<* e- ^eo^ Sol^ C 03 W K g 02 8 So O PQ [215] Sec. 3 CONDUCTORS AND WIRE TABLES 1 ^ oo ooo ooo o o o ^}*O> vHOC^ OO^U) O) CO CO o . * * ^^^ ^s*^*^ ' **i * ^ * ^ " ... c 5w ww3 SS3 S ^ "* 03 "S Q M "o 1 OOO CO C J OO OO CS -*l O M P 1 fc5 1 g | s s w 3 PH O O ^ -d fO ? M e.^- ^rfrf ^ ^' g o 'g, PQ W g ^J r"* _< d PJ C^ *3 Es & PU Q 118 |I8 SS3 ill Sii 1 : : rt *^ -j H TH TH r . rt *o C/3 ^ OQ 5 B 3 o a c pq 9^ CONN NN^H rH^'H lHl-40 OOO 03 3* 1 M c& 3 Oo ?S co ^' PQ tn to o m o to CT o in o o to o t- us u)t- ci> CM ui TH oo in co N en irj ^ CM rH o en CO VO 10 IO LO ^i ^ OO CO CO CONN NNN N TH r-l 73 g M 5 B 1 y g H D* 2 s W ctf 3 Q ALUM w c3 PQ ID co coo "* co eft co m * er> t- oo H THOOCO co en SSS SS5 SSS S5S 3S SS KS3 5^^ * -ti CO CONN NNiH TH*H*H TH TH o OOO OOO OOO * ft K * ? P5 H uoo u m o TH (0 co co us * TH o fj er> co cnmo^t>oc-<^NOee>(0 -N -o -co -to >S a. M (doo cotD^cocn coio^ent^oo THTHOOCOCOO) Scr>Tf ineDt* en^TH e^^oo ^THO ON^< t*oio OION oo Ncoun NOOO tf>TtKM THoen en c- u> m us <* * co eo Tj< ^ CO CONN N N TH TH TH TH TH TH O OOO OOO OOO i= D 8 , y Of q [ 217 ] Sec. 3 CONDUCTORS AND WIRE TABLES 1 1 | I j > 1 .1 sll ll 1.1 .1 . s ' |fis K9 s - B" '% ' ' ' ' *& <*> COCOC4 vHlHiH 1-4 i ! ! i r I s * SN iH tO t- t- IV> LT) Ti O . IH eoeoco te TH c- M -10 .at . ... iH i-4 CJ cj E p 6 oo c^ SA OO O O >A U> O (0 COLT50 t-C-00 UACO OC-U> <00t- CM O A ooo en oo t- t- to u IA rf ^< ^^ H E o ut-oo csi -^ LO eo o at LO M c-j o N A (OC-OO ! > 4 [218] CONDUCTORS AND WIRE TABLES Sec. 3 r^ ! O L, o g^ ^ Opq >lHC4 CO ** LO IDC- 00 OtOiH N CO T}< lAtOC- 00 -P S -S S SSS S5S S3S SSS SS |g 3 SS5 I : p! S3 .U> .> * :*: sll Sss SSI Ils sa ass ss^sss [ 219 ] Sec. 3 CONDUCTORS AND WIRE TABLES i | E i I S S 2S S5S S S to .9> (0COT-I (0 .00 .0> . ... i 3 co 'co (o TH to t- 1- 10 ^< e> " ' O> O> to rH -^ O) tO ^ H C~ ^ i --i i ^ ! ] 10 o eoo ooo o o S3 :3 c5SS ?=S 3 : : :a : : : : 3 H ,H ,H THr-l o i 0> C^ f^ 1 a 1 rf 04 1-nc 10 C- IO ^t ^1 CO P -iH ... W o w iH iH i-l p J3 . s w | s : C4AOO t- iH O O US 00 * C- CO N 1> cq CO (O iH ff> i-t rjt t- iH IO O Tjt t- ^ iH O 00 tD IA ^< CO CO O <0 U * * CO CO C4 iH 1-lT-l 3 w I g W fi g ^ ^ w * lOiO^H l-INN H o 1 1 * ^< CO CO C4 C4 TH iH T-l W " . 1 f PQ H 288 3S5 iss 38S 5S2 3 : p o PQ u 5< S S> e- S ? 5< co S S iS 53 S i" 1 i I i- 9 2 III III 8 Q 3 10 -3< j* cocoes ooo o IH cfl PO * 10 o t- oo ? [ 220] CONDUCTORS AND WIRE TABLES Sec. 3 o OM MO)C4 OO-^CV) N ^H O> O O> C4 CO i-l Ul <4 IHMU* t>eqe- co^-i^i c*u>t- co ^ ... w prf PL, * a a 1/5 ^ g SSS SSS 0S ^ . S g.g W w d Q O *^ i-ir-ItH CiNCO ^Jl 3d* H ^ ^ H m S o O g ISI S3 5S ^S5 S^S 9 orHH ^nesieii M";5 t-><>* 55o>u> TH o o wo^i A.UGE 00 4 ii c O K [ 221 ] Sec. 3 CONDUCTORS AND WIRE TABLES o a I O w o o S .8 2 )00 !S2 -* g :1 ill SisS S :s : : : : : i :i S S3 1 :S t2 : : : : : C4C~C4 OO CO C- O r-i F- O O ago QQ S -u a H i 3J J3Q~ ls SsiSai llsssol isslii iHi-HCM CM CM CM CO CO CO CO CO CO CO CO CO CO 5 * 5< <* i r- eo inc-o T-II > LO CM. CM CM CO C0_ CO CO CO CO CO CO CO ico e-oo o * 01^1 I rH CM CO ^ti ^^ LO CO CO rH in CO iO O C~ T-f CM iHO^C^COO)^* OO O OO O O ^tlOOO O }< C- 00 O TH CM CM CO Tjl -cM 5 S C- OO 5) in r-l Y-l TH CM CM CM CM CO CO CO CO CO CO CO CO CO CO CO CO -^ IT) C- O M r-( CO | rt< <* OO CO LO C- OO I I ,H Y-H ^ CM CM CM CM ( CO CO CO < HCMCMCMCMCM COCOCOCO< I CO CO CO CO^ COO)> e- IH o T-H io 4CO COCOCO 111111 ) co o>e> 111 illill illili eo eooico i O OOO sis! sggggg t- *i> Ot t- en co i SS SSS! IC40000 CMCO S S! i,H Mvv4MNM 01011 < CM Cl O i-< O 10 ft e t- 1- o> o TH 1 CM CM ?5 OJ CM CM CO CO O 0> 01 CO TH -i co CO CO CO CO iH IO CM t- OO ^ O ID t> O r-l CO C- LO C- Iss 01 OJ [COCO C o TH co c- S?SSS CM CM CM CM [ 223 ] Sec. 3 CONDUCTORS AND WIRE TABLES CD 3 .9 Zj p o O CO 3 I " to m o StD ^ti C vO H VO C*3 tD O) t>C-COOO O O O O TH TH TH * <* ^ ** * TJ< -*ji m m m m m 10 t~ to * TH CX] CO in t- 10 LO tO C- intomcooto TH m oo o TH w > TH ^1 l> O* C^ ^ tO TJ TH CO csi c*a c^ c-3 co co m in in in in m m to m co o co c- TH ^i>Omi ^^^ 33^55:3 3355! imo CO^cotoooo>o I m t- TH O M rH tO < ! TH e^ co < M > rH CN) CO CO < *< TI * ^< *)< *H if & if SC*THC*O3 iHtOCOI>" c* -^ ffi in o^ooc^i , ,_i ,H es CM co T* Tt< T m i S^g^SS SZZl g?35!333 335!: TH N T-I 0> to esi SSSS5? !^^!5 ig^^^^i ( ^ SO CO CO I ) co in ^t< TH to o o ff> t ^ o ino>c4*ctii JSSSSS S1S?S83 5J3SS! ( Tt< -3< -# * TJ< ^<^(TjB i-4rHiH CSJC4C4CqC4CO CO CO CO CO CO CO vHLACO O iH c^ -<^ O CT5 C5 C^4 CO ^ LT5 to CD C^ OO I-JT-JI-J O) oi 01 o cs c^ eocoeoeococo ocoeo o o to c-j oo oo m en to iHt>e-c^M^i oo o co ^ to o t- o cr> -ji 00 r-4 U) CO(OC-O)OX< CNJ 10 to ID -^ '-H C- OO 00 tO CO O ITS T-I Lf5 O - O LO C- CnOiH^lAOO O T-( ?5 CO ^1 1O Ln tO C- CO O O i-l i-l CM THTHrH THOIO4C4C4C4 < CO CO CO CO 10 10 O O IM (O C- iH CM ^1 OO 1O OO C- C-3 <* t i-H t-1 T-4THC S 4C> 1 Ol Ol Ol Ol Ol CO I | CO LO i ^si CO CO < er> co 10 c- oo o TH TH TH TH o CM ^ t THrH THrHOlOlOlOl OJ Ol CO CO CO CO CO CO CO CO CO CO CO CO CO ^ ^J OO * ^ iH 10 01 C~COCOOOOO O^*1OOI^O1 G>CO^t1COiH sasaa t^^HLAcq ococoooooo ^ 10 as o c^ o ^-I^OOOO IOC>OOC^U5 ^HC^rHOCCO SSol KSSSSS 8SSJ885 u 1-1 c- t> Tt< oo IA o (O to TH IH eo t- oo 01 eo u at to en oo i 1O CO to L-' Ol O Tii OllOtO 00 i-l 01 LO C-000>OrHS 01 CO-* 10 tO tO t- 0000. T-l T-l rH iH 01 Ol 09 01 MCI CO COCO CO CO CO CO CO CO CO CO CO c Sen IA 1-1 c- t- * oo 10 o (O (0 T-I 1-1 co c- oo 01 co 10 en (Oencjoeoio Soi ocoinenSrH en 04 eo co IH oo -^lOiocooo CM c- cs c- IH SH TJ< to t- oo o 01 10 to oo en o IH IH cs co rn 10 .> to c- t- OG oo en ,_i,-i TH^HTHOICSOI oioioicococo cococococoeo eococo coco [225] Sec. 3 CONDUCTORS AND WIRE TABLES TABLE 39 CAPACITY SOLID CONDUCTORS Microfarads per 1000 Feet of Circuit-Formed by Two Aerial Wires (2000 Feet of Wire) Inter- SIZE OP WIRE B. & S. GAUGE axial Distance, Inches 0000 000 00 1 2 3 4 5 6 S A .14710 .03160 .01812 .01303 .01030 .00861 .00743 Yz .05270 .02315 .01531 .01156 .00941 .00800 .00699 .00622 .00563 .00515 % .01038 .00864 .00746 .00659 .00591 .00539 .00495 .00458 .00427 .00401 1 .00701 .00625 .00564 .00516 .00476 .00443 .00414 .00389 .00367 .00349 2 .00415 .00390 .00368 .00349 .00332 .00317 .00302 .00290 .00278 .00267 3 .00340 .00324 .00307 .00296 .00284 .00273 .00263 .00253 .00244 .00236 4 .00303 .00290 .00279 .00268 .00258 .00249 .00240 .00232 .00225 .00218 5 .00279 .00268 .00258 .00249 .00241 .00233 .00226 .00219 .00212 .00206 6 .00263 .00253 00244 .00236 .00229 .00222 .00215 .00208 .00203 .00197 7 .00250 .00242 00234 .00226 .00219 .00213 .00207 .00201 .00195 .00190 8 .00240 .00232 00225 .00218 .00212 .00206 .00200 .00195 .00190 .00185 9 .00232 .00225 00218 .00212 .00206 .00200 .00195 .00190 .00185 .00180 10 .00226 .00219 00212 .00206 .00201 .00195 .00190 .00185 .00181 .00176 11 .00220 .00213 00207 .00202 .00196 .00191 .00186 .00181 .00177 .00172 12 .00215 .00209 00203 .00197 .00192 .00187 .00182 .00178 .00174 .00170 15 .00203 .00198 00192 .00187 .00183 .00178 .00174 .00170 .00166 .00162 18 .00195 .00190 00185 .00180 .00176 .00172 .00168 .00164 .00160 .00157 21 .00188 .00183 00179 .00174 .00170 .00166 .00163 .00159 .00156 .00152 24 .00182 .00178 00174 .00170 .00166 .00162 .00159 .00155 .00152 .00149 30 .00174 .00170 00166 .00162 .00159 .00155 .00152 .00149 .00146 .00143 36 .00168 .00164 00160 .00157 .00153 .00150 .00147 .00144 .00142 .00139 42 .00163 .00159 00156 .00152 .00149 .00146 .00143 .00141 .00138 .00135 48 .00159 .00155 00152 .00149 .00146 .00143 .00140 .00138 .00135 .00133 54 .00155 .00152 00149 .00146 .00143 .00140 .00138 .00135 .00133 .00130 60 .00152 .00149 00146 .00143 .00140 .00138 .00135 .00133 .00130 .00128 66 .00150 .00147 00144 .00141 .00138 .00136 .00133 .00131 .00129 .001280 72 .00147 .00144 00142 .00139 .00136 .00134 .00131 .00129 .00127 .001246 78 .001454 .001425 001400 .001371 .001346 .001321 .001298 .001275 .001254 .001232 84 .001436 .001407 001382 .001355 .001330 .001307 .001283 .001261 .001240 .001218 90 .001420 .001392 001366 001340 .001316 .001292 .001270 001248 .001227 .001207 96 .001403 001377 001352 001326 .001303 .001280 .001257 001237 .001216 .001196 102 .001390 .001363 001338 001314 .001290 .001268 .001246 001224 .001205 .001185 108 .001376 .001351 001327 001302 .001280 .001257 .001235 001216 .001195 .001176 114 .001364 .001339 001315 .001292 001268 .001247 .001227 001206 .001186 .001167 120 .001352 001328 001305 001282 001260 .001238 001217 001197 .001178 .001160 126 .001342 001318 001294 001272 001250 .001230 001208 001188 .001170 001152 132 .001332 001308 001285 001262 001241 .001220 001200 001180 .001162 001145 138 .001323 001299 001277 001256 001233 .001213 001194 001175 .001156 001137 144 .001315 .001291 001268 001246 001226 .001206 .001186 001167 .001148 001130 150 .001305 .001283 001261 001240 001218 .001200 001180 001160 001142 001125 156 .001298 .001276 001253 001232 001212 001193 001173 001155 001135 001119 162 .001290 .001269 001246 001228 001206 001185 001167 001149 001130 001113 168 .001283 .001262 001241 001220 001200 001180 001161.001142 001125 001108 174 .001277 001255 001233 001213 001193 001174 0011561.001138 001120 001104 180 .001270 001248 001228 001207 001187 001169 001150 1 . 001132 001115 001100 [ 226 ] CONDUCTORS AND WIRE TABLES Sec. 3 TABLE 39 Continued CAPACITY SOLID CONDUCTORS Microfarads per 1000 Feet of Circuit Formed by Two Aerial Wires (2000 Feet of Wire) Inter- axial SIZE OF WIRE B. & S. GAUGE Distance, Inches 7 8 9 10 11 12 13 14 15 s /s .00688 .00589 .00526 .00493 .00458 .00427 .00401 .00377 .00357 8 .00476 .00444 .00408 .00389 .00367 .00348 .00331 .00315 .00302 % .00378 .00357 .00335 .00323 .00309 .00295 .00283 .00272 .00262 i .00331 .00316 .00299 .00289 .00278 .00267 .00257 .00248 .00240 2 .00258 .00248 .00238 .00232 .00225 .00218 .00212 .00205 .00200 3 .00229 .00222 .00213 .00208 .00202 .00197 .00192 .00187 .00182 4 .00212 .00206 .00199 .00194 .00190 .00185 .00180 .00176 .00171 . 5 .00200 .00195 .00189 .00185 .00180 .00176 .00172 .00168 .00164 6 .00192 .00187 .00181 .00178 .001^73 .00169 .00166 .00162 .00158 7 .00185 .00181 .00175 .00172 .00168 .00164 .00161 .00157 .00154 8 .00180 .00176 .00170 .00168 .09164 .00160 .00157 .00153 .00150 9 .00176 .00172 .00167 .00164 .00160 .00157 .00153 .00150 .00147 10 .00172 .00168 .00163 .00160 .00157 .00154 .00150 .00147 .00144 11 .00169 .00165 .00160 .00157 .00154 .00151 .00148 .00145 .00142 12, - .00166 .00162 .00158 .00155 .00152 .00149 .00146 .00143 .00140 15 .00159 .00156 .00151 .00149 .00146 .00143 .00140 .00138 .00135 18 .00153 .00150 .00147 .00144 .00142 .00139 .00136 .00134 .00131 21 .00149 .00146 .00143 .00141 .00138 .00135 .00133 .00130 .00128 24 .00146 .00143 .00140 .00138 .00135 .00132 .00130 .00128 .00126 30 .00140 .00138 .00135 .00133 .00130 .00128 .00126 .00124 .00122 36 .00136 .00134 .00131 .00129 .00127 .00125 .00122 .00120 .30118 42 .00133 .00131 .00128 .00126 .00124 .00122 .00120 .00118 .00116 48 .00130 .00128 .00125 .00123 .00122 .00120 .00118 .00116 .00114 54 .00128 .00126 .00123 .00121 .00120 .00118 .00116 .00114 .00112 60 .00126 .00124 .00121 .00120 .00118 .00116 .00114 .00112 .00111 66 .00124 .00122 .00120 .00118 .00116 .00114 .001130 .001110 .001093 72 .001226 .001205 .001182 .001167 .001150 .001130 .001114 .001097 .001080 78 .001212 .001191 .001168 .001155 .001136 .001119 .001103 .001086 .001070 84 .001198 .001178 .001157 .001142 .001125 .001108 .001092 .001075 .001060 90 .001187 .001168 .001145 .001132 .001115 .001098 .001003 .001065 .001050 96 .001177 .001158 .001136 .001122 .001105 .001088 .001073 .001057 .001042 102 .001167 .001148 .001126 .001113 .001097 .001080 .001064 .001050 .001035 108 .001158 .001139 .001117 .001105 .001089 .001073 .001057 .001042 .001028 114 .001150 .001131 .001110 .001098 .001081 .001065 .001050 .001035 .001020 120 .001141 .001123 .001102 .001090 .001074 .001058 .001044 .001028 .001015 126 .001134 .001115 .001095 .001083 .001068 .001052 .001037 .001023 .001009 132 .001126 .001110 .001090 .001077 .001062 .001046 .001031 .001016 .001003 138 .001120 .001104 .001083 .001071 .001055 .001040 .001025 .001011 .000998 144 .001113 .001097 .001077 .001065 .001050 .001035 .001020 .001006 .000993 150 .001108 .001092 .001072 .001060 .001045 .001030 .001015 .001002 .000988 156 .001103 .001086 .001066 .001055 .001040 .001025 .001011 .000997 .000983 162 .001097 .001080 .001061 .001050 .001035 .001020 .001006 .000993 .000980 168 .001092 .001075 .001056 .001045 .001030 .0010)7 .001002 .000988 .000976 174 .001087 .001071 .001052 .001040 .001026 .0010)? .00098 .000984 .000972 180 .001083 .001067 .001048 .001036 .001022 .001007 .000994 .000980 .000968 [ 227 ] Sec. 3 CONDUCTORS AND WIRE TABLES 3 all tO CO t- **<> ssssss f-3 CS O O O 00 CO m crs o sgsasa sssss m ** e>a o o> t-j o o oo o o N vo tfj o> o M $3 2 J3 |] J*J "^ o m m CM o ** o to e/s o oo to * ^WMCOCSJCSI rq oogo|| I eooo -! o rq cs; TH lill in (0 O tO O CO CM O *J CM m- SggagggSSSSSS: oo o CM to ce to co m oo co M o esunomm sssssssssssssssss 5SS3 ICCM eMCMCMCMCMTH ,H ,=4 ,H TH -) TH ^V444*4i4 Mi4i4i4v4 SS8 qooooo ooooqo qoooq i m t- es IH i c- eo CM to f> Tioon) M IN in o m eM t 3S355 SSStSSS SSSS3 00000 00000 0000 [228] CONDUCTORS AND WIRE TABLES Sec. 3 W | I 5 s 331 |SJ PQ W o H 1 II I1IJ Sssi > O O O < SS3 sss ;SSi lii f O C%0 ^H ^1 ** TJH )CO ^t^LOC^COOO oo0>o>oo(0 SmdwJSS i-l Cfl CO ^ U t-0>iHC^^<(O LO IO LO IO LO LO LO t^ ^D C> CO M^^S^J ' C^ C5 ( ijjoo; i ro TJI - as; in I O TH CO i HH O t- < sssss ssssss sssss; lAOOON => O O O O Sss sss sllsis ssssss O t 1 I iH 40 < il 3! sss; t> O> ^H 1 sss; TH i? 00 O t- H T* < SSS SSSS! 111 ^^ > 185! 30 O ISSSSS [ 229 ] Sec. 3 CONDUCTORS AND WIRE TABLES 8 ^^ w PQ aj 2 s'a- C^J C- O i-< T-l CO 10 ifi ssssss iiii gilili 3SS8 S83S?S 3SS88; ggggi: 3385 sslli iiiiii ill! tggggs liiiis > OO O O ' : LO iH lO < SsiiiS ssssss SSS CO OO iH C4 CO (> TH co m m TJ< cs SSSSS5 !S5S SSSJS! iii igiii sss 00 8 ?H ? M S? 5< ? M S S S O O O issssi 111! lisas iSSSSS Sli i8 gi is s: I iH Tj< 1A < >r-(Mcqco co ^ * us us <0 ISSSS SSSSSS inlaSJHt^S SSSSSo CiOOvliHC^ O4 CO CO *tl Tj tO c^ co ^*i ue t- 10 u"3 10 L^ LO trs IS 5S; iiiii [ 230 J CONDUCTORS AND WIRE TABLES Sec. 3 w -^ O .is S ^ <1 2 H H a ri ~ ^ o g ^ B - o alls I S # O CO - O I Tfl Tjl *31 LA LA tD < I O O iH N C4 J H jg 5} ! 5 5 S !> JI C- NO ) LA LA O (O D t- o o ill iS^^Jn SSS333 SSSSSS srs ^ ^ ^ Z; ^ & OLA t- en ^ 10 to c- t> oq t- TH dio oto O Irt 00 iH OT-lT-l iHC^ !S35gSS issi I CO CO * ' OO O t-l r-t 28388! COC^U7i-1CS^* O1 O ! 13: 821 ' O CO OO CS I co co co ^ ss: !|M |85S 93S88S jisii IS3S3 iiill illl! linn iS^si [231] Sec. 3 CONDUCTORS AND WIRE TABLES 8 PQ <1 H 1 1- to c9 co > C- iH CO CO T-4 OO ^ O5 < :SSSS 5So?5J! > m *-( c*3 LO in c-3 ^ ggog gggg; ISSUES? 8S! IKS35 > T-l C4 N CO (MMMM linn mill ISSS hfj O O ] ustotooe-t- t-c-c-c-oooo oo oo oo oo oo oo ig^S^S SSS! SE OC^^tO OOOrHOO^< usStooto tot-ot-^-i ! CO O CSI C4 rii us C^ ^J 5| US US US irs us us to SS; to tO to tD tO i ISli !S3SS?2 S! CS ^H O t- t* < o> *JD c^a to o < r- o> TH esj -<* i Lft LO 4O CO O < !? S^SSS! ^H C^ C^ CO C IOC> t-00 OO(O < M tO 00 rH CO S E^ OG O S CO S< US S OO S> O S3 S M * SS U? to i 3Si: !u?8S8; !^ei> ) US US US tO tO tO to tO I TH H rH T-l H TH rH i-l r oo us o? t-H T i oitocNir-T-i^i t> oo < t~OCOUSOOO H CO u'S sO OO Ci OrH< SSSSSrH rHrHrHrHrHrH SSI isllss [232 ] CONDUCTORS AND WIRE TABLES Sec. 3 8g g *" i M W3" << LCS vH O OQ OO O OQ N U> O iH U> SsSSa > LO t- 00 00 C- M CO it- co e^i 1-1 e OO CO ( !S2J3S2 ^SS^^S Si ss: ^ to < issss ssss;ss3 |PI SspiS co to e ^ to TJ; co r- o ** to CM * LO LO * < iHt0Oi-4tOLO ^J4 to TH iH t O COLO^LO< c- a* IH ej co co Kj4 Tjt m LO o e c-ooooo>< 11 I 1-1 LOT* t- ' !i sill [ 233 ] Sec. 3 CONDUCTORS AND WIRE TABLES 1 1 1 * a a TH TH TH TH CM I CO CO CO CO CO 1 O CO CO CO CO CO n to o oo o T-I 8S|3g y> co co co co co 533352 CO CO CO CO CO CO llllll cocococococo cococococoi >|5je3|8 I TH CO I CO CO I C* tO TH KH CO I tO TH ^W I ' CO 00 T-I I M o t- r- I C4 C4 N C4 C4 N C4 CSCSCSCq. i oo o to m cr> I C- tO CO O tO i c-q cq esi cs o* C4 N I t- IAOO C4 [ Cl N C4 C4 < tt< rjt us in u in C4 C4 C4 C4 C4 N 5SSIS2S SSKSf^g ura to to to -J e- t- c- t- c ei M M I cq C4 P4 C4 N C4 c c ' ese-ies eq p< M N cfl e^j 5< 5 a i c^ es N 1 a " (N 00 rf< O CD 1>C SSS^i [234] CONDUCTORS AND WIRE TABLES Sec. 3 gin 3 35-3 S M It0^< OCOOmCOO> O t- O* ^Jl US US *>< IC^VH ^ o T-t c-3 TJ< U S to PP .00 oooooo oooooo So! ' Tf IAOeIM(O C4iHOOI 111 iiiiil iiilli !! I CO -rtl -<^ '000 VP VP W OOO o LT> o> c^^ooo9to o TH co LO o t- oo o -i ^H CM CM M (TJ 00 * -^ ^ << LT9 10 10 CO O t- s ilslii iiiiii Hill O O 1A C4^HOOOCA ^ 1O CM !> O ^ vt^ 1 " ScM0 5?^HOOC-SSs SoOOrHCO^ IO O OO O> O H CM M < S?M SSS^SS 5S55SS SSSS5S SS35! OOO OOOOOO OOOOOO OOOOOO OOOO< 323 SSSScSS SJS ooo ooeooe CkOOOO o oirt^i ^H co o c- m co -* T -i o eft o Sg^JggJS sss iilisS iiiiii ssssss [ 235] Sec. 3 CONDUCTORS AND WIRE TABLES Q W <-> 1 81 33 in t- oo oo en en o i-n pq oo co oo TJI * !< 10 i 10 us us us o r- c- r- t- incoc- oo co en o o H es cs M eo ^ *< 9 9 2 (Ooco(0t- S3 "*cot~- T -- ^ 553t- P-OOOOWOH ;-iesMc i oo co>AOOeOi-i c*s M TH oo <* c- ooOT-icoc.r> oo o cs co LO co ^^^ninioio us us us o to rH O 00 O O -l "> O CO O CM OO 00 Lf5 O CM t- C- m OO O BiES c-l oo CM IH oo t- co cn co to o> cs IA en IM IA oo o co ?5S t>t-MCnO>0 T-H ;-4 CSI CM N CO CO CO ** * 10 tAl OOO OOOOOrH iHt- I ^ ^COtO (NCO-*OOCOU3 C^ CV5 10 ^1 H 00 CO U9 O O -j CO CO rH OO TTI O O (AvHhO^lr-tCd t~C^COOCOLO OO CS tO CT> rH ^ UJ (X> O T-( co 10 10 us c- e- oo en o o H tH esi CM p e*> co co co ^ ^ ^ ^j >fi ^ ft CO *t o u c- oo io en S4v!v4MM N co co co -^ Tti 4< K TK 10 10 SO 000000 TH T-l iH *H TH iH TH TH T-l TH TH TH TH TH TH TH H ss q^s aaaasa > to oo TH 10 us o ua oo * 10 1- i^co o>ocncniOTii in us o ITHIO s us o r- oo en o o TH tOCO OOOOOO THTHTH co co o IA e N e* o co LOIOCOOO ^ c- o eMs o co us oo o CM * * O 00 O -OOOJO t- *fl ^m'-i CSIC4C4NOOOO CO t- t- US t- TJI o u? o eo t- o w^H 1 J go moo^o^-io E*5Sfi2B9 N o> 10 o m o> esi to o> M I vH csl CO ^ '-O C~ 00 C^ O T-f C ^^4U>CO(DO C t^ !> OO OS CO OO OO rt 00 CO ^< oo o e>4 co Oi-lrH T-l SO tH i-H C^ C*>1 CO CO ^< t/3 LO < t0 *> t^- I> t ( v li ^ t t^ i^ f^ t^^ OOOm-r-ICMt* COt*^OmO) COOCO^HCOO COt^O iH cocotnoe-oo OJOTHCMMCM co^-Smmco <> CD t- TH TH T-J TH T-J TH T-J vi M i CM CM ( CM N CS| CM CM CM CM_ CM CM CM J> < CMl c- i CM C^ I ) co eo^CM co CM t- i-t in en CM !h co TH >TH CM co ^ in co eo cnooTHCMCM CM co -^^ in m in co cc co t- >TH vHTHTHTHiHTH * ^ crt co co TH < J OO in T-H CD O *^THt*CMt-TH -^ OO " I -c^ THSS^CM CM 3 8 S S S S3 S S S J <> 10 co o 00 co co oo CO co co co co oo co cs OOO iHOtlO^^fLAC-* OO 0> O) O O vH T 1 * CSI CO CO CO "d< O -r- TH i- ^H TH T- - iHrHiHCCIC4 W Cfl W C>l C N W Cfl W C>l C N M g saassa sas 00. c c ggg sqqssa sta-saas sssqcq?? s^ ^ SS?5S^!S ScSSS^S SSSSSS ssg aqsa-aa iHsaaas ssssas? o o rH i-H cNCOCO - [ 237 ] Sec. 3 CONDUCTORS AND WIRE TABLES It fcoo H C t i^ cs'V 2 sill " !gggg IIIIII [ V5 irt ^ ^4* < isg ggg: Si! ggiiii issgis ggggg: gggggg gggggg ggggg! looooo oooooo oooooo iili 111! > o o o o o 000000 > Y-l *T OO CT? illss ,-H iH m e> =>.o exs... ISSS2S >peeee ssSsss SSS p oo pop oooooo :ssss? issss CON TH linn ISSSS ao to i* e^ ^H cr> o> o> o> o oooooo !=>><=!<=> =><=>=<=> |g|| SSSS SS3 ISoS pppppp pppppp igg gggggg si t-4 vH H H vH i 00000. igggg: !SS S e-to irt o>9> o p o p gggggg ggg! [ 239 ] Sec. 3 CONDUCTORS AND WIRE TABLES . n in g: in - EiAcSStHA oo to m T* oo c* o o oo t- e * >t-eotoi m in i m m in in <*< * * ^t< *ji i o o e> o o o o o o o o o o o o o o iggggg sgj > -* CO C3 < Isill 1 1 irt ** TJ< POOOO i ca co ooTt< e> oo i iillii ii iiilli iss aaj SO CD tO CO < O O O O < oo*!e4 ooo^c^SS cn>AC4 iHoooot-c- C- C-3 O OO CS I C- tO Lft M iH ) lA lA LA LT> iO | O O O O O SSSi cr> 10 l M O c- * oo m ID I 00 O -^ CS < I TH O 00 <0 ' i tD tf> LT5 lO i >0000< CO -^ ^ tH CO tD <7> O 00 ^*CM^ O O O CO -! T-( T-( CO OO lO OO Tj< OC^i S SS I iH O t- t-( v-4 CSI OO ^O I OO rH CO iH < >O i-H CO O ssssss .g iili H (N CO rj< 10 CO [ 240 ] CONDUCTORS AND WIRE TABLES Sec. 3 I ill '" Hill! iss il ! 1111 g 88888! illi ooooo! iillll 1333; 1333 00 O iiiiii CO CO CO 000 O (0 CSI OO ^* iH OO LO CO il < -* CO CO C^ CN4 CS rH TH T-H *-: . iiiiii iiiiii :sss s; 311; es o o cCO OI0 CO O iiiiii isssi :sss; ISSSi CO CSI ( 11; iiiiii *WfJ- sss: OOOC ss > O> C 1333: OO OT 1*1 OO ** T)< eo e> esi T-I ssssss ssssss ssssss 00 ^JO SON 00 1>000505OO [241] * O O CO t- 00 Sec. 3 CONDUCTORS AND WIRE TABLES 8I H fc fc S l i = fi C- ( SSaSS >-l J IO iH s^s?55S ssssss m n 111111 1 OOiHOO sss xy,tr>-*oq e-eooi imm^m sss: p.sp.s sp.a ss ai 1111 i' oo M or> t- cs co 33SSSS ;2i ass :n0 [ 242 ] CONDUCTORS AND WIRE TABLES Sec. 3 1.. R^. OOOOOO OOOOOO 000001 88.8. IIIII! ia * . :S S! ill! Isslll iiiii Si ililii > O> D E> *H i I ^ CO iH rH i IIIII ie * co ej -i o< ; ! i N t- N ( isssi !| 3 o e< SoSS^ MNiHOOtm wc^t-woS loin-^S.oco gggggS gSSSgg SSS5SS gggggg Hi-l .sii III !!! iiiii ^o?:S3S s: SSgggg g! ISSSS! [243 ] Sec. 3 CONDUCTORS AND WIRE TABLES "II I H ^5 o inoooo <> 10 a> ONca M oo us csi ot-irteo^ !O C rH t* IA OO O OO <0 ^J* C< CO C^ C-fl TH T-( O O O^ US -H OO <) CO iH t- LO Tj< O OO OT O5 OO OO e-io^i THWMCOMCS e e* e> e*i CM M e T~. r* ^^-tooto- O O D- O t> CO OO lO rH OOOt^tOLOtA * CO OO CN CN3 TH Y-I i ) O O ' qss ssssss gggggg gggggg gggg: sssss sggggg gggggg ggg: Si! iiiiii lllggl gggggg O t* ^* M < CM <-(*- if < |eSSS Sggggg gggggg ggggg g ggssSS SSSSSS gggggg ggggg !gg T) t~ (CLAtA^lpOCO CO CO CM C>4 C4 CN M C4 CM CM CM C4 C4 N C4 C4 C4 [244] CONDUCTORS AND WIRE TABLES Sec. 3 w II ll Q'-'W B o CS m H OO M MS Ifl O> <*! 0> l CO C S3! liiiii lilsli iiiiii isli; Ill o to in co o co t- o -^ ooo^oo o LO 01 c^ co 10 o>eoc*< ssi siissl iillsl isllls ill; oes coeST-i^jMCT) * -l< o e^ 00 u * to co d ^H e to oo e> t- e* sa rHCOCO OO^M-^t- iHO>lO<0000 <> OO CO H *-4 O* -^ t- C^ O LOCOAOOTHCO O*- ^O CO i-( O CO C^LO^COC^^H OO)O>OOOO gSS qsii.SS S8S883 SSSSSS 333SS O CO 00 CO OO CO C4 O OO O O O rH Tj< TH 0> O> ^1 C4 C4 N *< t- O "> SS3 ss: ss > OO O ' i in co t- in m co oe-3 in ^ co co -^ o co co co co o o 01 * o o -* <3 rH 3 S CO O S S tD C-I O> C- m -* C4OOOC-VOIA -^ M CS !N rH ;SS SSso oSSooo oooooo ooooo i O O O I :sss: SSSSS SSS [ 245 ] Sec. 3 CONDUCTORS AND WIRE TABLES CO P4 g 5s 2 eti O0 g g H fe o M w xo gco r O ^ s>, a JS O.a ) t- tO N t- 00 N CO tO to 00 O> fS ill iiisss ssssi T-liHC4 t- t- O <0 00 00 CN CO ** O* O 00 tP * CM O CT> OO O (0 IO ^ CO SS5 S3SS3SS SSSSSS SSSSSS SSSSS > C4 C^ CS CO *O CO >O> CO C- 4 iH CO t* ff> ^ -^ -^ C CN] OO O C-O *-1 O t LT5 CO C--1 O O)OOt*O 5S9M*H 000>0>0>0> O> OO OO OO OO OO C- C- C- C- I iH rH rH iH 1-4 TH iH iH O O O O O O O O O O O O O O I M ^ oo -^ TH rq c -tf u-5 i ,HicoMoto encoooCoe^o oo ^i es o oo t- .o ^j co ts TH ssss^a mmssss gggggg ggggg THlOOC* cs r-i -H o 1 oo c- m o> t TH O^COi OQO>A ^1 iH CO iH N C-eo to e- ^i o t- > eot-oooooeo i-t oo m eo T-I 53^ sssss sssss sssss SJSS SSSSSS SSSSSS 3! OOCOCS C CJ iH iH iH iH T-4 r* T-l ^H iH H T-l< MCS MM (M t-H to coooom>noo eo o oo t- < iH O> ^J< 00 CO t- 00 T-I W C* O tO * O t- IO CO iH O ^- JO I ssssiss qqssss ssssss ssssi o 10 oo to oo o 10 ^ r- 1-1 cue tc m sss IsiSSs asSSSi ssisss gilil * oo T-I o -* m o e-J oo to m i< I-KMOO mo-*uo>cq iH ^ o> 10 esi o co o t- m co e^j o o> oo t- to o% oo ^ji es o t- m -^ co C4 1-1 IH r-i o o o o en en m en en oo oo oo TticOM es CM {S rH TH T-J ^H^ITH^I^I^I ^1^(^1000 00000 PEK- 200 220 240 CLAD 3TXANDCD W/# FIG. 86 [ 249 ] Sec. 3 CONDUCTORS AND WIRE TABLES OUV& [250] CONDUCTORS AND WIRE TABLES Sec. 3 TABLE 54 AVERAGE TRACK RESISTANCE Per 1000 Ft. (2 Rails with 20" Bonds) Rail Weights Ibs. per yd. 30 ft. rails 60 ft. rails 1-0000 bonds 2-0000 bonds" 1-0000 bonds 2-0000 bonds 45 50 55 .01392 .01268 .01151 .01314 .01190 .01072 .01314 .01190 .01072 .01274 .01150 .01033 60 65 70 .01085 .01012 .009562 .01006 .00934 .00877 .01006 .00934 .00877 .009668 .008940 .008383 75 80 85 .009002 .008532 .008122 .00822 .007746 .007336 .00822 .007746 .007336 .007823 .007353 .006943 90 95 100 .007762 .007427 .007132 .006976 .006641 .006346 .006976 .00641 .006346 .006583 .006248 .005953 32. SPECIFICATION FOR GALVANIZED STEEL STRAND* M-Inch, 2300-pound Strand This strand shall be composed of seven No. 14 B. W. G. galvanized steel wires and shall be capable of withstanding an ultimate breaking strain of not less than 2300 pounds. %-inch, 5000-pound Strand This strand shall be composed of seven No. 12 B. W. G. galvanized steel wires and shall be capable of withstanding an ultimate break- ing strain of not less than 5000 pounds. Galvanizing. The wires composing a strand shall be galvanized in accordance with the National Electric Light Association standard specification for galvanizing. 33. SPECIFICATION FOR COPPER WIRES AND CABLES WITH WEATHERPROOF INSULATION* Conductor. The copper used in all conductors shall have a con- ductivity of ninety-eight percent of pure copper, Matthiessen's standard. Wire to be soft drawn,- having a tensile strength of not less than 34,000 pounds per square -nch; shall be uniform in quality, smooth, free from flaws and splinters, and drawn true to gauge. *N. E. L. A. specifications. [251 ] Sec. 3 CONDUCTORS AND WIRE TABLES All solid conductors shall be free from joints. All solid conductors shall be B. & S. gauge. Stranded conductors shall be composed of the number and size of wires called for in this specification. Insulation. Over the copper conductors shall be laid a triple- braided cotton covering; this braiding shall be closely woven and thoroughly saturated with an insulating compound, which shall render it non-absorptive of moisture, and which shall not drip at a temperature lower than 160 degrees Fahrenheit, nor lose its elasticity at o degrees Fahrenheit. The finish of the wires and cables shall present a smooth, hard and even surface. The finish weight of the various sizes shall be approximately as named below. The permissible variation in the finished weights not to exceed three percent under or over. SOLID Size B & S. Weight of Copper, Lbs. per 1000 Feet Approx. Weight of In- sulation, Lbs. per 1000 Feet Approx. Lbs. per 1000 Feet Finished Weight Pounds per Mile 0000 640.5 126 767 4050 000 508.0 121 629 3320 00 402.8 99 502 2650 319.5 87 407 2150 1 253.3 63 316 1670 2 200.9 59 260 1370 3 159.3 40 199 1050 4 126.4 38 164 865 6 79.5 32 112 500 STRANDED Size No. of Strands Size of Each Wire in Mils. Weight of Bare Cond. Lbs. per 1000 Feet Weight of In- sulation Lbs. per 1000 Feet Lbs. per 1000 Feet Finished Weight Pounds per Mile 0000 19 105.5 653 147 800 4226 000 19 94.1 517 136 653 3450 00 19 83.7 410 112 522 2760 19 74.6 323 101 424 2240 1 7 109.3 255 73 328 1735 34. SPECIFICATION FOR BARE HARD-DRAWN COPPER WIRE* Material. The material shall be of copper of such quality and purity that when hard drawn it shall have the properties and char- acteristics herein required. *N. E. L. A. specifications. [252] CONDUCTORS AND WIRE TABLES Sec. 3 Shapes. These specifications cover hard-drawn round wire, hard- drawn cable or strand, as hereinafter described. Finish. The wire, in all shapes, must be free from all surface imperfections not consistent with the best commercial practice. Packages. Package sizes for round wire and for cable shall be agreed upon in the placing of individual orders. The wire shall be protected against damage in ordinary handling and shipping. Specific Gravity. For the purpose of calculating weights, cross sections, etc., the specific gravity of copper shall be taken as 8.90. Inspection. All testing and inspection shall be made at the place of manufacture. The manufacturer shall afford the inspector rep- resenting the purchaser all reasonable facilities to enable him to satisfy himself that the material conforms to the requirements of these specifications. Dimensions and Permissible Variations, (a) Size shall be ex- pressed as a diameter of the wire in decimal fractions of an inch, using not more than three places of decimals; i. e., in mils. (b) The wire is expected to be accurate in diameter; permissible variations from nominal diameter shall be: For wire 0.100 inch in diameter and larger, one percent over or under. For wire less than 0.100 inch in diameter, one mil over or under. (c) Each coil is to be gauged at three places, one near each end and one approximately at the middle; the coil may be rejected if, two points being within the accepted limits, the third point is off gauge more than two percent in the case of wire 0.064 inch in diameter and larger, or more than three percent in the case of wire less than 0.064 inch in diameter. Physical Tests. The wire shall be so drawn that its tensile strength and the elongation shall be at least equal to the values stated in the following table. Tensile tests shall be made upon fair samples and the elongation shall be determined as the permanent increase in length, due to the breaking of the wire in tension, measured between bench marks placed upon the wire originally 10 inches apart. The fracture shall be between the bench marks and not closer than one inch to either mark. If by testing a sample from any coil of wire the results are found to be below the values stated in the table, tests upon two additional samples shall be made, and the average of the three tests shall determine acceptance or rejection of the coil. For wire whose nominal diameter is between listed sizes, the requirements should be those of the next larger size included in the table. Electrical conductivity shall be determined upon fair samples by resistance measurements, at a temperature of 20 degrees Centigrade (68 F.). The wire shall not exceed the following limits: For diameters 0.460 inch to 0.325 inch, 900.77 pounds per mile- ohm at 20 C. For diameters 0.324 inch to 0.040 inch, 910.15 pounds per mile- ohm at 20 C. [253] Sec. 3 CONDUCTORS AND WIRE TABLES Gauge Number Diameter Inches Area Cir. Mills Tensile Strength Lbs. per Sq. In. Elongation in 10 Ins., Per Cent 0000 0.460 211,600 49,000 2.7 000 0.410 168,100 51,000 2.6 00 0.365 133,200 53,oOO 2.4 0.325 105,600 54,500 2.3 . 1 0.289 83,520 56,000 2.1 2 0.258 66,560 57,500 2.0 3 0.229 52,440 58,500 1.9 4 0.204 41,620 59,500 1.8 5 0.182 33,120 60,500 1.7 6 0.162 26,240 61,500 1.6 7 0.144 20,740 62,500 1.5 8 0.128 16,380 63,400 1.4 9 0.114 12,996 64,200 1.3 10 0.102 10,404 64,800 1.2 11 0.091 8,281 65,400 1.1 12 0.081 6,561 65,700 1.0 13 0.072 5,184 66,000 0.9 14 0.064 4,096 66,200 0.9 15 0.057 3,249 66,400 0.8 ; ^ 16 0.051 2,601 66,600 0.8 17 0.045 2,025 66,800 0.7 18 0.040 1,600 67,000 0.7 Hard-drawn Copper wire, Cable or Strand Construction. For the purposes of these specifications, standard cable shall be that made of hard-drawn wire laid concentrically about a hard-drawn wire center. Cable laid up about a hemp center or about a soft wire core is to be subject to special specifications to be agreed upon in individual cases. Wire. The wire entering into the construction of stranded cable shall, before stranding, meet all the requirements of round wire, hereinbefore stated. Physical Tests. The tensile strength of stranded cable shall be at least 90 percent of the total strength required of the wires form- ing the cable. Brazes. Brazes made in accordance with the best commercial practice will be permitted in wire entering into cable; but no two brazes in wire in the cable may be closer together than fifty feet. Lay. The pitch of a standard cable shall be not less than 12 nor more than 16 diameters of the cable. The cable shall be laid left handed or right handed, as shall be agreed upon in the placing of the individual orders. 35. SPECIFICATION FOR HARD-DRAWN COPPER-CLAD STEEL WIRE* Material. 1. The material shall be composed of a steel core with a copper coat permanently welded thereto through intervening *N. E. L. A. specifications. [ 254 ] . CONDUCTORS AND WIRE TABLES Sec. 3 layers of copper-iron alloys, and of such quality and purity that when drawn hard it shall have the properties and characteristics herein required. Shapes. 2. These specifications cover hard-drawn copper-clad wire, as hereinafter described. Finish. 3. The wire in all shapes shall be free from all surface imperfections not consistent with the best commercial practice. Packages. 4. (a) Package forms for round wire shall be agreed upon in the placing of individual orders. (b) Each coil of wire shall be burlapped for protection against damage in* ordinary handling and shipping, and shall have the gauge of the wire, weight, etc., approximate length of wire in coil, marked on two tags, one of which shall be attached to the coil inside and the other on the wrapping. Inspection. 5. (a) All testing and inspection shall be made at the place of manufacture. The manufacturer shall afford the in- spector representing the purchaser all reasonable facilities to enable him to satisfy himself that the material conforms to the require- ments of these specifications. (b) On orders where no inspection is to be made, the manufacturer shall test ten percent (10%) of all coils for breaking weight and conductivity, and in the event of their conforming with the values stated in the following tables, the material shall be accepted. A copy of these tests shall be furnished when requested. (c) All orders shall state whether or not inspection is to be made. Test of Weld. 6. The wire when broken by torsion shall show no separation of the copper from the steel. The wire when broken by repeated bending shall show no separa- tion of the copper from the steel. The wire when heated to a dull red and quenched in iced water shall show no separation of the copper from the steel. Alloy Film. 7. When properly polished and etched the alloy film shall be distinctly visible under the microscope. Dimensions and Permissible Variations. 8. (a) Size shall be expressed as the diameter of the wire in decimal fractions of an inch, using not more than three places of decimals, i. e., in mils. (b) The wire is expected to be accurate in diameter; permissible variations from nominal diameter shall be: For wire 0.200 inches and larger in diameter, one percent (1%) over or under. For wire 0.200 to 0. 100 inches in diameter, one and one-half per- cent (1^%) over or under. (c) Each coil is to be gauged at three places, one near each end and one approximately at the middle; the coil may be rejected if, two points being within the accepted limits, the third point is off gauge more than two percent (2%) in the case of wire 0.064^ inches in diameter and larger; or more than three percent (3%) 'in the case of wire less than 0.064 inches in diameter. [255] Sec. 3 CONDUCTORS AND WIRE TABLES Physical Tests Breaking Weight. 9. The wire shall be so drawn that the breaking weight of ninety percent (90%) of the coils tested shall be at least equal to the values stated in the following table, and the remaining ten percent (10%) of the coils shall not be more than five percent (5%) below these values. Tensile tests shall be made upon fair samples. If upon testing a sample from any coil of wire the results are found to be below the values stated, tests upon two additional samples shall be made and the average of the three tests shall de- termine the acceptance or rejection of the coil. B. & S. Gauge Diameter in Inches Breaking Weight 0000 000 00 0.460 0.410 0.365 0.325 10,000 8,300 6,850 5,700 1 2 3 4 0.289 0.258 0.229 0.204 4,800 4,000 3,200 2,600 5 6 7 8 0.182 0.162 0.144 0.128 2,200 1,800 1,450 1,200 9 10 0.114 0.102 975 800 TINNED WIRE. The breaking weight of tinned wire shall be taken at ninety percent (90%) of the values given above. Electrical Conductivity. Electrical conductivity should be de- termined upon fair samples by resistance measurements at a tem- perature of 60 degrees Fahrenheit. The wire shall not exceed the following limits: (a) Forty percent (40%) of the conductivity of the same size copper wire. A variation of five percent below this is allowable, i. e., the conductivity of any coil may be as low as thirty-five percent of that of the same size copper wire. (b) If upon testing a sample from any coil of wire the results are found to be bekny the values stated, the manufacturer reserves the right to cut back into the coil; the result of this test shall determine the acceptance or rejection of the coil. INSULATED WIRE. All wire to be insulated must be inspected at the place of manufacture for mechanical and electrical tests before insulation, the inspector sealing all coils accepted. This inspection of the conductor to be final; further inspection to be made on the insulation only. [ 256 ] CONDUCTORS AND WIRE TABLES Sec. 3 36. SPECIFICATION FOR ALUMINUM WIRES AND CABLES, WEATHERPROOF INSULATION*. Conductor. Aluminum used in all conductors shall have a con- ductivity of sixty-two percent of pure copper, Matthiessen's stand- ard; shall have tensile strength of not less than 20,000 pounds per square inch; shall be uniform in quality, smooth, free from flaws and splinters, and drawn true to gauge. Conductors shall be composed of the number of strands of wire called for in this specification. Each length of stranded conductor shall be composed of wires without joint. Insulation. Over the aluminum conductors shall be laid a triple- braided jute or cotton covering. This braiding shall be closely woven and thoroughly saturated with an insulating compound which will render it non-absorptive of moisture, and which should not drip at a temperature lower than 160 degrees Fahrenheit, nor lose its elasticity at degrees Fahrenheit. The finish of the covering shall present a smooth, hard and even surface. The finished weight of the various sizes shall be approximately as named below. The permissible variation in the finished weights not to exceed three percent under or over. Aluminum Cir. mils. Copper Equiv. No. of Wires Wt. of Bare Aluminum Pounds per 1000 T?Qf Approx. Wt. of Triple Braid In- sulation Lbs. per Approx. Finished Weight Lbs. per 1000 ft. Standard Length of Finished Cable Feet X 1 66 1 1000ft. 336,420 0000 7 310.2 150 460 5060 266,800 000 7 245.7 124 390 3190 211,950 00 7 195.0 115 300 4020 167,800 7 155.0 90 245 5060 133,220 1 7 122.6 55 178 3200 105,530 2 7 97.2 47 144 4040 83,642 2 7 77.0 40 117 2535 66,370 4 7 61.2 37 98 3185 37. SPECIFICATION FOR BARE ALUMINUM WIRE* Material and Construction. All material used in these cables shall be of the best grade of commercially pure aluminum. It shall consist of strands laid up to form a concentric cable, the lay of the strands being as long as possible consistent with making mechanically good cable, in order to keep the increase of resistance due to strand- ing as low as possible. *N. E. L. A. specifications. 9 [ 257 ] Sec. 3 CONDUCTORS AND WIRE TABLES Strands. Each strand used in the cable shall be approximately round and true to the calculated diameter within one percent. Conductivity. The average conductivity of the finished strands of the cable shall be not less than sixty-one percent in the Matthies- sen's standard scale, as determined by test of the individual strands upon a standard conductivity bridge. Tensile Strength. "The tensile strength of the aluminum shall not be less than 23,000 pounds per square inch nor more than 30,000 pounds per square inch, as determined by tests upon individual strands in a standard tensile testing machine." Weight and Stranding. The weight and area per mile of bare cable shall not vary more than two percent from the following table. "The following table shows the usual method of stranding aluminum conductors. Variations from this standard stranding are permissible where the conditions make such variation advis- able." Aluminum Conductor Cir. Mils. Lbs. per M. Feet No. of Strands 66,370 61.2 83,642 77. 105,530 97.2 133,220 122.6 167,800 155. 211,950 195. 266,800 245.7 336,420 310.2 397,500 365. 19 477,000 439. 19 556,500 512. 19 636,000 585. 19 715,500 658. 37 795,000 732. 37 874,500 805. 37 954,000 877. 37 Inspection and Tests. The purchaser shall have the privilege of inspecting the wire called for on orders, and notification shall be given at least five days prior to the time that the material will be ready for inspection, so that his representative may be present. The manufacturers are to supply the apparatus necessary to carry out all tests, free of cost to the purchaser. The tests are to be made at one place, and are to be to the satisfaction of the pur- chaser's representative. Connectors. The manufacturer shall furnish the necessary con- nectors of a type to be approved by the purchaser. [258] CONDUCTORS AND WIRE TABLES Sec. 3 38. SPECIFICATION FOR RUBBER INSULATED TREE WIRE BRAIDED* Conductor. The conductors used shall consist of soft-drawn copper wire, with a conductivity not less than ninety-eight percent of pure copper, Matthiessen's standard, and a tensile strength of not less than 34,000 pounds per square inch. Conductors of sizes up to and including B. & S. may consist of solid or stranded wire. Conductors of sizes over B. & S. shall consist of stranded cable. All wires shall be thoroughly tinned. Insulation and Covering. The wire or cable shall be covered with a wall of insulation containing not less than thirty percent best Para rubber, free from substitutes and reclaimed rubber. The thickness of the rubber insulating wall shall not be less than the following: No. 6 solid /o- inch No. 4 " No. 2 " No. 1 " No.O " No. 00 stranded No. 000 " No. 0000 " The rubber insulating wall shall be covered with a drill tape, well filled with rubber, and with a double braided cotton covering. This braided covering shall be closely woven and thoroughly saturated with an insulating compound which shall render it non-absorptive of moisture, and which shall not drip at a lower temperature than 160 degrees Fahrenheit, nor lose its elasticity at degrees Fahren- heit. The braided covering shall be thoroughly slicked down, so that the complete wire or cable shall present a smooth, hard and even surface. 39. SPECIFICATION FOR CIRCULAR LOOM-COVERED TREE WIRE NO. 6 NO. 4 No. 2* General Description. The insulation shall adhere strongly to and have the same thickness of wall at all points from the conductor. The covering shall consist of a double wrap of tape, over which shall be placed a tightly woven cotton yarn thoroughly treated with a preservative compound containing powdered mica. Conductor. The conductor shall be of soft-drawn Lake Superior copper, having a conductivity of not less than ninety-eight percent (98%) Matthiessen's standard, and shall be thoroughly tinned. The conductors No. 6, No. 4 and No. 2 shall be solid American wire gauge. Tinning. All conductors shall be thoroughly and evenly coated with pure tin. * N. E. L. A. specifications. [259] Sec. 3 CONDUCTORS AND WIRE TABLES Insulation. The insulating wall shall consist of a vulcanized rubber compound of not less than thirty percent by weight of dry, "fine, up-river" Para gum, free from reclaimed rubber, shoddy or rubber substitutes, compounded with from two to three percent by weight of sulphur, not more than three percent of solid waxy hydro- carbons, such as ozokerite or paraffine, and with dry, inorganic mineral matter only as a matrix. The amount of extractive matter contained in the vulcanized compound, as shown by chemical analysis, shall not exceed five percent, of which not more than two percent shall be resinous matter and not more than three percent shall be waxy hydrocarbons. Mechanical. Test pieces cut from the insulating wall must stand stretching not less than ten (10) successive times to two and one- half times their original length before breaking. The portion stretched shall then return within one minute to a length not ex- ceeding 125 per cent of its original length, and a similar sample shall be stretched to three and one-half times its original length without sign of flaw or fracture. Electrical. Each and every length of conductor shall comply with the following table : Megohms per Mile at 60* F. Wall of In- sulation (with- out covering) Outside Diameter OverAll Voltage Test (at Factory) No. 6 2500 No. 4.... 2100 No. 2.... 1700 2/32 2^/32 2|/32 .500 .530 .594 5000 4500 4500 Tests. The testa shall be made at the works of the manufacturer, before the application of tape, braid or other covering. Tests shall be made after at least 36 hours' submersion in water and while still immersed. The insulation test shall follow the voltage test, and be made with a battery of suitable electromotive force, and the reading shall be taken after one minute's electrification. Tape. The plain insulation shall be served with a double wrap or rubber-filled cloth tape. Woven Covering. Over the tape shall be placed a covering of tightly woven cotton yarn, thoroughly impregnated with a pre- servative compound containing powdered mica. This shall be worked into the interstices of the weave and compound, so as to prevent the "flaking off" of the mica surface. Tests. The purchaser shall be allowed the privilege of sending a representative to the works of the manufacturer, who shall be afforded all necessary facilities to make the electrical and mechanical tests, and also assure himself that the specifications are being properly complied with. [260] CONDUCTORS AND WIRE TABLES Sec. 3 BIBLIOGRAPHY Publications of Various Manufacturers. General Electric Review, 1909. Foster's Electrical Engineers' Pocket Book. N. E. L. A. Report of Committee on Overhead Line Construction, 1911. U. S. Bureau of Standards, No. 31. SECTION 4 CROSS-ARMS, PINS AND POLE LINE HARDWARE * SECTION 4 CROSS-ARMS, PINS AND POLE LINE HARDWARE TABLE OF CONTENTS ARTICLE Cross-arms 1 Wood Cross-arms , 2 Specifications for Untreated Cross-arms 3 Specifications for Creosoted Pine Cross-arms 4 Steel Cross-arms 5 Patent Cross-arms 6 Pins 7 Standard Pin Threading 8 Specification for Wood Insulator Pins 9 Combination Wood and Metal Pins 10 Metal Pins 11 Screw Type 12 Cemented Type 13 Attaching Pins to Cross-arms 14 Line Hardware 15 (a) Cross-arm Braces. Specification for Cross-arm Braces. (b) Cross-arm Bolts, Carriage Bolts, Lag Screw and Washers. Specification for Cross-arm Bolts, Carriage Bolts, Lag Screws and Washers. (c) Pole Steps. Specification for Pole Steps. ^-inch gauge without forcing but not a 1 ^-inch gauge. Middle bolt hole %-inch gauge, without forcing Brace bolt holes %-inch gauge, without forcing All cross-arms not conforming to these requirements shall be rejected. [269] Sec. 4 CROSS-ARMS, PINS, ETC The pin and bolt holes shall be smooth and the arms shall not be badly splintered where the bits have broken through. The brace bolt holes shall not be drilled through the pin holes. STORAGE After the cross-arms are shaped they shall be stacked in cross- piles on skids in such a manner as to insure good ventilation. The stacks shall be roofed to prevent the penetration of rain, or the direct action of the sun, 4. SPECIFICATION FOR CREOSOTED PINE CROSS-ARMS.* Material. All cross-arms shall be made from sound, straight- grained, short leaf or loblolly pine. Quality. All cross-arms shall be free from loose or unsound knots over three-quarters (%) of an inch in diameter. They shall be free from loose hearts, rot, dote, red heart, worm holes, shakes or ex- cessive wane or pitch pockets. Workmanship. All material and workmanship shall be of the best commercial grade. Storing. If the cross-arms are to be stored by the manufacturer, they shall be so stacked in cross piles on skids as to insure good ventilation and shall be roofed to exclude sun and rain. Dimensions. All cross-arms shall be of the style and of the dimensions shown in drawing (Fig. 88), which drawing forms a part of this specification. Creosoting shall comply with the specification for creosoting in Section 9, article 14. 5. STEEL CROSS-ARMS are usually of angle or channel section. Such arms have not been standardized. Their length, the location of the pin holes and bolt holes are dependent upon the conductor spacing, the conductor arrangement which it is proposed to use, and upon the method by which the arm is to be attached to the pole. 6. SPECIAL CROSS-ARMS constructed of malleable iron, pipe fittings and various steel sections are available, two of which are illustrated in Figs. 89 and 90. Such cross-arms are manufactured for different conductor separations. 7. PINS may be divided into three general classes: (a) All wood pins; (b) Combinations of steel, wood and porcelain pins; (c) All metal pins. Wood, as a structural material for use in supporting line insulators, has for many years been regarded as desirable. It is cheap, easily fabricated and in some slight degree adds to the insulator strength. *From 1911 Report of the Committee for the Preservative Treatment of Wood Poles and Cross-arms. [ 270] CROSS-ARMS, PINS, ETC. Sec. 4 A properly impregnated pin of generous design is generally satis- factory, except when Used on higher potential systems. Thte fault with wood pins lies in the danger of burning or digesting of that portion of the pin adjacent to the insulator. At the threaded per- tion, the wood pin is of smallest cross-section, and being thoroughly dry at this point, the resistance to leakage or capacity current flow is greatest. Also the electrostatic flux density is greatest at the [271] Sec. 4 CROSS-ARMS, PINS, ETC. point of least cross-section, so that burning or digesting of the pin may occur. Metal pins entirely relieve the burning and digesting difficulty and also provide greater mechanical strength. In general, wood pins used in connection with insulators of very high factors of safety, in climates not affected by salt fogs or chemical fumes are reasonably satisfactory. Solid steel or iron pins are not as desirable as those pins which include some form of separable thimble, that can be economically and properly cemented into the insulator at the factory and in turn screwed on to the pin body erected on the poles or towers. Probably the greatest benefit of this iorm of construction is the ease with which broken insulators can be replaced. 8. STANDARD PIN THREADING. The standard pitch for pin and pinhole threading is 4 threads per inch and the standard diameters are 1" (standard pinhole) and 1%" (large pinhole). These diameters are the extreme diameters at the top of the pin and at the bottom of the pinhole as illustrated (Fig. 91). The FIG. 91. Standard pin threads. standard taper for the diameters of pins and pinholes is ^ " in- crease in diameter per 1" in length. The National Electric Light Association standard wood pin is illustrated in Fig. 92, specifications for which follow: 9. SPECIFICATION FOR WOOD INSULATOR PINS.* The quality of the materials used and the methods of manufacture, handling and shipment shall be such as to insure for the finished pins the properties and finish called for in these specifications. The manufacturer must make sure that all materials and work are in accordance with the specifications before the pins are delivered. The purchasing company is to have the right to make such inspections and tests as it may desire, of the materials and of the pins at any stage of the manufacture, such inspections not to include the in- spection of the processes of manufacture. The inspector of the * Standard National Electri Light Association Specification. [272] CROSS-ARMS, PINS, ETC. Sec. 4 purchasing company shall have the power to reject any pin which fails to satisfy the requirements of these specifications. Inspection shall not, however, relieve the manufacturer from the obligation of furnishing satisfactory material and sound, reliable work. Any unfaithful work or failure to satisfy the requirements of these specifications that may be discovered by the purchasing company on or before the receipt of the finished pins shall be corrected FIG. 92. Standard N. E. L. A. wood pin. immediately upon the requirement of the purchasing company, not- withstanding that it may have been overlooked by the inspector. General. These specifications cover the manufacture of standard locust pins as ordered. The drawings and specifications are intended to include all in- [273] Sec. 4 CROSS-ARMS, PINS, ETC. structions necessary for the manufacturer to guide him in his work. They are intended to co-operate with and supplement each other, so that any details indicated in one and not in the other shall be executed the same as if indicated in both. Figures upon the drawing shall be followed in preference to scale measurements. All material and workmanship, unless otherwise specified herein, shall be of the best grade. Material. All pins shall be made of sound, straight grained yellow or black locust, free from knots, checks, sapwood, worm holes, brash wood, cracks or other defects, except as hereinafter specified. Knots. The pins shall be free from large, loose or unsound knots. Small knots not over one-eighth (^g) of an inch in diameter are allowable on the shoulder and on the lower half of the shank of the pin. Checks. Small season checks are allowable on the shoulder and on the lower half of the shank of the pin. The number of such pins shall not exceed five (5) percent of the number furnished. Sapwood. Sapwood is allowable on the shoulder of the pin pro- vided it does not extend to the shank Worm Holes. If the wood is otherwise sound, worm holes are allowable on the lower third of the shank. The number of such pins shall not exceed five (5) percent of the number furnished. Finish. The grain of the wood on all pins shall be reasonably parallel to the axis of the pin. The grain through the center of the bottom of the pin shall not run out below the bottom thread. Seasoned Pins. All seasoned pins shall have four (4) threads to the inch, and the dimensions shown on drawing, Fig. 92. The threads shall be smooth and of uniform pitch, and such that a standard insulator can be readily screwed on to a standard pin, until the end of the pin touches the top of the insulator and, when in this position, there shall be no perceptible rocking or play of the insulator on the pin. The pins shall be as nearly as possible of a circular cross-section. Flat surfaces not over one-eighth (}/$) of an inch in depth are allowable on the shoulders of the pins; the number of such pins shall not exceed five (5) percent of the number furnished. Unseasoned Pins. Pins manufactured from green or partially seasoned wood shall, when seasoned, conform to the requirements above specified for seasoned pins. 10. COMBINATION WOOD, PORCELAIN AND METAL PINS, are usually made by using a wood top, a wood and porcelain top, or a metal and porcelain top and a steel through bolt as illustrated in Figs. 94-95. 11. METAL PINS. The construction of metal pins varies in the manner in which the insulator is attached to the pin and the manner in which the pin is attached to the crossarm. Insulators may be attached to the pin by either of two methods: [274] CROSS-ARMS, PINS, ETC. Sec. 4 FIQ. 93. Wood or solid metal pin. FIG. 94. Wood, steel, Fia. 95. Porcelain base through bolt pin. wood top pin. FIG. 96 Clamp pin, solid metal split head, with felt insertion. FIG. 97 Wire screw thread, clamp pin. F2751 Sec. 4 CROSS-ARMS, PINS, ETC. M, [276] CROSS-ARMS, PINS, ETC. Sec. 4 T 277 ] Sec. 4 CROSS-ARMS, PINS, ETC. (a) The screw type in which the insulator is screwed on to the pin. (Art. 12.) (b) The cemented type in which the insulator is cemented to the pin or a detachable portion of the pin. (Art. 13.) 12. SCREW TYPE. The designs of screw threads vary. A number of types are as follows: 1st. The solid metal pin (Fig. 93) because of the unequal expansion and contraction of the pin and the insulator, may cause failure of the insulator. When such pins are used it is customary to wrap the pin with a few layers of tape thus providing a cushion to relieve the stresses. 2nd. The solid metal pin in which the head is split (Fig. 96) and a piece of felt inserted, in order to relieve the unequal expansion and contraction stresses. 3rd. The spiral spring (Fig. 97) in which the stresses, due to the unequal expansion and contraction, are relieved by the lengthening or shortening of the spring, which slowly twists around in the insulator. 4th. The flexible stamped thread (Fig. 98) consisting of a solid pin on which is riveted a steel saw tooth shaped flexible stamping, which allows for the unequal expansion and contraction of the insulator and pin. A flat spring over the top of the solid part of the pin prevents breakage of the insulator when installing. 13. CEMENTED TYPE. Pins to which insulators are cemented are of two general classes: (a) Pins to which the insulator is directly cemented (Figs. 101 and 105.) (b) Pins with separable thimbles, the thimble only being cemented into the insulator. (Figs. 99, 100, 102, 103, 104.) The latter are the types generally used, as the former necessitate the removal of the pin when changing the insulator. 14. ATTACHING PINS TO CROSS-ARMS. Pins may be attached to the cross-arms by three methods: (a) A driving fit, (Fig. 93) in which the tapered pin shank is driven into a hole in the cross-arm. This type is generally used in connection with wood cross-arms and is usually confined to all wood pins. Where so used, a nail is driven through the cross-arm and the pin in order to secure the pin in position. (b) Bolted type (Figs. 94, 95, 99, 100, 102, 103, 104, 105) in which the pin is fastened to the cross-arm by means of a through bolt. (c) The clamp pin (Figs. 96, 97, 98, 101) in which the pin is so constructed that the cross-arm is girdled and the pin clamped into position. 15. LINE HARDWARE (a) Cross-arm Braces may be either of flat bar or angle section. For ordinary distribution work flat bar braces are generally used. F 278 1 CROSS-ARMS, PINS, ETC. Sec. 4 The standard section of steel bar braces is \Y' x %"; the length from 20" to 32". Angle iron braces in one piece, as illustrated in Fig. 106 have been used to some extent in wood pole work. The standard National Electric Light Association 28" brace is illustrated in Fig. 107, specification for which follow: FIG. 106. Angle iron cross-arm brace. SPECIFICATIONS FOR CROSS-ARM BRACES.* Workmanship. All material and workmanship shall be of the best grade. Material. All braces shall be made of iron or mild steel, "Manu- facturers' Standard," galvanized or ^sherardized, as provided in The National Electric Light Association standard specification for galvanizing or sherardizing. The holes in the braces shall be clear and free from superfluous zinc. Dimensions. All braces shall be made in accordance with the dimensions shown in drawing, Fig. 107. If J) FIG. 107. Standard N. E. L. A. Cross-arm brace. (b) Cross-arm Bolts, Carriage Bolts, Lag Screws and Washers. The National Electric Light Association standard cross-arm bolts, carriage bolts, lag screws and washers are illustrated in Fig. 96, specification for which follows: SPECIFICATION FOR CROSS-ARM BOLTS, CARRIAGE BOLTS, LAG SCREWS AND WASHERS.* This specification covers bolts with cut thread only, which must be furnished unless specific instructions are given otherwise. Lag * Standard National Electric Light Association Specification. [ 279 ] Sec. 4 CROSS-ARMS, PINS, ETC. CROSS-ARMS, PINS, ETC. Sec. 4 screws can be furnished with either fetter or twist threads, unless either one is particularly specified. The materials and styles called for are intended to be stock materials and sizes. Should the detail dimensions conflict with standard sizes, the manufacturer should state wherein the differ- ences exist, but in all cases the mechanical requirements must conform. Workmanship. All material and workmanship specified herein shall be of the best grade. Material. Cross-arm bolts, carriage bolts, lag screws and washers shall be made of iron or mild steel, "Manufacturers' Standard," and shall be galvanized or sherardized in accordance with the National Electric Light Association standard specification for galvanizing or sherardizing. Dimensions. The dimensions of this material shall be in accord- ance with drawing, Fig. 108. Finish. All bolts must be free from badly formed or otherwise defective heads. The heads of the bolts must be rounded or chamfered. The threads must be full and clean and concentric with the axis of the bolts. All nuts must be symmetrically formed and must have the hole centrally located. The axis of the threads must be perpendicular to the face of the nut. All nuts must be an easy fit for the bolt, so that the nut can be run the entire length of the thread without undue forcing with the fingers. All washers must be symmetrically formed and have the holes centrally located. Bolt heads, nuts, etc., shall be of sufficient strength to develop the ultimate strength of the bolt shank. Galvanizing. All galvanizing or sherardizing shall be in accord- ance with the National Electric Light Association standard specifica- tion for galvanizing or sherardizing. A coating of zinc shall be left on the threads of the bolts conform- ing in all respects with the said specifications for galvanizing or sherardizing. The threads of the nuts need not be galvanized. The holes in the washers shall be clean and free from superfluous zinc. The galvanizing shall not be chipped off when washers have stuck together. (c) Pole Steps. The standard National Electric Light Associa- tion wood pole step is illustrated in Fig. 109, specifications for which follow: SPECIFICATION FOR POLE STEPS* Workmanship. All material and workmanship shall be of the best grade. * Standard National Electric Light Association Specifications. [ 281 1 Sec. 4 CROSS-ARMS, PINS, ETC. Material. All pole steps shall be made of iron or mild steel, "Manufacturers' Standard," galvanized or sherardized in accord- ance with the National Electric Light Association standard specifica- tion for galvanizing or sherardizing. Dimensions. All pole steps shall be made in accordance with the dimensions shown in drawing, Fig. 109. Mechanical Requirements. When rigidly held by the head, the pole step shall be capable of being bent through an angle of 90 degrees, about a diameter equal to the diameter of the pole step, without breaking. FIG. 109. Standard pole step. (d) Guy Rods. The standard National ElectricLight Association guy rods are illustrated in Fig. 110, specification for which follows: SPECIFICATION FOR GUY RODS* This specification covers the construction of a standard guy rod. Workmanship. All material and workmanship shall be of the best grade. Material. All guys rods shall be made of iron or mild steel, "Manufacturers' Standard," galvanized or sherardized. Dimensions. All guy rods shall be made in accordance with the drawing shown in Fig. 110. Finish. The welded joints shall be of the best workmanship, thoroughly welded without being overheated. The threads on the bolts shall be full and clean and concentric with the axis of the rod. The thread end of the rod shall be rounded or chamfered. All nuts shall be symmetrically formed and shall have holes centrally located. The axis of the threads shall be reasonably perpendicular to the face of the nut. All nuts must be an easy fit for the bolt, so that the nut can be run the entire length of the thread without undue forcing with the fingers. * Standard National Electric Light Association Specification. [ 282 ] CROSS-ARMS, PINS, ETC. Sec. 4 [ 283 ] Sec. 4 CROSS-ARMS, PINS, ETC. All washers must be symmetrically formed and have the holes centrally located. Mechanical Requirements. The strength of the eye, nut and thread shall be sufficient to develop the ultimate strength of the rod. Galvanizing. All galvanizing or sherardizing shall be done in accordance with the National Electric Light Association standard specification for galvanizing or sherardizing. A coating of zinc shall be left on the threads of the rods. The threads of the nuts need not be galvanized. (e) Patent Guy Anchors. There are a number of different designs on the market. Among them are the screw type, the scoop or flat expanding plate type, the straight malleable-iron plate deadman and various kinds of harpoon-like designs. The screw type is set in the ground by means of a special wrench and requires no digging in its installation. The scoop and the expanding types of anchors require the digging of holes of small diameter with an earth auger. The expanding types are placed in straight auger holes and then by hammering a shoulder or lug with a tamping bar, multiple discs or arms are projected into the walls of the hole. The value of a patent guy anchor in any particular soil is dependent upon the effective bearing area that it possesses. Where guys supporting excessive strains are used, the deadman or anchor log type will usually prove the more satisfactory. (f ) Pole Brackets. The number of designs of pole brackets are so numerous and their selection is so dependent upon the type of con- struction adopted, that illustrations or descriptions to be of any value require considerable space. In general, such brackets should be carefully selected with respect to strength and stability of con- struction, and should be galvanized or sherardized in accordance with the National Electric Light Association specification for galvanizing or sherardizing. BIBLIOGRAPHY N. E. L. A. Overhead Line Construction Committee, 1911. Publications of various manufacturers. [2841 SECTION 5 INSULATORS SECTION 5 INSULATORS TABLE OF CONTENTS ARTICLE General 1 Porcelain 2 Wet Process 3 Dry Process 4 Glazing and Firing 5 Relative Advantage of the Wet and Dry Processes 6 The Properties of Insulator Glazing 7 Glass Insulators 8 The Cementing Together of Built up Insulators 9 Composition Insulators 10 The Effect of Mechanical Stress on Insulators 11 The Effect of Different Types of Pins on Insulator Characteristics 12 Electrical Characteristics 13 Ageing of Insulators 14 Testing Insulators 15 Insulator Tests 16 Elimination Tests on Pin Type Insulators 17 Elimination Tests on Suspension Type Insulators 18 Dry Arc-over Test on Pin Type Insulators 19 Dry Arc-over Tests on Suspension Type Insulators 20 Rain Arc-over Tests on Pin Type Insulators 21 Rain Arc-over Tests on Suspension Type Insulators 22 Mechanical Test on Pin Type Insulators 23 Mechanical Tests on Suspension Type Insulators 24 Puncture Tests 25 Method of Measuring Test Voltage 26 Insulator Protection 27 Voltage Distribution on the Suspension Insulator String 28 Effect of Leakage 29 Capacity of Insulator String 30 Effect of Capacity. 31 Calculated Characteristics 32 Grading the Capacity of Insulators 33 [287] 1. General. Insulators may be divided into three general classes: (A) Pin type. (B) Suspension type. (C) Strain type. The first two types are made of porcelain, glass or composition and the third of porcelain, glass, composition and wood. Pin type insulators are of a pedestal form and designed to carry the wire above the cross arms or structure support. Suspension and Strain insulators are similar in type; so designed that the maximum mechanical stress is applied along the axis of the insulator and not at right angle thereto, as in the pin type in- sulator. FIG. 112. Porcelain pin FIG. 111. Porcelain pin type msu- type insulator, line vol- lator, line voltage 70,000 volts. tage 45,000 volts. 2, PORCELAIN insulators are made from clays. The clays are formed from decomposed feldspar and granites, and may be divided into two main classes: (a) Residual, or clay found in the localities in which it was formed. (b) Sedimentary, or clay that has been transported by water and deposited in beds. Clays vary in their chemical, mechanical, electrical and workable characteristics, depending upon the localities from which they are secured. Insulator manufacturers combine the various clays, each making a special mixture in order to conform to their particular method of manufacture and to some .extent varying the mixture, depending upon whether the clay is to be used in the wet or dry process of manufacture. The mixing of the clay is a mechanical process in which great care is taken to thoroughly mix the compound in order to be assured of a uniform product. The mixture is put through a number of processes until a plastic thoroughly mixed compound is produced. The actual manufacture of porcelain insulators can be divided into two classes: (a) The wet process. (Art. 3.) (b) The dry process. (Art. 4.) 10 [ 289 ] Sec. 5 INSULATORS [ 290 ] INSULATORS Sec. 5 3. Wet Process. In the manufacture of insulators by the wet process the plastic clay is worked into a mould, care being taken to completely fill all the cavities in the mould. The inside of the piece is formed by a plunger. Some manufacturers revolve the mould and others the plunger. All the higher voltage insulator parts are made in this manner except that in the manufacture of very small insulators, the plunger is so designed that it also forms the inside thread of the insulator. The moulds containing the partially formed insulators are then placed in a drying room where, when partially dried, the mould is removed and then the piece is allowed to become bone dry. This bone dry piece is placed on a revolving mandrel and its surface is scraped and finished. The parts that come in contact with the FIG. 115. Porcelain pin type insulator, line voltage 44,000 volts. cement and also the side wire groove are turned, after which the insulator is ready for glazing and firing. 4. Dry Process. In the manufacture of insulators by the dry process the mixture of clay is different from that used in the wet process. After thoroughly mixing, it is allowed to become dry. It is then crushed into a fine powder and pressed into shape in a steel mould. The mass is removed and when it has become bone dry, it is ready for glazing and firing. 5. Glazing and Firing. Insulators are glazed by dipping the formed clay into a glazing solution, protecting the surfaces which are to be left unglazed, from the solution. Different glazing mate- rials are necessary for different colored glazing. Three colors are generally used, white, brown and blue or slate color. White glaze [291] Sec. 5 INSULATORS is made of the same material as the body of the piece with an extra fine quality of flux, i.e., feldspar. Brown glaze is a pure earthy matter in suspension, manganese oxide and iron oxide being some- times used. Blue or slate colored glazes may be secured by use of co- balt oxide. The pieces which have been dipped in the proper glazing FIG. 116. Porcelain pin type insula- FIG. 117. Porcelain pin type insula- tor, line voltage 25,000 volts. tor, line voltage 22,000 volts. solution are then packed and fired in kilns, in which the insulators are so arranged that they are protected from direct contact with the fire. Proper firing requires from 40 to 48 hours and necessitates con- stant attention, in order that the insulators or parts shall not be over or under fired. After proper firing of the insulators or insulator FIG. 118. Glass pin type insulator, line voltage 25,000 volts. FIG. 119. Glass pin type insula- tor, line voltage 20,000 volts. parts, they are allowed to cool slowly and are then sorted to eliminate pieces having visible flaws. 6. Relative Advantage of the Wet and Dry Processes. Where high voltage test requirements must be met, insulators made by the wet process should be used, as the body is dense, homogeneous [ 292 ] INSULATORS Sec. 5 and uniform. Porcelain insulators made by the dry process do not possess these features to as great an extent and are, therefore, less dependable and should only be used on comparatively low volt- age installations. FIG. 120. Glass pin type insulator, line voltage 10,000 volts. 7. The Properties of Insulator Glazing. Insofar as most com- mercial forms of insulators are concerned, the glaze adds practi- cally nothing to the dielectric strength, its prime use being to keep the insulator clean and to present a smooth glossy surface, which tends to prevent the permanent adherence of dust. All glazes which have colors contain metallic oxides, and even some of the transparent glazes have a large percentage of metallic oxide in the form of lead, zinc, tin, manganese, iron or cobalt. All of these can be used with success in insulator glazes, and are used FIG. 121. Composition pin type insulator, line voltage 38,000 volts. by all of the manufacturers to a large extent. The brown glazes owe their coloring to iron and manganese oxide. The puncture value is practically independent of the material used in glazing. The glaze is essentially glass and, therefore, has the same mechanical characteristics as 8. GLASS INSULATORS. Glass for insulators is manufac- tured from sand, lime and soda ash, which materials when properly mixed are melted in a furnace at a temperature of about 2600 F. The materials, as they become completely melted are in the form of a clear liquid glass, which has a plastic nature. The mass is pressed into a mould of proper form where it is allowed to cool, after which it is removed to an annealing oven and thoroughly an- nealed. When the insulators are removed from the annealing oven, [293] Sec. 5 INSULATORS they are allowed to stand in the open air for about one month. Then they are sorted and tested. 9. THE CEMENTING TOGETHER OF BUILT UP IN- SULATORS. Porcelain and glass insulators particularly of the FIG. 122. Porcelain suspension type FIG. 123. Porcelain suspension in- insulators. sulator string for 100,000 volts. FlQ. 124. Porcelain suspension type insulator. FIG. 125. Porcelain through pin type insulator, line voltage 23,000 volts. [ 294 ] INSULATORS Sec. 5 higher voltage type are made up of a number of pieces, the proper cementing together of which necessarily is of great importance. Portland Cement is chiefly used. Other cements are available, the principal ones of which are Sulphur, Condensite and Plaster of Paris. When using cement, pure Portland Cement of the best FIG. 126. Composition suspension FIG. 127. Porcelain suspen- type insulator. sion type insulators. quality without any other ingredients is desirable in order to be assured of good mechanical strength. Compared to porcelain, cement is a good electrical conductor and therefore acts to a greater or less extent as a conducting condenser plate between the two insulator parts which it connects. FIG. 128. Porcelain strain insulators. Condensite seems to be the most successful cement that can be used for cementing together parts of glass insulators and while it has good electrical characteristics, it is very expensive. Sulphur is good mechanically and electrically, but it has a low melting point and, if the insulator heats slightly, the sulphur will melt, causing mechanical failures. [295] Sec. 5 INSULATORS Plaster of Paris is comparatively mechanically weak and there- fore seldom used. Care should be taken to use a cement which does not act chemic- ally on the metal parts, for instance, producing an oxide on their surface thus enlarging them and producing stresses which may cause the porcelain to crack. 10. COMPOSITION INSULATORS are made from various non-conducting mineral compounds and are usually forced into the moulds when in a heated plastic form. They are generally built in one piece. The manufacturers of such insulators claim very high mechanical and electrical values for their product. 11. THE EFFECT OF MECHANICAL STRESS ON INSU- LATORS. In an insulator, as in a steel spring, the maximum stresses to which it is subjected will materially affect its life and its reliability. Carrying the comparison still further, surges with steep D-Oiomofhoie FIG. 129. Porcelain strain insulators. wave front may start an initial breakdown in the dielectric, the performance being similar to that of a spring worked to a point where the elastic limit is exceeded, beyond which point crystalliza- tion takes place very rapidly. If the severe conditions are main- tained the fife of the insulator or spring is necessarily very short. Since the mechanical requirements of insulators are usually de- finite and as the mechanical loading affects the electrical factors of safety, such factors must be considered in insulator design. The suspension insulator being free from bending moments has many mechanical advantages over the pin or pedestal type insulator. When the insulator is light and the span short the internal me- chanical stresses of the insulator may usually be neglected with safety. Long spans and large conductors produce high working loads setting up stresses which, when combined with the internal stresses, may so lower the factor of safety that destruction of the dielectric will follow. [ 296 ] INSULATORS Sec. 5 For the porcelain insulator it is necessary to consider the stresses set up by the working loads, those due to differences in the coeffi- cients of expansion of the porcelain and the metal parts and the stresses set up by the cement or by the oxidation of the metal. For glass insulators, in addition to the above, the very uncertain internal stresses, due to uneven shrinkage in cooling, must also be considered. The safe mechanical stresses that may be applied to insulators are generally determined experimentally, as they vary with the material and the design. 12. THE EFFECT OF DIFFERENT TYPES OF PINS ON IN- SULATOR CHARACTERISTICS. The pin has practically no effect on the mechanical characteristics of an insulator, as the insulator is usually much stronger than the pin. A load applied to the insulator sufficient to produce a bending moment on the pin will usually bend or break the pin before any damage occurs to the insulator. Metal pins or pins with metal through bolts, mounted on grounded arms or on steel structures, carry the ground potential into the pin hole and, therefore, increase the electrical stress on the insulator head. Metal pins on wood arms have practically no effect on insulator characteristics. All wood construction relieves the electrical stress on the insulator, as a part of the dielectric strain is taken up by the wood. On transmission lines for the higher voltages there is more or less leakage of electricity over the insulator to the pin. This dis- charge in some cases produces a gradual charring or burning of the surface of the pin, that sooner or later destroys it. In others the wood does not appear to burn, but a peculiar destructive action not fully understood sets in and destroys the pin. The phenomenon resembles a rapid dry rot. The pin threads crumble away and the fibres disintegrate until the pin may be crumbled into dust by the hand. According to one theory the leakage over the pin produces a certain amount of nitric acid that gradually corrodes and destroys it. In order to prolong the life of wood pins it is customary to boil them in some insulating compound, such as oil or paraffin. When this process is carefully conducted by boiling the pin in a vacuum so that the air that is inevitably contained in the wood may be exhausted and the cells filled with the boiling preservative com- pound the life of the pin is much prolonged and its insulating qual- ities much improved. When glass insulators are used, insulatorpins should be composed of wood, steel shanks with wood thimbles, or so arranged that a cushion is provided between the insulator and the pin. This is necessary because of the relatively low coefficient of expansion of glass, which, when all metal pins are used, causes mechanical fail- ure. _ .. ^ ...... 13. ELECTRICAL CHARACTERISTICS. Insulators should be designed so that they will flashover before puncturing. On pin type insulators the ratio between puncture and flashover is about 1.35 to 1. The present tendency is to increase this ratio. [ 297 ] Sec. 5 INSULATORS The ratio between puncture and flashover voltage for suspension type insulators is practically the same. This applies, however, to each unit in the string. The number of units required in a string may change this ratio depending upon the insulator design, the distance maintained between insulator units, and the distance be- tween the insulator string and adjacent metallic object. Various types of Pin, Suspension and Strain Insulators are illus- trated in Figs. Ill to 132. 14. AGEING OF INSULATORS. Insulators that have sais- factorily passed factory and subsequent tests by the purchaser have FIG. 130. Wood strain insulator. Fio. 131. Composition strain insulator. FIG. 132. Composition strain insulator. in some cases shown poor performance after having been in service for several years. There is considerable difference in opinion as to whether there is any change in the physical properties of an insu- lator which can be attributed to ageing. Fatigue of materials is known to exist in cases where continuous mechanical stress is applied. It is therefore plausible to believe, until some proof to the contrary is furnished, that dielectric ageing due to electrical shock does exist. Insulator failures may also [ 298 ] INSULATORS Sec. 5 be due to the gradual breakdown of the dielectric rather than to physical change due to continued electrical shock, or may be the result of very high frequency disturbances, which will puncture rather than flashover the insulator. The so-called ageing is probably due to the development and gradual spreading of small cracks. These cracks may be started by internal strains, loads working too near then* mechanical break-down point, cement expanding and over-voltage surges (cumulative effect). 15. TESTING INSULATORS. It is the practice of many com- panies to subject all insulators to tests in addition to the usual factory tests. Such tests will necessarily vary, depending upon the line under construction and the availability of testing equipment. The following^ests are given as representing general practice. Any one or all of them may be applied, depending upon the desires of the individual purchaser. 16. INSULATOR TESTS. The tests on insulators may be di- vided into five (5) sections as follows: TESTING (a) Elimination Tests. 1-Pin type (Art. 17.) 2-Sus. type (Art. 18.) (b) Dry Arcing Tests. 1-Pin type (Art. 19.) 2-Sus. type (Art. 20.) (c) Rain Arcing Tests. 1-Pin type (Art. 21.) 2-Sus. type (Art. 22.) (d) Mechanical Tests. 1-Pin type (Art. 23.) 2-Sus. type (Art. 24.) (e) Puncture Tests. 1-Pin type (Art. 25.) 2-Sus. type (Art. 25.) 17. Elimination Tests on Pin Type Insulators. Such tests usually consist in testing all the complete insulators by inverting them in a pan of water, of such a depth as to cover the center of the side wire groove. The inside of the insulators is then filled with water until the thread is covered. Voltage is applied between the water inside and outside of the insulator. The value of this voltage is generally regulated so that it is just below the arc-over value of the insulator and it is applied for about one minute. By such a test the faulty insulators are eliminated. The insulator, when tested in this manner, will arc-over at a lower voltage than when mounted in its proper position, as the total amount of leakage surface is reduced by an amount proportional to the ratio of the leakage surface covered by water, to the original leakage surface. 18. Elimination Tests on Suspension Type Insulators. Each unit is tested in the same manner as that used for testing Pin In- sulators, thus eliminating any defective units before assembling. Completed insulator strings may also be so tested. [ 299 ] Sec. 5 INSULATORS 19. Dry Arc-Over Test on Pin Type Insulators.* A proportional number of assembled insulators are mounted on metal pins under con- ditions resembling those to which the insulator will be subjected when in service, and voltage is applied between the pin and a rod attached to the insulator in a position similar to that which the line wire will occupy. The arc-over voltage obtained in such a test will be considerably higher than that obtained in the elimination tests. 20. Dry Arc-Over Tests on Suspension Type Insulators.* A pro- portional number of units for given service conditions are assembled and suspended from a metal hook or clamp. A rod is then attached to the wire clamp of the lowest insulator in a position similar to that which the line wire will occupy. Voltage is applied between the cap of the top insulator and the rod until a flashover occurs. The arc-over voltage of several units in series will not be a multiple of that of one unit, but each additional unit will increase the flash- over voltage by approximately the amount the second unit adds to the arc-over voltage of one unit when two are placed in series. 21. Rain Arc-Over Tests on Pin Type Insulators. There are so many variables entering into results obtained in this test that it is not safe to compare various types of insulators unless all the con- ditions of the test are similar. Some of the conditions causing dis- crepancies are as follows : The quality of water. The quantity of water. The pressure of water. The distance of nozzles from unit under test. The fineness of the spray. The angle of contact with the unit under test. The barometric pressure. Some of these conditions are difficult to regulate. The quality of water will vary with the locations at which the test is made. Care- ful experimenters have found that it is practically impossible to exactly duplicate results, even with laboratory methods and appa- ratus. This test, however, will give a general idea of what the in- sulators will do under adverse conditions and when made at any one testing station, furnishes fairly reliable comparative information. The usual method of making this test is to mount the insulators in the same manner as that used when making the dry arc-over test, throwing a fine spray of water on the insulator from an angle of about 45 to the horizontal. The precipitation is adjusted to equal approximately 1 inch in five minutes. A determination of the flashover voltage is obtained during precipitation which value obviously will be materially lower than the dry flashover voltage. * The arc-over voltage of insulators decreases with increasing altitudes or decreasing barometric pressure. For instance, if the arc-over voltage is "E" at sea level, it will be considerably less than "E" at a higher altitude, say 6000 feet. Allowance should, therefore, always be made for thia phenomenon. [ 300 ] INSULATORS Sec. 5 22. Rain Arc-Over Test on Suspension Type Insulators. In- sulator strings are mounted in a manner similar to that used in meas- uring the dry arc-over value and a fine spray of water is thrown upon the assembled string at an angle of 45 from the horizontal, the pre- cipitation also being regulated to equal approximately 1 inch in five minutes. The wet arc-over voltage is obtained during pre- cipitation. 23. Mechanical Test on Pin Type Insulators. The usual test applied to pin type insulators consists of mounting the insulator on a rigid pin and applying a pressure at the side tie wire groove in a direction perpendicular to the vertical axis of the insulator. In general, it may be said that a high voltage insulator should stand a pull that will bend or break any metal pin on which it is likely to be used. For general use, a two thousand pound pull which is an aver- age value to apply in such tests, should not cause any fracture. 24. The Mechanical Tests on Suspension Type Insulators consist in applying tension between the metal cap on the top of the unit and the connection link beneath the unit. The ultimate breaking load for suspension insulators varies from 4,000 to 30,000 pounds in ac- cordance with the design of the insulator. 25. Puncture Tests. Tests on a certain percentage of each 1000 insulators, not exceeding one-quarter of one percent should be made to determine the ability of the insulator to resist puncture. This test is best made by submerging the insulator in oil. Suspension insulators should be completely assembled with the standard fittings with which they are to be used in service. With pin type insulators there should be attached to the head of the insulator, wires representing the tie and line wires, and a metal pin should be placed in a proper manner in the pin hole. The test should then be applied to the fittings in each case. The puncture value obtained under these conditions should not be less than 135 percent of the dry flashover voltage. In making the test, apply to the insulator a voltage 30 to 40 per- cent below the dry flashover value for 30 seconds, then raise the voltage by steps at a rate of about 1000 volts per second until punc- ture occurs. 26' Method of Measuring Test Voltage. The method of deter- mining the value of the test voltage should be in accordance with that described in Art. 23a Sec. 6 Part I. 27. INSULATOR PROTECTION. Power arcs are frequently started by lightning discharges and result in burning and breaking of the transmission cables, whereupon the towers are subjected to unbalanced stresses which sometimes cause their failure. Light- ning arresters, suitable for the protection of station apparatus, are available, but such arresters do not protect the lines themselves. A number of special devices may be employed at points on the line where lightning is likely to be severe, in order to prevent the [ 301 ] Sec. 5 INSULATORS burning of conductors and the shattering of insulators. The arcing horns and the double ring scheme are two such devices. The former consists of two horns, one connected to the insulator head and the line and the other to ground, the gap between them being adjusted so that a discharge will take place across it, rather than across the insulator. The double ring device consists of a ground ring sup- ported by the crossarm so that it encircles the lower petticoat of the insulator with several inches clearance, and of a second ring connected to the line and resting near the edge of the top petticoat. A flash- over will usually occur between the rings without shattering the insulator. 2 3 RESISTANCE FIG. 133. 28. THE VOLTAGE DISTRIBUTION ON THE SUSPENSIpN INSULATOR STRING, where all units are alike varies depending upon the ratio of the leakage current to the capacity current. If leakage predominates the voltage will be equally distributed between the units of the suspension string, but if the capacity effect predominates the voltage will be highest across the insulator nearest the line wire and gradually diminish ; the unit nearest the ground having the least voltage stress. 29. Effect of Leakage. E = total voltage across string. r 2 = leakage resistance of each unit. it = current flowing over insulator surface from line to ground. n = number of insulator units in a string. [ 302 ] INSULATORS Sec. 5 If a number of equal resistances are connected in series in a string as in Fig. 133 and voltage E is applied across the string the total current is E The voltages across all resistances are equal; ei=e 2 ........................ =e n = itr 2 and E =ne! =nea = ......... =ne n This represents the voltage distribution when both the upper and lower insulator surfaces are wet and the leakage resistance rather than the capacity of the insulator string determines the voltage distribution. e n VOLTS The voltage distribution due to the combination of the capacities of the insulators in the string, from line to ground and from each insulator to ground, is as follows: Let Fig. 134 represent a string of suspension insulators grounded at one end, G, as at the tower. Each insulator may be represented as a condenser with a capacity Ca, and each connecting link and cap may be represented as a condenser with a capacity ci to ground. Greater capacity current passes through insulator (1) than through [303] Sec. 5 INSULATORS insulator (2), etc., hence, the voltage across the insulator (1) is greater than across insulator (2), etc., or, the voltage is not balanced along the string. The greater Ci is, when compared to c 2 the greater the unbalancing. Also the greater the number of units in a string, the greater the unbalancing. The voltage across the different insulators of a given string can be readily calculated if the ratio Ms known, and it is assumed there is no surface leakage or corona. Ci Leakage or corona will not appreciably affect the results at operating voltage. Referring to Fig. 134 an expression for the total capacity of a string of n insulators may first be written. 30. Capacity of Insulator String. Let c 2 = x d Then the total capacity for a string of n insulators is; One insulator Two insulators h Ci+C 2 C 2 Three insulators k 2 + c 2 For a string of n insulators. k n -i r-i = - C 2 +k n - , 2 / 1 . k n = Ci +c 2 -- r-i = c 2 1 - H C 2 +k n -i V X 31. Effect of Capacity. Let E be the voltage across the string to ground (Fig. 135). i = total capacity current. _ c 2 c 2 = mutual capacity or the capacity of each insulator. Ci Ci = capacity to ground. k n = total capacity of the string. k =^- Ci Then i = 2 TT f k n E ii' = 2 TT f ci E Then the voltage across the first or line insulator is i-i'! 27rfE (kn-cQ 61 27rfc 2 C 2 X (k n - Cl )_ E (k-1) Hj [304] INSULATORS Sec. 5 "I FIQ. 135. JOO 1* 80 I" Z 60 O tn 60 I 40 3 30 2 20 10 V \ \ \ Y NO. 3F Ul ITS N SEF IES- )( -: \ \ No. 1 IS UNIT NEXT TO LINE ASSUMING: cy c ,= 2 ,=ioo V V. " v s Jl-3 ~ X ^ ^ __ \ ^^, **^. n=? ,, Fio. 136. C H ^> 5 > o 2 91234567 UNIT NUMBER alculated voltage across different insulators in a string of "n" units. v > NO. DF Ul ITS N SE IES- n* \ * \ No. 1 IS UNIT NEXT TO LINE ASSUMING: \^ n-3 - ^ ^ \. =4 X ^ ^ S ^ it-b . _H 7 01234 567 UNIT NUMBER FIQ. 137. Calculated voltage across different insulators in a string of "n" units. [ 305 ] Sec. 5 INSULATORS The voltage e 2 across the second insulator is found thus: x 27T f d i' 2 = 2 TT f e' 2 Therefore fl) = E x k( 2 7T f C 2 X 2 For the third insulator x (x + 1) (k e 3 = E For the nth insulator (k-l)-x (x + 1) From the above the following equations may be written for solv ing numerical problems. Total capacity of a string of n insulators. 2c 2 +ci c 2 2 Write fraction to n 1 of the 2 c 2 +Ci terms. 2c 2 + Cl 100 90 do H Z70 3 Z60 J250 040 30 x 20 1 ^_ NO. lOF UKITS H SERIE6,j=SJ ^ ^ S^ No AS' 1 1< UM u^ NG ^lc\ IIT t JEX rroL lf IE \ ^ n-3 = 10 e ,=10 1 \ ^N * s ~-^ ^^__ n-4 N, ?s X 4si \ ' n=5 *s ^^_ * *^ ' < n=/ 01234567 UNIT NUMBER Fio. 138. Calculated voltage across different insulators in a string of "n" units. [ 306 ] INSULATORS Sec. 5 100 90 h 80 l*> GO ^350 o s 40 5 30 20 10 "S ^ NO. OF U NITS N SE HIES, n= !, ^ ^ 71 = S *> S \ 1 _. n= NO.1 IS UNIT NEXT TO LINE ASSUMING C 2/ / 6 .=20 !=100 X \> 5 - _ n~i \ ^-^ > ^ n^ ^ - "^ fc - __ n =10 1 2 3 A 5 6 7 8 9 10 UNIT NUMBER FIG. 139. Calculated voltage across different insulators in a string of "n" units. ! 10 01234567S910 UNIT NUMBER FIG. 140. Calculated voltage across different insulators in. a string of "n" units. (2) Volts across first or line insulator of string of n is Ci (3) The voltage across the mth insulator of a string is e m-i +e m-2 + ....... +ei E e m = e m 1 (4) 307 1 Sec. 5 INSULATORS When the arc-over voltage of a single unit alone e a is taken for ei. (4a) E a = , a = arc-over voltage of string. K. J. ._ (5) String efficiency = a = ., _ String efficiency is materially effected by the type of, and the spacing between insulator units, as the performance of some types of closely spaced insulators results in the breaking down of the air paths between the terminals, before a flashing potential is obtained across any unit. 32. Calculated Characteristics. The method of calculating the characteristics of insulators in series, for different lengths of string and different values of , using formulae 1, 2, 3, 4 and 5 fol- lows: TABLE 55 Ratio cj/ci 1 2 5 10 15 20 50 100 500 1000 No. of insula- tors in series Values of K 1 2~000 sTooo 000 11.000 16.000 21.000 51.000 101.00 501.00 1001.00 2 1.667 2.200 3.728 6.238 8.742 11.244 26.247 51.21 251.25 501.25 3 1.625 2.048 3.135 4.842 6.387 8.197 18.998 34.89 173.22 334.89 4 1.619 2.012 2.927 4.263 5.546 6.814 14.350 26.87 126.87 251.87 5 1.618 2.003 2.846 3.988 5.049 6.083 12.172 22.20 102.20 202.20 6 2.001 2.814 3.851 4.777 5.676 10.777 19.19 85.83 169.29 7 2.000 2.801 3.781 4.623 5.421 9.863 17.15 74.36 145.82 8 2.795 3.743 4.574 5.265 9.238 15.69 65.68 128.18 9 2.793 3.724 4.505 5.178 8.797 14.63 59.03 114.63 10 " 2.792 3.713 4.465 5.108 8.481 13.85 53.85 103.85 11 < 3.708 4.447 5.069 8.251 13.23 49.68 95.09 12 " " 3.705 4.415 5.044 8.083 12.84 46.22 91.85 13 " " 3.703 4.411 5.036 7.958 12.52 43.29 81.75 14 " " 3.702 4.409 5.024 7.865 12.33 40.93 76.58 15 ' ; ' 3.702 4.407 5.015 7.796 12.17 38.81 72.21 To find the total capacity of the string, k n , take the k above for the required ratio ' anc ^ ^ ne 8i ven number of insulators in series and multiply by ci. As an example of use of formulae, assume c* 5 - =x Cl k n n = 3 E = 100 k=-^- From (1) k n = Ci-f-c 2 2 c 2 -f-ci c 2 2 2c 2 +ci [ 308 ] INSULATORS Sec. 5 10+1 From (2) Gl = (k-1) 100 =^R3.135-1) o e ' ~ E From (3) = 427+ 42.7-100 =313 o e=e i e 3 ~ 1 + e 3 ~ 2 ~ E = I e 2 +e t -E x x ,31.3+42.7-100 63 = 31. 3 H - =26 o E= e l +e 2 +e 3 = 100 If 42.7 is considered as the arc-over voltage of a unit then the string efficiency is OT=- 78 = 78 v / 1,:,,*, v 1 | Figs. 136 to 140 and Table 55 are given as an aid in calculating the voltage distribution across an insulator string. The values in each figure are calculated for various numbers of insulators in a string, assuming ratios of - and the voltage across the insulator next to the line equal to 100 kv. If this voltage is less, the voltage across the remaining insulators of the string will also be proportionately less. Values of k are given in Table 55 for various values of and for various numbers of insulators in series. To demonstrate the use of the table and curves the following problem is given: Problem. Find the distribution of voltage across each unit of a suspension insulator string consisting of four units where the voltage from the line conductor to ground is 100 kv., assuming a ratio of mutual capacity to capacity to ground of five. x=-^-=5 n=4 E=100kv. From Table 55 for = 5 and n = 4. Findk= 2.927. [309] Sec. 5 INSULATORS Then 100 - nr (2.927-1) = 38.54 kv. String efficiency 100 4 x 38.54 0.649= 64.9%. From curve Fig. 137 assuming ei = 100 kv. The relative values of e 2 , e 3 and e 4 may be found, and the actual value then obtained by proportion. From Fig. 137 Actual d 100.00 kv.= 38.54 e 2 68.5 " = 26.35 e 3 51.0 " = 19.60 e 4 42.5 " = 16.35 100.84 error .84% Assuming that 50 kv. is the flashover value of one unit, the flash- over value of the string is E a = 50 x 4 x 0.649 = 129.8 kv. The drawn curves in Fig. 141 are the theoretical ones for e a = 74 kv. for dry insulators and = 10, ^- = 15, and ^- = 20. 400 c 2/r J 20 ^ ^ r CO OOQQ ^ 2 kl ^ ''' s 100 ^ > X-MBASUR CURVES C/> ED ARC OVER- T NO. 5 LCULATED FOR * f ' I 1 012345678 NUMBER OF INSULATORS PER STRING FIG. 141. Comparison of calculated and test curves. The crosses (Fig. 141) are the measured values. This illustrates the effect of automatic grading due to corona and leakage. For short strings the points follow the curve for = 10, which if con- tinued would give a very low flashover efficiency. Automatic grading causes the points to gradually shift to the curve for ^- = 20. The actual value of Bunder operating voltage [310] INSULATORS Sec. 5 is probably between 5 and 10. Thus, while arc-over tests for long strings may indicate a fair efficiency, the insulator string is in reality operating at a very bad unbalance of voltage. The curves in Fig. 142 illustrate how moisture affects the voltage distribution of the string. The curve of dry arc-over voltage follows the law of capacities. The curves of rain arc-over voltages follow the law of resistances. IUU \ V 3, s TEST NO.5 22C - 74Cm.b z u o t 80 Ul | TO CO 60 500 400 tn 1- _j Ss c s ^ \ x ^ ' <& $' > ,' 1 ' ,& ? ^^ ^ *" s & r KTLOVC .$ X r^ / / /' ^ fe f max- = the total maximum magnetic flux. N = the total number of turns on the transformer primary winding. Im = the effective value of the magnetizing current in am- peres. A = the area of the core in square centimeters. 1 = the length of the magnetic circuit in centimeters. n = the permeability of the iron. [330] TRANSFORMERS Sec. 6 Then 4 TT N I m V2 A /z 1.26 N I m V2 A /* - -- Therefore 10 max 1 10 max 1 4 TT V2 N /x 4 TT V 2 A N M The exciting current of the transformer is found by combining the quadrature vector sum of the power and wattless components. Thus Ie = Vl c 2-fl m 2 The no-load power factor of the transformer is found by dividing the energy component of the current by the total exciting current. Thus Cos. 9'=A le 11. Induced Voltage. The calculation of the ratio between the impressed electromotive force and the counter electromotive force of the transformer winding is dependent upon the reactance and resistance drops in the transformer primary winding. This difference is usually a few percent and the method of deter- mining it is given in Section 7, Article 49. The relations between the counter electromotive force of the transformer coil and the various factors, such as flux density, number of turns, frequencies, etc., are determined by the following formuke. These equations are based on the assumption that the electromotive force is a true sine wave and are the most important formulae used in the design of transformers. Let E = the effective induced electromotive force in volts. max- = the total magnetic flux. /3 max. = the lines of magnetic flux per square inch. A = the cross section of the magnetic circuit in square inches. N = the total number of turns on the transformer primary winding. f = the frequency in cycles per second. Then E = 27rfJN0 max ^4.44 f N fc 30 20 /O ' ft / ^ \^ *^. ^ / f \ X 1 I / / / "0 /O 20 30 40 SO 60 70 SO W 100 HO I2C FIQ. 163. Increase in hysteretio loss of iron due to continued heating. [338] TRANSFORMERS Sec. 6 3rd. The effect of baking the core for four days in a temperature of 200 C., indicating a decrease in hysteretic loss which would seem to show that prolonged heating is productive to partial recovery in permeability. 200\ I I I I I I I I I I I I I I I AG&MG rcsr ON SAMPLES or IROM Ur FROM TH3An3HeT Of M HATD TO DtrrceENT TMPeATU83 FIG. 164. Fia. 165. [339] Sec. 6 TRANSFORMERS 20. Power-Factor and Reactive Factor. The power-factor in alternating-current circuits or apparatus is the ratio of the effective (i.e. the cyclic average) power in watts to the apparent power in volt-amperes. It may be expressed as follows: effective power _ effective watts _ effective current _ apparent power ~~ total volt-amperes ~" total current effective voltage total voltage The Reactive-Factor is the ratio of the reactive volt-amperes (i.e., the product of the reactive component of current by voltage, or reactive component of voltage by current) to the total volt- amperes. It may be expressed as follows: reactive power _ reactive watts _ reactive current _ apparent power total volt-amperes total current reactive voltage total voltage Power-Factor and Reactive-Factor are related as follows: If p = power-factor and q = reactive-factor, then with sine waves of voltage and current, p z +q* = l With distorted waves of voltage and current, q ceases to have definite significance. It will be noted that for sine waves the relation between the apparent power and the effective power is a cosine relation, thus for power-factors of circuits in which the shape of the voltage and current waves are a true sine, cos. may be used to designate the power-factor of the circuit and 6 to designate the power-factor angle. Let cos. 9 = the power-factor of the load. cos.O' = the power-factor of the transformer. W = the power output of the transformer in watts. We = the core loss of the transformer in watts. w c = the copper loss of the transformer in watts. Im = the magnetizing current of the transformer. Io = the load current of the transformer at power-factor, cos.9. E = the effective primary voltage of the transformer, xt = the reactance of the transformer referred to the primary. Then T ft' - E Im+xtIo 2 +Wtan.e ian. o W+We+Wc values of tan.6 may be found for values of cos.O from the trigono- metric tables in Section 1. [ 34o ] TRANSFORMERS Sec. 6 ffi / / 1 J/ 1 REGULATION AT 100 % RK- 2.10% 80% -230% \\ A 1 EXCITING CUMENTX/OO . 3.00% x I FULL LOAD CUWENT ^ X 1 X J / ..^ ^ ^ ^/ J Tn ^ ^ ^x X 1 TO 0^, X J ^- - ^-- rn p^l H- = ^ ^ M\ ^ Lt(. ^_ "M ^ ** i ,^-- -^ oLL. e= ^7 Zf JJ7 %LOAD 15 100 3 K.V.A.TnANsroenci? 60 Cracs Z20O VOLTS PeiriAKr 220///0 VOLTS SECONDARY Fio. 166. REGULATION AT 100 % RK-t 80% "Z.SS% EXCITING CUWENTX/OO _ FULL LOAD CUWENT ~' JO %LOAD 7S 2200 VOLTS PeinARr 220//lOVoLTS~SKONDMr Fia. 167. [341] Sec. 6 lOOr TRANSFORMERS 2S SO %LOAD 15 100 SO K.V.A.TRANsroerice 60 CYCLES 2200 VOLTS Pei n Mir 220/110 VOLTS SECONDARY FIG. 168. 125 4200 80% "2.40% EXCITING CUWENT 'x /OO _, ^ FULL LOAD CUPPENT = ~ ^ ISOO 1200 bOO 2S SO %LOAD 15 100 200 K.V.A.TRANsroenEi? 60 CYCLES 2200 VOLTS PpinAur 220/ffO VOL rs SECONOAP? FIG. 169. [342] KS TRANSFORMERS Sec. 6 240 GSUUmtf AT 100% R>-4J8 % 80% =4.14 % fyctTtM CURRENT x 100 - 25 JO %LOAD 75 2200 VOLTS PRIMARY 220///0 VOLTS SECONDARY FIG. 170. an p ^s Of) ' 7/7 ^ 1400 REGULATION AT 100 % RK > 80% ' EXCITING CURRENTX/OO , -t.7S% ^/ ^ * 66 x / innn FULL LOAD CURRENT / ? 2 / x fnn X ? x 4(j \ ui x X n 9* \ & X Jo ^ ^ r 9* y 400 200. Q f 20 - - K= = - - ~ ^. ~ /p. ^ .^. J ^ ^ ^ ^ ^ = =: . 2 -~ 5 s T %L ~A ~i 5 7 & FIG. 171. [ 343 ] Sec. 6 TRANSFORMERS 100 on X P"*^ w ** tt- / Xn X 7/1 X REGULATION AT 100% RE 80% > ' EXCITING CuwENTxIOO . ^ / ? / j / y ^ FULL LOAD CUWENT x ^ ^ / / AH " X J X U ?^l 7 I 10 X (( p !x ^ JL -^ *. ***" * fff V >1 J x ^ ^ ^ ^^ **' Wr- U-KT1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 II 25 JO %LOAD 75 100 / SO K.V.AJRANsroeriEK 60 CrcLCs 6600 VOLTS PeinAKr Z20//IO VOL rs SecoNDAer FIG. 172. \ Y J( / M ^x TU REGULATION AT 100 % f>F.~/.SO % 80% " "3.20% x -ill ^ X TP EXCITING CUWENTX/OO _ ^ ^ J FULL LOAD CUWENT ^ / 1 x ,s 4J\ x ' X M l,u i> , X u 5 X JC1 ** X ^ ff ? L|i !> o i^. -" -' * - K= = ** . - 2f JO %LOAD 15 SO IWAJnAHsroenEi? 13200 VOLTS PeinAKr 220/1/0 FIG. 173. [344] IZS TRANSFORMERS Sec. 6 Values of the power-factor of the transformer on the primary side cos.O' may be found from values of tan. 6' in the trigonometric tables in Section 1. At no-load tan.6' =5JE w c 21. Transformer Characteristics. Figs. 166 to 173 inclusive illustrate the average characteristic of transformers for use on 2200, 6600 and 13,200 volt systems. The characteristics of trans- formers ranging in potential from 22,000 to 66,000 volts will vary approximately as follows: The efficiency will vary with the kv-a. rating, and inversely with the voltage. The regulation at 100% P.F., resistance drop and exciting current, will vary with the voltage and inversely with the kv-a. rating. The reactance drop will vary from 3 to 8 percent and the regulation at 80 P.F. from 2^ to Q}4 percent, depending upon the kv-a. rating, voltage and frequency. The power-factor at no load will vary be- tween the limits of 12 and 30 percent. 22. TRANSFORMER TESTING. The following transformer tests are not intended to illustrate shop practice, but are included as the simple accurate tests which may be made by operating companies. 1st. 2nd. 3rd. 4th. 5th. 6th. 7th. 8th. 9th. Insulation. Heating. Core loss and exciting current. Resistance. Copper loss. Reactance Drop. Regulation. Ratio. Polarity. (Art. 23.) (Art. 24.) (Art. 25.) (Art. 26.) (Art. 27.) (Art. 28.) (Art. 29.) (Art. 30.) (Art. 31.) 23. INSULATION.* (I) INSULATION RESISTANCE. Insulation Resistance is the ohmic resistance offered by an in- sulating coating, cover, material or support to an impressed voltage, tending to produce a leakage of current through the same. Ohmic Resistance and Dielectric Strength. The ohmic resis- tance of the insulation is of secondary importance only, as compared with the dielectric strength or resistance to rupture by high voltage. Since the ohmic resistance of the insulation can be very greatly increased by baking, but the dielectric strength is liable to be weak- ened thereby, it is preferable to specify a high dielectric strength rather than a high insulation resistance. The high-voltage test for dielectric strength should always be applied. *A. I. E. E. rules are in the process of revision. Revised rules should be used instead of above. [345] Sec. 6 TRANSFORMERS Recommended Value of Resistance. The insulation resistance of completed apparatus should be such that the rated terminal voltage of the apparatus will not send more than of the 1,000,000 rated-load current, through the insulation. Where the value found in this way exceeds one megohm, it is usually sufficient. Insulation Resistance Tests should, if possible, be made at the pressure for which the apparatus is designed. (II) DIELECTRIC STRENGTH. Test Voltages. Definition. The dielectric strength of an insulating wall, coating, cover or path is measured by the voltage which must be applied to it in order to effect a disruptive discharge through the same. Basis for Determining Test Voltages. The test voltage which should be applied to determine the suitability of insulation for commercial operation is dependent upon the kind and size of the apparatus and its normal operating voltage, upon the nature of the service in which it is to be used, and the severity of the mechanical FIG. 174. Insulation test. (Using special testing transformer.) and electrical stresses to which it may be subjected. The voltages and other conditions of test which are recommended have been de- termined as reasonable and proper for the great majority of cases and are proposed for general adoption, except when specific reasons make a modification desirable. Condition of Apparatus to be Tested. Commercial tests should, in general, be made with the completely assembled apparatus and not with individual parts. The apparatus should be in good con- dition and high- voltage tests, unless otherwise specified, should be applied before the machine is put into commercial service, and should not be applied when the insulation resistance is low owing to dirt or moisture. High-voltage tests should, in general, be made at the temperature assumed under normal operation. High-voltage tests considerably in excess of the normal voltages to determine whether specifications are fulfilled are admissible on new machines only. Unless otherwise agreed upon, high- voltage tests of a machine should be understood as being made at the factory. [ 346 ] TRANSFORMERS Sec. 6 Points of Application of Voltage. The test voltage should be successively applied between each electric circuit and all other electric circuits including conducting material in the apparatus. The Frequency of the alternating-current test voltage is, in general, immaterial within commercial ranges. When, however, the frequency has an appreciable effect, as in alternating-current apparatus of high voltage and considerable capacity, the rated fre- quency of the apparatus should be used. Table of Testing Voltages. The following voltages are recom- mended for testing all apparatus, lines and cables, by a continued application for one minute. The test should be with alternating voltage having a virtual value (or root mean square referred to a sine wave of voltage) given in the table, and preferably for tests of alternating apparatus at the normal frequency of the apparatus. Rated Terminal Voltage of Circuit. Rated Output. Testing Voltage. Not exceeding 400 volts Under 10 kw i ,000 volts. Not exceeding 400 volts 10 kw. and over .... 1,500 volts. 400 and over, but less than 800 volts Under 10 kw 1,500 volts. 400 and over, but less than 800 volts 10 kw. and over. . . .2,000 volts. 800 and over, but less than 1,200 volts Any 3, 500 volts. 1,200 and over, but less than 2,500 volts Any 5,000 volts. 2,500 and over, Any . . Double the normal rated voltages. Exception. Transformers. Transformers having primary pres- sures of from 550 to 5,000 volts, the secondaries of which are directly connected to consumption circuits, should have a testing voltage of 10,000 volts, to be applied between the primary and secondary windings, and also between the primary winding and the core. Special insulation testing transformers should be used in making insulation tests; the diagrammatic connections of which are il- lustrated in Fig. 174. However, standard transformers may be connected to give the desired test voltage. When standard trans- formers are used they should be well insulated from the ground in order to protect the transformer windings. Fig. 175 illustrates a method of connecting six standard 110 2,200 volt transformers in order to obtain 13,200 volts for testing purposes. Transformers A, B, and C, are used to insulate the remaining transformers from the source of energy, and if it is not necessary to protect the circuit they may be omitted. When the scheme of connections illustrated in Fig. 175 is used, the lead marked O should be connected to ground and one side of the voltmeter should also be connected to ground to prevent any dangerous difference of potential from the voltmeter to the ground. In order to prevent over-straining the insulation of the trans- former under test, a spark gap, in series with a resistance should be connected across the test wires. The spark gap should be so adjusted that accidental over- voltage will discharge across the gap, before reaching a value injurious to the transformer insulation. Over-voltage may be caused by a poor generator voltage wave form, or may be caused, when a regulating resistance is used, by the [347] Sec. 6 TRANSFORMERS distortion of the supply voltage wave form, due to the magnetizing current of the testing transformer flowing through this resistance. The use of a small alternating current generator, the voltage of which can be varied by a field rheostat, is preferable to the use of regulating resistance in a constant voltage supply. The spark gap should be set in accordance with Tables. (Art 63, Sec. 7.) Should a discharge occur across needle gaps, the needle points must be renewed, as a discharge destroys their calibration. Go. FIG. 175. Insulation test (using standard transformers.) The primary voltage may be found by multiplying the reading of the voltmeter V in Fig. 175, by the ratio of transformation of one transformer, times the number of transformers in series on the high potential side. Let high potential voltage. the reading of the voltmeter on the low tension side, the ratio of transformation of one transformer, the number of transformers in series. E V n n' Then E = V n n' All testing connection should be tightly made as an arc may cause undue high potential strain. The primary and secondary leads of the transformer under test should be connected as shown in Figs. 176 and 177. [348] TRANSFORMERS Sec. 6 Insulation test between primary and core Fig. 176. " secondary . . " 176. " secondary and core " 177. It is necessary to make the above connections, as portions of the windings not connected to the testing transformer will be subjected to induced stresses which may exceed the supply voltage. This is caused by the capacity which exists between primary and second- ary windings, and between these respective windings and the core. When the connections have been made, as illustrated in Fig. 175, close the low voltage switch and slowly adjust the alternator fields or the regulating resistance until the voltage is increased from the lowest obtainable value to a value on the voltmeter V, indicating that the voltage on the high potential side of the testing transformer has reached the desired maximum. After this voltage has been maintained for the required time, slowly decrease the voltage to the lowest value possible and open the switch. The frequency should be maintained at approximately normal value during the test. A record of this may be obtained by in- Tb Te-sr/A/G T&ANS. \H. PI 7- FIG. 176. FIG. 177. serting a frequency meter in the circuit or by determining the gen- erator speed. 23a. FOR MEASURING THE TEST VOLTAGE, two instru- ments are in common use, (1) the spark gap and (2) the voltmeter. 1. The Spark Gap is ordinarily adjusted so that it will break down with a certain predetermined voltage, and is connected in parallel with the insulation under test. It ensures that the voltage applied to the insulation is not greater than the break-down voltage of the spark gap. A given setting of the spark gap is a measure of one definite voltace, and, as its operation depends upon the maximum value of the voltage wave, it is independent of wave form and is a limit on the maximum stress to which the insulation is subjected. The spark gap is not conveniently adapted for comparatively low voltages. In Spark-Gap Measurements, the spark gap may be set for the required voltage and the auxiliary apparatus adjusted to give a voltage at which this spark gap just breaks down. The spark gap should than be adjusted for, say, 10 percent higher voltage, and [349] Sec. 6 TRANSFORMERS the auxiliary apparatus again adjusted to give the voltage of the former break-down, which is to be the assumed voltage for the test. This voltage is to be maintained for the required interval. The Spark Points should consist of new sewing needles, supported axially at the ends of linear conductors which are each at least twice the length of the gap. There should be no extraneous body near the gap within a radius of twice its length. Tables of approximate striking distances are given in Sec. 7. These tables should be used in connection with tests made by the spark-gap methods. A Non-inductive Resistance of about one-half ohm per volt should be inserted in series with each terminal of the gap so as to keep the discharge current between the limits of one-quarter ampere and two amperes. The purpose of the resistance is to limit the current in order to prevent the surges which might otherwise occur at the time of break-down. 2. The Voltmeter gives a direct reading, and the different values of the voltage can be read during the application and duration of the test. It is suitable for all voltages, and does not introduce disturbances into the test circuit. In Voltmeter Measurements, the voltmeter should, in general, derive its voltage from the high-tension testing circuit either directly or through an auxiliary ratio transformer. It is permissible, however, to measure the voltage at other places, for example, on the primary of the transformer, provided the ratio of transformation does not materially vary, during the test; or that proper account is taken thereof. Spark Gap and Voltmeter. The spark gap may be employed as a check upon the voltmeter used in high-tension tests in order to determine the transformation ratio of the transformer, the variation from the sine wave form and the like. It is also useful in conjunction with voltmeter measurements to limit the stress applied to the insulating material. 23b. OVER-POTENTIAL TEST. For testing the insulation between turns, double potential at no-load for one minute is main- tained. The connections for such tests are made in a manner similar to that for a core loss test except that higher voltages are used, depending upon the rated primary voltage of the transformer to be tested. When making over-potential tests the frequency of the supply voltage should be increased in approximately the same proportions as the voltage; otherwise, the exciting current will be excessive and may be sufficient to injure the windings of transformers having a small kv-a. rating. 24. HEATING TESTS. There are three general methods of making heat tests on transformers, two of which approximate service conditions, the other applying actual full load to the transformer. The first method consists of operating the transformer at full load for a definite length of time. This is never used on large [ 350 ] TRANSFORMERS Sec. 6 transformers, due to needless waste of energy, but may sometimes be used to advantage on small units. Fig. 188 illustrates diagrammatically the connections necessary when loading a small transformer. Voltmeter, ammeter and fre- quency meter readings should be taken and adjustments made in order that the transformer may be operated under normal conditions. Temperatures may be measured by thermometer or by resistance, using in the latter case either the Wheatstone Bridge or the Fall of Potential Method. Resistance measurements should be made before the test is started and at different times during the test. The temperature may then be calculated from the increase in resistance as follows: Let t = the final temperature. to = the initial temperature. r = the final resistances. r = the initial resistances. a = the temperature coefficient depending on whether t is in degrees C or F (Section 3). Then _r (1-fq to)-r ~r*r: For copper and temperature in degrees C. r (1+. 00428 to)-r .00428 r Necessary precaution should be taken to obtain the correct temperature of the copper when measuring the initial resistance, since a transformer taken from the outside into or transported from one room to another may have a decidedly different temperature than the room. The temperature rise is found by subtracting to from t, assuming that the transformer was at room temperature when the test began. If t is not the standard room temperature (25 C.), then the room temperature, instead of to, is subtracted from t. If the room tem- perature is above the standard temperature of 25 C., the temperature rise is decreased one-half of one percent for each degree that the room temperature is above 25 C. If the room temperature is below 25 C. one-half of one percent is added for each degree that the room temperature is below 25 C. Temperature Correction. Assuming the room temperature during test is 30 C. and the measured temperature rise is 40 C. the actual temperature rise is found as follows: 30C.-25C.=5C. *A. I. E. E. Rules are in the process of revision. Revised rules should be used instead of above. [351] Sec. 6 TRANSFORMERS Therefore the correct temperature rise is 40C.-1C. = 39 C. Barometric Pressure.* A barometric pressure of 760 mm. and normal conditions of ventilation should be considered as standard, and the apparatus under test should neither be exposed to draught nor enclosed, except where expressly specified. The barometric pressure needs to be considered only when differing greatly from 760 mm. Barometric Pressure Correction.* When the barometric pressure differs greatly from the standard pressure of 760 mm. of mercury, as at high altitudes, a correction should be applied. In the absence of more nearly accurate data, a correction of one percent of the ob- served rise in temperature for each 10 mm. deviation from the 760 mm. standard is recommended. For example, at a barometric pressure of 680 mm. the observed rise of temperature is to be reduced by 760 6SO 8 percent. In the second method energy equal to the losses only is supplied. It requires the use of two similar transformers connected as illus- trated in Fig. 178. Circuit A supplies energy equal to the iron fierce FIG. 178. Heat test of two similar single-phase transformers. (Losses only supplied.) losses in the transformers. Circuit B circulates full load current through the windings. It is general practice to magnetize the transformer on the low voltage side and introduce the circulating current on the high voltage side, as this method permits the use of standard voltages, whereas the reversed conditions would neces- sitate a high voltage on the primary side with a very low voltage on the secondary side, resulting in many complications in the appa- ratus necessary for testing. The voltage required on circuit A is that of the rated secondary voltage of the transformer coil. The voltage required on circuit B is double the impedance voltage of one transformer. [ 352 ] TRANSFORMERS Sec. 6 The total energy required in circuit A is that equal to the full load iron losses of both transformers. The total energy required in circuit B is that equal to the full load copper losses of both transformers. If the transformers under test are 2,200-220 volts, 220 volts is required on the secondary side and approximately 220 volts is required on the primary side. These voltages may be reduced to 110, by connecting both the primary and the secondary windings of each transformer in parallel. If a three phase transformer or three single phase transformers are to be tested, connections may be made as illustrated in Fig. 179. This is exactly similar to that illustrated in Fig. 178 with the ex- FIG. 179. Heat test of on a three-phase circuit. -phase or one three-phase transformer (Losses only supplied.) ception that it has been altered so as to conform to the requirements of three phase connections. It will be noted in both Figs. 178 and 179 that the copper loss and iron loss currents are not equal in all the transformer windings. In Fig. 178 it is the vector sum in one winding and the vector differ- ence in the other winding, depending upon the phase relation of circuits A and B. In Fig. 179, it is the vector sum or the vector difference of the iron loss and copper loss currents depending upon the phase relations of circuit B to the various phase voltages of circuit A. However, the difference in heating is so small that it is negligible. The calculations of temperature rise may then be made as described in the first method. 3rd Method. When one transformer only is to be tested, it is possible to apply full load current to the primary and secondary 12 [ 353 ] Sec. 6 TRANSFORMERS winding without wasting any energy except that incident to the losses in the transformer. This presupposes that circuits of voltages equal to the primary and secondary voltage of the transformer are available. By inserting an induction regulator in the primary or the secondary circuit, it is possible to regulate the transformer voltage so that full load current will flow through the transformer windings. (Fig. 180.) If circuits of these required voltages are not available, a transformer of larger capacity can be used (Fig. 181). FIG. 180. Heat test of single-phase transformer when circuits are available having the same voltage as the primary and secondary windings. (Losses only supplied.) If the primary and secondary windings of a transformer are divided into two or more sections, energy equal to the full load copper losses of the transformer may be supplied as illustrated in Fig. 182, (circuits A and B). Energy equal to the iron losses of the transformer may be supplied as illustrated in Fig. 183. FIG. 181. Heat test of single-phase transformer using induction regulator and testing transformer. (Losses only supplied.) r These two connections are alternately made and maintained in order to artificially create heating in the transformer equal to that which would occur at full load under operating conditions. This test is called the compromise test. To obtain the equivalent heating of full load losses in a transformer it is necessary to increase the copper and iron losses to values much higher than normal. This is necessary because of the fact that [ 354 ] TRANSFORMERS Sec. 6 their heating effects are not superimposed and must be increased to give the same average value. The standard connections may also be used for the compromise test (Figs. 183 and 187). 25. CORE LOSS AND EXCITING CURRENT TESTS. Con- nections for the core loss tests are illustrated hi Fig. 183. This test is made at the normal operating voltage of the transformer, less the voltage loss due to the load current in the primary. If TffANS. UND&? TzST FIG. 182. Connections that may be used in copper loss test, in connection with the compromise heat test. voltage adjustments are made by means of a variable resistance, the core loss of the transformer may be as much as 12% in error, depending upon the shape of the voltage wave impressed upon the transformer. It is, therefore, necessary to use some means of cor- recting for this wave distortion, or else use a source of energy supply in which the voltage is a pure sinusoidal wave. As tests on low voltage line transformers are usually made by using a source of TKA NS. UNDER rcsr Fia. 183. Iron loss test. supply which cannot be independently controlled, the transformer is adjusted for the proper voltage by means of a rheostat. When this is done an iron loss voltmeter should be inserted in the circuit as shown in Fig. 183, and the voltage adjusted until the iron loss voltmeter records the operating voltage of the transformer. Read- ings of the wattmeter and ammeter then indicate the uncorrected value of the exciting current and iron loss. The magnetizing cur- rent may be calculated by the method given in Section 7, Article 49. [ 355 ] Sec. 6 TRANSFORMERS The frequency should be maintained at a constant value during this test. The wattmeter reading should be corrected for the power loss in the voltmeter and iron loss voltmeter by subtracting the losses in these instruments from the wattmeter reading. The losses in the iron loss voltmeter are indicated on a watt scale and E 2 those of the voltmeter are -^-. it 25a. Iron Loss Voltmeter. The iron loss voltmeter is essentially a wattmeter arranged to read the iron loss of a standard iron circuit which is a part of this instrument. Variations in wave shape effect the iron loss in the standard core C. (Fig. 184.) If the wattmeter is calibrated to read directly in volts and an adjustment of the supply voltage is made until the desired voltage is read on this wattmeter scale, the iron loss is equivalent to the iron loss produced by a sine wave of the same effective value as the value indicated by the wattmeter scale. This type of instrument permits the testing of transformers on any commercial circuit, and the results FIG. 184. Internal connections of iron, loss voltmeter. obtained are the same as though the test were made under true sine wave conditions. Fig. 184 shows the diagrammatic connections of an iron loss voltmeter. C is the standard laminated core on which a winding W is placed. Connections from this winding pass through a stationary coil S to the terminals P P, which are connected to the supply voltage mains, as shown in Fig. 183. The shunt circuit consists of a moving coil M in series with a non-inductive resistance R and the compensating coil C C which is wound parallel to the series coil S and of an equal number of turns. This is essentially a watt- meter movement and it can readily be seen that the deflection of the wattmeter moving coil M will be caused by the total input to the instrument. This input is the hysteretic and eddy current loss in the standard iron circuit C and in addition the copper losses in the winding W and the winding of the wattmeter movement. Before calibrating the instrument for a certain frequency the adjustment of the ratio of the eddy current losses in the ring, plus the shunt copper loss to the total loss, is made by changing the non- inductive resistance in the shunt circuit and the turns on the ring. This ratio of R I 2 loss to the total loss is made to be about 20% at [ 356 ] TRANSFORMERS Sec. 6 about two-thirds of the full scale voltage. After this adjustment is made, the instrument is calibrated in parallel with an alternating current voltmeter on a pure sine wave voltage of the required fre- quency from a small smooth core alternator. The scale of the watt- meter is drawn to agree with the readings of the alternating current voltmeter. This wattmeter measuring the iron loss of the standard iron core will always read the watts loss in the iron core independent of wave shape. Therefore, if the supply voltage is so adjusted that correct voltage indications are given on the iron loss volt- meter scale, the watts consumed by the standard core are the same as for a pure sine wave of equal value. The dotted curves in Fig. 185 illustrate the errors for variation in wave form when using a square root of mean square voltmeter to regulate the voltage for the iron loss tests on transformers with characteristics recorded in Table 56. The full line curves represent the error when using an iron loss voltmeter. With a variation of 10% in frequency there will not be an error in loss greater then l/^%. Core losses should always be measured on the low tension side of the transformer to avoid using a high potential test circuit. TABLE 56 Curve Transformer with Tested with A B C D E F 14% eddy loss 20% eddy loss 30% eddy loss 14% eddy loss 20% eddy loss 30% eddy loss R. m. s. voltmeter R. m. s. voltmeter R. m. s. voltmeter Iron loss voltmeter Iron loss voltmeter Iron loss voltmeter 26. RESISTANCE MEASUREMENTS. The resistance of a circuit varies with temperature, and for comparative purposes all values for resistance are corrected in order to indicate the true resistance at a temperature of 25 C. Methojds of correcting for temperature are illustrated in Section 3, Art. 19. The resistance of the coils of a transformer may be determined by the use of a Wheatstone Bridge, or by The Fall of Potential Method. When resistance values are determined by the Wheatstone Bridge no corrections other than for temperature are necessary. This method is seldom used for measuring resistance values of less than one or two ohms. The Fall of Potential Method, as commonly used, necessitates the use of direct current, as the inductive effect of- alternating current will prevent the determination of accurate results. Fig. 186 illustrates diagrammatically the circuit arrangement necessary when determining resistance by The Fall of Potential [ 357 ] Sec. 6 TRANSFORMERS Method. The illustration applies to the measurement of the re- sistance of the secondary coils, but is equally applicable to the measurement of the resistance of the primary coils. When measuring resistance by the fall of potential method, the voltmeter pointer may show a continued tendency to vibrate, due to the changing magnetic field (building up) in the transformer core. To eliminate this, the opposite winding should be short circuited. Remove the short circuit before changing value of current for a second or third reading. Corrections must be made for the current flowing through the voltmeter, which value varies in accordance with its resistance. FIG. 185. Error in measured iron loss with variation in form-factor of voltage wave. The following formula will give the correct value for the resistance of the coil, under test. Let R =the resistance of transformer coil under test. R' =the resistance of the voltmeter. E =the voltmeter reading. I = the ammeter reading. I v = the current flowing through the voltmeter. Ic =the corrected current or the actual current flowing through the coil under test. E Ic =I-I [358] TRANSFORMERS Therefore the resistance of the coil under test is E Sec. 6 When measuring the resistance of a large transformer the ratio of I v to I is negligible. With the resistance of both primary and secondary windings known, it is possible to calculate the copper loss I 2 R of the trans- former in each winding; and the sum of these should correspond very fuse Trsr FIG. 186. Measurement of resistance by the fall of potential method. closely to the copper loss of the transformer as measured by a watt- meter. When making tests in accordance with the connections shown in Fig. 186, the following procedure should be applied: Close the switch and regulate the controlling resistance until full load current is obtained. Read the voltmeter and ammeter. Increase the resistance until a lower value of current is obtained, then also read the instruments. TKAMS. UNDER 7&r 000 OOO OOO OOO 000 000 Fuse oe VARIABLE RCS/STANCE FIG. 187. Copper loss or impedance test. Take several readings on each coil at different current values. Disconnect voltmeter before opening circuit. Reduce the current to a minimum before opening the switch. The current should flow through the transformer windings for as short a time as is possible, as the heating produced will appreciably affect the values of the resistance obtained. 27. COPPER LOSS TEST. It is usual to measure the impedance drop and the copper loss of a transformer on the high voltage side, for on the high voltage side more accurate voltage readings can be [359] Sec. 6 TRANSFORMERS obtained. The connections for a copper loss test are illustrated in Fig. 187 and indicate all the meters that are required. If extreme accuracy is desired, the wattmeter and the ammeter readings must be corrected for the current taken by the voltmeter and the watt- meter potential winding. The wattmeter reading may be corrected by subtracting the energy absorbed by the potential coils of the wattmeter and voltmeter. The value of the absorbed energy may be obtained by multiplying the square of the voltage indicated by the sum of the reciprocals of the resistance of the voltmeter and voltage coils of the wattmeter. The result subtracted from the watt- meter reading will give the input to the transformer in watts. The ammeter indicates not only the current in the transformer but also the current flowing through the potential coil of the wattmeter and voltmeter. Therefore, the amount of current indicated is slightly greater than that actually flowing through the transformer coils. However, this is practically negligible. The corrected wattmeter readings, taken when the voltage has been adjusted so that full load current flows through the ammeter, will give the sum of the full load copper losses in the primary and secondary coils of transformer. During the test, the frequency should be maintained at a constant value. 28. REACTANCE DROP. The reactance drop of a transformer may be calculated in accordance with the formulae following : Let E = the voltmeter reading, Fig. 187. I =the ammeter reading, Fig. 187. We =the corrected wattmeter reading, Fig. 187. X =the total reactance of the transformer windings referred to the primary, in ohms. z =the total impedance of the transformer windings referred to the primary, in ohms. r p =the resistance of the primary winding of the transformer, in ohms. r s = the resistance of the secondary winding of the transformer, in ohms, rt =the total resistance of the transformer windings referred to the primary, in ohms, n =the ratio of transformation, f =the frequency in cycles per second. The reactance may be found by two methods: Tfi 1st. z = -y- from copper loss test. rtl = p from copper loss test. We rt = A/E 2 -r t 2 P /- =vz 2 -r t 2 [ 360 ] TRANSFORMERS Sec. 6 E 2nd. z ~T~ fr m copper loss test. rt =r p +n 2 r s from resistance test. A/E 2 -r t 2 I 2 . " - "V 2 it The various values necessary in this calculation are obtainable in accordance with the methods described herein. In both formulae given, the inductance of the transformer coils referred to the primary may be found as follows : 2xf henries From the values of resistance and reactance thus obtained, the regulation of the transformer for any power factor may be obtained. (Section 7, Article 49.) 29. REGULATION. The regulation of a transformer may be obtained by calculation as given in Sec. 7, Article 49, or on small transformers it is possible to measure the regulation directly by con- necting the transformer to a constant voltage source, Fig. 188, and fuse First: Fio. 188. Connections for regulation test. loading it to its full capacity with a lamp bank or other non-induc- tive resistance. The secondary voltage of the transformer at full load and at no load is then determined, and the ^difference between these values divided by the secondary voltage at full load, multi- plied by 100, gives the regulation in percent. The regulation of a transformer on a non-inductive load is about 2%; therefore, this method of obtaining regulation is not very accu- rate, as an error in the voltage readings of 1% will result in an error of approximately 50% in the measured regulation. Much more accurate results may be obtained by calculation. 30. RATIO. In order to guard against possible mistakes in coil winding and assembling, a test should be made to accurately de- termine the ratio of the primary to the secondary voltage. This may be done by connecting the transformer under test to a trans- former of known ratio as illustrated in Fig. 189. The readings of the voltmeter will give the ratio of the transformer under test. [361] Sec. 6 TRANSFORMERS Any convenient voltage readings large enough to obtain the desired accuracy may be used. Let n E' 'the secondary voltage of the standard transformer. = the ratio of the standard transformer, 'the secondary voltage of the transformer under test, n' =the ratio of the transformer under test. Then . no Jiio n' = E' 31. POLARITY. The phase relation between the transformer pri- mary and secondary terminal electromotive forces is termed the polarity of the transformer. FIG. 189. Connections for ratio test. When the windings of a transformer are so connected that the in- stantaneous flow of current is into terminal A and out of terminal C, then if A is considered positive, C, Fig. 190, is also positive. FIG. 190. (A) The polarity of a transformer may be determined when determining the ratio by connecting the transformers under test as illustrated in Fig. 189. If the polarity is the same as that of the standard transformer the lamps will both be bright. If it is the opposite, the lamps will both be dark. (B) The polarity of a transformer may also be determined by connecting a direct current source of energy to the low tension wind- [ 362 ] TRANSFORMERS Sec. 6 ing, breaking this connection and noting the deflection of a direct current voltmeter connected to the high tension winding. If the deflection on the voltmeter scale is positive, the lead of the trans- former connected to the positive terminal of the voltmeter is a positive lead, and the terminal of the low voltage side connected to the negative wire of the direct current supply is also positive. (C) Polarity may be determined by the method shown in Fig. 191. If 220/volts a-c. is supplied to the high voltage winding of a trans- former with a ratio of 10 to 1, the voltage of the low voltage winding is 22. If B and D are connected, a voltmeter connected to A and C will, when the transformer is of positive polarity, read the difference between the impressed voltage and the induced voltage, or 220 22 = 198 volts. If, however, the transformer polarity is negative, then the voltmeter connected to A and C will read the sum of the impressed and induced voltages, or 242 volts. Polyphase transformers may be tested for polarity in a manner similar to that for single phase transformers; more satisfactory f> 5 Fia. 191. Connections for polarity test. results are obtained by testing each phase of the transformer sepa- rately. TRANSFORMER SPECIFICATIONS 32. Transformers. In purchasing transformers definite values for the following data should be obtained : 1. Kv-a. capacity of transformer. 2. Power factor of load. 3. Primary voltage of transformer. 4. Secondary voltage of transformer. 5. Frequency of system. 6. Single phase or polyphase transformers. 7. Efficiency at %, Yi, %, full and 1^ full load. 8. Regulation at full load and power-factor given in item 2. 9. Core loss. 10. Exciting current. 33. Transformer Oil. As there is some variation in manufac- turers' oil specifications, two different specifications are given. The first specification was obtained from the Westinghouse Elec- [ 363 ] Sec. 6 TRANSFORMERS trie & Manufacturing Company, and the specification contained in Table 57 from the General Electric Company. Transformer Oil Specification. Quality: The oil must be a pure mineral oil obtained by frac- tional distillation of petroleum, unmixed with any other substances. It must not contain moisture, acid, alkali, or sulphur compounds. FIG. 192. Distribution of electrostatic field for different shaped terminals. Flash and Fire: The flash point of the oil must not be less than 171 C. (340 F.) and the fire point must not be less than 198 C. (390 F.). Evaporation: The oil must not show a loss by evaporation of / 2 3 4 S 6 7 D/STANCC //V /NCHCS FIG. 193. Disruptive value of dry oil for different shaped terminals. more than twenty-five hundred ths of one percent (0.25%), after heating for eight hours at a temperature of 100 C. Insulation: The oil must show an average breakdown test of not less than 35,000 volts on a 0.15" gap. Color: It is desirable that the color of the oil be as light as possible. [ 364 ] TRANSFORMERS Sec. 6 Viscosity : It is desirable that the oil be as fluid as possible, low viscosity being a point in its favor. Deposit: The oil must not show a deposit or any change other than a darkening of color, after being raised to a temperature of 232 C. (450 F.) by heating gradually and uniformly for one hour and then allowing it to stand at room temperature for twelve hours. The break-down voltage of oil is affected by the shape of the testing terminals. The electrostatic field between discs, spheres and needle points is illustrated in Fig. 192. The disruptive voltage of dry oil measured between variously shaped terminals is given in Fig. 193. There are two standard methods for testing the dielectric strength of oil. 1st. method. This method consists of testing terminals made of y brass balls fastened to T y rods. These terminals are placed vertically in a glass tube and so arranged that they may be adjusted for different distances, 0.15'' usually being considered standard. With this gap spacing average dry oil should not break down at less than 35,000 volts with a sine wave e.m.f. 2nd. method. This method consists of two half-inch brass discs, mounted on %" rods and arranged horizontally in a receptacle hold- ing oil. The discs may be adjusted for different distances, although 0.2" has been adopted as standard. With this gap spacing dry oil should not break down at less than 30,000 volts, with a sine wave e.m.f. Table 57 gives the characteristics of two oils furnished by the General Electric Company. The No. 8 oil is used for water-cooled and oil-cooled transformers and is designed for a normal temperature rise not to exceed 40 C. The No. 12 oil is for oil-cooled apparatus when the operating temperature rise is about 40 C. The dielectric strength of these oils is 30,000 volts when the test is applied between two }/% discs set 0.2" apart. TABLE 57 TRANSFORMER OIL . No. 8 Oil No. 12 Oil Flashing Temperature 130 C. 145 C. -15 C. 0.830 40 160 C. 175 C. -10 C. 0.850 60 Burning Temperature Freezing Temperature Specific Gravity (15.5 C.) Viscosity (,40 C ) 33a Moisture in Oil. Moisture in oil may be detected by testing samples obtained from the bottom of the transformer case. If water is present in large quantities it will be apparent to the eye. [ 365 ] Sec. 6 TRANSFORMERS If present in small quantities it may be detected by inserting in the oil an iron wire heated to a temperature slightly below a dull red; a very decided hissing or crackling sound will indicate the presence of moisture. If moisture is present copper sulphate crystals finely pulverized and placed on a watch crystal will turn a very deep blue when covered with the oil under test. The best test, however, is a test of dielectric strength by the spark gap methods mentioned above. Fig. 194 shows the effect of various percentage of water in medium and Fig. 195 in light oil. 30\ 20 .OS JO ./S .20 .ZS .30 FIG. 194. Influence of moisture on the dielectric strength of oil of medium viscosity. 34. THE OPERATION OF LARGE vs. SMALL TRANSFORM- ERS. The capacity of transformers for pole line used is limited, not only because of the mechanical problem of properly supporting them, but also because of the limited distance to which low tension current can be economically transmitted. Large installations of light or power usually require individual transformers, but when it is possible to select a load center from which a number of relatively small consumers can be economically reached, a considerable saving in investment and in energy loss can be effected. Relatively small transformers connected to a number of small individual loads usually require a transformer capacity of approximately 80% of the connected load. Relatively large trans- formers connected to a number of small consumers usually require a transformer capacity of from 30% to 50% of the connected load. [366] TRANSFORMERS Sec. 6 This reduction in transformer capacity necessary per kw. connected load is due to the diversity factor of the individual loads connected, and in a distributing system is one of the most important problems encountered. .05 JO .IS .20 .25 .30 FIG. 195. Influence of moisture on dielectric strength of light oil. It is self-evident that the grouping of loads on a single transformer can be overdone, in that, when the secondary distribution is ex- tended for great distances from the transformer, the cost of copper will more than offset the transformer economies. Therefore, this problem must be studied locally, giving due consideration to the character of the individual loads, their distance apart and the saving in transformer investment and in transformer efficiency that may be effected as illustrated by the following. A relatively large transformer is superior to a number of relatively small transformers having the same total capacity, since The cost per kv-a is less; The core loss per kv-a is less; The copper loss per kv-a is less. Increased economy in distribution may be effected by the parallel operation of transformers connected to a net work as illustrated in Article 8, Section 7. 35. A POLYPHASE TRANSFORMER is a single unit designed to transform polyphase energy to polyphase energy. Polyphase transformers are lighter in weight and cost less per [3671 Sec. 6 TRANSFORMERS kv-a than single-phase transformers of equal total capacity, but the failure of one section of a polyphase transformer necessitates re- moving it from the line. If single-phase units are used, one trans- former can be readily replaced in case of damage. Therefore, when polyphase transformers are used, it is necessary to carry a more expensive reserve stock than would be necessary if single-phase transformers are used. These factors usually decide in favor of single-phase transformers. 36. PARALLEL CONNECTING OF TRANSFORMERS. When connecting transformers for parallel operation it is generally ad- visable to test the polarity of the various transformers before per- manent connections are made. This may be done by connecting the primary leads of all the transformers to the primary circuit. The secondary leads of one of the transformers are then con- nected to the secondary mains, establishing secondary voltage or voltages to which the secondary voltages of the other transformers must conform. This is determined as follows: Connect one lead of each of the remaining transformers to one of the secondary mains. The remaining transformer secondary leads may be connected to the other secondary mains, provided voltage does not exist between the lead and the main to which it is to be connected. This condition may be determined by either a voltmeter or a lamp. When the polarity of single-phase and two-phase transformers is known, the connections can be readily determined. The phase relation of three-phase transformers or of single-phase transformers connected to a three-phase system is complicated and therefore vector diagrams are given in order to show the phase relation existing in the more important connections. In the following illustrations each transformer lead is identified by a number which is placed on the vector diagram to indicate the transformer lead which that particular end of the vector represents; thus, in Fig. 196 the vertical line on the left hand side illustrates the FIG. 196. primary winding. If the polarity of the corresponding secondary winding is positive, the numbers indicating the respective ends of the vector for the same phase relation will be identical. If the polarity, however, is the reverse or negative, then the numbers on the ends of the vectors are reversed, indicating that the phase relation [ 368 ] TRANSFORMERS A Sec. 6 _ f % PR/ MARY VECTORS /WvwJf JVwwvU JWwv/vAS 4^3 /AA/V 3/Wy J-AA^6 6A/ " 7 I I b \ \ C / \a TRANSFORMER SECONDARY VECTORS 3 A' B' SECONDARY MAIN VECTORS Fio. 197. Transformers connected "A" primary and "A" secondary. A VECTORS 7RANSrO*f1E# 2 . PR/MARY VECTORS SECONDARY VECTORS SECONDARY MAIN VECTORS FIG. 198. Transformers connected "Y" primary and "A" secondary. [369] Sec. 6 TRANSFORMERS of the corresponding secondary leads is opposite that of the primary leads. The voltage between the supply mains is used as a basis of refer- ence, as this voltage is independent of the method used in connecting the apparatus to the source of energy. Therefore, in Fig. 197 the voltages between A, B and C are " A " voltages. All vectors are assumed to rotate in a counter-clock-wise direction. Lead 1 of transformer a is connected to supply main A. Lead 2 of trans- former a is connected to supply main B. Therefore the phase rela- tion of transformer a is the same as that of the voltage between supply mains A and B. In a like manner transformers b and^c have the same phase relation respectively as the voltages between supply mains B C and A C. These transformers are assumed to have positive polarity. Therefore, the voltage vectors between the secondary leads of the transformers will be in phase with their respective primary voltages and the phase relation of the voltages between secondary mains A', B' and C' will be the same as between supply mains A, B and C. This method of connection is known as the delta delta connection. If the ratio of transformation is one to one, A may be connected to A', B to B' and C to C'. The connections in Fig. 201 are similar to those in Fig. 197, but negative transformer polarity has been assumed. Therefore, as the voltages are 180 out of phase, it is impossible to parallel these trans- former banks with symmetrical connections. By comparing the secondary vectors of Figs. 197 and 201, it will be noted that, al- though the vector representing the voltage of transformer a, Fig. 197, bears the same angular relation to that representing the voltage of the transformer a, Fig. 201, it is reversed and the delta voltages are reversed. If the secondary leads of each one of these transformers be re- versed, the vector relation of the secondary voltage becomes the same as that shown in Fig. 197 (compare Fig. 202). The crossed leads thus compensate for the negative polarity and make it possible to connect this bank in parallel with that shown in Fig. 197. Transformers may be connected with the primary in Y and the secondary in A as shown in Figs. 198 and 203. In Fig. 198, which is for positive polarity, No. 1 lead of transformer a is connected to the supply main A, No. 3 lead of transformer b is connected to the supply main B, No. 5 lead of transformer c is connected to the supply main C. Leads 2, 4 and 6 are connected together. Therefore, their vector relations are as illustrated for the transformer primary vectors. The voltage in each transformer secondary coil is in phase with the primary voltage and since lead No. 2 is connected to lead No. 3, lead No. 4 to No. 5 and lead No. 6 to No. 1, the voltages of the transformer secondary will be as illustrated in the diagram. Therefore, the voltages between A', B' and C' are in phase with the secondary voltages, but at an angle of 30 from the primary voltage. In Fig. 203, the secondary phase voltages are 180 in phase relation from those in the primary. Therefore, the delta voltage between the secondary leads of the transformer and between the secondary [370] TRANSFORMERS A Sec. 6 A B SUPPLY MAIN vccroKs B i i , w \ a J_^ J_^ /v /vwwvk 3www4 J^wws/^ j^_ \? x p ? j ^ j ryy ' C' * /I o' C' Fia. 199. Transformers connected "A" primary and "Y" secondary. A A 3\ SECONDARY VCCTOeS FIG. 200. Transformers connected "A" primary and "Y" secondary. [ 371 ] Sec. 6 TRANSFORMERS A /Vwwvtf jUww^ ^U/\AA/J S. VECTORS 7/PANSrORMEX 'P^vw 3 6 4 A' B 1 C' \ /c . A B' .t. , B 5KONOAKY MAIN VKTOKS FIG. 207. Correct method of connecting two transformers between the phase wires and the neutral wire of a three-phasr system. Posinw: ft>LAK/rr A B N AA^ ^AAA SUPPLY MAIN VECTORS 4^ 4/c t)***+i. .xsw ^ ^^ >SECONQA*Y MAIN vecrozs FIG. 208. Incorrect method of connecting two transformers between the ph* wires and the neutral wire of a three-phase system. [ 376 ] TRANSFORMERS A Sec. 6 Jl/PPLY MA/N wwww^ 3 TffANSFOifflfl? M- /AAAA^ 3/\/\N\4 A' B' C 1 D' 4*3 srcoMOAfY rrcroes K ^zeroes D 1 - FIG. 209. Transformer connections for transforming from three- to two-phase. B C AAAA? 4 4 S 3 3. 6 4 A' &' C' D SecONOAKY VKTOB3 FIG. 210. Transformer connections for transforming from three- to two-phase. [ 377 ] Sec. 6 TRANSFORMERS mary and, in consequence, the voltages between A' and B', and C' and D' will be the same as in the transformers a and b. In Fig. 210 the secondary voltages are reversed, as the polarity of the transformers is negative instead of positive, and it is, there- fore, impossible to parallel the transformers as illustrated in Figs. 209 and 210 on the secondary side. If, however, A' Fig. 209 is connected to B' Fig. 210; and B' Fig. 209 to A' Fig. 210; C' Fig. 209 is connected to D' Fig. 210, and D' Fig. 209 is connected to C' Fig. 210, and providing their characteristics are the same the trans- formers may be operated in parallel. 37. SCOTT TRANSFORMATION VECTOR ANALYSIS (Fig. 211). Illustrating the transformation from a three-phase system, in which the delta voltage is E to a two-phase system in which the phase voltage is E, draw an equilateral triangle A, B, C to a scale pro- portional to E, which represents the delta voltage of the three-phase system. Draw AO from the point A to the center of BC, which represents the voltage on the three-phase side of the transformer in /~~q Tfl -HI Fig. 209 and is equal to the -^-J|- X E ; OB = - - and OC = - -repre- J & A senting respectively the voltages impressed on the windings b and c of the transformer illustrated in Fig. 209. Draw OD equal to CB. This represents E the voltage of one phase of the two-phase system. Draw OF equal to BC. This represents the voltage of the other phase of the two-phase system. 2 The ratio of OF to OA is equal to 7=.. Draw Oa at an angle 6 from A/3 O A representing the power factor on the three-phase side of the trans- former. The length of Oa is proportional to the load current I on the three-phase side of the transformer. Draw Oc and Od propor- tional to I, each 120 from Oa. These represent the currents flowing in each half of the transformer connected to B C . Since the ratio of OF 2 to OAis . the current flowing in the two-phase side of the trans- former must be equal to I X . Lay off Ob equal to this value, Ob 2 then represents in value and phase the current in the two-phase winding of the transformer. Connect d and c, then drop a per- pendicular line from O to dc bisecting this line at e. Draw Of parallel to dc and equal to ec. This represents both in value and in phase the current in the other two-phase winding of the transformer, and is equal to I X - , one-half dc is used, as the difference in these two currents is in effect only flowing through one-half of the coils on the three-phase side of the transformer. 38. THE SPECIAL SERIES INCANDESCENT LIGHTING TRANSFORMER (Fig. 212) is a constant potential transformer [ 378 ] REGULATORS Sec. 6 constructed with a number of primary taps, by the use of which it may be connected to primary circuits with various percentage drops. Numerous leads are also brought out from the secondary winding to permit its connection to series circuits, in which the numbers of lamps may vary. Each lamp is supplied with a small inductance in parallel with the lamp filament. The resistance of the lamp filament and this inductance are so proportioned that when the filament is intact the major part of the line current flows through the filament. If, however, the filament is broken the current will flow through the inductance and the circuit will remain closed. In Fig. 212 the current is shown flowing through one of the in- ductances at a location where the filament of the lamp has been FIG. 211. Vector analysis of three-phase, two-phase transformation. broken. Under such conditions the voltage across each lamp and the current flowing in the circuit are practically the same as when all the lamps are burning. The power-factor of the transformer will vary with the number of lamps burning, i. e. the power-factor will be lower when the per- centage of lamps burning is small than when all are burning. A typical regulation curve is given in Fig. 213. Such transformers may be tested in a manner similar to the method used when testing commercial power and lighting transformers. INDUCTION REGULATORS 39. General Description. The induction regulator is a special type of transformer built like an induction motor with a coil-wound [ 379 ] Sec. 6 REGULATORS secondary, which is used for varying the voltage delivered to a syn- chronous converter or alternating-current feeder system. In comparison with a variable ratio transformer it possesses the ad- vantage of being operated without opening the circuit and without short-circuiting any transformer coil. However, it has a larger magnetic leakage and a higher value of exciting current than a transformer of equal capacity. The primary of the induction regula- tor is subjected to the constant voltage of the supply system. The delivered voltage being varied by combining with the supply voltage the e. m. f. generated inductively in the secondary. The primary is normally at rest, although it is movable at will for the purpose of varying the voltage. There are two distinct types of induction regulators, possessing different inherent characteristics but performing similar duties, namely, the single phase and the polyphase. The former is used for single-phase lighting circuits while the latter is generally employed in connection with rotary converters and similar apparatus. In the single-phase induction regulator the voltage generated \\ fc vl PRIMARY/ or TRANS., WITH PERCENTAGE TAPS S&H n n n COIL o o~ o ^BROKEN LAMP SECONDARY or TRANS., WITH VARIOUS TAPS TO rURNISH THE EXACT VOLTAGE REQUIRED. Fia. 212. Special series incandescent lighting transformer. in the secondary varies with the mechanical position of the rotor, but the voltage at all times remains directly in time phase with (or time phase opposition to) the primary e. m. f. Thus the resultant delivered e. m. f. is equal to the arithmetical sum (or difference) of the primary and the secondary e. m. f. the latter depending upon the position of the movable element. Referring now to the diagrams of Figs. 214 and 215, showing the values of the primary and secondary electromotive forces, let OA be the value and time phase position of the e. m. f . of the primary coil, and let OD or OE be the maximum value of the e. m. f . of the second- ary; this e. m. f. may be either subtracted from or added to the primary e. m. f . (according to the mechanical position of the moving member) in order to produce the resultant e. m. f. If now the line OE be allowed to represent also the mechanical position (in electrical space degrees) of the moving member when the maximum secondary e. m. f. is additive in phase with the primary e. m. f., then OD (180 electrical space degrees from OE) is the mechanical position of the [ 380 ] REGULATORS Sec. 6 moving member when the maximum e. m. f. is subtractive in phase with the primary e. m. f. When the mechanical position of the moving member is OB (Fig. 214) the secondary e. m. f. may be con- sidered to have the value OC (CB being perpendicular to OD), but it remains in time phase (opposition) with OA, so that the resultant delivered e. m. f. is CA> similarly when the mechanical position of the moving member is OB' (Fig. 215) the secondary e. m. f. is OC' 10 20 30 40 JO 60 70 80 f* I/, 4 i FIG. 214. E. M. F. circuit and current diagram of a single-phase induction regulator in a negative boost position. demagnetizing (or magnetizing) effect of the secondary current on the magnetic core. The load current supplied to the regulator circuit is the arithmetical sum of the primary and secondary currents when the secondary e. m. f. is added to the primary e. m. f. while it is the arithmetical difference between these two currents when the resultait delivered e. m. f. is the difference between the primary e. m. f. and the secondary e. m. f. [381] Sec. 6 REGULATORS It is interesting to note what occurs when the moving member occupies a mechanical position 90 electrical space degrees from the position indicated by OD or OE in Figs. 214 and 215. In this position the value of the secondary e. m. f. is zero, because the flux due to the primary exciting current passes through the secondary core parallel to the secondary windings. The resultant delivered e. m. f . is therefore equal to the primary e. m. f . When the regulator is in use, even when the secondary e. m. f . is of zero value, the second- ary current may have the full load value because it depends solely upon the delivered e. m. f . and the impedance of the delivery circuit. With the moving member in the position here assumed, the magneto- motive-force of the secondary current would be opposed in no respect by any primary current so that a large value of flux would tend to interlink with the secondary coil and produce an enormous reactance therein. To overcome this defect there is placed upon the primary core, in electrical space quadrature with the primary coil, a separately insulated coil which is electrically closed upon itself and forms a 7 4^ ^T [ "r s3 4? 1 r /> ^ D P/> \lp o \ p T r A^ ^ -^-1 FIG. 215. E. M. F. circuit and current diagram of a single-phase induction regulator in a positive boost position. short circuited secondary to the real secondary coil of the regulator which acts as its primary coil. This coil may be referred to as the tertiary coil of the regulator. The primary and the tertiary coils are usually placed on the movable, and the secondary on the stationary member, when the movable member of the regulator is in the maxi- mum, positive boost position or the maximum negative boost position (Figs. 214 and 215) the secondary m. m. f. is directly opposed by the primary m. m. f. and no current is produced in the tertiary coil. At intermediate positions the secondary m. m. f . is opposed in part by the m. m. f. of current in the primary coil and partly by m. m. f. of current in the tertiary coil; the resultant of these two m. m. f's. being just equal to the secondary m. m. f. so that the reactance of the secondary is reduced to that due to the magnetic leakage between the stationary and the movable members. The polyphase induction regulator in every essential detail is a polyphase induction motor whose polyphase coil-wound rotor can be locked in any position desired. The primary windings are con- nected across the supply lines just as are the primary windings of a [382] REGULATORS Sec. 6 polyphase induction motor; however, instead of being closed upon themselves as is true of the secondary windings of an induction motor, the secondary windings of the phases of the induction regulator are separately insulated and separately connected in series in the de- livery circuits from the regulator. When polyphase e. m. f.'s are impressed upon the primary windings, the e. m. f. generated in each secondary coil is of the same frequency as the primary e. m. f . Its value is constant and entirely independent of the mechanical position of the movable member; the time-phase position of these e. m. f's., however, varies directly with the electrical space position of the movable member. This resultant delivered e. m. f. is the vector sum of (or difference between) the primary and the secondary e. m. f's. : it is not constant in value but varies largely with the position of the movable member. Referring to Fig. 216, let OA repiesent the e. m. f. of a certain primary phase both in value and time-phase position, let OE (or OD) represent the e. m. f. of the corresponding secondary phase winding in the maximum positive (or maximum negative) boost position. Let OE (or OD) simultaneously represent the mechanical position (in electrical space degrees) of the moving member when the second- ary e. m. f . is in time-phase with (or time-phase opposition to) the primary e. m. f. In any mechanical position of the moving member, such as OB, the secondary e. m. f. has a value equal to OE (or OD) and its time-phase position is correctly represented by the line OB. This fact is attributable to the existence of a revolving field produced by the combination of the fluxes of the separate primary phases. For the present discussion the revolving field may be considered to have a constant strength, so that the time-phase position of the e. m. f. produced in any conductor subjected to this field will vary directly with its relative electrical space position. Since in Fig. 216 the primary e. m. f. is OA and the secondary e. m. f. is OB the re- sultant e. m. f . must be AB, both in value and in relative time phase position. E O D FIG. 216. Vector diagram of a polyphase induction regulator. The current in the delivery circuit (which is the same as that in the secondary coil) depends directly upon the resultant delivered e. m. f. and the impedance of the delivery circuit. In the polyphase induction regulator, there is no special tertiary circuit, but each primary phase winding acts in part as the tertiary circuit for the remaining primary phase windings and the several secondary phase windings. Thus the m. m. f . of the current in any secondary phase winding in any position whatsoever is fully counterbalanced (except for magnetic leakage) by the m. m. f. of the current, or currents, of [ 383 ] Sec. 6 REGULATORS one or more primary phase windings, and the reactance of the sec- ondary is reduced to that due to the magnetic leakage between the stationary and movable members. 40. The Pole Type Induction Regulator has been developed in order that long lightly loaded branch feeders may be connected to heavily loaded main feeders. Unless an intermediate voltage con- trol is installed, regulation on such a branch is very poor, es- pecially when connected to a main feeder close to the station. The general construction of the regulator is illustrated in Figs. 217 and 218. The usual regulator construction is departed from, due to the small amount of space available. See Fig. 219. The stator or FIG. 217. Pole type induction regulator showing cast lugs for hanging on trans- former hooks. secondary core has two slots only, in which a form wound coil is placed. The rotor or primary core has four slots, two of which are occupied by a single primary coil, wound directly on the core. The remaining slots, which are in quadrature with the slots contain- ing the primary winding, are opposite the secondary coil in Fig. 219. These slots contain round copper rods riveted to the cast brass flanges located at the top and bottom of the rotor, thus clamping the primary punchings and also acting as a tertiary coil. The flanges attached to these brass castings hold the rotor in alignment. Diagrammatic connections are illustrated in Fig. 220. The rotor is operated by a continuously running single-phase motor, by [384] REGULATORS Sec. 6 means of a ratchet and pawls. A voltage relay controls the pawls, so that, to raise the voltage the ratchet wheel is revolved in a given direction and to lower the voltage in an opposite direction. The relay is designed so that there are no arcing contacts. Such regulators are built in 10, 15, 25, and 50 ampere sizes, for 60 cycle circuits up to and including 2300 volts. The range of regulation is 10% above or below normal. The motor and relay are designed to operate on 110 or 220 volts. FIG. 218. View of mechanism and core of pole type induction regulator. 41. INDUCTION REGULATOR TESTS may be divided as follows: 1. The Insulation Test is made in a manner similar to such tests for transformers (Figs. 174 and 175), except that the secondary or stator coils should be tested at the same voltage as that of the primary or rotor winding, the condition under which they normally operate (Art. 23). 2. The Heating Test can be simplified as it is not necessary to have an external source of current supply to circulate the loading current. Full load conditions may be obtained when testing two regulators of the same general characteristics (Fig. 181) by setting 13 [ 385 ] Sec. 6 REGULATORS the rotating elements at such positions as to cause full load current to flow. If only one regulator is to be tested the rotating element may be set so that full load current will flow in the short-circuited secondary when normal voltage is impressed upon the primary. As full load SECONDARY FIG. 219. Section of regulator winding and core. conditions are not obtained in the primary, this is an approximate test. 3. Iron Loss Test (Art. 25). 4. Resistance Tests (Art. 26). 5. Copper Loss Tests and Impedance Tests are made in a manner [ 386 ] REGULATORS Sec. 6 similar to that for transformers (Art. 27), except that they should be made at several positions in the mechanical rotation of the primary or rotor. -Stcondoryof Loaa QfstrWuting Transformer FIG. 220. Connection diagram of pole type regulator. 6. The Range of Regulation may be determined by connecting a voltmeter to the secondary winding and rotating the primary, operated at normal voltage, through an arc large enough to obtain readings from zero to a maximum value as indicated on the volt- meter. The values thus obtained corrected for the impedance drop at full load represent one-half the total range of the regulator. Let E s = the maximum effective value of the regulator secondary voltage. e =the percent variation in voltage from no load to full load referred to full load voltage, for maximum boost position. (This is found in the same manner as for transformers. Art. 49, Section 7.) Then the range of the regulator is Range in volts = 2 E 3 (1 TsJ BIBLIOGRAPHY A. I. E. E., July, 1909, Mr. L. W. Chubb. " 1910, Mr. H. W. Tobey. Publications of Various Manufacturers. Pennsylvania Electric Association, 1912, Mr. F. W. Shackelford. Alternating current, Franklin & Williamson. Foster's Electrical Engineers' Pocket Book. Standard Handbook for Electrical Engineers. American Electricians' Handbook. [387] SECTION 6 PART II LIGHTNING PHENOMENA IN CONNECTION WITH ELECTRIC CIRCUITS, PROTEC- TIVE APPARATUS, GROUNDING SECTION 6 PART II LIGHTNING PHENOMENA IN CONNECTION WITH ELECTRIC CIRCUITS, PROTECTIVE APPARATUS, GROUNDING TABLE OF CONTENTS ARTICLE Lightning Phenomena in Connection with Electric Circuits. General 1 The Electric Charge 2 An Impulse or Traveling Wave .- 3 Standing Waves 4 High Currents 5 Protective Apparatus General 6 Multigap or Low Equivalent Arresters 7 Compression Type Arresters 8 Circuit Breaker Type Arresters 9 Aluminum Cell or Electrolytic Arresters 10 Single Gap and Multipath Arresters 11 Location of Lightning Arresters 12 Installation of Lightning Arresters 13 Horn Arresters 14 Choke Coils 15 Ground Wires 16 Switches 17 Fuses 18 The Link Fuse 19 The Enclosed Cartridge Fuse . 20 The Expulsion Fuse 21 Grounding General 22 Laws of the Resistance of Pipe Earth Connections 23 Making the Earth Connections 24 Testing Grounds 25 [391] LIGHTNING PHENOMENA IN CONNECTION WITH ELEC- TRIC CIRCUITS 1. General. The phenomena causing trouble in electric systems may be divided into three general classes. 1st. High voltage. (Art. 2-4.) 2nd. High frequency. (Art. 2-4.) 3rd. High current. (Art. 5.) In any system of energy transmission there are three types of phenomena causing strains; namely, steady stresses, impulses or blows, and vibrations. In an electric system high frequency and high voltage cause the same types of stresses; namely, (a) Steady stress or gradual electric charge. (Art. 2.) (b) Impulse or traveling wave. (Art. 3.) (c) Standing wave or oscillation and surge. (Art. 4.) 2. The Electric Charge. The total potential difference between the ground and an electric circuit, may gradually rise by the ac- cumulation of an electric charge in the circuit, until the "lightning arresters discharge or the insulation is punctured, depending upon which is the point of least resistance. Some of the factors causing such a steady and gradual accumula- tion of electric charge are: (a) The collection of static charge from rain, from snow drift, or from fog, carried by wind across the line. The presence of accumulated static may be indicated by a series of peri- odic lightning arrester discharges. (b) An accumulated static charge may follow the passing of charged clouds due to electrostatic induction. Assuming for instance, a charged cloud passing over a transmission line. The ground below the line carries an electrostatic charge of opposite sign, corresponding to the charge of the cloud. The line should have a charge also, higher than that of the ground since projecting above -it. If the line is insulated from ground, without the charge required for electrostatic equilibrium, it thus appears at a potential against ground; that is, at cloud potential. With the ap- proach of a charged cloud to the transmission line, the poten- tial of the line against ground rises until a discharge takes place between the ground and line, charging the line to ground potential. Inversely, with the cloud receding from the line, the line charge is not bound by the charge of the cloud and therefore discharges to ground. (c) Potential differences between the line and ground due to differences of atmosphere potential in different regions traversed by the line, especially so if the line passes through different altitudes. Sec. 6 PROTECTIVE APPARATUS (d) Accidental electrostatic charges "entering the circuit as from frictional electricity from belt-driven machinery. (e) Unsymmetrical conditions of the generator potential such as the grounding of a wire on a three-phase system which will give the system, as a whole, an alternating potential difference to ground, equal to the voltage between a phase wire and the neutral of the system. (f) The existence of higher harmonics in the electro-motive- force wave of a polyphase system may cause trouble if they are of such an order that they coincide in the different phases; that is, the whole system rises and falls with their frequency. In a three-phase system, the third, ninth, fifteenth, etc., harmonics coincide. The effects of steady electrostatic stress, where uni-directional, and caused by external agents as items a to d or alternating and caused by internal agents, as items e and f , appear not only in the circuits in which they originate, but in circuits electrostatically con- nected to them. The danger of such accumulations of potential lies in their lia- bility to damage the insulation of the system by puncture or by their discharge, producing other and more serious disturbances. 3. An impulse or traveling wave is caused by sudden local electro- static charges on a transmission line, such as a lightning stroke, induced potential caused by the sudden discharge of a cloud, or any other sudden local change in conditions. This wave of potential and current travels along the line just as a water wave travels over the surface of the ocean. The wave front is very steep, i. e., has high voltage at the point of impact, but gradually flattens out, and if the line is of unlimited length ultimately disappears. If the line is of definite length the wave is reflected and combines with the incoming waves to form a system of nodes and maxima, called standing waves. When apparatus is connected to the line, the traveling wave di- vides, part is transmitted and part is reflected. The impulse is thus broken up into a number of secondary impulses and local stand- ing waves, which may reach much higher voltages than that of the traveling wave. Impulses or traveling waves may be caused by : (a) Direct or secondary lightning strokes, which generally do local damage, but do not travel far, as the disturbance is generally confined to a very few impulses of steep wave front but of short extent. (b) Electrostatic induction from lightning discharges. While each of these impulses is rarely of sufficient power to do serious damage, due to their frequency of recurrence, they may lead to the production of destructive internal surges. Impulses originating thus are felt more generally through [ 394 ] PROTECTIVE APPARATUS Sec. 6 the system, but do not cause as much local damage as those originating from direct strokes. (c) The discharge of slowly accumulated potential resulting in a series of successive impulses. (d) Any spark discharge from line to line or from the line to ground. (e) Arcing grounds. (f) Sudden changes of load, switching, etc. \\ FIG. 221. \ FIG. 222. \\ FIG. 223. Impulses may be caused by external or internal disturbances. Items a and b may be classed as external causes, c and d as both external and internal causes, e and f as internal causes. 4. Standing waves are formed when a wave train is reflected, as the waves neutralize at some points forming a node and add at other [ 395 ] Sec. 6 PROTECTIVE APPARATUS points forming a wave crest, of greater or less amplitude than that of the original wave, depending upon the phase relations of the original and reflected waves. Fig. 221, shows these waves in phase opposi- tion; Fig. 222, about 90 degrees apart in phase, and Fig. 223 practi- cally in phase. In each figure O is the original wave, F the re- flected wave and P the resultant wave. An oscillation is the phenomenon by which the flow of power in an electric circuit restores its equilibrium after a disturbance of the circuit conditions. Any circuit disturbance may, and usually does, produce an oscillation which may be local only, that is, contain only very high frequency harmonics, but it may become universal by including the fundamental and its lower harmonics. In the latter case it is usually called a surge. Some of the typical forms of oscillation are : (a) Spark discharges to and from the line as over lightning arresters; the breaking up of a traveling wave entering the station, results in the formation of very high frequency oscillations, millions of cycles per second. (b) Arcing grounds and other arc discharges to ground from a line of an insulated system; reflected waves, etc., give oscillations which, while still of very high frequency, are considerably lower in frequency than item (a), that is, hundred thousand of cycles per second. (c) Charge and discharge, of the line as when discharging an accumulated electric charge over a path of low resistance; connecting a dead transformer to the line, etc., results in high frequency oscillations containing also an appreciable low frequency component. (d) Sudden changes in load, connecting or disconnecting a transmission line; opening a short circuit suddenly, etc., give oscillations in which the fundamental frequency pre- dominates. (e) Low frequency surges, consisting primarily of the funda- mental wave, may be produced by certain transformer con- nections. See Art. 17, Sec. 7. The most powerful oscillation is the short circuit surge of a system, or oscillation produced by rupturing a short circuit as by a self -rupturing arc. 5. High currents cause damage in an electrical circuit due to the intense mechanical strains to which they subject the apparatus. The rapid interruption of high current phenomenon causes high voltage disturbances. PROTECTIVE APPARATUS 6. General. The principal protective apparatus for overhead lines may be divided into six general divisions as follows: 1. Lightning Arresters. (Arts. 7 to 11.) 2. Horn Arresters. (Art. 14.) [ 396 ] PROTECTIVE APPARATUS Sec. 6 3. Choke Coils. (Art. 15.) 4. Ground Wires and Lightning Rods. (Art. 16.) 5. Insulator Protectors. (Art. 27, Sec. 5.) 6. Switches and Fuses. (Art. 17, 18-21.) Lightning Arresters. The function of a lightning arrester is two- fold; to discharge any high voltage disturbance that may occur on a line and to accomplish this while preventing the formation of a power arc which may cause greater voltages by oscillation, or which may interrupt service by forming a short circuit on the system. (a) Multigap or Low Equivalent Arresters. (Art. 7.) (b) Compression Type Arresters. (Art. 8.) (c) Circuit Breaker Type Arresters. (Art. 9.) (d) Aluminum Cell or Electrolytic Arresters. (Art. 10.) (e) Single gap and Multipath Arresters. (Art. 11.) 7. MULTIGAP OR LOW EQUIVALENT ARRESTERS. The general theory of this arrester is as follows : When voltage is applied across a series of multigap cylinders, the voltage distribution is not un- iform. There is a capacity effect between the cylinders and from each cylinder to ground, which concentrates the voltage across the gaps nearest the line. When the voltage across the end gaps reaches a certain value, they arc across, passing the strain back to the other gaps, which in turn arc-over until the spark has passed entirely across the arrester. The arrester thus arcs over at a lower voltage than if the voltage were evenly distributed across the gaps. When the arresters have arced over and current is flowing, the voltage is evenly distributed between the gaps and for this reason is too low to maintain an alternating current arc. The arc, there- fore, lasts only to the end of the half cycle and then goes out. Alloys of metals with high and low boiling points are used for lightning arrester cylinder gaps. The metals with low boiling points tend to cool the arc while the metals with high boiling points tend to pre- serve the shape of the cylinder gaps. In addition to the cooling effect of the cylinders, the temperature of the arc is affected by the amount of current flowing, which amount may be limited by the use of resistances. If some of the gaps are shunted by a resistance high frequency disturbances will pass directly across the gaps, but the dynamic cur- rent will pass through the resistance and be limited. By using graded resistances connected to different gap cylinders the arrester may be designed to care for high frequency and low frequency disturbances equally well. This type of arrester is illustrated in Figs. 224 and 225. This effect can be still further intensified with good results by bringing a connection at or near ground potential, near the series gaps, thus increasing the capacity current across the upper gap and lowering the breakdown voltage. An arrester embodying this feature is shown in Fig. 226. It consists essentially of a number of non-arcing metal cups, insulated from each other by porcelain spacers and connected in series with a resistance rod. Through the center of the metal cups passes a metal rod connected to the bottom cup but [ 397 ] Sec. 6 PROTECTIVE APPARATUS [ 398 ] PROTECTIVE APPARATUS Sec. 6 thoroughly insulated from all others. The electrostatic effect of the close proximity of this rod to the upper cups causes the breakdown voltage of these gaps to be greatly lowered, and permits the use of more series gaps than would be possible were the control rod not present. The upper end of the rod is cemented into an insulator having a cap with a cast-in eye by which the arrester may be sus- pended. The lower end of the arrester carries a hook, to which another arrester can be attached when two in series are needed for high voltage lines. Good contact with the resistance rod is insured by a spring shunted by a flexible lead inside of the tube which en- closes the resistance rod. This arrester may be used outdoors, and FIG. 226. Low equivalent lightning arrester, single pole. for this service is equipped with a metal rain shield over the spark gaps. 8. COMPRESSION TYPE ARRESTER. The compression type arrester is a particular design of the Multigap arrester. Fig. 227 illustrates the arrangement of the parts of the compression chamber arrester. On the outside, there is a porcelain base with four screw holes to connect it to a cross-arm. Immediately inside of this base are the antennae. The antennae vary in form in different arresters, but as illustrated they consist of two metal strips in the form of a "U" that fit inside of the holder or base. Inside of the antennae is placed a straight porcelain tube. The porcelain tube is held in place by insulating cement. Inside of the porcelain tube the gap units are placed. Each gap unit consists of two punched metal hats of special alloy. The crowns of these hats are turned so they face each other, and both crowns are knurled. Between the rims of the two metal hats there is a short porcelain tube which holds the crowns of the metal hats about -fa* (0.9 mm.) apart. These gap [399] Sec. 6 PROTECTIVE APPARATUS units are stacked one on top of the other inside the porcelain tube between the arms of the antenna?. On top of the gap units is placed a resistance rod of low ohmic value. The gap units and resistance rods fill the long porcelain tube. On top of the resistance rod a spring contact is made, and a porcelain cap is fitted over the end of the tube and cemented thereto. The connecting wire projects through the porcelain cap. The ground connection is a wire which passes through the bottom of the base and is connected to the antenna as well as to the lower gap unit. The arrester is hermetically sealed so that no dust, dirt or moisture can enter. Due to the effect of the antenna? in this arrester, it is possible to LINE LEAD SWING CONTACT COM POUND - PORCELAIN ^EPAKATOR GfOI/ND LEAD PORCELAIN CA? -RESISTANCE ROD PORCELAIN BASE ANTENNA -METAL ELECT/WOE FIG. 227. Compression type arrester. use more than the usual number of gaps in series. In consequence the resistance in series with the gaps may be very low in value. The average value of this resistance is 23 ohms. The discharge current to ground per phase will be approximately equal to the lightning potential divided by 23 ohms. The use of the antennae gives uniformity in the spark potential regardless of the surroundings; its use also reduces the spark po- tential of the series of gaps used in this arrester, to exactly one-half the spark potential without the antenna?. This permits the use of twice as many gaps as would otherwise be possible. Each gap has the function of extinguishing a certain potential applied to it. There- [400] PROTECTIVE APPARATUS Sec. 6 fore, when the number of gaps is doubled, the arc-extinguishing power of the arrester is greatly magnified. Each gap is enclosed in a sealed chamber, and any expansion of gases in that chamber will cause an increase in pressure, which tends to extinguish an arc. Furthermore the porcelain tube which encloses the gap has its cooling surface in close proximity to the arc. Another arrester operating on the compression principle is de- scribed as follows : This arrester is sometimes used for the protec- tion of series D. C. arc circuits. It consists of two sets of metal electrodes mounted flush with the surface of a lignum vitae block. Charred or carbonized shallow grooves provide a ready path for the discharge, while a second block, fitting closely over the first block, confines the discharge and limits the formation of gases and vapors. Such gases as do form are highly compressed and are expelled violently through grooves transverse to the discharge path, thus rupturing the arc. As no series resistance is used with this arrester it has great freedom of discharge. 9. CIRCUIT BREAKER TYPE ARRESTER. This type of arrester is illustrated in Fig. 228 and consists essentially of the combination of small air gaps, low series resistance and a mechanical circuit breaker. High frequency disturbances enter the arrester at line connection A, and pass to ground across gaps B and C, resistance rod D, and gaps E and F. Coil H and the mechanical circuit breaker are connected in multiple with the gaps E and F. This shunt path is of lower resistance than these gaps, but has a higher inductive or choking effect. The coil will therefore shunt any dynamic current following the discharge to ground from gaps E and F. High frequency dis- turbances, however, will not flow through this highly inductive shunt path, but will take the path across gaps E and F. When the flow of dynamic current following the discharge to ground through the arrester is small, it is cut off by the action of the air gaps B, C, E, and F as the voltage wave crosses zero value. Under these conditions, the arc lasts only to the end of the half cycle and then dies out. These discharge electrodes are made of alloys of metals with high and low boiling points. The metals of low boiling points vaporize under the dynamic arc and tend to cool the gaps, while the metals of high boiling points tend to* preserve the shapes of the discharge electrodes. Whenever the flow of dynamic current to ground exceeds the values that will be cut off by the air gaps alone, this heavier flow is shunted from gaps E and F due to the low resistance of coil H; flows through the coil and so produces a magnetic field which raises the plunger J, thus cutting off the current inside the fiber tube and extinguishing the arc. The path of this dynamic current is indicated by the dashed lines. These arresters may be used for higher voltages than that of each unit (Fig. 229) by connecting the units in series as shown in Fig. 230. For pole work the arresters are mounted in wood boxes, and are usually supported from the arms by iron hangers. [401] Sec. 6 PROTECTIVE APPARATUS B ; [402] PROTECTIVE APPARATUS Sec. 6 10. ALUMINUM CELL OR ELECTROLYTIC ARRESTERS. The aluminum cell arrester consists of plates of aluminum arranged as electrodes of a battery. The electrolyte may be anyone of a number of solutions. When current passes through an aluminum cell, an insulating film forms on the surface of the metal. This film has a certain dielectric strength. If the voltage rises above the critical value, current can flow through the cell with very little im- pedance. When the line has been relieved of disturbances the voltage falls to the normal value (below the critical voltage of the arrester), and the film at once reforms and shuts off the current flow. If an alter- nating voltage with a maximum value above the critical voltage of the cell is impressed across an arrester, the peak of each voltage wave will be cut off by the arrester. 400 ^ 320 I I \~ so t I 1 f- ' / 23 4 6 FIG. 231. Characteristic curve of aluminum cell or electrolytic lightning arrester for alternating current. The volt-ampere characteristic curve (Fig. 231) of the aluminum cell will vary somewhat according to whether direct or alternating currents are used. A comparatively low voltage arrester is illustrated in Fig. 232, while in Fig. 233 is illustrated an arrester for high voltage lines. W T hen an aluminum cell arrester is disconnected from the circuit for any great length of time, part of the filrn is dissovled and when reconnected to the circuit there is a momentary rush of current which reforms the film. The value of this current depends upon the length of time the arrester is disconnected from the circuit. To prevent this film dissolution, it is advisable to charge the arrester once every twenty-four (24) hours, which may be accom- plished by short-circuiting the gaps. Where it is deemed necessary resistance may be inserted to damp out oscillations resulting from charging, or to reduce the initial rush of current. Horn gaps with charging resistance are shown in Figs. 234, 235. When the arrester cells are so assembled that one section is not connected directly to the line when charging, it is necessary to install a transfer or reversing switch connecting this section and one of the line sections so that the relative connections of the sections may be [403] Sec. 6 PROTECTIVE APPARATUS reversed. The films on all the cells may thus be formed to the same critical voltage value. 11. SINGLE GAP AND MULTIPATH ARRESTERS. A type of low voltage arrester is shown in Fig. 236. This type consists of two heavily beaded brass discs, A and B, separated from each other at the beads by a -fa inch air gap by means of a high resistance disc C. Wires P and E are soldered to these discs, one of which is connected to the line wire, the other to the ground. FIG. 232. Three pole electrolytic lightning arrester for thee-phase 6,600 volt circuits. FIG, 233. Single pole aluminum cell lightning arrester for 110,000 volt circuits. Light charges of lightning and of accumulated static find a path from line to ground by leaking through this high resistance disc. When subjected to a heavier charge the high resistance disc prevents the charge leaking to ground quickly enough; hence, these heavier charges jump across the -$ inch air gap to ground. [404] PROTECTIVE APPARATUS Sec. 6 !! [405] Sec. 6 PROTECTIVE APPARATUS The flow of line current following the high potential discharge to ground is usually very small, and when the voltage of the circuit crosses zero value, the arc dies out. The metallic beads being large and cool, cool the arc vapors to such an extent that when the voltage FIG. 236. Diagrammatic view of single gap lightning arrester. wave builds up to a maximum value, the voltage is not sufficient to again start an arc at the air gap. The assembled arrester is illustrated in Fig. 237. FIG. 237. Single gap lightning arrester. The multipath arrester (Fig. 238) consists of a carborundum block enclosed in a cast iron shell or box. A small spark gap of slightly over ^th of an inch, mounted inside of the case in series with the carborundum block, serves to keep the latter normally [ 406 ] PROTECTIVE APPARATUS Sec. 6 insulated from the line. The terminals to the circuit and the ground connection are attached to metal plates on either side of the block and all discharges must pass between them. . The static discharge spreads itself over the carborundum block along a number of minute discharge paths (multipath). The voltage across each gap is very low; therefore, the line voltage cannot main- tain an arc across them. The action is analogous to that of a coherer in wireless telegraphy in that the body of the block becomes momentarily conducting as a result of the shock given the slightly separated particles. Thus, while the ohmic resistance to slowly applied low potentials is several megohms, the equivalent spark gap is very low. These arresters are single pole and may be mounted on a pole or used in the station, and are suitable for eithe^ alternating current or direct current circuits up to 1000 volts. FIG. 238. Multipatn lightning arrescer. 12. LOCATION OF LIGHTNING ARRESTERS. No general rule can be made governing the required number or the spacing of lightning arresters. Installations sufficient to 'give protection in some localities will give insufficient protection in others. The factors governing the location of lightning arresters are: the intensity and frequency of lightning storms, the location of the line in relation to natural protective features, such as tall trees, build- ings, conditions of altitudes, etc., the potential of the line, since a lightning disturbance that may cause damage on a low voltage line may be unnoticed on one of higher potential. 13. INSTALLATION OF LIGHTNING ARRESTERS. The wir- ing connections of lightning arresters are of utmost importance. The discharge circuit should contain minimum impedance, and hence must furnish the shortest and most direct path from the line to ground. The most severe disturbances which an arrester is called upon to handle [ 407 ] Sec. 6 PROTECTIVE APPARATUS are those of high frequencies, and it is therefore, imperative to elim- inate all unnecessary inductance. The features favorable tojlow in- ductance are short length of conductor, large radius bends and a con- ductor or large surface area. For wiring high voltage arresters the use of copper tubing is strongly recommended. Such copper tubing has the advantage over either copper strip or solid conductors in that it is easily supported, requires fewer insulators, and is, therefore, cheaper to install. Copper tubing connections can be designed so that all sharp bends are eliminated and there are no points where corona or brush discharge may take place. The wiring for pole type arresters should never be wound in a spiral [ 408 ] PROTECTIVE APPARATUS Sec. 6 coil. If this is done, the usefulness of the arrester is practically counteracted by the inductance of the wire coil. Even one turn will greatly reduce the effectiveness of the arrester and in some cases may entirely prevent its discharge. The wiring from the arrester to the ground should be as short and straight as possible. This connection may be made by copper wire, rod, or strap, and should be protected by a wood cover extending from the ground line to a point seven feet above. When an iron pipe ground is made, the copper connection from the arrester to the pipe should be securely fastened to the top of the pipe and not carried down the inside of the pipe. FIG. 240. Horn gap lightning arrester combined with choke coil for constant potential circuits. The wire should not be wound around the pipe before connecting thereto. Lightning arrester grounds should be kept separate from all other grounds. For methods of making grounds, see Arts. 22, 23, 24 and 25. 14. HORN ARRESTERS. Horn arresters should not be consid- ered as true lightning arresters, but rather an insulation intentionally weak. If -due, for instance to direct stroke the insulation of a line must fail, it is much more preferable that it should do so over a horn [ 409 ] Sec. 6 PROTECTIVE APPARATUS arrester. Horn arresters with resistance are usually useless, except on constant current circuits, as the current of discharge is too limited to relieve the line. With no resistance, or with resistance low enough to relieve the line, synchronous apparatus will be thrown out of FIG. 241. -Choke coil. step and the line shut down before the arc can be extinguished. The line, however, can be immediately put into service again, which could not be done if the insulation was punctured. The place for FIG. 242. Choke coil. horns, therefore, is along the pole line at short intervals, setting the gaps for very high voltage arc-over. For constant current arc lamp circuits, horns form an excellent [410] PROTECTIVE APPARATUS Sec. 6 arrester, as only a small current is required to relieve the line, and resistance can be used. For mercury arc rectifier arc-lamp circuits, this arrester is especially well adapted, as the multigap arrester will not operate on direct current. A typical horn arrester is shown in Fig. 239, and a type combining the horn gap and choke coil is shown in Fig. 240. 15. CHOKE COILS or reactances have the function of retarding high frequency disturbances, thus giving the lightning arresters an opportunity to relieve high potential stresses before they enter the apparatus. Choke coils are not effective in retarding low frequency disturbances. Several types of choke coils are illustrated in Figs. 241, 242, 243. 16. GROUND WIRES AND LIGHTNING RODS. Wire conduc- tors placed underground or insulated wire conductors surrounded by a metallic sheath and hung overhead are protected from electrostatic FIG. 243. Choke coil charges due to cloud lightning. As it is generally impractical to sur- round the wire conductor by a metallic sheath the next best thing to do is to place some object at ground potential over the line. This may be done by stringing a grounded wire over the line. The greater the distance between the grounded wire and the line, the better partial protection is afforded the line. Dr. Steinmetz recommends that an overhead grounded wire be so placed that two imaginary lines drawn from this wire 45 down from the horizontal will include' all line wires between them. Each additional overhead ground wire, properly placed, gives some additional protection against induced static electricity from the clouds. The overhead grounded wire also has the function of protecting wood poles from being shattered by a direct stroke of cloud lightning. It also has the possibility of carrying a direct stroke of cloud lightning to ground, past the line wires, without shattering the insulators or causing a short circuit. [411] Sec. 6 PROTECTIVE APPARATUS FIG. 244. Air break 3 P. S. T. switch. FIG. 245. Air break S. P. S. T. disconnecting switch for 300 amperes and 35,000 volts. FIG. 246. Air break S. P. S. T. disconnecting switch for 300 amperes and 90,000 volts. [ 412 ] PROTECTIVE APPARATUS Sec. 6 Lightning rods at each pole will add a slight probability that a direct stroke will strike at the pole and not between poles. If the overhead grounded wire is earthed at every pole, direct strokes of lightning are likely to find a more direct path to earth. The wave front of a direct stroke is usually so steep that the charge finds the natural inductance of the horizontal wire a great im- pedance, and consequently it is likely to side-flash to other lines and also over insulators to its natural terminum, the earth. If the earth connection is made at every third pole instead of at every pole, there is a possibility that a direct stroke will hit a midway point and have a greater distance to travel, parallel to the line wire, before it reaches the earth. The parallel movement of the charge gives electromag- netic induction on the power wires. Practically all reports of dam- ages to lines by direct strokes confine the line damage to about seven FIG. 247. Horn gap air break S. P. S. T. switch for 300 amperes and 44,000 volts. successive poles. Therefore, a close study of operating conditions should be made in order to determine the necessity for frequent earth connections. 17. SWITCHES. Switches may be divided into two general groups. 1. Air break switches. 2. Oil switches. Air break switches are usually used as disconnecting switches and on lines of low amperage capacity may be used to open a loaded cir- cuit or branch line. They are seldom used, however, to break short circuit currents. Several types of air break switches are illustrated in Figs. 244-247. When air break switches are used in connection with series circuits they take the forms illustrated in Figs. 248 to 251. [413] Sec. 6 PROTECTIVE APPARATUS The switches illustrated in Figs. 248-249 are used in connection with individual arc lamps and are so arranged that each unit may be completely disconnected from the circuit without interrupting the passage of current. The switches illustrated in Figs. 250 and 251 serve the purpose of disconnecting a number of units simultaneously and are so arranged that both the main circuit and the disconnected loop are closed, thus permitting the operation of the remaining portion of the series circuit when the loop has been disconnected. Fig. 250 is a non-automatic switch, while Fig. 251 is an automatic switch, the operation of which is as follows: FIG. 248. Absolute arc lamp cutout. Let the circuit under normal conditions, which starts from the terminal T of a constant current dynamo or constant current trans- former, pass through the series lamps L, etc., along the flexible con- ductor J, to the laminated contact B and contact plate C, through the lamps N, N, etc., to contact plate C' and laminated contact B', along flexible conductor J', through balance of lamps L, etc., to ter- minal T' of the dynamo or transformer. The section of the above circuit which is being protected by the automatic series cut-out, extends from contact plate C, through lamps N, N, etc., to contact plate C'. Let a break occur in the circuit protected by the cut-out, say at O. Immediately the full potential difference of the line will exist across the adjustable gap G between the carbons E and E', the carbons being so adjusted that this potential difference will be sufficient to [414] PROTECTIVE APPARATUS Sec. 6 break down the air gap. For an instant the current flows from T through lamps L, to carbon E, across gap G to carbon E', through solenoid coil S to R, through lamps L, to terminal T'. This condi- tion exists but for a moment, as the current immediately energizes the solenoid S, causing core A to be drawn up, carrying with it the porcelain insulator P and contacts B and B', thus opening the circuit [415] Sec. 6 PROTECTIVE APPARATUS containing the lamps N, N, etc., at C and C'. A.t the same time the contact B makes contact with D, thus short circuiting the gap G. Consider the break at O as having been repaired. The loop circuit is still dead and can be started by disconnecting the circuit at T T' FIG. 251. Automatic arc loop cutout switch. for an instant, allowing the core A to drop, thus reconnecting the loop. If, however, the circuit for any reason has not been properly re- paired, or another break has occurred, an arc will again be established FIG. 252. Non-automatic oil switch 3 P. S. T., 100 amperes, 2,200 volts. across gap G, the solenoid energized and the defective line again cut out in the same manner as previously explained. This pro- cedure will continue until the defective circuit is properly closed. [ 416] PROTECTIVE APPARATUS Sec. 6 Oil switches may be sub-divided into two classes: 1. Automatic. 2. Non-automatic. An automatic oil switch is an oil switch so arranged that it will disconnect the circuit under a predetermined condition. Such switches are seldom used on pole line work, especially in systems where the kv-a. capacity of the generating system is large, as a switch that would successfully open a short circuit would be too large and expensive. There are many instances, however, where space is available and the cost permissible, in which automatic oil switches may be used to advantage to replace fuses. In outdoor substation installation where the kv-a. capacity is sufficient to warrant the cost, and protection from overload or short FIG. 253. Automatic oil switch 3 P. S. T., 100 amperes, 2,200 volts. circuit conditions is desired, automatic oil switches are in general use. Figs. 252-254 illustrate various types of oil switches some of which may be made automatic or non-automatic by a slight change in the design of the operating mechanism. The time switch (Fig. 255) is a semi-automatic oil or air break switch in that its operation may be controlled by a time clock and the circuits opened and closed at predetermined intervals, but is .non- automatic in that its operation is independent of any phenomena occurring in the circuit. When it is undesirable to connect branch lines to mains by fused connections or automatic switches, non-automatic pole type oil switches may be used to advantage, as their use facilitates the loca- tion of operating troubles. 18. FUSES. Probably no part of an electrical system is subjected to more severe conditions than is the electric fuse. Coupled to this, 14 [ 417 ] Sec. 6 PROTECTIVE APPARATUS is the fact, that when once installed the fuse is usually regarded as part of the distribution or transmission circuit and, with the exception of very occasional inspections, is given no operating attention. The fuse installation therefore must not only be able to withstand all weather conditions and all kinds of varying loads, but from its very nature must operate when occasion demands and open the circuit satisfactorily. On systems of moderate capacity the problem is not serious as there FIG. 254. High voltage oil switch 3 P. S. T. Design ranges from 100-800 amperes and 22,000-110,000 volts. is no possibility of concentrating a large amount of energy in case a fault develops in the protected circuit. On larger systems, however, those which receive energy from a generating source of relatively high capacity the conditions are much more severe. Here the fuse must be able to operate under very heavy loads and must interrupt without damage, a flow of energy amounting to thousands of kilowatts. The interruption of the circuit under such conditions means the very rapid dissipation of the consequent heat, and in its effects this is comparable in many cases, to a violent explosion. In addition, the heat caused by the rapid expansion of the air and [418] PROTECTIVE APPARATUS Sec. 6 gaseous metallic vapors in the electric arc, if allowed to continue for a period of more than two or three cycles, is sufficient to destroy fuse holders, terminals, etc. These two conditions, (a), the explosion effect at the time of opera- tion, and (b), the fusion of terminals, etc., due to the heat of the electric arc, may be considered as the most important factors in the design of a satisfactory fuse. Particular attention should be given these points, and the fuse construction which guards against dangerous rises in gaseous pres- sure, and operates to minimize the effect of heating is to be recom- mended. This latter condition is secured by rapid extinction of the arc formed, combined with ample heat radiating qualities. In the design of terminals, the contacts and the insulating supports, particular attention must be directed to the current-carrying capaci- FIG. 255. Air break 3 P. D. T. 100 amperes, 220 volt time switch. ties and the insulation strength. When fuses are mounted in metallic boxes, exceptional care should be exercised that arcing from the terminals to the box is made impossible. When such conditions are possible the operation of the fuse particularly the open link type will invariably cause a breakdown and will result in the consequent destruction of the fuse installation. Proper contact area is also of great importance as a great number of fuse failures are due entirely to lack of this. When the fuse clips are light, and the current density for maximum fuse rating is high, the chances of trouble are greatly increased. When the connection is a knife blade contact, the removal and replacement of the fuse will necessarily change the value of the contact resistance, and, for this [ 419 ] Sec. 6 PROTECTIVE APPARATUS reason, particularly on heavy current circuits, a design of fuse holder may be considered most desirable which operates on a removable hinge principle. Light contact clips which can easily be bent or damaged by care- less handling of the fuse holder should be avoided. One form of fuse contact obviates this danger by employing a special backing post, which affords adequate protection to the clip without impairing the flexibility of contact. As the fuse is obviously the weakest part of the electric circuit, or, at least should be made such, particular care is necessary to secure conditions, external to the fusible strip, which shall be constant in nature, or proper operating of the circuit will be impaired. Proper fuse testing is necessarily dependent on a clear under- standing of fuse rating. There are no definite or general rules cover- ing this, other than those issued by the Board of Fire Underwriters, which may be said to apply particularly to low voltage fuses. All fuses, because of the principle upon which they operate, have an inverse time action, i.e., they will carry a momentary current of a much higher value than that which will cause them to operate, should the current be sustained. It is unreasonable to expect a fuse to operate with the accuracy of a circuit breaker. It would seem, how- ever, that the method of rating fuses, as practiced by the various manufacturers, should be clearly understood by operating companies in order that a properly selected protective device may be installed. A summation of the more important points in the general con- sideration of satisfactory fuse operation may be noted as follows: (1) The type of fuse, for any given installation, should be de- termined by a consideration of the maximum concentration of energy, which is possible at any protected point of the distribution system. (2) The general construction of the fuse should be such that it will be able to withstand the most severe climatic conditions without serious deterioration. (3) The current carrying parts should be rugged, self-aligning and of sufficient capacity to carry 50% overload with a rise in tempera- ture not to exceed 40 C. (4) The design should be such that it will provide for the removal or the replacement of the fuse without the possibility of accidental contact with any live parts. (5) The insulation of all current-carrying parts and particularly the insulation of the leading in wires, should be such that a breakdown between circuit and fuse box supports, or between opposite poles of the circuit, after the fuse has blown, is impossible. The principal forms of fuses used in electrical distribution are covered by the three following classifications: (1) Link Fuses. (Art. 19.) (2) Enclosed Cartridge Fuses. (Art. 20.) (3) Expulsion Fuses. (Art. 21.) 19. THE LINK FUSE is the simplest type and consists essentially of a strip of fusible metal extended between two terminals of a fuse [ 420 ] PROTECTIVE APPARATUS Sec. 6 block. This fuse block or holder is usually of porcelain or other suit- able insulating material, arranged in two parts: (I) the enclosing body with suitable arrangement for fastening to the fuse support, and (II) the fuse holder or plug which is made removable in order to FIG. 256. Fuse holder for 30 amperes, 2,200 volt link fuse. allow the replacement or inspection of the fuse. Metal boxes for enclosing the fuse base and block are employed in some designs. Unless, however, extreme care is exercised in this construction, par- FIG. 257. Horn gap link fuse. ticularly relating to the breakdown distances from live parts to the metal box, this type may prove unreliable in operation. The most satisfactory link type of fuse is that in which copper terminal clips form the ends of the fuse strip. The use of these [421 ] Sec. 6 PROTECTIVE APPARATUS tends to prevent damage to the fuse strip when it is fastened to the terminal studs and also insures a better contact. In addition the fusible strip is often provided with a tubular asbestos envelope which not only protects the fuse while in service, but tends towards its more satisfactory operation when the fuse is melted. (Figs. 256 and 257.) 20. THE ENCLOSED CARTRIDGE FUSE consists of a fusible strip encased in an insulating tube which serves also as a container for an insulating substance which completely surrounds the fuse strip. The tube is usually made of fibre, and the filling material is com- posed of Calcium Sulphate (Plaster of Paris) or Calcium Carbonate (Whitening), or Levigated Amorphous Infusorial Earth, usually pow- dered or granular in form. A combination of any two or three, will result in a substance suitable as a heat dissipating material, but any siliceous materials such as sand or glass or any of the porcelain clays FIG. 258. Enclosed cartridge fuse and fuse box. 100 amperes, 2,200 volts. are not suitable owing to the ease with which they may be fused and rendered conducting. The filling serves the three-fold purpose: (a) of absorbing the heat liberated when the fuse is blown, (b) of condensing the vapor of the molten metal and (c) of breaking the continuity of the electric circuit. The ends of the fuse are soldered or riveted to the metal contacts which also serve to seal the tube, thus holding in the filling compound. When a portion of the strip is turned into vapor upon the opera- tion of an enclosed fuse, pressure results and the vapor seeks to ex- pand through the filling material. The hot gases pass over the sur- faces of the minute particles which, on account of their lower tem- perature, condense the gas, but when the initial expansion occurs the air entrained between the particles of filling material must find escape. To this end vents are provided in the end closures of the cartridge and in order to prevent the dislodgement of the dust and [422] PROTECTIVE APPARATUS Sec. 6 F 423 ] Sec. 6 PROTECTIVE APPARATUS finer particles of filling, vent screens of cloth, canvas, asbestos cloth, etc., are placed within the ferrules. In some installations the enclosed type fuse has many advantages over the simple link fuse. On account of its enclosed construction its general characteristics are more nearly uniform and therefore its operation should be far more definite. (Fig. 258.) In addition to the standard type of enclosed fuse, several other designs are found in commercial use; one of which (Fig. 259), con- sists of a glass tube containing a spiral spring, the lower end of which is connected to the bottom ferrule. The upper end of the spring connects to the fuse wire, passing through a cork, the upper end of the fuse wire being connected to a short wire soldered to the cap on the top ferrule. At the top of the spiral spring and just below the cork is a funnel-shaped liquid director. The glass tube is filled with a non-inflammable liquid of high dielectric strength. FIG. 260. Oscillogram illustrating the action of the fuse in FIG. 259 when opening a short circuit. The melting of the fuse wire releases the spiral spring which con- tracts instantaneously, drawing the fuse wire down towards the bottom of the tube and thus introducing a very large gap. Simul- taneously with the introduction of this gap, the Mquid extinguishes the arc and interrupts the current flow, the rapidity of its action being accelerated by the liquid director which is drawn down with the spring and so forces the liquid directly onto the moving terminal. Another consists of a metal box filled almost completely with oil, into which the fusible strip is immersed except for a small part of its [424] PROTECTIVE APPARATUS Sec. 6 length. (Fig. 261.) The portion exposed to the air will melt first, due to the more rapid conduction of heat by the oil; when the fuse blows an arc is established above the oil level and as the metal fuse burns down to the oil the arc will be automatically extinguished and the circuit thereby interrupted. FIG. 261. Oil fuse box showing details of construction. The oil fuse cutout illustrated in Fig. 262 consists of an oil tank in which oil immersed contacts are provided. A removable element is designed to carry the fuse, and a vent is placed in the top of this element to permit the escape of the gases generated when the fuse operates. FIG. 262. Oil fuse cutout. The removable element is designed so that it is necessary to insert it completely and then turn it before contact is made with the stationary contacts in the tank. This locks the fuse plug in pos- ition, thus protecting the operator from accidents which may occur due to refusing when a short circuit exists. [425] Sec. 6 PROTECTIVE APPARATUS Metal boxes for enclosing and supporting the standard enclosed type of fuse are very generally used. Since there should be no liberation of metallic gaseous vapor when the fuse blows, which vapor would tend to cause a breakdown between live parts and the metal case, no special precautions are necessary to protect against such conditions. Other materials of construction, such as asbestos lumber or im- pregnated wood are used and have proven more or less satisfactory. 21. THE EXPULSION FUSE. This type employs what is essen- tially an open link fuse in combination with a container having in its FIG. 263. Expulsion fuse block and box, 100 amperes, 2,500 volts. construction an explosion chamber. This form of design utilizes the explosive action of the gases liberated when the fuse is blown, directing these gases across the arc in such a way as to extinguish it and thus rupture the circuit. For overhead line service there are two types of expulsion fuses. One consists of two blocks of insulating material, between which the fusible strip is securely clamped. (Fig. 263.) Midway along the fusible strip is located an expulsion chamber. Where the fuse strip passes through this chamber its cross section is reduced, resulting in a definite point at which the fusing will first take place. This [426] PROTECTIVE APPARATUS Sec. 6 fusing point is located directly back of the discharge vent in the holder and the explosion caused when the fuse operates forces the gaseous vapors through the opening provided, thus extinguishing the arc. The melting of the fuse is usually confined to the length of the fuse strip contained in the expulsion chamber. In order to prevent injury to the block, at these points, it is usual to provide strips of non-inflammable material along the parts of the fuse which are directly in contact with the fuse holder. These strips are made FIG. 264. Expulsion fuse for from 6,000-22,000 volts. FIG. 265. Expulsion fuse for 50 amperes, 15,000 volts. either of asbestos lumber, of lignum vitse or of lava and may be readily replaced at a nominal cost. The other form of expulsion fuse in general use consists of a tubular holder which serves as a container for an open link fuse. (Figs. 264 to 267.) This holder is constructed of an insulating mater- ial, usually fiber, which is closed at one end by a metal explosion chamber. The other end of the holder is left open and provides an exit for the discharging gases when the fuse blows. The principal of operation of this type is identical to that already described. One other type (Fig. 268), which is of comparatively recent de- [427] Sec. 6 PROTECTIVE APPARATUS sign, employs the use of an extremely high pressure gas receptacle which is connected to one end of a special form of fusible strip ; this strip being connected in the electric circuit by means of the tubular arrangement above mentioned. In its operation, this fuse melts at a predetermined point, thereby, releasing the gas from the her- metically sealed container. The gas does not support combustion and in its discharge through the arc path interrupts the circuit by violently blowing the metallic vapor through the open end of the tube. In addition, the rapid expansion of the gas cools the terminals to very low temperatures and thus prevents the burning of the metal parts. Fuse boxes similar to those for enclosed fuses are constructed of wood, metal or asbestos, or a combination of asbestos and metal. The latter construction eliminates all metal except a skeleton frame, FIG. 266. Expulsion fuse and box for 60 amperes, 2,200 volt circuits. and provision is made so that the asbestos board sides can be readily replaced in case of damage. GROUNDING. 22. General. Earth connections are necessarily made by elec- trolytic conduction. To obtain low resistance, it is therefore neces- sary to have electrolytic moisture in contact with the earth plate, or, lacking thus a fair degree of conductivity, it is necessary to have a very large area of cross section for the current. There are no dry earths that are conductors. If the earth contains no soluble sub- stances which are electrical conductors, it is necessary to add elec- trolyte. The one precaution in choosing an electrolyte is to avoid one which attacks the metal conductors chemically. It is impossible to make a rule or practice to coyer all cases, but investigations have shown that the general practice of using pipe [ 428 ] PROTECTIVE APPARATUS Sec. 6 earths can be justified in nearly every case. Coke, so often recom- mended for earth connections, is not a good conductor in itself. It attracts and holds moisture, but since that moisture does not con- tain an electrolyte in solution, it leaves the earth connection with high resistance. On the basis of the first cost, and of inspection, resistance measurements, etc., the iron pipe earth is to be recom- mended. Iron is the cheapest available metal and has thoroughly proven its serviceability, even when imbedded in salty marshes. For an electrolyte, salt or washing soda is to be recommended. In the majority of conditions, salt is preferable as its resistance is less, notwithstanding that it has a greater chemical effect on the iron. FIG. 267. Expulsion fuse, 60 amperes, 6,600 volts. 23. Laws of the Resistance of Pipe Earth Connections: (a) Resistance Versus Depth of Pipe. The resistance varies approximately inversely as the depth in the conducting stratum. (b) Resistance Versus Specific Resistance of the Earth. Practically all of the resistance in the earth is in the immediate vicinity of the pipe. This resistance depends on the specific re- sistance of the material. The specific resistance depends upon the amount of moisture and the electrolyte in the moisture. The lowest possible resistance obtainable is secured by pouring salt water around the pipe. (c) Resistance Versus Multiple Pipe Earths. When it is desired to lower the resistance to earth below that of a single pipe earth, drive others at a distance of not less than six feet from each other. Then the total conductance is only slightly less than the sum of the individual conductances, and the total re- sistance is the reciprocal of the total conductance. For conditions [ 429 ] Sec. 6 PROTECTIVE APPARATUS of uniform soil, the approximate rules may be stated : That two pipe earths connected together give one-half the resistance of one, ten pipe earths give one-tenth the resistance of one, etc. (d) Resistance Between Pipe Earths at Variable Distances Apart. For distance between pipe earths up to one foot the resistance be- tween them increases rapidly. For every additional foot, the added resistance becomes less and less. At a distance apart of six feet, the resistance has reached nearly a constant value. Stated otherwise, the resistance between two pipe earths at any distance apart greater than six feet is nearly equal to the sum of the isolated resistance of each. Fio. 268. Compression fuse and box for 200 amperes, 2,500 volts. (e) Potential Distribution Around a Pipe Earth. Since the resistance of a pipe earth lies mostly in the immediate vicinity of the pipe, the greatest potential drop when the current flows will also be concentrated there. Heating and drying out will tend to magnify this value. (f) Ampere-hour Capacity of a Pipe Earth. The quantity of electricity that can be passed through a pipe earth without materially changing its resistance, increases directly with the wetness of the earth in contact with the iron, and the area of the iron surface exposed to the passage of the current; and de- creases as the resistance of the earth in contact with the pipe in- creases. Certain critical values of current may be carried con- tinuously by a pipe earth without varying the resistance. The higher the current above this critical value, the more rapid the drying out. To increase the ampere-hour capacity it is necessary to keep the pipe earth wet with salt water. [430] PROTECTIVE APPARATUS Sec. 6 (g) Resistance of Pipe Earth Versus Diameter of Pipe. The resistance of a pipe earth does not decrease in direct pro- portion to the increase in the diameter of the pipe. Two pipes driven side by side and connected together will have only a slightly less resistance to earth than one pipe; a pipe two inches in diameter has a resistance only about six to twelve percent less than that of a pipe one inch in diameter. (h) Minimum Inductance of Leads to Pipe Earths. The connecting wire between the conductor or apparatus to be grounded and the ground should be as short as possible, by taking as direct and straight a path as possible. Loops in the lead introduce unnecessary impedance to high fre- quency impulses. The inductance of a conductor to high frequency may be said to decrease with the increase of the surface area. A hollow metal tube conducts as well as a solid wire of the same circumference. A flat strip is an economical way of getting large surface with a small weight of metal. The minimum degree of inductance with the minimum weight of metal is obtained by using separated parallel wires. Copper is best on account of its conductivity and durability, but, since only the surface layer of metal carries the current, gal- vanized iron may be used in some cases. 24. Making the Earth Connection. (a) General. To make the earth connection, take plain pieces of standard one and two inch pipe and drive them as much over six feet into the ground as is convenient. Solid metal spear heads and sleeve joints on the pipe, which make holes larger than the diameter of the pipe, should not be used, as the contact resistance is thereby excessively increased. If the pipe drives with too much difficulty, a solid crowbar may first be used to open up the hole. If there is no stand available for starting a pipe eight feet or more long, a shorter pipe, slightly larger in diameter, may be driven several feet and then withdrawn to make a start for the longer pipe. After the pipe is driven to place, a basin should be scooped out of the surface of the earth around the pipe and salt brine poured in. The amount of salt water needed depends upon the local conditions and also upon the importance of the ground connection. Where the resistance of a pipe earth is less than 100 ohms without salt, a bucket full of brine may suffice. Where the pipe earth does not reach moisture below, and the resistance, therefore, is quite high, several buckets of brine may be necessary. A few handfuls of crystal salt should also be placed around the pipe in the basin. Whether the basin is to be filled with dirt or made permanent by the use of a tile with a cover, depends upon the importance of the earth connection. The connection to the ground from the system or the apparatus to be grounded should be made by as direct a path as possible and with a copper conductor of sufficient area to take care of the maximum discharge which may occur at that point. Angles and short curves [431] Sec. 6 PROTECTIVE APPARATUS should be reduced to a minimum and loops in the connecting con- ductor should be carefully avoided as they introduce unnecessary impedance to the high frequency impulses. The connecting wires should be attached to a pipe or pipes by first making a good, mechanically strong connection and then well Fia. 269. Ground cone. FIG. .270 Ground box. FIG. 271. Ground plate. soldering the joint. The point of connection should be at some point on the pipe above the deposit of salt in the basin in order to avoid any voltaic action between the copper and iron. Ground wires should not be run through iron conduits. If the pipe earths are at some distance from the apparatus to be grounded, [432] PROTECTIVE APPARATUS Sec. 6 the ground wire may be run buried in the earth, but such connection should be avoided and should be frequently inspected for possible deterioration of the conductor. (b) Earth Connection for A. C. Lightning Arresters. In general, drive two or three iron pipes into the earth at a point near the loca- tion of the lightning arrester. Then drive other pipes at a minimum distance of six feet apart encircling the station or pole structure, and connect all of them with a common wire. In choosing the size of conductor for the common wire connecting the pipe earths, con- sideration must be given to the possible maximum discharge which it may be required to handle and the size chosen accordingly. This common ground conductor should be protected from possible electrolytic action. (c) Grounding Secondaries. When the secondaries of distribut- ing circuits are grounded, the connection should be made as near the transformer pole as possible, and, if it is on the same pole as a trans- former, it may be connected to the earth connection of the trans- former case, care being taken that this earth connection is sufficiently good for the purpose. Secondary ground connections should be kept separate from lightning arrester grounds and should be protected by a wood cover extending from the ground line to a point seven feet above. (d) Grounding Transformer Cases. When grounding trans- former cases the connection should be made solidly and of sufficient size to take care of any possible breakdown. Transformers on poles may be grounded to one pipe. (e) Water Pipe Grounds. In any system of grounding it is ad- visable, where possible, to make a permanent connection to a water supply system. This may be accomplished by fastening and soldering a pipe clamp securely to the pipe and then soldering the ground wire to the clamp. When a flat copper strap is used for a ground connection it may be clamped securely to the pipe and soldered. 25. Testing Grounds. The greatest difficulty in making ground connections is in obtaining reliable grounds. When rigid and perma- nent connections can be made to water piping systems, such connec- tions will be found to give the most satisfactory grounds. It is generally difficult to obtain such connections to the water piping system, except where the ground is made on a consumer's premises and the consumer has also a water service. In making ground con- nections outside, it will, in practically all cases, be necessary to use some form of ground plate or ground rod. The efficiency of these methods of grounding depends almost entirely on the nature of the soil, such grounds, unless made in permanently damp soils, being practically useless. It is generally considered that a ground is satisfactory if the re- sistance is less than twenty (20) ohms. Therefore, in order to de- termine whether or not satisfactory grounds have been obtained, re- sistance readings should be made. In taking such readings, if a [433] Sec. 6 PROTECTIVE APPARATUS water piping system is available, so that a test wire can be attached to a water hydrant or service cock, the resistance can be measured be- tween the ground to be tested and the water piping system. A convenient method of making this test is as follows: After the ground has been installed on the neutral wire of the 220- volt secondary system, or on one leg of the 110- volt secondary system, connect the ungrounded leg of the system through a 5- ampere fuse to an available point on the water piping system. If sufficient current flows to blow this 5-ampere fuse the ground con- nection may be considered satisfactory. If the ground wire is installed on the neutral wire of a 3-wire, 440-\olt secondary system, or on one leg of a 220- volt system, and connections are made as above, the current flowing should be suffi- cient to blow a 10-ampere fuse. BIBLIOGRAPHY A. I. E. E., June, 1907. Steinmetz. A. I. E. E., June, 1907-12. Creighton. General Electric Review, Feb., 1913. Electric Bond & Share Co. Publications of Various Manufacturers. [434] SECTION 7 SYSTEMS OF DISTRIBUTION AND TRANSMISSION ELECTRICAL CALCULATIONS SECTION 7 SYSTEMS OF DISTRIBUTION AND TRANSMISSION TABLE OF CONTENTS ARTICLE Introduction Description of Systems Direct Current 1 Direct Current, Two-Wire System 2 The Edison Three-Wire System 3 The Direct Current Series Arc Lighting System 4 The Thury Direct Current Series System 5 Alternating Current 6 The Single-Phase System 7 The Single-Phase Two-Wire System 8 The Single-Phase Three- Wire System 9 The Two-Phase System 10 The Two-Phase Three-Wire System 11 The Two-Phase Four-Wire System 12 The Two-Phase Five-Wire System 13 The Three-Phase System 14 The Three-Phase Three-Wire System 15 The Three-Phase Four-Wire System 16 Comparison of "Y" and "A" Transformer Connections.. 17 The Alternating Current Series System 18 Comparative Weight of Conductors Necessary in Various Systems 19 Vectors and Vector Diagrams General Discussion 20 Vector Addition 21 Direction of Arrows 22 Single-Phase Transmission t 23 Two-Phase Four- Wire System 24 Two-Phase Three-Wire System ; 25 Three-Phase "Y" Connected System. 26 Three-Phase "A" Connected System 27 Effect of Charging Current on Line Calculations 28 Inductance Formulae 29 Capacity Formulae 30 Methods of Calculating Transmission Losses General 31 Direct Current Two- Wire System 32 [437] Sec. 7 ELECTRICAL CALCULATIONS ARTICLE Two-Wire Direct Current Railway System 33 The Edison Three-Wire System 34 Direct Current Series System 35 Calculation of Alternating Current Systems 36 Explanation of the Line Loss Tables 37 Single-Phase Two-Wire System 38 Single-Phase Three-Wire System 39 Two-Phase Three-Wire System 40 Three-Phase Transmission 41 Graphical Solution of a Three-Phase Transmission Line. . . 42 Additions to Existing Systems 43 Alternating Current Series System 44 Choice of Voltage on Transmission Lines 45 Corona and Corona Loss 46 Locating the Center of Distribution 47 Transformer Calculations Calculation of Transformer Capacity 48 Calculation of Transformer Regulation 49 Calculation of Transformer Efficiency 50 Voltage Regulators General 51 Regulation 52 Single-Phase System 53 Two-Phase System 54 Three-Phase Three-Wire System 55 Three-Phase Four-Wire System 56 Regulator Capacity 57 Resultant Power-Factors 58 Power-Factors of Various Types of Loads 59 Economics of Transmission 60 Transpositions 61 Constant Voltage Transmission 62 Sparking Distances 63 438 ] INTRODUCTION No attempt will be made in this section to cover the solution of all the electrical problems involved in the transmission of electrical energy. However, fundamental formulae are included, together with definitions of the various standard systems of distribution, and the use of the formulae included will enable the solution of the majority of electrical problems encountered. The tables have been arranged to facilitate the use of a slide rule and the values contained are well within its accuracy. DEFINITIONS OF TRANSMISSION AND DISTRIBUTING SYSTEMS. 1. Direct Current is unidirectional current. It may be constant, or periodically fluctuating, as a rectified alternating current. A continuous current is a steady non-pulsating direct current. In reality, the commonly so-called direct current systems more nearly approach the definition of continuous current than direct current. Therefore, in the following paragraphs continuous and direct current systems alike will be termed Direct Current Systems. 2. The Two-Wire Direct Current System (Fig. 272) consists of a two-wire multiple circuit upon which, when used for light and power, is maintained a constant potential difference of from 110 to 550 volts. Such systems operated at 220 volts have been used to a large extent in isolated plants. These, however, are being succeeded by the three-wire direct or alternating current distributing systems. For railway work (Fig. 273) a constant potential mul- tiple circuit is maintained, using the trolley contact wire or a third rail as the positive conductor, and the track rail as the negative conductor. The track rail is made the negative in order that elec- trolytic action, which occurs where current leaves a conducting body, will be confined to a section close to the power house. In such systems 600 volt circuits are the usual standard. However, on interurban railway work 600, 750, 1200, 1500 and 2400 volt circuits have been used depending upon local conditions, such as the length of the line, the volume of traffic, train schedule, topog- raphy, etc. J-J/OM>Lr LAMPS //v Jff/tt OH SSO I/OL TS. 2-/!Ott>LT Aec-LAMPS M 5tt/S ON 220 K LAMP f/O $2ZO Fig. 272. D. C. two-wire system. f 439 | Sec. 7 ELECTRICAL CALCULATIONS 3. The Edison Three-Wire System is essentially two, two-wire systems, in which the positive of one and the negative of the other circuit are combined in one wire known as the neutral. It is a development of the two- wire direct current system. Its use allows the distribution of the same amount of energy at the same usable voltage as that of the two-wire system and at a great saving in copper. (Double voltage being maintained between the outside wires). The neutral wire carries only the unbalanced load of the system. As adapted to central station practice, it is usual to connect the wires in a network (Fig. 274) and feeders are extended from the generating station to the various load centers. It is necessary to extend the neutral from the station only to points where conditions of unbalanced load are known to exist. Because of the small areas covered by isolated plants, a system of mains and branches is used in such installations instead of a net-work. The difference of potential between the outside wires of the three- wire direct current system is usually maintained at 220 volts; and that between either outside wire and the neutral is 110 volts. Posmvc fcrDces^ \\ -* TKOLLCV Z4OO VOLTS 1 KAIL _ ' Fig. 273. D. C. railway system. 4. The Direct Current Series Lighting System (Fig. 275) is one in which the current is maintained at a constant value; the voltage varies with the number and characteristics of the lighting units connected. The system consists essentially of a single continuous conductor run from, and returning to, the source of energy. In this way the area to be served is covered, and into the circuit are connected in series the arc or incandescent lighting units. This system is usually confined to the transmission of energy for street lighting. 5. The Thury Direct Current Series System is similar in char- acter to the direct current series lighting system, except that the circuits are of higher voltage and greater kw. capacity. The source of energy consists of a number of generators connected in series by which means high direct current voltages are obtained. This is distinctively a system for the distribution of energy for power and as such, is used to some extent in Europe. The problem of insu- lating the generating and the receiving apparatus is difficult, because of the high voltages maintained. [440] ELECTRICAL CALCULATIONS Sec. 7 AOCMf vll/ ^y + 101 /Z/f ffPS v^ 1 Sa i 2201S 1 ruses //OK \ + Q 5JS /(OK i ,_, 999 *a* + //OK X + 7-N //^?^ 1 O^ /-L^ ~~ ' + /; r^ Jia^ zzoy. + , ,_ LAMPS //OK Fig. 274. Edison three-wire system. 6. Alternating Current. An alternating current or e.m.f. is a current or e.m.f. which, when plotted against time in rectangular co-ordinates, consists of half waves of equal area in successively opposite directions from the zero line. A Cycle is two immediately succeeding half waves. The number of cycles per second is known as the frequency. Standard American frequencies for the distribution of energy for light and power are 25 and 60 cycles. : Cur-ours i CUT-OUTS -X Aec LAMPS ~ Fig. 275. Direct current series arc lighting system. [441] Sec. 7 ELECTRICAL CALCULATIONS f 442 ELECTRICAL CALCULATIONS Sec. 7 7. Single-Phase System. A term characterizing a simple alter- nating current circuit energized by a single alternating e.m.f. Such a circuit is usually supplied through two wires. The currents in these two wires, counted positively outwards from the source, differ in phase by 180 degrees or half a cycle. 8. The Alternating Current Single- Phase Two-Wire System (Fig. 276) is similar in circuit arrangement to the direct current two wire system. When used for the distribution of energy for light and power, it is usually part of a polyphase system. For railway installations potentials of 11,000 volts are in successful operation, confined however to systems using a trolley contact wire. When a single phase system is used for the distribution of energy for light and power, the following secondary connections can be made: Single-phase two-wire. Single-phase three-wire. 9. The Single-Phase Three-Wire System (Fig. 276) is nearly always confined to secondary distribution and is similar in circuit arrangement to the Edison Direct Current three wire system, es- pecially when interconnected to form a network. In such a network the transformer secondaries are connected at those points to which, in an Edison three-wire system, feeders would be extended. Main and branch distribution connected to a single transformer is more often used, because of the fact that failures in such a system confine themselves locally, without disturbing a number of con- sumers, as may occur in a network. When such a system is used, it is generally a part of a polyphase primary distributing system. 10. A Two-Phase System is one in which the energy is contin- uous and in which two alternating voltages are impressed upon the receiving circuit. The maximum values of these two voltages are 90 electrical degrees apart in time phase. 11. The Two-Phase Three-Wire System (Fig. 277) consists of two single phase circuits (differing in phase by an angle of 90) supplying energy over three wires, one wire acting as the common return for both circuits. When the load on such a system is bal- anced, the current in the common wire is 41 percent greater than that in each outside wire. The phenomena of unbalanced voltage and phase angle distortion in this system depend upon many variables, some of which follow: the amount of the load, the proportion of the load on each phase, the power-factor of the circuit, the voltage, the frequency, the spacing and diameter of conductors and the length of line. (Art. 25). The above phenomena may be negligible with a low power-factor load if the low power-factor load is a small part of the total load on a circuit having a high power-factor; and if the conductors are spaced closed together, fairly long lines may be used without trouble from this cause. The system has been adopted to some extent for the reason that [443] Sec. 7 ELECTRICAL CALCULATIONS [444] ELECTRICAL CALCULATIONS Sec. 7 more energy can be transmitted over the same weight of conductor than is possible in a two-phase four- wire system. Against this, how- ever, must be considered the necessity for higher insulation, as the voltage between the outside phase wires is 41 percent greater than the single phase voltages. The following secondary connections can be made to such a system : Single-phase, two-wire. Single-phase, three-wire. Two-phase, three-wire. Two-phase, four-wire. Two-phase, five-wire. Three-phase, three-wire. 12. The Two-Phase, Four -Wire System (Fig. 278) differs from the two-phase, three wire system in that two independent single- phase circuits are maintained (differing in phase by an angle of 90) supplying energy over four wires. This system is being extensively used for power distribution. For transmission its use is gradually giving way to three-phase, three- and four-wire systems, by the use of which a considerable saving in conductor material is made possible. The following secondary connections may be made to a 2-phase 4- wire system. Single-phase, two-wire. Single-phase, three-wire. Two-phase, three-wire. Two-phase, four-wire. Two-phase, five-wire. Three-phase, three-wire. 13. The Two-Phase, Five -Wire System (Figs. 277 and 278) is a two-phase secondary system in which the middle points of the trans- formers in each phase are connected together. From which connec- tion the fifth wire is run. This establishes two single-phase, three-wire systems with a common neutral. Such a combination is sometimes used where power and light are to be supplied from the same transformer bank. 14. A Three-Phase System is one in which .the energy is con- tinuous and in which three alternating voltages are impressed upon the receiving circuit. The maximum values of each of the three alternating voltages occur 120 electrical degrees apart in time phase. 15. The Triree-Phase, Three -Wire System (Fig. 279) consists of three single phase circuits, respectively differing in phase by angles of 120 and supplying energy over three wires. In such a system the algebraic sum of the current in all three wires is zero at any instant, the algebraic sum of the current in any two wires is equal, but opposite to that in the thkd wire. The effective voltages between all three wires are equal. The system is generally used for transmission work, for the reason [445] Sec. 7 ELECTRICAL CALCULATIONS [446] ELECTRICAL CALCULATIONS Sec. 7 [447] Sec. 7 ELECTRICAL CALCULATIONS that from the standpoint of conductor material, it affords the most economic method for the transmission of electrical energy. Transformers at the source of supply may be connected either Y or "A" without affecting the method of connecting the trans- formers at the point of energy consumption (termed the "receiver" end). Transformers are arranged in "A" (Fig. 279) by connecting three single transformers or three coils of a three-phase transformer, in such manner that a closed series circuit is formed. The three line wires of the three-phase system are then tapped respectively to the points at which the transformers have been con- nected together. Transformers are arranged in Y or star (Fig. 279) by connecting together one terminal of each of three single-phase transformers or one wire of each of the three coils of a three-phase transformer. The three line wires of the three-phase system are tapped one to each of the unconnected wires from each of the three coils. When connecting transformers to a three-phase system, the phase relations must be maintained as illustrated in Sec. 6, Part 1, Art. 36. The following secondary connections can be made to a three- phase three- wire system: Single-phase, two-wire. three- wire. Two-phase, three-wire. four- wire. five- wire. Three-phase, three-wire. four- wire. The connection "Y" primary and "Y" secondary is seldom used, except in a three-phase, four-wire primary and secondary system; the disadvantage being that the third harmonic magnetizing current of the transformers distorts the voltage distribution, also the neutral is unstable, and unbalanced loads will force it to shift, reducing the voltage on the most heavily loaded phase. When a "A" secondary is used with a "Y" primary, the third harmonics circulate in the closed "A" and preserve the voltage distribution. In a three-phase, four- wire system, the third harmonic magnetizing current flows through the neutral wire and the voltage distribution on the transformer will be undisturbed. 16. The Three-Phase, Four- Wire System (Fig. 280) is three single-phase circuits, respectively differing in phase by angles of 120 and supplying energy over four wires. In such a system stan- dard voltage transformers may be connected in "Y" and the advan- tage of the higher "A" distributing voltage be obtained. The fourth wire is necessary, as it is impossible to maintain single-phase loads absolutely balanced at each point of the distributing system. Unbalancing wilt cause considerable distortion in voltage, similar [448] ELECTRICAL CALCULATIONS Sec. 7 15 [ 449 ] Sec. 7 ELECTRICAL CALCULATIONS in effect to the opening of the neutral of an unbalanced Edison three wire system. The following secondary connections may be made to a three-phase four- wire system: Single-phase, two-wire. three- wire. Two-phase, three-wire, four- wire, five-wire. Three-phase, three-wire, four- wire. 17. Comparisons of the Relative Merits of "Y" and "A" Trans- former Connections. (1) When transformers are connected in "A" a disabled trans- former may be cut out and the remaining transformers will continue to operate, in open "A" at reduced capacity without otherwise affecting the system. When connected in "Y," one transformer, if cut out, will completely disable the secondary system. It is not advisable to operate transformers in open "A" continuously; for under such circumstances unbalanced electrostatic conditions exist, wEich may cause high frequency disturbances. (2) When transformers are connected in "Y" or in accordance with the "Scott" method, the coils, or parts of coils are in series between phase wires, and, should break-downs occur, one trans- former may act as a reactance in series with line capacity, causing high voltage disturbances. Such occurrences are confined to cases in which one transformer bank is used, and seldom occur when two or more transformer banks are connected in parallel. Trans- formers connected in "A" are free from such disturbances. (3) "Y" connected systems, operated with a grounded neutral, limit the voltage which may occur between the conductor and ground. However, should a ground develop on one phase, a short circuit will result. When operating ungrounded, a ground developing on one phase increases the potential between the other two phases and the ground. 18. The Alternating Current Series System (Fig. 275) is similar in type to the direct current series system and its use is generally con- fined to the supply of energy for street lighting. It is more flexible than the direct current system, in that transformers may be installed which not only protect the receiving apparatus from the high voltage of the system, but permit the use of apparatus requiring a current value other than that of the main system. 19. COMPARATIVE WEIGHT OF CONDUCTORS NECES- SARY IN VARIOUS SYSTEMS. The values given in Table 58 are based on the following assump- tions: similar conducting material, equal voltages at the lamps or other receivers, equal amounts of power transmitted, equal line losses, unity power-factor, and balanced conditions. The weight of the conductors of a two-wire direct current system has been assumed to be 100 percent. [ 450] ELECTRICAL CALCULATIONS Sec. 7 FIG. 281. /W\* /00V t /0 200X t i ' .., i 2 PHASE 2P/fASC Ml/ ' 9trfn MII/ * 3WlKE f/Ml/ \ fflfll/ 41Y/KC i _f i _ //?/?/' 1 FIG. 282. FIG. 283. Fie . 284. J t _ /71A' t ** AS "T' 3PHASC t&KflM /f 5^ 3PftA$e RC jg0% 3W/KC \ "\" /OOtf \__4WiKC /OOK | -|- | A/fc/r#AL FIG. 285. FIG. 286. FIG. 287. TABLE 58 COMPARISON OF CONDUCTOR WEIGHTS FOR VARIOUS SYSTEMS System Size of wire Compared to 2 Wire D. C. Per Cent. Diagram 2 wire D. C 3 wire D. C. Neutral equal to outside Neutral one-half outside Neutral equal to outside Neutral one-half outside Common wire equal to outside Common wire 1.41 times outside Neutral equal to outside Neutral one-half outside Neutral equal to outside Neutral one-half outside 100.00 37.50 31.25 100.00 37.50 .31.25 75.00 72.90 100.00 31.25 28.12 75.00 33.33 29.16 Fig. 281 Fig. 282 Fig. 282 Fig. 281 Fig. 282 Fig. 282 Fig. 283 Fig. 283 Fig. 284 Fig. 285 Fig. 285 Fig. 286 Fig. 287 Fig. 287 3 wire D. C Single phase A. C. two wire Single phase A. C. three Single phase A. C. three wire Two phase A. C. three wire Two phase A. C. three wire Two phase A. C. four wire Two phase A. C. five wire Two phase A. C. five wire Three phase A. C. three wire Three phase A. C. four wire Three phase A. C. four wire 20. VECTORS AND VECTOR DIAGRAMS. The solution of many alternating current problems is greatly simplified by the use of vectors. A vector is a quantity which has both magnitude and [ 451 J Sec. 7 ELECTRICAL CALCULATIONS direction. It may be defined by giving its components in the direction of arbitrarily chosen axes of reference, or by its angular deviation from and projection on some given reference axes. The latter definition is illustrated in Fig. 288. Draw the lines O'O" and e f at right angles through the point O. Draw a line OA from the point O and consider it to be rotating in a counter-clockwise direction at an angular velocity of . 6 is the angle in radians between the rotating line OA and the reference line O'O". (One radian is an angle in which the length of the cir- cular arc and radius are equal. There are 2 TT radians in one cir- cumference, therefore, one radian equals 57.295 and the trigono- metric functions apply to angles measured in radians as well as to angles measured in degrees.) At every instant in its rotation there FIG. 288. is a projection of the line OA on e f equal to OB, but OB equals AC and AC = OA sin e. If O'O" is considered as the instant of zero time, and values of 6 as abscissas, and corresponding values of OB as ordinates are plotted on rectangular co-ordinates, the trace or curve shown In Fig. 289 is produced, which is known as the curve of sines. When there are a number of these curves formed by various lines, all rotating at the same velocity, the sum of all of them at any instant can be obtained by considering the rotation stopped and adding the lines one to another, maintaining, however, the angular relation to O'O" as shown in Fig. 290. In each case the projection on e f is equal to the length of the line to be projected, times the sine of the angle between the line and O'O", therefore, the sum of these projections will be equal to the projection of the line N on the line e f. Vectors may be applied to the solution of alternating current prot> [452] ELECTRICAL CALCULATIONS A Sec. 7 Fig. 289. lems since the design of alternating current machinery is such that it produces voltage and current waves which very closely approximate the curve of sines, and because the curve of sines is the result of plotting the formula Y = A Sine X, which is deduced from the vector, it holds that the vector represents alternating current and voltage variation. Sec. 7 ELECTRICAL CALCULATIONS Further, the vector represents the maximum values of an alter- nating voltage or current wave, but since the effective values of sine waves those values read on voltmeters and ammeters are related to the maximum values as follows : E e ff = ^=~it follows that the A/2 effective values mayjbe used directly, instead of multiplying the effective value by v 2 to obtain the maximum value, then applying the resulting values to the vector analysis and finally dividing the solution by the V% to obtain the result as an effective value. 21. Vector Additions. Vectors representing current and vectors representing voltage cannot be added vectorally, i.e., vectors repre- senting the same^physical phenomenon only can be added or sub- tracted. A vector representing a voltage generated in an alternator winding may be added to, or subtracted from, the vector representing the voltage drop due to a current flowing through a resistance, an inductance, or a capacity, but not to the vector representing the current itself. In all the following vector diagrams the vectors are considered as that part of the total voltages absorbed in resistance, inductance, etc., and not the counter e.m.f. induced, because these latter values are 180 out of phase with the absorbed voltage and would need- lessly complicate the diagrams. 22. Direction of Arrows. The arrow heads on the ends of vectors when taken in connection with the angular deviation from the reference axis of zero time, O'O" (Fig. 288) indicate the instanta- neous direction of voltage, or the instantaneous direction _pf current flow with respect to an arbitrarily chosen point.* The direction of arrows in a vector diagram may be selected as follows: Take any point in the circuit and consider it the reference basis; currents flowing away from this point are considered positive, and flowing towards it, negative. Voltages above this reference point are positive, and below neg- ative. The arrows on the end of the vectors are always drawn furthest away from the reference point. As an example the end of rib at the dotted line, Fig. 293, is taken as the reference point. The arrow heads on all vectors must neces- sarily be away from this point. If the ends of LI a and wLIc had been taken as reference points, all the vectors would be reversed but the resulting values would be the same. The manner of choosing, a reference point is merely that of locating one that is most convenient as the analysis depends upon the relative and not the actual location of the various quantities in the problem. 23. Single-Phase Transmission. (Fig. 291.) Draw the vector E from the origin O to a scale proportional to the voltage at the receiver, draw the vector I to a scale proportional to the current *By "direction" is meant the flow toward or away from a given point, and not direction in space. [454] ELECTRICAL CALCULATIONS Sec. 7 at the receiver and at an angle from E, where 6 is the angle, the cosine of which is the power factor of the load. From the end of the vector E, and parallel to vector I, draw a line rl to the same scale as E, rl being the product of the total resistance of both line wires and the load current. From the end of the line rl and in phase 90 ahead of the line I draw the line wLI to the same scale as E; toLI being the product of the total inductive reactance of both line wires and the line current. The voltage necessary to counteract the self-induced voltage of the line wLI is drawn 90 ahead of the line current I; since the voltage of self-induction is in time phase 90 behind the current I producing it. The voltage necessary to counteract the voltage of self -inductance is, in time phase, 180 from the voltage of self- induction, therefore, the voltage necessary to counteract the voltage of self-induction must be, in time phase, 90 ahead of I. By con- necting the end of the line wLI, and the origin O, the resultant __ T 7 ' Fig. 291. Single phase system line E' represents the voltage at the generator to the scale of E. The angle between E' and I, 6', is the angle of lag at the generator, and cos. 6' is the power factor at the generator. 24. The Two-Phase Four- Wire System is calculated as two separ- ate single phase systems, since there is no inter-connection, and by properly locating the wires in reference to each other (Art. 61) mutual induction may be reduced to a negligible quantity. Fig. 292 illustrates the circuits that may replace the actual lines, using concentrated instead of distributed inductance and resistance, also the vector analysis of this problem. All values are obtained as in Fig. 291, and the vectors are marked with the subscript of the phase which they represent. Under balanced conditions, the angles and vector values are the same in both phases, therefore, the angle between the resultant voltages is the same as that between the initial voltage, i.e., 90, and there is no dephasing action. [455] Sec. 7 ELECTRICAL CALCULATIONS 25. In the Two-Phase Three-Wire System the relations are more complex since there is a common connection between phases which carries a current that lags in relation to one phase and leads in relation to the other, thus disturbing the angular relation of the A.PHASE Cos. &a rl c KomMMMA/*- C. PHASE Cos. & c Fig. 292. Two phase, four wire system. resulting voltages. As the voltages at the generator have a fixed 90 relation, the solution is started by first considering conditions at the generator and working toward the resulting conditions at the receiver. [456] ELECTRICAL CALCULATIONS Sec. 7 The accurate calculation of the voltage relations in a two-phase, three-wire system is difficult. The value of the current or power-factor at the generator cannot be determined until the voltage at the receiver is found; and the voltage at the receiver cannot be determined until the line drop and dephasing angle are known. Again, the line drop cannot be determined until the line current and powerf actor are known; therefore, the line drop cannot be determined until the voltage at the receiver is known. Since the line drop and receiver voltage are both unknown, it is impossible to find either without first assuming one, making a trial solution for the other and so continuing until fairly accurate results are obtained. By solving a two-phase, three-wire line as though it were a two- phase, four-wire line and neglecting the dephasing action of the com- mon wire, a value of voltage drop will be obtained which is equal to the average of the accurate drops. The drop will generally be greater in the leading phase and less in the lagging phase. The construction of the vector diagram is illustrated in Fig. 293, as follows. Draw E' a and E' c to a scale proportional to the generator volt- ages and 90 apart. Draw I a and Ic to a scale proportional to the load current and in phase relation 6' behind E' a and E' c where cos. Q' is the powerfactor at the generator. Draw Ib, the resultant of I a and Ic. Draw wLI a and LIc to the same scale as E' a and in phase 90 ahead of I a and Ic. These vectors represent the voltage ab- sorbed in the inductive reactance of the outside wires. Draw rl a and rlc to the same scale as E' a and in phase with I a and Ic. These vectors represent the voltages absorbed in the resistance of the out- side wires, and are drawn from the ends of the reactance drop vectors, E a and E c being the unknown quantities; therefore, they must be omitted in the voltages given in the diagrammatic sketch of the line and the drop in the b or common wire must be next considered. From O draw rib to the same scale as E' a and in phase with Ib, the current in the common wire. This represents the voltage ab- sorbed in the resistance of the common wire. Draw wLIb to the same scale as E' a and in phase 90 ahead of Ib. This represents the voltage absorbed in the inductive reactance of the b or common wire. If the line E a is drawn from the end of the vector ooLIb to the end of the vector rl a , the A voltage at the receiver is obtained both in value and phase; likewise the line joining the ends of the vector ojLIb and rlc represents the phase relation and value of the C phase receiver voltage EC. 26. Three-Phase "Y" Connected System. (Fig. 294.) Draw E a , Eb and E c from the point O to a scale proportional to the receiver voltages and 120 apart. Draw I a , Ib and Ic from the point O to a scale proportional to the receiver current and Q a , b and 6 C degrees from their respective voltages; a , b and O c being [457] Sec. 7 ELECTRICAL CALCULATIONS Fig. 293. Two-phase, three-wire system. [458] ELECTRICAL CALCULATIONS Sec. 7 Fig. 294. Three-phase system. [459] Sec. 7 ELECTRICAL CALCULATIONS the angles, the cosines of which are equal to the power-factor of the circuit. Draw rl a parallel to I a and to the same scale as the voltage E a . Draw coLIa 90 ahead of I a and to the same scale as E a . The line connecting O and the end of o>LI a represents the voltage E' a at the generator. Eb' and E c ' are found in the same manner. Lines connecting E a ', Eb' and E c ' represent the "A" voltages. 27. In the Three Phase "A" Connected System (Fig. 294), the line drop is the same as that in the "Y" connected system. If the "A" voltages E^a, EAb and EAC, are given it is necessary to a find E a , Eb, etc., by the formula E a = -^=. If the current in the single phase circuit of the "A" is known, then the line current I a = IAE'VO- When these transformations have been made, the vector diagram, Fig. 294, also applies to the solution of a "A" connected system. 28. THE EFFECT OF CHARGING CURRENT ON LINE CALCULATIONS. Charging current has been neglected in the above solutions, in order to simplify the vector analysis. All polyphase transmission lines may be solved as single phase lines, transmitting half the total amount of energy; (Sec. 7, Art. 36), therefore, in correcting for charging current the single phase system only will be considered. (Fig. 295.) Draw E to a scale proportional to the receiver voltage. Draw the energy component of the current I parallel to E and to a scale pro- portional to the energy component of the load current; draw I m in phase 90 behind E and equal to I tan. 0, where cos. 6 equals the power-factor of the circuit. I is the total current at the re- ceiver. Assume one half of the capacity of the transmission line concentrated at the receiver and one half at the generator. Ic equals the total charging current of the line at voltage E. Subtract 3/Ic from I m and combine with I, which represents the total current corrected for charging current It. Draw rl to a scale proportional to E, from the end of E and parallel to I. This represents the voltage absorbed, due to the energy component of the load current flowing through the total resistance of the line. Draw wLI from the end of rl and in phase 90 ahead of I. This represents the voltage absorbed due to the energy component of the load current flowing through the line reactance. From the end of &>LI draw r(I m -/^Ic) parallel to I m This repre- sents the voltage absorbed, due to the difference between the wattless component of the load current and one half of the charging current, flowing through the line resistance. From the end of r(I m -^Ic) and in phase 90 ahead of (I m -3^Ic) draw o>L(I m -3/2lc), which represents the voltage absorbed, due to the difference between the wattless component of the load current [460] ELECTRICAL CALCULATIONS Sec. 7 [461] Sec. 7 ELECTRICAL CALCULATIONS and one half of the charging current, flowing through the line reactance. A line connecting the end of L IB COB.QI These formulas are accurate for concentrated inductance, re- sistance, and capacity, but are incorrect for distributed inductance, resistance and capacity. When the ratio of the charging current of the line to the energy component of the load current is less than 0.05 the charging current may be neglected. For overhead lines in length up to 60 miles at 25 cycles and 50 miles at 60 cycles, for potentials not exceed- [ 462 ] ELECTRICAL CALCULATIONS Sec. 7 ing 55,000 volts delivered, the error introduced by neglecting the condenser effect of the line is usually unimportant. Accu- rate formulae may be found in the references made a part of this section. The increase in voltage at no load due to the charging current of the line flowing through the reactance may be found by using the following formula. e = voltage rise in per cent. 1 = length of line in miles, f = frequency in cycles per second. _ 57 I 2 f 2 10 9 20. FORMULAE FOR INDUCTANCE OF NON-MAGNETIC WIRES. Symbols: d = distance between wires in inches. r = radius of conductor in inches. h = distance between wire and ground, in feet. L = inductance in millihenries. f = frequency in cycles per second. x = reactance in ohms. Inductance of Single Conductor When Using the Ground as a Return Circuit. L = 0. 1408 flogxo ") +0.0152 millihenries per 1000 feet of V r J conductor. x = v ohms per 1000 feet of line. Inductance of Two Parallel Line Wires. L =0.2816 ( logio ^+0.0305 millihenries per 1000 feet of \ * J line (2000 ft. of wire.) x = ohms per 1000 feet of line. 30. FORMULAE FOR CAPACITY. Symbols : r = radius of wire in inches. d = distances between wires in inches, h = height of wire above ground in feet. C = capacity of wires in microfarads. Ic = charging current in amperes. [463] See. 7 ELECTRICAL CALCULATIONS f = frequency in cycles per second. E = effective voltage between lines or voltage between line and ground. Capacity of One Conductor to Ground. C = -r microfarads per 1000 ft. of conductor. m ^~Ell logic I c == ~^Tr$ m amperes per 1000 ft. of line wire. E = voltage between wire and ground. Capacity Between Two Parallel Conductors. C =- QQ3677 microfarads per 1000 ft. of line (2000 ft. of con- log!,) ductor). c\ f r~* "p 1 Ic = r^ - amperes per 1000 ft. of line. E = voltage between wires. 31. METHODS OF CALCULATING TRANSMISSION LOSSES. The calculations of practical transmission problems may be divided into three general classes: (a) Load, length of line, voltage, and size of wire given. Find voltage drop and power loss. (b) Load, voltage, length of line, and per cent voltage drop or power loss given. Find size of wire required. (c) Size wire, voltage, length of line and per cent voltage drop or power loss given. Find possible load. 32. Direct Current Two- Wire System. Symbols : r = resistance in ohms per 1000 ft. of wire. 1 = length of line in feet. W = load in kilo watts. E = voltage between wires at load. e = per cent voltage drop. ?= per cent power = load current. Formulae : WXIOOO ~E~ 2rll e=p = 10 E f 464] ELECTRICAL CALCULATIONS Sec. 7 (I) Problem. Determine the percentage power loss and voltage drop when 100 kilowatts are transmitted a distance of 1000 feet at 220 volts using 500,000 cir. mils copper cable with weatherproof insulation. r from Sec. 3 = 0.02116. 100X1000 I = 220 = amperes. 2 X 0.02116 X 1000 X 454 P=e= 10 X 220 ' =8 ' 74% - .. eE 8.74 X 220 Volts drop=-^-= JQQ = 19.21 volts. pW 8.74 X 100 Power 1088=-^- = =7^ =8.74 kilowatts. 1UU iOO The current, 454 amperes, is within the specified current carrying capacity of 500,000 cir. mil. Triple Braid Weatherproof Copper Wire. (II) Problem: Determine the size copper conductor necessary to transmit 100 kilowatts a distance of 500 feet at 220 volts, allowing 5% voltage drop. Formulae : W X 1000 211 100X1000 220 5 X 220 X 10 454 amperes. = 0.0242 ohm. 2 X 500 X 454 From Sec. 3 the size copper wire having a resistance of 0.0242 ohm per 1000 ft. will be found to be 450,000 cir. mils (nearest size). The current, 454 amperes, is within the specified current carrying capacity'of 450,000 cir. mils. Triple Braid Weatherproof Copper Wire. (Ill) Problem: Determine the power that can be transmitted a distance of 500 feet at 220 volts, using 0000 solid copper wire. Assume a power loss of 10%. [ 465 ] Sec. 7 ELECTRICAL CALCULATIONS Formulae: 10 2rl 2rl El ~ 1000 From Table 35 in Sec. 3, find r 10 X 220 X 10 I 0.04893. = 450 amperes. 2 X 0.04893 X 500 This exceeds the current carrying capacity of No. 0000 Triple Braid Weatherproof wire, which is 325 amperes. Therefore the maximum load that can be transmitted is: W = 325 X 220 1000 = 71.5 kilowatts. 33. Two- Wire Direct Current Railway System. These calcu- lations are the same as for the two-wire Direct Current System when there is a negative and positive feeder from the station to the load. When connections are made as in Fig. 296, the resistance of the trolley wire and rails must also be considered. F/reoe* Fig. 296. Symbols: r = resistance in ohms per 1000 ft. of trolley wire. r = resistance in ohms per 1000 ft. of feeder wire. ri = resistance in ohms per 1000 ft. of rails and bonds. 1 = length of line in feet. W = load in kilowatts. E = voltage between trolley wire and rails at load, j e = per cent voltage drop. p = per cent power loss. I = load current. I = current carried by feeder. (I) Problem: Determine the per cent power loss, in transmitting 90 kilowatts a distance of 5000 feet at 600 volts, assuming a 250,000 cir. mils cop- [ 466 ] ELECTRICAL CALCULATIONS Sec. 7 per Triple Braid Weatherproof feeder cable, a No. 0000 copper trolley wire, a single track, composed of 80 Ib. rails bonded with 2-20" No. 0000 copper rail bonds. Formulae : n = total resistance per 1000 ft. of line. T _WX 1000 E _R1I ~ P ~IO~E T -( r See Sec. 3 for resistances. r = 0.04233 ohm, r = 0.04893 ohm/n = 0.007746 ohm. , 90X1000 1KA I = - = 150 amperes. 0.030376 X 5000 X 150 P= 10X600 ~ 3 - 8% - T 0.030376-0.007746 w 1 _ A QA . Io= OQ4233 - X 150= 80.4 amperes. This current is very much below the allowable current carrying capacity of the conductors considered. (II) Problem: Determine the size feeder necessary to transmit 90 kilowatts 10,000 feet at 600 volts, assuming No. 0000 copper trolley wire, a single track of 80 Ib. rails, bonded with 2-20" No. 0000 copper bonds. The voltage loss assumed to be 10%. Formulae : I = WX1000 pE 10 _ eE 10 ~TT~ ~TT~ (R rO TO [467] Sec. 7 ELECTRICAL CALCULATIONS e = 10%. , 90 X 1000 gOQ =150 amperes. w 10X600X10 R= 107000X150 =ao4 ohms - (0.04-0.007746)0.04893 _ nnQ ,, r-p u.uy-o. 0.04893 +0.007746 - 0.04 Size feeder from Sec. 3 is No. solid. Io= 0.04893+OX)9811 X15() = 50 (III) Problem: A railway has been transmitting 50 kilowatts at 600 volts over a 300,000 cir. mil. copper feeder connected to a No. 0000 copper trolley wire. The distance of transmission is 20,000 ft. The single track consists of 80 Ib. rails, bonded with 2-20" No. 0000 copper bonds. Find the energy that can be transmitted at 1,200 volts, allowing 10% power loss. r r T = eE 1Q = P E 10 Rl = Rl = 1000 See Sec. 3 for resistances. r = 0.03531 ohm, r = 0.04893 ohm, r x = 0.007746 ohm. 10X1200X10 .028226-0.007746^ 0100 Io = - 0"6353T~ ~ X212 - 2 = 123 - 2 amperes. The value is well within the carrying capacity of the cable. , 1,200X212.2 <-,__,., w= 1,000 =255 blowatts - The more complex problems covering net-works will not be given, A general solution for such problems is of little value because of the multiplicity of variable conditions prevailing. [ 468 ] ELECTRICAL CALCULATIONS Sec. 7 34. The Edison Three-Wire System. The calculation for feeders in this system is similar to that of the two-wire system. The voltage used is that between the two outside wires and not the voltage be- tween the outside and neutral wire. Two wire taps from a three- wire system are also calculated in the same manner. The voltage used depending upon whether the tap is made between the outside and neutral or between the two outside wires. In the former case the voltage between the outside and neutral wire, and in the latter the voltage between the outside wires is used. 35. Direct Current Series System. Symbols: r = resistance in ohms per 1000 feet of wire. I = current of lamps. E = voltage of lamps. E' = machine voltage. 1 = length of line in feet. N = number of lamps. Problem: Find the voltage at the generator when No. 6 copper wire is used to transmit energy for 50 4 ampere lamps, each consuming 80 volts; the total length of line being 20,000 feet. Formulae : The resistance of No. 6 copper wire= 0.3944 ohm. (See Sec. No. 3.) E , = 0.3944 E' = 4,03 1.55 volts. It will be noted that the voltage drop is such a small part of the total voltage that the calculation depends upon the number of lamps, rather than the length of the line. A line 40,000" ft. long will have a voltage drop of 31.55X2= 63.10 volts = 1.555% drop. 36. CALCULATION OF ALTERNATING CURRENT SYS- TEMS. Before making any calculation the relations that the vari- ous systems bear to each other should be known. The following short discussion is based upon an equal size wire in each leg of the transmission line and an equal voltage between phase wires: I = load current. r = resistance of one wire. W = power transmitted in watts. [469] Sec. 7 ELECTRICAL CALCULATIONS E = effective voltage between wires, cos. 6 = power-factor of load. p = ratio of power loss to power delivered. Determine the per cent power loss for, single-phase, two-phase four- wire; two-phase three- wire, and three-phase three- wire systems. Single-phase : W Po 'E cos. 8 W 2 "E 2 cos. 2 Power loss in one wire is rP- 2 '- Total power loss is 2r W 2 The ratio of power loss (p) to load is _ 2rP _ 2rW 2 W ~WE 2 cos. 2 2rW P ~ E 2 cos. 2 Two-phase, four- wire: W " 2Ecos. e T2= W 2 4 E 2 cos. 2 6 Loss in one wire rP = 4 E 2 cos. 2 6 Loss in four wires 4rW 2 rW 2 ~ 4 E 2 cos. 2 6 ~ E 2 cos. 2 6 _ 4 r PQ _ rW 2 r W W ~W E 2 cos. 2 6 ~ E 2 cos. 2 F 470 ] ELECTRICAL CALCULATIONS Sec. 7 Two-phase, three-wire: la 4 E 2 cos. 2 9 Ib =IaV2 4E 2 cos. 2 9 2E 2 cos. 2 9 Total loss rW 2 rW 2 rW 2 r W 2 rI 2 a+rI 2 b+rI 2 c = , m _ , Q +TI?, ^ , Q + 4E 2 cos. 2 6 ' 2 E 2 cos. 2 6 ' 4E 2 cos. 2 9 E 2 cos. 2 9 _ Total loss_ r W 2 r W W ~WE 2 cos. 2 9 ~E 2 cos. 2 9 Three-phase, three-wire: W V3 E cos.9 W 2 I2 = 3E 2 cos. 2 9 Loss in one wire rW 2 rP =; "3 E 2 cos. 2 Loss in three wires. 3rW 2 3rl 2 3 E 2 cos. 2 . 6 _3rI 2 _ rW 2 rW p W ~WE 2 cos. 2 E 2 cos. 2 Summary : Single-phase P = E 2 Vos^9 rW Two-phase, 4-wire P = E 2 cos 2 e r W Two-phase, 3-wire P= E2coSt2e r W Three-phase, 3-wire P = E 2 cos 2 e Thus it follows, that with the same size wires and equal voltage between wires, the per cent power loss is the same hi the two-phase four-wire; two-phase three-wire; and three-phase three-wire [471] Sec. 7 ELECTRICAL CALCULATIONS systems, and in all these systems it is only one-half of that of a single-phase system. Therefore, by considering one-half the load and solving as a single-phase two-wire line, the correct results will be obtained for each of the three systems mentioned. This also holds true for per cent voltage drop, with the exception of the two-phase three- wire system, in which the average voltage and not the actual voltage drop will be obtained because of the dephasing action of the common wire. 37. EXPLANATION OF THE LINE LOSS TABLES. Symbols : r = resistance in ohms per 1,000 ft. of wire. = ratio of reactance to resistance, r, 1 = length of the line in feet. W = load in kw. E = voltage between wires at the receiving end of the line, p = power loss in per cent of energy at the receiving end of the line. e = total voltage drop in per cent of the receiver voltage, e' = voltage drop due to the energy component of the load current flowing through "the line resistance, in per cent of the receiver voltage. I = energy component of the load current. Io = total load current. I c = total charging current of the line at voltage E. a = voltage drop factor, Table 61, Sec. 7. b = power loss factor, Table 59, Sec. 7. q = ratio of the total current to the energy component of the current, Table 62, Sec. 7. Formulae: Single phase: WX1000 I = e' = E 2rll 10 E e ="' e'b Io =ql Polyphase:' WX1000 I = e' = 2E 2rll 10 E F 472 1 ELECTRICAL CALCULATIONS Sec. 7 e =e'a p =e'b I = q I The charging current of the line, Ic is found by obtaining the value of I,*, from the Tables in Sec. 3, for the proper size of conductor and the separation of the conductors in feet; per thousand feet of line, per thousand volts between wires. Then Ic locEl 10 8 The energy component of the current I and the per cent voltage drop due to this energy component of the current flowing through the line resistance, may be found from the formula given above. Divide I c by I. Apply this ratio to Table 59 in conjunction with the power-factor of the load, and find the value of b. Multiply e' by b, securing the power loss in per cent. To find the correct power-factor at the receiving end of the line, apply the power loss factor b to the Power-factor, Conversion Table 60, Sec. 7. This power-factor is used in conjunction with Table 61, Sec. 7, to calculate the a-c. voltage drop. Find the ratio of the inductive reactance to ohmic resistance - for the size, spacing and material of the conductor from the reactance and resistance tables in Sec. 3. With this value of and the corrected power-factor, find values of a from Table 61, Sec. 7. These values multiplied by e' will give the per cent voltage drop. To find the generator power-factor, divide (100 +p) by (100 +e); and multiply by the corrected power- factor. This will give the uncorrected power-factor at the generator end. Multiply -y- by (100+e) 2 , divided by (100+p), thus obtain- ing the corrected values for ratio of charging current to the energy component of the current. Apply these values to Table 59 as before, and the resultant value of b when applied to Table 60 will give the correct power-factor at the generating end of the line. The for- mulae for this are as follows: K Ic (100 +e) 2 I I A (100+p) The values in Table 62 for the power-factor and for the various systems give a constant q by which the energy component I may be multiplied, obtaining the actual load current flowing in the wire. NOTE: All tables in this section may be interpolated in a manner similar to that used in the interpolation of logarithmic tables. f 473 ] Sec. 7 ELECTRICAL CALCULATIONS TABLE 59 POWER LOSS, VALUES OF "b Ic I P.F. 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 .40 .45 .50 .55 6.25 4.94 4.00 3.31 6.02 4.74 3.83 3.16 5.80 4.55 3.66 3.01 5.59 4.37 3.50 2.87 5.37 4.19 3.35 2.74 5.17 4.01 3.20 2.61 4.97 3.84 3.05 2.49 4.77 3.67 2.91 2.37 4.58 3.51 2.77 2.25 4.39 3.36 2.64 2.14 4.21 3.20 2.52 2.04 .60 .65 .70 .75 2.78 2.37 2.04 1.78 2.65 2.25 1.94 1.69 2.52 2.14 1.85 1.61 2.40 2.04 1.76 1.54 2.28 1.94 1.67 1.47 2.17 1.85 1.59 1.40 2.07 1.76 1.52 1.34 1.97 1.67 1.45 1.28 1.87 1.59 1.39 1.23 1.78 1.52 1.33 1.19 1.69 1.45 1.27 1.15 .80 .85 .90 1.56 1.38 1.23 1.49 1.33 1.19 1.42 1.27 1.15 1.36 1.22 1.11 1.30 1.18 1.08 1.25 1.14 1.06 1.20 1.10 1.03 1.16 1.07 1.02 1.12 1.05 1.01 1.09 1.03 1.00 1.06 1.01 1.00 .95 1.11 1.08 1.05 1.03 1.02 1.01 1.00 1.00 1.00 1.01 1.03 .98 1.04 1.02 1.01 1.00 1.00 1.00 1.01 1.02 1.04 1.06 1.09 .99 1.02 1.01 1.00 1.00 1.00 1.01 1.03 1.04 1.07 1.10 1.13 1.00 1.00 1.00 1.01 1.02 1.04 1.06 1.09 1.12 1.16 1.20 1.25 .99 .98 .95 .90 1.02 1.04 1.11 1.23 1.04 1.06 1.14 1.29 1.06 1.09 1.18 1.34 1.09 1.13 1.23 1.40 1.12 1.16 1.28 1.47 1.15 1.21 1.33 1.54 1.20 1.25 1.39 1.62 1.24 1.31 1.46 1.70 1.29 1.36 1.53 1.78 1.35 1.43 1.61 1.87 1.41 1.49 1.69 1.97 .85 .80 .75 .70 1.38 1.56 1.78 2.04 1.45 1.64 1.87 2.15 1.52 1.72 1.96 2.26 1.59 1.81 2.07 2.37 1.67 1.90 2.17 2.49 1.76 2.00 2.28 2.61 1.85 2.10 2.40 2.74 1.94 2.21 2.52 2.88 2.04 2.32 2.64 3.02 2.14 2.44 2.77 3.16 2.25 2.56 2.91 3.41 NOTE: Values below heavy lines are for leading power-factors. 38. Single-Phase Two-Wire System. Problem: Find the power loss in kw. and the voltage drop in volts, when transmitting 50 kw. at 220 volts, 80% power-factor, on a single phase 60 cycle line 200 feet long, using No. 0000 stranded copper T. B. W. wire, spacing between wires 12 inches. I = 50X1000 220 = 227 amperes. From Table 36, Sec. 3, r= 0.04997. 2X0.04997X200X227 e = 10X220 2.06 [474] ELECTRICAL CALCULATIONS Sec. 7 TABLE 60 CONVERSION TABLE To find power-factor from power loss table.' P.F. b P.F. b P.F. b P.F. b 1.00 1.000 0.80 1.562 0.60 2.780 0.40 6.250 0.99 1.020 0.79 1.602 0.59 2.872 0.98 1.041 0.78 1.643 0.58 2.972 0.97 1.063 0.77 1.686 0.57 3.077 0.96 1.085 0.76 1.731 0.56 3.187 0.95 1.108 0.75 1.777 0.55 3.305 0.94 1.131 0.74 1.826 0.54 3.429 0.93 1.156 0.73 1.876 0.53 3.567 0.92 1.181 0.72 1.930 0.52 3.698 t 0.91 1.207 0.71 1.977 0.51 3.844 0.90 1.234 0.70 2.041 0.50 4.000 . 0.89 1.262 0.69 2.100 0.49 4.164 0.88 1.291 0.68 2.162 0.48 4.340 , 0.87 1.321 0.67 2.227 0.47 4.526 0.86 1.352 0.66 2.295 0.46 4.725 0.85 1.384 0.65 2.367 0.45 4.939 mt 0.84 1.417 0.64 2.441 0.44 5.165 0.83 1.450 0.63 2.512 0.43 5.408 0.82 1.487 0.62 2.601 0.42 5.668 0.81 1.524 0.61 2.687 0.41 5.948 From Table 45, Sec. 3, x, for 60 cycles = 0.0953 x = 0.0953 r ~ 0.04997 1.91 From Table 61, Sec. 7 for = 1.91 and 80% power-factor, find a= 2.487 From Table 59, Sec. 7 for y = 0.0 and 80% power-factor, findb= 1.56 From Table 62, Sec. 7 for single phase and .80% power-factor find q = 1.25 e = 2.06X2.487 = 5.125% p = 2.06X1.56 =3.21% I = 1.25X227 =284 amperes. I is within the current carrying capacity of the No. 0000 stranded copper T. B. W. wire. _. u , 5.125X220 Volts drop = Power loss = 100 3.21X50 100 = 11.28 volts. = 1.605kw. [4751 Sec. 7 ELECTRICAL CALCULATIONS O w h-1 i o o m in 10 m m us o in o o o o ooooo I CO ** ^fl m U} tO O C* t" OO OO O> O) O OvHr-(C^Cg 1,-lYHlHY-l ,-1 -rH TH ,-i rH iH ^H i-H rt 0>00>0> OOOO^H TH^-Irt SSiSSSS 3352 SSSSS 5S^S SS82S SSiSS 5SSSS SSISSS ?3gSS 288 5S5SSS OO Ift iH 00 O M O 5 (T> mojOOCOO t^ CM t- OO > COT|itAiAU> I>OOOOO>O> O i-J rH C4 CO CO ^jj * lO O N C4 N C4 C4 O4 CM C4 C4 C4 COCOCOCOCO COCOCOCOCO o LO o e VH vocgoocoot 10 o us I-H t- CM oo o I-H o cgcnto ooi-Ht-ies c>cocoTi;-oo ^'-jes 5-3 c^ r esc^escoco cococo m oo in co t- o * t- o co oo TH -* oo i-no * TJ< U IO US to to O B-t-C-OOOO OOO>O> Iguoi^oagl UIOJ jI IN iH Tt< t> M tA O>O4OHtA O> CO OO CS o o 1-1 1-1 1-1 eg i c> co eo co * ^< us us irt <> to e- ooooo>o> SSSSS SSSSS i ^( UIOJ^ [476] ELECTRICAL CALCULATIONS Sec. 7 TABLE 62 ^ VALUES OF q 2-PHASE, 3-WlRE Phase 4-Wirea Outer Common 3-Phase Wires Wire 1.00 1.00 1.00 1.00 1.414 1.154 .95 1.052 1.052 1.052 1.488 1.215 .90 1.111 1.111 1.111 1.571 1.282 .85 1.176 1.176 1.176 1.667 1.357 .80 1.250 1.250 1.250 1.768 1.443 .70 1.429 1.429 1.429 2.02 1.649 .60 1.667 1.667 1.667 2.357 1.923 .40 2.50 2.50 2.50 3.535 2.885 .20 5.00 5.00 5.00 7.07 5.77 39. Single-Phase Three-Wire Systems are calculated in a manner similar to that for the single-phase 2-wire circuit, using the voltage between the outside wires for the value of E. 40. Two-Phase Three- Wire Systems. Problem: How far, and with what average voltage drop can 500 kw. at 2,200 volts, 60 cycles, and 85% power-factor be transmitted on a two-phase, three-wire system, using No. 00 stranded copper wire, spaced 12 inches from center to center, assuming a 10% power loss. In Table 45, Sec. 3, for 60 cycles and 12" spacing find x = 0.1006. In Table 36, Sec. 3, find r= 0.07935. x 0.1006 0.07935 = 1.268 Table 61, Sec. 7 for - 1.268 and power-factor.of 85% a = 1.804. Table 59, Sec. 7 for y = 0.0 and power-factor of 85%, b = 1.38. p = 10 13.1% Percent volts drop e =7.25X1.804 WX1000 I = 2E 477 ) Sec. 7 ELECTRICAL CALCULATIONS . _ e' 10 E 2rl , 500X1000 = 2x2200 ==113<5 am P eres - 7.25X10X2200 . -2X0.07935X 113.5 ~ 8 ' 86 The power loss calculations are correct, but the voltage drop calculations give the average drop on each phase. The leading phase will have the greatest drop. See Art. 25, Sec. 7. See Table 62, Sec. 7. q = 1.667. I = 113.5X1.667= 189.4 amperes in the common wire. This is within the allowable carrying capacity of No. 00 stranded copper T. B. W. wire. If the common wire differs in size from the outside wires, use the average resistance as r in the formulae. (The resistance of one outside wire plus the resistance of the common wire, divided by two.) Treat the reactance in the same manner. Then use these average values to find and proceed in a similar manner as when all wires are of equal size. 41. Three-Phase Transmission. The following problem illustrates the effect of capacity current: Find the power loss and voltage drop in per cent, when trans- mitting 20,000 kw. at 100,000 volts, 85% power-factor, on a three phase, 60 cycle line 100 miles long, using 250,000 cir. mil. aluminum conductors, spaced 10 feet from center to center. From Table 51, Sec. 3, find the charging current, loc per 1000 ft. of line, per 1,000 volts = 0.0529 X10- 2 _ IocXlX5.28XE_0.0529 100,000 1000 I c = 27.95 amperes. T 20,000X1,000 2X100,000 = 10Q amperes. Table 36, Sec. 3. For aluminum cable r = 0.0679 ohm. Table 45, Sec. 3. x= 0.1462 ohm. x 0.1462 [478] ELECTRICAL CALCULATIONS Sec. 7 I c 27.95 I 100 =0.2795 , 2 r 1 IJ2, X 0.0679 X 5,280 X 100X100 - ~ 10 E ~ 10X100,000 Table 59, Sec. 7, for -y-= .2795 and 85% power-factor find b = 1.230. Table 60, Sec. 7 for b = 1.230 find power-factor = 90% Table 61, Sec. 7 for 90% power-factor and =2.16 find a = 2.18 Table 62, Sec. 7 for 90% power-factor, 3-phase find q= 1.282 e = 7.16X2.18= 15.4% p = 7.16X1.233= 8.68% I = 100X1.282= 128.2 amperes. Voltage at the generator = 1.154X100,000= 115,400 volts Power at the generator = 1.0868X20,000= 21,735 kw. cos. (1 - 154)2 1.0868 Apply these values to Table 59, Sec. 7 and find b'= 1.219. In Table 60, Sec. 7 for b' = 1.219 find 90.5% power-factor at the generator. The rise in voltage at no load is 57Xl 2 Xf 2 10 9 57X100X100X60X60 10 9 =2.05% Therefore the actual voltage variation at the. generating station from no load to full load is 15,400+2,050= 17,450 volts. To determine if the conductor is of sufficient size to carry the load current, obtain q from Table 62 for a three-phase circuit and 90% power-factor. q= 1.282. I = 1.282X100= 128.2 amperes. The current 128.2 amperes is within the allowable current carrying capacity of a 250,000 cir. mil. cable. (Sec. 3.) 42. Graphical Solution of a Three-Phase Transmission Line. The proceeding problem is solved graphically in Fig. 297. More [479] Sec. 7 ELECTRICAL CALCULATIONS FIG. 297. accurate values will be obtained by the graphical method if drawn to a large scale. Obtain I c , I, and e' in the same manner as obtained in Article 41. Ic = 27.95 amperes. 1= 100 amperes, 1 ~ f = 0.1397 =2.16; e' = 7.16. In Sec. 1, for cos. =0.85 find tan. 9 = 0.62. In Fig. 297, lay off OA to the scale of E = 100,000 volts. Draw AB from A and parallel to OA "= = ~j7j() " = 7,160 volts. At 90 from AB draw BC = ^'x-y- = 100>0 ^ Q X7 - 16 X2.16 = 15,450 volts. Draw AC. Draw CD at right angles to AC and through the point C. Scale AC = 17,028 volts, lay off CE = AC Tan. 9 = 10,540 volts. From E lay off EF toward C, equal to AC X-^-= 17028X0.1397 = 2379 volts. Connect O and F and scale this distance. The value obtained is 115,300 volts. This is the generator voltage. Lay off OG to the scale of 1= 100 amperes. Lay off OH= I tan. 0= 100X0.62 = 62 amperes. From H toward O lay off HJ = -~ = 13.97 amperes. Draw JK and GK parallel respectively to OA and OH. Draw KL from K and at right angles to OF. Lay off KM = ~ X - = 2 .b amperes. 16.12. Draw OM and scale; OM = 103.5 [ 480 ] ELECTRICAL CALCULATIONS Sec. 7 With a protractor measure the angle between OM and OF. This angle is 24 degrees. In Sec. 1, find Cos. (24) = 0.9135, which is the power-factor of the generator, 91.35%. The per cent power loss is found as follows: Single phase: E' I g cos. 6 g _ 10W For polyphase: 2 X 115,400 X 103.5 X 0.9135 im _ n ^ P= 10X20,000 Fig. 297 is not drawn to scale as the values of AB, BC, etc., are so small in comparison to OA that they will not definitely show the construction. Obiviously however, in laying this off an exact scale must always be maintained. The values for power loss as obtained graphically and as obtained from calculation do not agree. The graphical value may be in error, since large quantities are calculated and a small error in the quantities may make a large error in their difference. 43. Additions to Existing Systems. Where the voltage of a transmission extension is fixed due to its connection to an existing system, the calculations may be greatly simplified by means of a table, such as Table 63. This has been calculated from Tables 59 and 61. Table 63 gives the per cent power loss and the per cent voltage drop per 1000 kw. per 1000 feet of line for 3 phase, 60 cycle, 13200 volt transmission, with a separation between wires of 24 inches. Only four sizes of wire have been considered. A problem will show the simplicity of this method. Problem: It is desired to transmit 5000 kw.,. 20,000 ft. at a power-factor of 80%. What is the power loss and voltage drop in per cent? Solution. It is necessary to use a No. 0000 copper wire in order to secure proper current carrying capacity. (Table 64.) In Table 63, for No. 0000 copper wire and 80% power-factor e = 0.0782 per 1000 ft. per 1000 kw. The total voltage drop is 0.0782 X 5 X 20= 7.82%. p = 0.0438 per 1000 ft. per 1000 kw.; therefore, the total power loss is 0.0438 X 5 X 20= 4.38%. All calculations in the above problems have been made with a slide rule. No corrections were made for change in resistance due to temperature. This may be readily allowed for, however, as shown in Sec. 3. 16 [ 481 ] Sec. 7 ELECTRICAL CALCULATIONS When large cables are used, it is also necessary to correct the resistance for the skin effect. For such corrections the values of resistance taken from the table are multiplied by the factors given in Table 25, Sec. 3. For copper covered steel wire, the resistance in the table must be increased by the percentage indicated in curves Figs. 78-81, Sec. 3, for copper covered steel. The increase in internal inductance of copper covered and aluminum core steel wire, is very small and need not be considered. However, if it is so desired, curves Figs. 84-87 shown in Sec. 3 for copper covered steel wire may be used. The percentages there given apply only to the factors 0.0152 and 0.0305 in the formulae for inductance. 44. Alternating Current Series System. Symbols : E = voltage of each lamp. E' = voltage at the generator. 1 = length of the line in feet. I = current of the circuit in amperes. r = resistance per 1,000 ft. of wire in ohms. cos. = power-factor of the circuit. N = number of lamps. a = factor in Table 61, Sec. 7. T?' M p I arllocos. 9 ~WcT~ Problem: Find the voltage at the generator when No. 6 copper wire is used to transmit energy for 100, 60 cycle, 80 volt, 6.6 ampere arc lamps at a power-factor of 70%. The total length of the line, which is erected 30 feet from the ground, is 20,000 ft. From the inductance formulae, Art. 29, calculate x for 1,000 feet of line. x = 0.5342 (approximate). r = 0.3944. In Table 61,[for 70% power-factor and = 1.35 find a = 2.37 I E'- (100X80) + (2.37X0.3944X^000X6.6X0.7) E' = 8,000 + 86.4 = 8,086.4 volts From this it may be seen that for most series alternating current circuits the line cLrop is negligible. [ 482 ] ELECTRICAL CALCULATIONS Sec. 7 11 C/D pq ^ B 8 w H g-. O)(O>A sssss sssggs sssss 4vH to CO -liH H 1 & guaeoooo ^ [487] Sec. 7 ELECTRICAL CALCULATIONS If it is desired to use any other sea level barometric pressure than 29.92 inches as a basis, calculated corrections should be made. (Sec, 11.) Inspection of Table 65 will show that an increase of 500 feet above sea level makes practically the same difference in 5 as an increase in temperature of 10F. To extend the tables for tem- peratures beyond the range given, proceed as follows: If it is desired to find the value 5 for 2000 ft. above sea level and a temperature of 120F. In Table 65 for 2000 feet and 90 is found the factor 0.916. 120 is 30 above 90, therefore by adding 1500 feet to 2000 feet, the value of 5 for 2000 feet and 120 is found to be 0.876; the value for 3500 feet and 90F. This is an approximation only. The values of ki are given in Table 66 for various distances be- tween wires and for various sizes of wire, both stranded and solid. This has been multiplied by a constant so that "1" may be used in feet rather than in miles in order to conform to the other tables. The values of k 2 in Table 67 have been calculated for various distances between wires and for various radii of wires. To find the visual corona forming voltage, it is necessary to use the value of k 3 which has been calculated for various values of 8 and for various radii of stranded and solid wire. The method of using these tables is illustrated in the following problem. Problem: Find the power loss and corona forming voltage on a No. 00 B. & S. stranded copper wire, located 6000 feet above sea level, for fair and stormy weather; on a three phase, three wire, 60 cycle line, 100 miles long, operated at 88,000 volts; wires spaced 10 feet apart and an air temperature of 70 F. 1 = 528,000 n= 3 In Table 65 for 70 F and 6000 ft. 5= 0.845 Table 66 for 10 ft. spacing and No. 00 stranded copper wire ki = 4.38 Table 67 for 10 feet spacing and No. 00 stranded copper wire k 2 = 71.44 For No. 00 stranded copper wire and 6= 0.845. Interpolate Table 68 and find k 3 = 1.22 m = 0.87 (See symbols.) m v = 0.72 for local corona and m v = 0.82 for decided corona e = -?L = -^L = 50.88 kilovolts. e =0.87X0.845X71.44=52.51 ev =0.72X71.44X1.22=62.76 Fair weather e is less than e [488] ELECTRICAL CALCULATIONS Sec. 7 TABLE 66 VALUES OF Kt K! = 104.5 xV~j- S branded SEPARATION OF WIRES IN FEET 2 4 G 8 10 12 500,000 450,000 400,000 13.69 13.28 12.86 9.82 9.36 9.11 7.86 7.64 7.43 6.85 6.64 6.38 6.09 5.94 5.76 5.57 5.40 5.26 350,000 300,000 250,000 12.44 12.02 11.60 8.79 8.46 8.19 7.16 6.91 6.69 6.21 5.98 5.79 5.55 5.35 5.19 5.07 4.89 4.74 0000 000 00 10.98 10.30 9.77 7.76 7.30 6.91 6.34 5.97 5.65 5.49 5.17 4.89 4.91 4.62 4.38 4.48 4.22 3.99 1 9.24 8.67 6.53 6.14 5.33 5.01 4.63 4.34 4.13 3.88 3.77 3.54 Solid 0000 000 00 10.29 9.66 9.06 7.24 6.83 6.45 5.91 5.58 5.26 5.12 4.83 4.56 4.58 4.32 4.08 4.17 3.94 3.71 1 2 8.60 8.11 7.67 6.08 5.72 5.42 4.97 4.76 4.75 4.31 4.06 3.84 3.85 3.63 3.41 3.51 3.36 3.13 3 4 5 7.24 6.83 6.45 5.11 4.83 4.56 4.17 3.94 3.71 3.62 3.42 3.22 3.19 3.05 2.89 2.96 2.79 2.63 6 6.08 4.31 3.51 3.04 2.69 2.45 Therefore p = Stormy weather p _ 3X528,000X60X4 0.845 X 10* = 389.0 kw. -j"50.88-(0.8X52.51)l The following facts should be noted: The voltage along a transmission line is not constant, but varies depending upon the distance from the station, the amount of load, the power-factor, etc. Therefore, the power loss due to corona is necessarily a summation of short lengths of line, in which the voltage at both ends is assumed to be equal. When corona exists on a wire, [489] Sec. 7 ELECTRICAL CALCULATIONS TABLE 67 VALUES OF K 2 K 2 = 123.4r logic Stranded SEPARATION OF WIRES IN FEET 2 1 4 6 8 10 12 500,000 450,000 400,000 89.20 85.26 81.68 104.38 99.57 97.25 113.26 106.72 103.15 119.59 113.88 108.20 124.49 118.44 113.02 127.20 122.15 115.48 350,000 300,000 250,000 77.36 73.16 69.59 89.94 84.76 80.44 97.35 91.67 86.86 102.53 96.73 91.42 106.60 100.31 95.00 109.93 103.39 97.84 0000 000 00 64.03 58.24 53.30 73.78 67.00 61.07 79.58 72.05 65.76 83.66 75.76 68.97 86.86 78.47 71.44 89.45 80.81 73.53 1 48.74 44.05 55.77 50.22 59.84 53.79 62.68 56.26 64.90 58.24 66.75 61.07 Solid 0000 000 00 57.25 52.31 48.98 65.76 59.96 55.89 70.82 64.53 60.09 74.40 67.49 62.92 77.11 69.95 65.14 79.33 72.05 67.00 1 2 43.55 39.60 36.15 49.48 44.91 40.96 53.05 48.12 43.68 55.52 50.34 45.65 57.50 52.07 47.25 59.10 53.42 48.49 3 4 5 32.82 29.86 .27.14 37.01 33.56 30.60 39.48 35.78 32.57 41.33 37.38 33.93 42.69 38.62 35.04 43.80 39.60 35.90 6 24.68 27.64 29.49 30.72 31.71 32.45 the capacity of the line is increased due to the increase in effective diameter. For complete details covering corona phenomena see A.I.E.E. proceedings of July 1911, June 1912 and June 1913. 47. LOCATING THE CENTER OF DISTRIBUTION. When several loads are distributed along an approximately straight line and it is desired to locate the center of distribution, the method is as follows (Fig. 298): Wi, W 2 , W 3 , W 4 , etc., denote the kilowatt capacity of the respective loads. Through Wi, W 2 , W 8 , W 4 , etc., draw the line OX, and at any point on the line OX locate a point O. The distance from this [ 490 ] ELECTRICAL CALCULATIONS Sec. 7 point to Wi, W 2 , etc., designate as li, 1 2 , la, U, etc. These lengths may be in feet or in miles . Let l x = the distance from O to the center of distribution G, then: , IiWi + 1 2 W 2 + 1 3 W 3 + l4W 4 etc. Wi + W 2 + W 3 + W 4 etc. In which l x is the distance from O (in feet or miles according to the values of \ lf 1 2 , etc.) to the center of distribution. If the point O is taken at one of the loads, Wi, the equation is slightly simplified. The distances in this case are measured from Wi, and therefore li will equal zero, and the equation becomes lx 1 2 W 2 + etc. W 2 + W 3 + W 4 etc. The distance l x is laid off from Wi giving the same point G. The power loss increases as the square of the distance between the actual point of the feed and the point G. \\ - <# V Si-3 ' f 7 ^ * FIG. 298. Where loads are located at various points, not on a straight line, as shown in Fig. 299, the following procedure is adopted: Let Wi, W 2 , W 3 , etc. = respective loads. Draw the line OX through any convenient point so that the loads are all located on one side of the line. Draw OY at right angles to OX so that all the loads are included in the angle between OY and OX. Let 1 : , 1 2 , Is, etc., be the distance between OY and the loads in feet or miles. Let l' : , 1' 2 , 1' 3 , etc, be the distance between OX and the respective loads. Let l x be the distance between the center of distribution G and OY and l y be the distance between the center of distribution G and OX. Then and lv = A +W 2 1 2 +W,1 etc. W!+W 2 +W 3 etc. Wil'i+W 2 l' 2 +W 3 l' 3 etc. etc. [491] Sec. 7 ELECTRICAL CALCULATIONS + sss sss siS RS Iss sis ssl a sis s sss OtOO O CM M< -^ CO i-t C- ID C4t~CO O O TH Tf O LfS u ^4M -*-0C41A OO C4 U O> "**}(** * TJI << Tif LTJ to irt us tnuaus LO Co to to e> t- e> (4 eo co }! t> ^ ooo N tr> es 5 SS 55S S3SS SSS 83 SSS SS S5S9 88 5S PO COCOCO COW** ** ** -^TlllO UU( SSS SSS 8 388 SSS SSS CSCMC^ COCOCO M-* COMC4 *** <A'A O9>t- 00 O O 00 O T-l r< iH ^O 0> US i-l O O i-l ooooen OC4M SJt-oi 43 t> O) iH * t- 5 co (O T-(T^^H NNCSI CMCMC^ COM C4C4CO ^M-^ **".* SSSS SSS SSS SS SS5 SSeS SSS 3 ^"S Si-H H 1HNC4 C4N C4CSN C4 OS CO CO CO TJ) iss in us s isa asx C- US Cfl CM CM TH t>(OUS USO> O (31 O M (O O I- Si! Sis sss s sss sss s O O^TJ [492] ELECTRICAL CALCULATIONS Sec. 7 These two values measured respectively from OY and OX, and at 90 degrees from the same, give the location of the point G. The equations may be slightly simplified by taking OX and OY through one of the loads. If OX and OY are drawn through W$ the following formulae will apply. WJi +WJ, etc. lx = and Wi+Ws+Wsetc. Wil'i+W a r 2 etc. W : +W 2 +W 3 etc. Distances that were formerly la and 1' 3 are now zero and the distance l lt l\, 1 2 , 1' 2 , etc. are measured from OX and OY running /J ^ FIG. 299. through W 3 ; l x and l y are measured from these lines passing through W 3 giving the same location of G as before. The*power loss increases as the square of the distance between the location of the actual point of feed and G. If OX and OY in Fig. 299, or the point O in Fig. 298, are located between the loads so that some of the loads fall on one side and some on the other side of the lines or point, it is necessary to place a negative sign before the loads times the distances on one side of the lines or point, and a positive sign before the loads times the distances on the other side of the lines or point. In calculations for alternating current systems, the kilovolt amperes of the load should be used rather then the kilowatts, i.e. Wi, W 2 , etc. equal the kilovolt amperes of the respective loads. Also, when making the above calculations care must be taken [493] Sec. 7 ELECTRICAL CALCULATIONS to use the actual lengths of the distribution lines rather than the air lines, provided, however, that this manner of calculation does not hopelessly complicate the problem. 48. CALCULATION OF TRANSFORMER CAPACITY. Let W = the total kw. capacity of the delivered load, cos. 6 = the power-factor of load. q = the factor given in Table 62, Sec. 7, for different systems and power-factors. kv-a = kilovolt ampere capacity of each single transformer in the bank. E = the effective voltage on any system, i.e. on a single phase, 3-wire system, it is the voltage between the out- side wires. On a 3-phase Y connected system, it is the delta voltage; on a 2-phase, 3-wire system, it is the voltage between the common wire and the outside wire. On a 2-phase, 5-wire system, it is the voltage between the phase wires and not from the neutral to the phase wires. In all other systems it is the voltage between phase wires. I = line current. Et = voltage across transformer primary winding. I t = the current in the transformer primary winding. E 9 = voltage of secondary system and bears the same re- lation to the manner of connection as E in the primary. Is = the secondary line current. E't = the voltage across transformer secondary winding. I't = current in the transformer, secondary winding. Table 69 gives the ratio that these various factors bear to one another. (I) Problem: Find the capacity of three transformers required to transmit 1,200 kilowatts at 80% power-factor. The system is three phase, three wire A primary and Y secondary. 1st Method: W 1200 kv-a. of each transformer is ^-TT -= ., = 500 kv-a. o x cos. y kv-a. 2xvr In this problem, the first method is the more simple. Assuming 2,200 volts between primary wires and 220 volts between secondary [494] ELECTRICAL CALCULATIONS Sec. 7 wires, the primary and secondary current of each transformer is found as follows: W 1,200,000 = 393.5 amperes. VSEcos.G v 3X2,200X0.8 The current in each transformer primary winding is: I 394 = Vjf = v 7 ? = am P eres - The voltage of each transformer primary winding is: E t = E = 2200 volts. The current in each transformer secondary winding is: I't = Is = 3935 amperes. The voltage of each transformer secondary winding is: E' t = -^ = ^ = 127 volts. V3 V3 Assume that all conditions are similar except that the secondary is a three-phase four-wire system and the potential is 220 volts between the neutral wire and the outside wires. Then, E 8 = _ 1,200,000 V3X220 V3X0.8 I't = Is = 2,270 amperes. K 220V ^ V3 V3 (II) Problem: A load of 1,200 kilowatts at 80% power-factor is to be transformed from 2,200 volts, three-phase, three-wire, to 220 volts, three-phase, three-wire, using V or open delta connections. Find the transformer capacity. 1st Method: TTH- 1 onn kv-a. = j= - = / =866 kilo volt-amperes. Vs cos. 9 V3X0.8 2nd Method: W 1 9OO -IL q = iL^ xlt4 43 = : 866 kilovolt-amperes. 2i 2> [495 ] Sec. 7 ELECTRICAL CALCULATIONS TABLE 69 CALCULATION OF TRANSFORMER CAPACITY Values of Symbols kv-a CAPACITY OF EACH TRANSFORMER System kv-a kv-a , It Primary Connec- tion Single 2 and 3 wire 2.J.3, 4 and 5 wire 3 , 3 and 4 wire 3 , 3 and 4 wire 3 0, 3 and 4 wire 3 phase 4 wire 3 phase 3 wire 3 Teaser Transformer* 2to 3 (/> Main Transformer 3 (j> to 2 $ Teaser Transformer* 3 to 2 Main Transformer W Wq Wq 2 Wq E E E E E IP V3 IP Io A A Y Y V H T i 1 Cos. e w 2Cos. 6 w 3Cos. w 2V3 Wq 3Cos. w 2V3 Wq 3Cos. 6 w 2\/3 Wq 2V3 Wq 2 Wq 2 Wq E 3Cos. w E E E V3E V3 Cos. W 2Cos. W 2Cos. W 2 2Cos. W 4 Wq 2 2 E \/3 Cos. * Assumes the teaser transformer wound for 86.6% of the line voltage; if an 86.6% tap is used the capacity is the same as the main transformer. [ 496 ] ELECTRICAL CALCULATIONS Sec. 7 TABLE 69 Continued CALCULATION OF TRANSFORMER CAPACITY Values of Symbols kv-a CAPACITY OF EACH TRANSFORMER System kv-a E't I't Secondary Connec- tion Single $ 2 and 3 wire 2<}> 3, 4 and 5 wire 3 , 3 and 4 wire 3 , 3 and 4 wire 3 4>, 3 and 4 wire 3 phase 4 wire 3 phase 3 wire 2 to 3 (/> Teaser Transformer* 2to 3 Main Transformer 3 4> to 2 (/> Teaser Transformer* 3* to 2 * Main Transformer W Wq Wq 2 Wq E s E s E s Is Is Is I Y A A Y V -1 1 t -*J_ r t Cos. e w 2Cos. W 3Cos. W 2V3" Wq V3 E 3 E a E s 3Cos. W 3CosT0 W 2A/JT Wq V3~ Is V3^ I S Is Is I 8 Is Is 2\/3^ Wq 3Cos. W Vscos. e w 2V3 Wq 2 A/3Wq V3~ ES \/3Es 2 E a E s E s 2Cos. e w 4 Wq 2 Wq 2 Wq 2 V3Cos. W 2Cos. W 2Cos. * Assumes the teaser transformer wound for 86.6% of the line voltage; if an 86.6% tap is used the capacity is the same as the main transformer. [497] Sec. 7 ELECTRICAL CALCULATIONS In this problem the second method is the more convenient. The primary voltage and current, and the secondary voltage and current equal the line voltage and current. For polyphase transformers it is only necessary to determine the total kv-a. by dividing the energy in kilowatts by the power- factor. The capacity of the individual windings are determined by the manufacturers. NOTE : Many attempts have been made to so connect transformers on a polyphase system that each single phase load will be balanced on the polyphase system. It is possible to so connect transformers that the currents delivered to the single phase load from each phase of a polyphase system will be equal, but in such cases the power- factors will vary greatly. The fact that the transfer of energy in a single phase system is pulsating while that in a polyphase system is continuous indicates that it is impossible to preserve balanced condi- tions on a polyphase system for each single phase load without the aid of rotating machinery, in which the energy from the polyphase system may be stored in the rotating element of the machine in the form of mechanical energy during the period of zero energy transfer in the single-phase system. 49. Calculation of Transformer Regulation. The regulation of constant potential transformers is the ratio of the rise of secondary terminal voltage from rated non-inductive load to no load (at constant primary impressed terminal voltage) to the secondary terminal voltage at rated load. (A.I.E.E.) This is for 100% power-factor only, but holds true for other power-factors if in the definition "inductive load" is substituted for " non-inductive load." The regulation of a transformer may be calculated by several methods when the resistance, the reactance, and the magnetizing current are known, one of which follows: Let r = the total resistance of the transformer coils referred to the primary. x = the total reactance of the transformer coils referred to the primary. kv-a. = capacity of transformer in kilovolt amperes. E = impressed primary voltage. I = energy component of load current, cos. = power-factor of the load as a decimal. I m = magnetizing current. I e = exciting current of transformer. We = core loss in watts. Formulae : _ kv-a. X cos. 6X 1000 E [498] ELECTRICAL CALCULATIONS Sec. 7 rl a a tan. a = -^ reg. %= 100 [ 1 +e+e a a cos. a For most purposes cos. a is so near unity that it may be neglected and the formulae then become reg. % = 100[e+eaoaJ The magnetizing component of the no-load current may be found as follows: cos. We EI e Im = -^r- tan. ft If the power-factor of the load is leading, tan. 6 becomes negative, but the remainder to the formulae is the same. Problem: Find the regulation at 100%, and 80% (inductive load) power- factor of a 10 kv-a. 2,000 volt transformer having 8 ohms resistance and 32 ohms reactance referred to the primary winding. The exciting current = 0.5 amperes. The core loss is 600 watts. In Sec. 1 for cos. ft =0.6 find tan. = 1.327 fiftfl Im = ^X 1.327 =0.398 For 100% power-factor 10,000X1. T.fe* 32 ao = -g-=4 [ 499] Sec. 7 ELECTRICAL CALCULATIONS tan. 0=o Im 0.398 I 5 = 0.0796 = a 4-0.0796 3.9204 .-_._ tan. a = - - =5:^ =0.0765 -^+(4X0.0796) + ! In Sec. 1 for tan. a = 0.0765 find cos. a =0.997 reg %= 100 ..._ 1 . 29% By the more simple formula reg. % = 100 Fo.02 + (0.02X4X0.0796)]! =2.64% For 80% power-factor 10,000 x 0.8 2,000 = 4 Amperes 8X4 =0.016 2,000 ao =4 tan. = 0.75 when cos. 0=0.8 a =0.75+0.0995 = 0.8495 tea. a = , 4 ~- 8495 - =0.0471 aoT 6 +(4X0.8495) + l Find cos. a = 0.999 reg.%= 100 By the shorter method reg.%= 100 [0.016 + (0.016X4X0.8495)] = 7.04%. 50. Calculation of Transformer Efficiency. The efficiency of a transformer is the ratio of the power output to the power input. The all-day efficiency of a transformer is the net power output for 24 hours divided by the gross power input for 24 hours. W = kilowatts output (maximum). r = resistance of transformer coils referred to the primary. [500] ELECTRICAL CALCULATIONS Sec. 7 J = primary load current. w e = core loss in watts. I W E cos. 6 W r w 1 Efficiency % = 100 I w e +rlo 2 L " 1,000 J efficiency of a transforme 24 W L 1 24 W LI 24 w e 224 rF 24 W L+ 1QOO 1 100Q J The all-day efficiency of a transformer expressed in per cent is: = 100 In the above equation all the symbols are the same as previously used with the addition of L for the load factor as a fraction and S 24 rl 2 , which is the summation of the power loss in resistance, where I is equal to the square root of the mean square of the current flowing for 24 hours and r is the resistance of the transformer coils referred to the primary. VOLTAGE REGULATORS 51. General. Automatic voltage regulators for pole line use permit better regulation and service from a long line with regularly distributed consumers for the greater part of its length. When regulators are installed along the line it becomes necessary to make calculations of regulator capacity and per cent regulation for various consumers' demands. Transformers may be used to increase the line voltage at a given point, but do not improve the line regulation, as the voltage addition is constant. 52. Regulation. To calculate the range of regulation necessary, data are required covering the variations of voltage at the point where the regulators are to be installed. 53. Single-Phase System. (Fig. 300.) Let V = the maximum effective voltage variation in volts. E = average effective line voltage between outside wires. e = per cent of regulation of regulators. Then The reason the percentage voltage regulation of a regulator is one-half the voltage variation of the line, lies in the fact that voltage regulators are so designed that the secondary voltage coil adds to, [ 501 ] Sec. 7 ELECTRICAL CALCULATIONS or subtracts from the line voltage, thus giving the regulator double the range of the voltage of the secondary coil. 54. Two-Phase System. If two single-phase regulators are used, the calculations are the same as for a single-phase system. If a ~T \ "-'VVVVVV"- 1 AAA/VWVWWV t FIG. 300. two-phase regulator is used V is the average of the phase voltages; otherwise the calculations are identical. 55. Three-Phase, Three-Wire System. Single-phase or poly- phase voltage regulators may be used for this service. When single- phase regulators are employed they should all have the same reg- i t I rvvvvvv^ L-VWWWVWVSAr- f n r-VWVWWWW- LAAAAAA^ 1 ?' FIG. 301. ! * ^VVVVVV L >AAAAAAAAAAAA^ A" 1 L! ^A A A A A A A i " V V V V V V ' WwWWWWVAr-i I i JA^AAAAA/N FIG. 302. ulating characteristics. If two regulators are used, connected as in Fig. 301 the calculations for per cent regulation are the same as for single-phase regulators. If, however, three regulators are con- nected "A" as illustrated in Fig. 302, the per cent regulation must be found by the following formulae: [ 502 ] ELECTRICAL CALCULATIONS Accurate formulae : Sec. 7 e= 100 /-"(I)' V ()'- Approximate formulae (less than ^ of 1% error for commercial ranges) 100 V e = 3E The calculations for a polyphase regulator are the same as for a single-phase regulator with the exception that V is the average of the three-phase voltages. 56. Three-Phase, Four-Wire System. Three single-phase units may be used on this system connected between the neutral wire and the outside wires. In such cases, if V is "A" voltage, E should be "A" voltage; if V is Y voltage, E should be Y voltage, and the solution remains the same as for a single-phase system. (Fig. 303.) Calculations for polyphase regulators are made in the same manner as for the three-phase three-wire system. I fVVVVVV' f 3 WvAAAAAAAA/WV-J /-/-^ AAAAAAA' ^ f \ E 1 i I LvVAAAAAAAAAAyV-" V5~ -A A A A A A A f i ~ V V V V V V i /-^y 4 LwvwCvCww M 3C3 At " 7; '' / FIQ. 303. 57. Regulator Capacity. Let I = the effective line current, kv-a. = kilo volt ampere capacity, of regulator. E = effective line voltage, e = the per cent regulation. Then (1) The capacity of a single-phase regulator on a single-phase, or of each of two single-phase regulators on a two-phase system is I eE kv-a. 10 5 [503] Sec. 7 ELECTRICAL CALCULATIONS (2) The capacity of each of two or three regulators connected to a three-phase, three-wire system, as shown in Figs. 301 and 302. is I eE kv - a -=-TtfT (3) The capacity of each of the single-phase regulators on a three- phase, four-wire system is (Fig. 303) I Ee If E is "A" voltage. Case (2) kv-a. = If E is Y voltage. (4) The capacity of a two-phase regulator is 2I Ee The capacity of a three-phase regulator is Case(l)kv-a.= V3 ^ Ee If E is the "A" voltage, and If E is the Y voltage. If a transformer is used the per cent increase in voltage is fixed by the ratio of transformation: Let ' n= the ratio of transformation, all other quantities remaining 100 the same -as before. The percent voltage increase is e = The transformer capacity is found by the following formulae: E I _ e E I kv-a. 1000 n 10 5 Therefore the formulae used to find regulator capacities may be used for transformers. Problem: The voltage of a 2,200 volt single-phase line varies 110 volts. The line current is 100 amperes. Find the percent regulation and kv-a. capacity of the regulator required to correct this. [ 504 ] ELECTRICAL CALCULATIONS Sec. 7 _ 110X100, 2X2,200 100X2.5X2,200 kv-a. = - g^= = 5.5 kv-a. 58. RESULTANT POWER-FACTORS. Where several loads of different power-factors are connected to the same feeder, the resultant power-factor may be found by means of the following formulae: Symbols: Wi = kilowatts supplied to Load No. 1. cos. 61 = power-factor of Load No. 1. w 2 = kilowatts supplied to Load No. 2. cos. 2 = power-factor of Load No. 2. w 3 = kilowatts supplied to Load No. 3. cos. 03 = power-factor of Load No. 3, etc. cos. r = resultant power-factor. Then Wi tan 0i+w 2 tan 2 +w 3 tan 3 etc. tan. 0r = ; ; 7 Wi+W2+w 3 etc. Find tan 0i, tan 2 etc. from cos. 0i, cos. 2 etc. in Sec. 1. Find cos. r from tan r in Sec. 1. Problem: Find the combined power-factors of 200 kw. at 70% power-factor, 100 kw. at 80% power-factor, and 50 kw. at 50% power-factor. cos. 0i= 0.70 tan. 0i= 1.0176 cos. 2 = 0.80 tan. 2 = 0.75 . cos. 3 = 0.50 tan. 3 = 1.732 200X1.0176 + 100X0.75+50X1.732 , n , tan - 6r= 200 + 100+50 Power-factor = cos. r = 0.692. 59. Power-Factors of Various Types of Loads. Values in Table 70 have been calculated for various ratios of "connected lighting to connected power load. Large and small capacity motors, loaded with an average load of about one-quarter full load and three- quarters full load, have been used. This combination may give much lower or higher power-factors, depending upon the type of machinery used. Motors from ^ to 3 H.P. are considered small motors, and motors from 5 H.P. to 50 H.P., large motors. Symbols. w = connected kw. of incandescent lighting. Wi= connected h.p. of motorsXO.746 [ 505 ] Sec. 7 ELECTRICAL CALCULATIONS TABLE 70 POWER-FACTORS Relative propor- tions of lighting to power, con- nected load Large motors at M load Large motors at M load Small motors at M load Small motors at % load W=l Wi=0 1.00 1.00 1.00 1.00 W=.75 Wi= .25 .99 .98 .97 .96 W =.5 .95 .90 .90 .80 W =.25 Wi=.75 .90 .75 .80 .60 W =0 Wi=l .85 .40 .70 .35 60. ECONOMICS OF TRANSMISSION. Economic conditions cannot be formulated with any great degree of accuracy. In many cases it is necessary to keep down initial expense, even at consider- able sacrifice otherwise, or economy in a certain direction may be sought at the expense of economy in some other direction. For these reasons, it is necessary that individual skill and judgment be used. In general, however, use may be made of Kelvin's law: that the greatest economy is obtained where the interest deprecia- tion and taxes on the investment are equal to the cost of the total power losses in the line per year. As the market for power and light is usually uncertain, and the proportion of power to light unknown except within wide limits, the total amount required can only be determined by future conditions. An approximate estimate of the average load, even after the most careful investigation, defies accurate calculation. Thus, the following tables must be used with the utmost care, and are only included herein that they may give, in part, a general idea of the conditions affecting the line itself, but do not include such conditions as cost of right-of-way, cost of the type of structure to be erected, and the many other features which oftimes influence the location of the line and the investment that can be made in conductors. Symbols: Wm = weight of conductor in Ibs. per cir. mil foot. p = resistance per cir. mil foot, a = area of conductor in cir. mils, n = ratio of total power loss to loss in one wire of system used. [ 506 ] ELECTRICAL CALCULATIONS Sec. 7 TABLE 71 VALUES OF K4 Cost of En- ergy, cents per Kw- hr. COST OP METAL, CENTS PER POUND 10 11 12 13 14 15 16 17 18 19 20 H i)4 2 | 6.32 4.47 3.65 3.16 2.58 2.24 6.63 4.69 3.82 3.32 2.70 2.34 6.93 4.90 4.00 3.46 2.82 2.45 7.2 5.1 4.16 3.6 2.94 2.55 7.48 5.29 4.32 3.74 3.05 2.64 7.75 5.47 4.47 3.87 3.16 2.74 8.00 5.65 4.62 4.00 3.25 2.82 8.25 5.83 4.76 4.12 3.36 2.92 8.48 6.0 4.90 4.24 3.46 3.00 8.71 6.16 5.04 4.35 3.56 3.08 8.94 6.32 5.16 4.47 3.65 3.16 2.00 1.82 2.10 1.91 2.19 2.00 2.28 2.08 2.36 2.16 2.45 2.24 2.52 2.31 2.60 2.38 2.68 2.44 2.76 2.52 2.82 2.58 DI = ratio of total weight of conductors used to weight of one conductor. I = maximum effective load current. 1 = length of line in feet. GI = cost of conductor per Ib. C 2 = cost of energy per kw-hr. i = interest as a decimal. d = depreciation as a decimal. t = taxes as a decimal. h = number of hours of operation per year. Considering the load constant the total cost of the kw-hrs. lost per year in cents is Power cost I 2 hc 2 1000 a No. 1 The investment cost per year is Investment cost= ni w m a 1 GI (i+d+t) No. 2 One and two must be equal according to Kelvin's law n Pi V h c 2 = n i w m a 1C : (i+d+t) 1000 a I ( . E ii W m Ci (i+d+t) 1000 rii Wm (i+d+t) 1000 I { ' V P n h c 2 \ [ 507 ] p n h XA / Sec. 7 ELECTRICAL CALCULATIONS TABLE 72 VALUES K 5 = VALUES IN TABLE X-^- 6 Copper /^i -i Alu- System Size of Wires {W|P?? r dad Af\O7 minum *U /c 20 C. 20 C. 2 wire D.C. 122 74.5 53. 3 wire D.C. Neutral equal to outside 150 91 65 3 wire D.C. Neutral one-half outside 137 83 59.5 Single-phase A.C. two- wire 122 74.5 53 Single-phase A.C. three- Neutral equal to wire outside 150 91 65 Single-phase A.C. three- Neutral one-half wire outside 137 83 59.5 Two-phase three-wire Common wire equal to outside 106 64.5 46 Two-phase three-wire Common wire 1.41 times outside 122 74.5 53 Two-phase four-wire 122 74.5 53 Two-phase five-wire Neutral equal to outside 137 83 59.5 Two-phase five-wire Neutral one-half outside 130 79 56.5 Three-phase three-wire 122 74.5 53 Three-phase four-wire Neutral equal to outside 141 86 61.5 Three-phase four-wire Neutral one-half outside 132 80.5 57.5 w m ci (i+d+t) 1000 P n h c = It The above formulae indicate that the current density in amperes per circular mil area is proportional to the square root of a factor depending upon the number of wires, the weight and resistance per mil foot, the number of hours used and the interest depreciation and tax cost times the square root of the ratio of the cost of material to the cost per kw-hr. of energy. In Table 71 values of K 4 have been calculated for various costs of metal and costs per kw-hr. To extend this table for costs twice as great as those given in the table, multiply the values in the table by 1.41. This will extend costs up to 40 cents per pound. The cost per kw-hr. may be ex- [ 508 ] ELECTRICAL CALCULATIONS Sec. 7 tended to twice the values in the table by dividing by 1.41, or if the cost per kw-hr. and per pound of material are both doubled, the values will be the same as that given in the table, i.e. cost of material, 32 cents; cost per kw-hr. 6 cents. The ratio of 32 to 6 is the same as the ratio of 16 to 3, therefore K 4 = 2.31. In Table 72, the values of K 5 have been calculated for copper, 40% copper-covered steel, and for aluminum, for the different systems enumerated. They are based on an interest rate of 6%, deprecia- tion rate of 5%, tax rate of 1 ^2% ; and for a continuous use of energy for 300 days at 8 hours per day, and they give a general indication of the economic current density. However, it is better if possible to obtain the square root of the mean square load current over the total time of operation. I divided by this effective current = 03. Then c = A =C3 K 5 K 4 61. TRANSPOSITIONS. The transposition of overhead lines is a means of eliminating mutual inductance between two circuits and of balancing the self-inductances of unsymmetrically spaced Citcuir */ a a I a a., i a J a_ FIG. 304. lines. Fig. 304 shows a three-phase circuit in which no transposition to equalize the self -inductance of the wires is necessary. Fig. 305 shows a three-phase circuit in which it is necessary to transpose the wires as shown in Fig. 306 in order to equalize the self-inductive effect in each wire. In calculating the inductance and capacity when the wires are transposed as shown in Fig. 306 it is necessary to use the separation between adjacent wires for two thirds, and between outside wires for the remaining one-third of the length of the line. With the average separation so determined and substituted in the formulae or table, the proper value for the capacity or inductance is obtained. It has also been shown that the geometric mean of these three dis- tances will give a value that may be used in finding inductance and capacity. [509] Sec. 7 ELECTRICAL CALCULATIONS In Fig. 306 di = 12 inches, cb = 24 inches. Then by the first method d r : 2x12+24 3 = 16 By the second method d r = ^12X12X24 = 15.1 The first method has been longer in use. The second method is practically new and was formulated by J. G. Pertsch, Jr. a a a a ft a a a FIG. 305. FIG. 306. [FiG. 307. In Fig. 305 it is unnecessary to transpose the circuits to avoid mutual inductance if Circuits 1 and 2 only are considered. With Circuits 1 and 3, however, there must be a transposition to prevent the effect of mutual inductance. Fig. 307 indicates how this may be accomplished. [510] ELECTRICAL CALCULATIONS Sec. 7 With two-phase circuits as shown in Fig. 308 the arrangement for Circuit No. 1 has no mutual inductance between the phases. The arrangement for Circuit No. 2 will give mutual inductance between phases and to annul this must be transposed as shown in Fig. 309. In Circuit No. 3 there is practically no mutual induc- tance between the A and B phase, but there is mutual inductance between the A phases of Circuits 3 and 4, and the B phases of Circuits 3 and 4; and each phase of one circuit must be transposed as shown in Fig. 310 to annul mutual inductance. Transpositions must be Cr*CUlT*Z a* 1 1 *& t* ! 4 Q g. \ 1 fipjutr *ft ft* r-a ^> 1 I C/*CVtT " % a a* \ \ \ FIG. 308 y? >?- X FIG. 309 A, a X D 2 FIG. 310 made between the generating station and any important load if it is desired to accurately balance inductive effects. Transpositions are seldom necessary in distribution work as the amount of current is too small and the lengths of line too short to disturb the voltage relations. 62. CONSTANT VOLTAGE TRANSMISSION. Due to the necessity of spacing wires far apart on high voltage long distance [511] Sec. 7 ELECTRICAL CALCULATIONS transmission lines, the reactance is consequently very large. To transmit a large load and preserve commercial regulation, it is neces- sary to have a comparatively large number of parallel lines. To overcome this difficulty and reduce the cost of transmission, a method is used consisting of the installation of synchronous machinery at the receiving end, controlled by automatic voltage relays in such manner that they operate to vary the power-factor of the line with variation in load, and counteract the voltage drop due to the load j 1 f 4 , , / /so / / / / 120 SO 60 40 20 /) / / / / / / ^ x / i / I / 024 6 B /O 12 /4 /& /& 20 22 24 26 28 30 D/3rAWC IN /AfCfffS FIG. 311. current flowing through the reactance and resistance of the trans- mission line. Installations of this type have already been installed and are being operated very successfully. 63. SPARKING DISTANCES: Needle Gaps. There are many factors affecting the discharge voltages of a needle gap with a given separation of needle points. , [ 512 ] ELECTRICAL CALCULATIONS Sec. 7 (1) Air density. 2) Humidity. 3) Sharpness of the needles. 4) Location of the gap with respect to surrounding bodies. (5) Size and proximity of the needle supports. The sparking distances in inches and centimeters in air between Sharp No. 6 opposed needle points for various effective sinusoidal voltages are given in Table 73 and Fig. 311. This table and curve are approximately correct for the following conditions: A barometric pressure of 29.92 inches of mercury, a temperature of 77 F. and about (75-80) per cent humidity, which are average conditions. A non-inductive resitance of about % to 4 ohms per volt should be inserted in series with the gap. No extraneous body should be nearer the gap than a radius of twice the gap length. It is not good practice to use the needle gap for voltages above 100 kv. The Sphere Gap, discharge voltage is affected by fewer variables than the needle gap. _ TABLE 73 SPARKING DISTANCES NEEDLE POINTS DISTANCE DISTANCE Kilovolts Kilovolts R. M. S. R. M. S. Inches Cm. Inches Cm. 5 0.225 0.57 140 13.95 35.4 10 0.47 1.19 150 15.0 38.1 15 0.725 1.84 160 16.05 40.7 20 1.0 2.54 170 .17.10 43.4 25 1.3 3.3 180 18.15 46.1 30 1.625 4.1 190 19.20 48.8 35 2.0 5.1 200 20.25 51.4 40 2.45 6.2 210 21.30 54.1 45 2.95 7.5 220 22.35 56.8 50 3.55 9.0 230 23.40 59.4 60 4.65 11.8 240 24.45 62.1 70 5.85 14.9 250 25.50 64.7 80 7.1 18.0 260 26.50 67.3 90 8.35 21.2 270 27.50 69.8 100 9.6 24.4 280 28.50 72.4 110 10.75 27.3 290 29.50 74.9 120 11.85 30.1 300 30.50 77.4 130 12.90 32.8 17 [513] Sec. 7 ELECTRICAL CALCULATIONS (1) Air density. (2) Location of the gap with respect to surrounding bodies. (3) Size of the gap supports. In spheres larger than 10 cm. in diameter the third item noted above is practically negligible. The sparking distances in inches and centimeters in air between different size spheres for various effective sinusoidal voltages will be found in Tables 74 to 76 and Figs. 312 and 313. These tables and curves are correct for a barometric pressure of 29.92 inches of mercury and a temperature of 77 F. No data are at present available for sphere gap corrections, but at or near sea level, corrections for variation in barometric pressure and temperature may be made by multiplying the values in the table by 17.91 b 459 +t in which b = barometric pressure in inches of mercury. and t = temperature in degrees fahrenheit. A non-inductive resistance of about ^ to 4 ohms per volt should be inserted in series with the gap. No extraneous body should be nearer the gap than a radius of twice the gap length. It has been suggested that for most commercial testing, needle gaps may be used up to about 60,000 volts and sphere gaps from about 50,000 up to the highest voltages now used. TABLE 74 SPHERE GAP SPARK-OVER VOLTAGES 12.5 cm. SPHERES [SPACING KILOVOLTS EFFECTIVE Cm. In. Non-Grounded Grounded 0.25 0.098 6.5 6.5 0.50 0.197 12 12 1 0.394 22 22 1.5 0.591 31.5. 31.5 2 0.787 41 41 3 1.181 59 59 4 1.575 76 75 5 1.969 91 89 6 2.362 105 102 7 2.756 118 112 8 3.150 130 120 9 3.543 141 128 10 3.937 151 135 12 4.72 167 147 15 5.91 188 160 17.5 6.88 201 168 20 7.87 213 174 [514] ELECTRICAL CALCULATIONS Sec. 7 TABLE 75 SPHERE GAP SPARK-OVER VOLTAGES 25 cm. SPHERE SPACING KILOVOLTS EFFECTIVE Cm. In. Non-Grounded Grounded 0.5 0.197 11 11 1 0.394 22 22 1.5 0.591 32 32 2 0.787 42 42 2.5 0.983 52 52 3 1.181 61 61 4 1.575 78- 78 5 1.969 96 94 6 2.362 112 110 7.5 2.953 135 132 10 3.937 171 166 12.5 4.92 203 196 15 5.91 230 220 17.5 6.88 255 238 20 7.87 278 254 22.5 8.85 297 268 25 9.83 314 280 30 11.81 339 300 40 15.75 385 325 TABLE 76 SPHERE GAP SPARK-OVER VOLTAGES 50 cm. SPHERES SPACING KILOVOLTS EFFECTIVE Cm. In. Grounded Values 2 0.787 40 4 1.575 76 6 2.362 112 8 3.150 145 H ] 10 3.937 185 12 4.72 220 14 5.50 250 16 6.28 275 18 7.07 300 20 7.87 320 22 8.65 345 [ 515 ] Sec. 7 ELECTRICAL CALCULATIONS s \ *5 \ \ ^ ] \ ha A S * k s S \ ^ bf \ \ C? \ s \ \ + k! s \ i ^ ^ i^S ^ jj ^ (^ * x s ^ *** v. **- ^ M M M i <: S* M \l n ii H 5 ? h <= 5 c H n ^ n H ^ P ^v I * ^ ^ 5 ^ \ \ \ *-' \ '$ ^ \ ^ \ s ** ^ V \ s\ s *j x ^ ^1 "** ^ ^ s^ s *>x. x ' v >^ CX [516] ELECTRICAL CALCULATIONS Sec. 7 BIBLIOGRAPHY American Electrician's Handbook. Foster's Electrical Engineer's Pocketbook. Standard Handbook for Electrical Engineers. Electrical Appendix D'Este's Steam Engineer's Manual. Franklin & Williamson's Alternating Current. Calculations of Alternating Current Problems. (Cohen.) Overhead Electric Power Transmission. (Still.) Proceedings A. I. E. E. Corona F. W. Peek, Jr., July 1911, June 1912, June 1913. Transmission Calculation. Transmission Calculation (Fender), June 1908, July 1911. Transmission Calculation (Thomas), June 1909. Transmission Calculation (Kennelly), Dec. 1911, June 1912. Transmission Calculation (Dwight), June 1913. U. S. Weather Bureau. Electric Journal, 1905, 1906. General Electric Review, 1912. General Electric Review, 1913. [617] SECTION 8 MECHANICAL CALCULATION OF TRANS- MISSION AND DISTRIBUTION LINES SECTION 8 MECHANICAL CALCULATIONS OF TRANSMISSION AND DISTRIBUTION LINES TABLE OF CONTENTS ARTICLE General 1 Fundamental formulae Wind pressure 2 Compression and tension 3 Shearing stress 4 Bending moment 5 Torsion 6 Strength of timber Table 77 Moment of inertia and section modulus Table 78 Bending moment Table 79 Solution of sag problems General 7 Weight of wire 8 Weight of wire and ice 9 Wind pressure 10 Resultant load of ice and wind pressure 11 Temperature changes 12 Symbols and formulae 13 Problems 14 Loading, sag and length Tables Cross-arms General 15 Bending moment due to weight of wires 16 Bending moment due to unbalance tension in wires 17 Pole stresses . 18 Wind pressure on pole and conductor 19 Dead end loading 20 Bends in line 21 Guying 22 Concrete and Steel Structures 23 [521] 1. GENERAL. The mechanical problems met with in the design of a transmission line can in general be divided into two classes: (a) Stresses incident to the plan of a line, (b) Stresses which occur due to changes in temperature and to abnormal weather conditions. The stresses incident to the design of a line are those which occur at dead ends and at bends in the line. The stresses which occur due to changes in temperature and to wind and ice loads must be assumed and vary with local conditions. The solutions of the mechanical problems involved entail the application of fundamental formulae whicfi formulae are listed below. The problems solved herein have been calculated on the slide rule wherever possible, which method is suggested as being suffi- ciently accurate since variations in material will more than offset any error incident to slide rule calculation. FUNDAMENTAL FORMULA 2. Wind Pressure Formulae. V = actuel velocity of wind in miles per hour. F = pressure in pounds per square foot. B = barometric pressure in inches. Then for small flat surfaces. F = 0.004 X^rX V 2 ~. -~~ For the projected surface of a cylinder (diameter X length). F = 0.0025 V 2 3. Compression and Tension Formulae. s = tension or compression stress in pounds per square inch. a = area in square inches at right angle to the direction of the force producing the stress. \Vt = total weight or force in pounds producing tension or com- pression stresses. 4. Shearing Stress Formula. s = shearing stress in fibre in pounds per square inch. a = area in square inches parallel to shearing force. Wt = total weight or force in pounds producing shear. Then s = Ei 5. Bending Moment Formulae. M = bending moment in pound-inches. s = maximum fibre stress per square inch. [ 523 ] Sec. 8 c MECHANICAL CALCULATIONS distance from neutral axis to point of maximum fibre stress. I = moment of inertia. Q = section modulus. 6. Torsion Formulae. Mt= torsion moment in pound-inches. s = maximum shearing stress per square inch. c = distance in inches from neutral axis to point of maximum fibre stress. J = polar moment of inertia. Ii = least reactangular moment of inertia about two axes passing through the centre. I; = greatest reactangular moment of inertia about two axes passing through the centre. TV/T sj M t - 7. SOLUTION OF SAG PROBLEMS. The sag necessary in any span is dependent upon the following: a. The character and size of the conductor (Art. 8). TABLE 77 STRENGTH OF TIMBER In Ibs. per sc[. in. Untreated Timber Bending Compression Port Orford Cedar 6900 (69001 L ^ Long Leaf Yellow Pine 6000 6000 White Oak . . 5700 5700 Douglas Fir 5400 5400 5100 5100 Washington Cedar 5100 5100 5100 5100 Idaho Cedar Short Leaf Yellow Pine 4800 4800 Bald Cypress (heartwood) 4800 4800 Red Cedar 4200 4200 Redwood 3900 3900 Eastern White Cedar 3600 3600 Juniper 3300 3300 Catalpa 3000 3000 L = Length in inches. D = Least side, or diameter, in inches. [ 524 ] MECHANICAL CALCULATIONS Sec. 8 TABLE 78 Shape of Section Moment of Inertia I Section Modulus Q Sq. Least Radius of Gyration d 4 12 fed 3 12 ~l2~ 6d 3 -6'd' 3 d 3 6 6d 2 6 I 7 d 2 12* 12 m '' ff f J 1 ^$%$$$& | !-f- 12 7 %%%%%j X wr* ^ "_t] 12 .0491 (d 4 -d /4 ) bd?-2b'd' 3 .5d ^, or .0982 d 3 oZ 0982^3^ A d 2 16 d 2 +d' 2 * -of? HI B OQ x w5T \ d f \> j i 16 7 , X 1 X'>s x T r J 12 Ad 2 ,. ^g(Approx.) Ad 2 0.5 d ^ (Approx.) Ad ( . A 7 A 7 J: -A ^5 7.34 ),Q I A NOTE. A = total area of section. In calculating the least radius of gyration be sure to use the least moment of inertia, x x' denotes the neutral axis, and the value of / given ia that about this axis. [525] Sec. 8 MECHANICAL CALCULATIONS TABLE 79 Method of Loading Maximum Bending Moment M. Maxi- mum Load W Deflection D. Length in Feet Load in Pounds Ft.-Lb. In.-Lb. Lb. In. W L W L 6 W L 2 WL ~T~~ W A 2 W A 3W L 2W L QW L 12 W L 3W L 6 W A QW A 2QS 3L QS 2L QS 6L 12 L QS 3L SA 6A QS QA 384 E I WP WEI SE I WP 3E 1 Wl 3 48 El 48 E I (3 / 2 -4 a 2 ) Between Supports. Wa 1QE~I* (1-2 a) 2 L length in feet; 1= length in inches; W= total load in pounds; E modulus of elasticity; 7= moment of inertia; Q = section modulus; S=safe stress on the extreme fibres of the beam section ( = modulus of rupture -r-fector of safety). In figuring deflections, all lengths must be expressed in inches; and small letters I, a, and 6 are used as reminders. [ 526] MECHANICAL CALCULATIONS Sec. 8 b. The maximum load to which it will be subjected (Art. 9. 10, 11). (Weight of wire plus ice and wind load.) c. Maximum variation in temperature (Art. 12). 8. The Weight of the Wire depends upon The material. The area of cross-section. Whether solid or stranded. Whether insulated or bare. The weight of conductor per foot may be found in Tables 80 to 85, Sec. 8, and per 1000 feet in Tables 33 and 34, Sec. 3. 9. Weight of Wire and Ice. (Tables 80 to 85.) d = diameter of wire in inches. t = thickness of ice in inches (assuming a cylindrical forma- tion). W = weight of wire in pounds per foot. Wt= total weight of wire and ice in pounds per foot of con- ductor (assuming ice weighs 57.2 Ibs. per cu. ft.). W t = W+1.248 (dt+t 2 ). 10. Wind Pressure on Wires. (Tables 80 to 85.) F = wind pressure in pounds per square foot. d = diameter of wire in inches. t = thickness of ice in inches. Fo = force in pounds per foot length of wire. For wire alone For wire and ice _, F (d+2t) ~12~ 11. Total Resultant Load produced by the weight of the wire plus the wind and ice loads. FO = horizontal force in pounds per foot length of wire. Wt = the total weight or the vertical force' in pounds per foot length of wire. This may also be solved trigonometrically (Fig. 314) as follows: W- W < ~ . FIG. 314. [ 527 1 Sec. 8 MECHANICAL CALCULATIONS 12. Temperature Changes. Changes in temperature affect the solution of the sag problems in that the total length of wire, and therefore the sag increases and decreases with increasing and de- creasing temperature. 13. Symbols and Formulae. The resultant sag is determined by combining all the above factors in one solution, the formulae for which follow : These formulae in connection with the curves in Figs. 318 to 320 may be used to solve the mechanical problems met with in the * stringing of conductors. The curves Figs. 318 to 320 are illustrated on a very small scale and for calculations should be increased in size. The data necessary for the preparation of these curves are given in Table 86, from which table curves of sufficient size to obtain accurate results may be plotted. D = distance in feet between supports. d = sag in feet at stringing temperature "t." t = stringing temperature in Degrees F. T = total tension in the wire in pounds at temperature "t." s = stress per square inch at tension "T." a = effective area of wire in square inches. W = weight per foot of wire. di = sag in feet at desired change in temperature or tempera- ture at maximum stress. ti = temperature at which stress is desired, or temperature at maximum stress. Ti = tension in wire in pounds at temperature ti. Si = stress per square inch at tension TI. Wi = weight of loaded wire (includes ice load or ice and wind load). a = co-efficient of linear expansion per degree F. E = modulus of elasticity. r _ length of wire at temp, (t) ~D~ length of wire at temp, (ti) 11 nD- length of wire at temp, (t) . , unstressed length of wire at temp. D X= f Xi = -jj- [52SJ K = sa WD si a MECHANICAL CALCULATIONS Sec. 8 f r change in temperature only. o fl, KI = YT^-J} for change in temperature and in load. T = sa Ti = si a When wire loading is unchanged, but temperature is changed. Then lo = I--1- V = lo-o (t-ti) When conditions are given at heavy loading in order to find con- ditions at light loading. W l lo = lo' + a (t-ti) When conditions are given at light loading in order to find con- ditions at heavy loading. lo' = lo-a (t-ti) When the supports for the wire are at different levels, the distance from the higher support to the lowest point of the wire in the span is determined and the problem solved for a span twice the length of the distance so determined. Xi = distance in feet from the lowest point in the span to the higher support. h = difference in level in feet between the wire supports d = sag in feet measured from the higher support. D = the horizontal distance in feet between wire supports. x = D I hsa = D [ Kh [529] Sec. 8 MECHANICAL CALCULATIONS also When Xi has been determined, solve the problem as though fo\ level wire supports, but for a length of span equal to the corrected length DI, where 14. PROBLEMS: Problem 1. Determine the change in the sag and in the tension of the conductor due to a drop in temperature to 10 F. when strung under the following conditions : Length of span 200 feet. Sag at stringing temperature 1.5 feet. Stringing temperature 70 F. Conductor Bare, Hard drawn, Stranded No. 00 Copper wire. D = 200 feet. d =1.5 feet. t = 70 F. ti = 10 F. W = 0.406. (From Table 82.) a = 0.1045. (From Table 82.) E = 16,000,000. (From Table 81.) a = 0.0000096. (From Table 81.) Solution: In Fig. 315 lay off X a parallel to oy. Draw Kc parallel to ox and through the intersection b of X a and the sag curve. Drop a perpendicular line dl from the intersection d of Kc and the length curve. K = 16.3 1 = 1.000156 KWD 16.3X0.406X200 0.1045 = 12,600 Ibs. per sq. inch. 1 - = ,.0001-- = 0.9993645 Lay off the difference between 1 and 1 (Fig. 315) =1 -0.9993645 0.0006355, from O. Draw a line from 1 through d. [ 530] MECHANICAL CALCULATIONS Sec. 8 [531] Sec. 8 MECHANICAL CALCULATIONS V = 0.9993645- 0.0000096 (70 - 10) V = 0.9993645 - 0.000576 = 0.9987885 Lay off the difference between 1 and 1' . = 1 - 0.9987885 = 0.00121 15 from O and draw 1 e parallel to 1 d intersecting the length curve at f . Draw Kig through f parallel to ox and where it intersects the sag curve h, drop a perpendicular Xih Then Ki = 24.3 Xi = 0.0051 From which Ti = K! VV D = 24.3 X 0.406 X 200 = 1,975 Ibs. K t WD 24.3X0.406X200 81 = ""-T~ -01045- = 18 ' 9 lbs Per Sq ' m ' di = \! D = 0.0051 X 200 = 1.02 feet. di= 1.02X12 = 12.24 inches. Problem 2. Determine the sag and the tension of the conductor when strung at a temperature of 70 F., so that when subjected to a temperature of F. and the additional load of }/2 of sleet, and a wind pressure of 8 lbs. per square foot, the stress in the conductor will be within 17,000 lbs. per square inch, for the following structural conditions: Length of span 200 feet. Conductor Triple Braid Weatherproof, soft drawn solid No. 00 copper wire. D = 200 feet, t = 70 F. ti = F. Wi= 1.518. (Table 84.) W = 0.502. (Table 84.) a =0.1045. - (Table 84.) E = 12,000,000. (Table 81.) a = 0.0000096. (Table 81.) s = 17,000 lbs. Solution : _ BI& _ 17,000 X0.1045_ gog ~WiD~ 1.518X200 In Fig. 316 draw Ki a parallel to ox, where this line intersects the length curve at a drop a perpendicular line a li and obtain li li = 1.001225 T i Sl 1 nmo9* 17,000 lo=l1 E- = L001225 -12,000,000 To = 0.999809. [ 532] MECHANICAL CALCULATIONS Sec. 8 Sec. 8 MECHANICAL CALCULATIONS Lay off the difference between 1 and 1' =1-0.999809=0.000191 from 0. 0502\ 1' = 1.000279 Lay off 1' from and erect a perpendicular intersecting Ki a at b, draw r o c through 1' and b. lo = I'o + a(t-ti) 1 = 0.999809+0.0000096 (70-0) =0.999809+0.000672 1 = 1.000481 Lay off 1 from and draw I d parallel to l' c intersecting the length curve at c. Draw Kf parallel to ox through e and where Kf intersects the sag curve at g, drop a perpendicular gX. X = .0194 K = 6.475 d = XD = 0.0194X200 =3.88 ft. d = 3.88X12 = 46.56 inches T = K W D = 6.475X0.502X200 = 650 Ibs. KWD 650 0.1045 = 6210 Ibs. per square inch. Problem 3. Determine the sag and tension of a conductor at 10 F. when loaded with Yz' of sleet and a wind pressure of 8 Ibs. pr square foot for the following structural conditions. Length of spans 200 feet. Conductor Bare, stranded No. 00 aluminum wire. Stringing temperature 70 F. Sag 4.5 feet. D =200 feet. d = 4.5 feet. t = 70 F. ti = 10 F. W = 0.122. (From Table 85.) Wi = 1.168. (From Table 85.) a = 0.1045. (From Table 85.) E =9,000,000. (From Table 81.) a =0.0000128. (From Table 81.) Solution: d 4.5 D 200 Continued on page 545. [ 534 1 ' MECHANICAL CALCULATIONS Sec. 8 9 [535J Sec. 8 MECHANICAL CALCULATIONS : ,1 I 11111 1 to irf TjT co" CM TH |. 8|| O CO CO O .5 c"3 '"'S IIIII I < i-H S^ 5|oig * Q iif 2*2 Si ggg ai 8|85 g 1 51 s,g ' 1 53 J^ sslis H^ a| fe _; ^ <=> d <=>' o A tk a Q^ * ri ^ O^U,0 @ w 3^ Q 00000 2 3 5 91 CiO H* ... .1 iiii! 'g s ssssa (H : 1 1 1 flo W'^ C to 4> c^ ... . iiiii ' s" a" a" 3 s " Committe 1 1 p 1' 2 ii : : : :| IIIII a 1 ^g 9 0^ "1 "1 ^ S. 00 U 0> O s 11 tO S CO < IM VO -S 35 SSS N l-l l-> lH o c CQi-H 2 b g|,l Ho iH M U (O CO O i-l T-I i I ^ ^ H 5 ^v ^^ * [536] MECHANICAL CALCULATIONS Sec. 8 d o c- O i-l (0 O0>OOF4 S8S- S5S T-* - - t-. O O O C- ^ C- iH iH iH Tj( CT> SSSS 8'888 SSSS SSSSS SSS S 8 O>0>00 tl> 2S COC4NC4 SiHO>i-l MNiHiH 00 fq CO ^ CO rq CS) TH o>e>o o TH co ITS CD :- to c- o^<0>us C- Ss ^1 C4000(0 TKCOC^TH THOO>0> USIO^ITH oo i^Sgg S co CM o in SSSS S S SS5S S es o o> i> to us * sc> SSSS i--4cj> OOOO USOOO us S88.S ssss s MC400S eODUS^I CO USUS^O sags lO^C^OO^"^ r^t-O^O^ eqC^O^TH^ t r4 OO 10 ^rHart^ tO * V9 &i C* C*t r4 i-t H iH ^ us TH o o us c4 oo usonc~r-i co oo S3 S 3 S 8 $ S S S S3 S S 5! S? CO CO CO C NHHTH 1-1000 00 5 SSS5 S S S S OOi-H S8S i Tf ^ co cc [ 538 ] MECHANICAL CALCULATIONS Sec. 8 , oo o s! 33 fit I Jl y^ 3* fid- . M Q ^ $2 ^ _El_ I* 8 1111 1111 ii s s s a s s" a a" as ousesio e-to^co CON SCO O i l . ^ M eels IssS Is e4<0<0 e^MC>iA t- to T-I ITS ceMOOlO NO ut<<# co co es cs NC4 5JS8S 3SSS > 10 ^1 CO NC4*HiH iH iCOtAtA ot>o<-i tA 1A <-i oo ' "' 5S3S t-lTHO> S3 IAN SSS O ir> uo IH 00 CM o- SP? pa 2" ** Si p cSpq iiii ii|i |f ISIS |gs iiis 3 a 13 is SS CD uo co is oooe oooo oo 1 1 3 1 P.P. " " OCOIAO SSSS -T- IO <9 t- o t- eo mmt-io o s s s s s s oo e>r-(D 3 35 to tom O Oi T-IIAIACD 33 S S S Ills gsss ssss Si CM C- t> H 0>O> N fe * M 1-4OOO OO SS35 S5SS SSS tr> ^ iO -^ ^04CO 04CO *00*0 [541] OOr-t Sec. 8 MECHANICAL CALCULATIONS & I *. 0,2 It [542] MECHANICAL CALCULATIONS Sec. 8 5-1 1 I \ \ \ \ \ \ V \ s \ i %- \\ ^ \J \ . \ v^ ^ % ^ x ^^ , . . / 1.0001 LOOK 10003 1.0004 I.OOOS /.000& 1.0007 1.0008 1.00011.0010 WOU U0012 1.0013 UDOI4 I.OC .01 .02 FIG. 319. Relation between, length and sag per foot of span, and total stress in conductor per pound of conductor one foot long. [543] Sec. 8 MECHANICAL CALCULATIONS / / 7 MECHANICAL CALCULATIONS Sec. 8 TABLE 86 DATA FOR PLOTTING LENGTH AND SAG CURVES 1 X k 1.0000042 1.0000051 1.0000061 1.0000071 1.0000082 0.00125 0.00138 0.00150 0.00162 0.00175 100.0013 90.9105 83,3348 76.9247 71.4303 1.0000094 1.0000107 1.0000118 1.0000136 1.0000151 0.00188 0.00200 0.00212 0.00225 0.00238 66.6685 62.5020 58.8257 55.5578 52.6339 1.0000167 1.0000261 1.0000372 1.0000511 1.0000667 0.00250 0.00313 0.00375 0.00438 0.00500 50.0025 40.0031 33.3371 28.5758 25.0050 1.000104 1.000150 1.000266 1.000417 1.000598 0.00625 0.00730 0.01000 0.01250 0.01500 20.0063 16.6742 12.5100 10.0125 8.3483 1.000817 1.001066 1.001351 1.001668 1.002017 0.01751 0.02001 0.02252 0.02502 0.02753 7.1604 6.2700 5.5781 5.0250 4.5730 1.002402 1.003754 1.006680 1.010444 1.015068 0.03004 0.03757 0.05017 0.06283 0.07556 4.1967 3.3709 2.5502 2.0628 1.7422 1.020542 1.026881 1.034093 1.042191 1.051185 0.08840 0.10134 0.11441 0.12763 0.1410U 1.5170 1.3513 1.2255 1.1276 1.0501 1.061089 1.083691 0.15455 0.18226 0.9879 0.8965 Draw X a parallel to oy and intersecting sag curve at b ; draw Kc through b parallel to ox and intersecting length curve at d. Drop a perpendicular dl. (Fig. 317.) K = 5.6. 1 = 1.00134 KWD 5.6X0.122X200 10 __ 1U . -, = 1308 IDS. per square inch. 0.1045 18 [545] Sec. 8 MECHANICAL CALCULATIONS 1308 = 1.0011947. Lay off 1 from 0. 1' = 1.002586. Lay off 1' from and draw l'e parallel to oy, intersecting Kc at f. Draw log through f . I'o = lo - a(t-ti)= 1.0011947 -0.0000128 (70 -10) = 1' = 1.0004267.' Lay off I'o from and draw 1' h parallel to I g intersecting the length curve at i; draw a line KJ parallel to ox through i and inter- secting the sag curve at m, drop a perpendicular line Xim from m. Xi = 0.02515. Ki = 5.025. Then Ti =Ki Wi D=5.025X1.168X200 = 1176 pounds. 6i = KlWlD ^L 1 !??;! = 11,230 pounds per square inch. L pJ.J.U4O dj = XiD=0.02515X200 = 5.03 feet. di = 5.03X12 =60.36 inches. CROSS-ARMS 15. General. The ordinary stresses on cross-arms may be divided into two classes. 1. The stress produced by the bending moment caused by the weight of the wires. (Vertical.) (Art. 16.) j h * ' \ * 1 * i 4 * \ ( "i fl h i i i 5 ( 3 *> \ \ *S Vi \ \ 1 7 | 1 1 * _ X m y L-4- ^ , l_ y _ f . ** *.g | - - | c 7 Fia. 321. [546] MECHANICAL CALCULATIONS Sec. 8 2. The stress produced by the bending moment caused by an unbalanced tension of the wires. (Horizontal.) (Art. 17.) The solution of problems to determine the following stresses has not been included for the reasons outlined below, although in some cases they may be of importance. 1. Shear and compression, as calculations indicate that such stresses in cross-arms are negligible. 2. Torsion, since the bending of the cross-arm renders calculated stress values very unreliable. 3. Torsion on poles and cross-arms due to broken wires as the relative flexibility of the pole will introduce an error of approximately 50% in the calculated results. 16. Bending Moment Due to the Weight of the Conductor. (Fig. 321.) Let DI & D2 = length of adjacent spans in ft. T u = the unbalanced tension in the conductor in Ibs. li, 12, la etc. =the lever arm or distance from the center of the pole to the center of the pins in inches. 1 = the distance between pins in inches (assuming the distance from the center of the pole to the pole pin equals 1). Wti, Wt2, Wts, etc. =the total weight of the respective conductors supported by the pins, n = the number of pins in the cross-arm. M = the bending moment in pound-inches. Then M = (Wti ll+Wta Is +Wt5 Is + +Wtn-! In-i) or M = (W t2 l 2 +W t4 U + W tP l 6 + +W tn In). The above formula) are simplified when all the wires have the same weight, then M = W tl 1 Problem: Find the fiber stress in pounds per square inch in a six pin, 8 ft, 3J/2 x 4^ standard cross-arm, each pin supporting a No. 00 stranded bare copper wire, with the additional load of Y^' covering of ice; assuming 200 ft. spans. Solution : From Table 82. Wt = 0.978. F547] Sec. 8 MECHANICAL CALCULATIONS (Di+D)Wt 400X0.978 = 195.6 Ibs. i M = 195.6X14.5(1+2+3). M = 195.6 X 14.5X6 = 17,020 Ibs.-inches. s = Fiber stress. 6= ra Table 78 - b = Dimensions of cross-arm in inches at 90 to force. d = dimensions of cross-arm in inches parallel to force. 6X17,020 8 = o t-^fA K xo = M43 lbs - P er square inch. O.O A. (^t.O) The weight of the insulators and ice on the cross-arm, the reduc- tion in cross-section due to the bolt holes, and the supporting effect of the braces have not been considered as they effect the result by less than 5% and are generally covered by the factors of safety used. 17. Bending Moment Due to the Unbalanced Tension in Con- ductors exemplified by dead ending the line. Problem: Find the fiber stress in pounds per square inch in each of two 4- pin 5 ft. 7 inches, 3^" x 4 Hi" standard cross-arms and supporting through pin type insulators to each of which is attached a No. 00 hard-drawn stranded bare copper wire. Solution: If a through pin type insulator is used on two arms and consider- ing the wire stress T u = 1,975 Ibs. (From Art. 14.) Then M = 1,975X14.5 (1+2) =86,000 Ibs. inches for two arms. M =43,000 Ibs. inches for one arm. 6X43,000 45X (3 5 )2 4,675 Ibs. per square inch. Double arms, as generally used, to which wires are connected to insulators in tandem, complicate the problem in that a form of canti- lever truss is thereby produced. In the solution of such problems, the load is divided by two and the fiber stress for a single arm is calculated. This solution assumes 548 MECHANICAL CALCULATIONS Sec. 8 that the load is equally divided between the two cross-arms and neg- lects the truss effect. 18. POLE STRESSES Forces Producing Pole Stresses. Wind pressure on the pole. (Art 19.) Wind pressure on the conductors. (Art. 19.) Unbalanced wire tension. a Dead ends. (Art 20.) b Bends in a line. (Art. 21.) 19. Wind Pressure on Pole and Conductors. Symbols: F = the wind pressure in pounds per sq. ft. of projected area of pole or wires (Art. 2). FO = the wind pressure in Ibs. per ft. length of wire. (Art. 10.) s = the fiber stress of pole in Ibs. per square inch. H = the height of pole in feet above ground, di = the diameter of pole at ground in inches. d 2 = the diameter of pole at top in inches. d 3 = the diameter of pole where effect of load is applied. DI & D 2 = the adjacent spans in feet, ni = the number of wires at dist. LI from ground. n 2 = the number of wires at dist. L 2 from ground. L = the effective lever arm in feet. P p = the total wind pressure on pole. PCI = the total wind pressure on wires LI feet from ground. P C2 = the total wind pressure on wires L 2 feet from ground. M p = the bending moment of pole. MCI = the bending moment of wire at dist. LI from ground. M C2 = the bending moment of wire at dist. L 2 from ground. Mt = the total bending moment. Then FH 2 (di+2d 2 ) M p = ^- Ib.-ft. 24 [549] Sec. 8 MECHANICAL CALCULATIONS M t =Mp+Mci+M C 2 Ib.-ft. T M t f ~ d 3 = di (di d 2 ) -^r inches. n. _Mt Ibs. K in 2 . 18.1152 Whendx^l.Sda ** K dl3 122.208 When di~1.5 d 3 For values of K for variations in di and d 3 see Fig. 322.* The curves in Fig. 323 1 were obtained as follows: Symbols: d = rot diameter in inches, di = diameter at ground line in inches. d 3 = diameter where load is applied in inches. MO = bending moment on rotted pole in Ib.-ft. M = bending moment on new pole in Ib.-ft. s = fibre stress per square inch at bending moment M. s = fibre stress per square inch at bending moment M c = Mp _(di-d 3 )d 3 2 s 18.1152 M - d 3 s "122.208 _]Vlp_ dp 3 SQ ~H "122.208 (di ds) d 3 2 s 18.1152 18.1152 s '122.208s 'Adi o ** The weakest section of a wood pole is where the diameter is equal to 1.5 times the diameter of the point of application of the resultant load. * For sawed square timber K as found from Fig. 322 should be increased 70%. ] t Curves are equally correct for sawed square timber or round timber. [ 550 ] MECHANICAL CALCULATIONS Sec. 8 ,J7 2 // Or?* *Y z 8 10 12 14 /6 18 20 22 24 2 6 28 30 22 D/AMr IN INCHES AT THE POIMT OF SUPPOBT, (THE GROUND LINE] -of/ FIG. 322. Fibre stress in ; per Ib-ft. of bending moment,=i. [551] Sec. 8 MECHANICAL CALCULATIONS too 70 20 .6 d, FIG. 323. Relation between rotted diameter of pole, bending moment and fibre stress. [ 552 ] MECHANICAL CALCULATIONS Sec. 8 di d as a percent of d] 3 The curves in Fig. 323 illustrate the percent of the original diame- ter to which a given pole may rot before the strength is less than that of a sound pole; also the percent of the original diameter at which the pole will break. If the bending moment remains constant, iy = l; the percentage rot diameter i.e., the ratio of the diameter of the rotted pole to the original ground line diameter will vary in accordance with curve (1) depending upon the ratio -p. If the stress is greater the value of the rotted diameter will be determined by the curve indicated by the value of -, tj remaining equal to one. So If the load on the pole is increased TJ will be greater than one and the rotted diameter of the pole is determined by the curve indicated by the value of TJ . These curves may be interpolated with ac- SQ curacy. Problem: Find the top and ground line diameter necessary for a 40 ft. chest- nut pole, set 6 ft. in the ground to which are attached 3 No. 00 bare stranded copper wires, one at the top and two 3 ft. from the top; the wires coated with ^" of ice, and a wind pressure of 8 Ibs. per square foot on the pole and the ice covered wires. The adjacent spans are 150 and 200 feet long. Solution: Solve first for wire and ice load alone. Table 82 for No. 00 stranded copper, % ice and 8 Ibs. wind F = 0.947. Wire on top of pole. MCI = 1 X0.947X34 ( 15Q + 2QQ ) =5)65 o lbs.-ft. Wires on cross arms. M C2 = 2X0.947X31 ( 150 + 20 Q} = 10,290 lbs.-ft. Mci+M c2 = 15,940 lbs.-ft. Since the top and ground line diameter of the pole are not known, it is necessary to assume a value for the maximum allowable fibre stress which in this solution is made 1200 Ibs. per square inch. [553] Sec. 8 MECHANICAL CALCULATIONS Then Mci + MC2, 15,940 _ = ~~ From Fig. 322 for K = 13.3. A 40 ft. class " B " pole, Sec. 2, Art. 16, may be used, since it has a ground line and top diameter equal to about 13" and 7" respectively. Since, as mentioned in the foregoing, the wind pressure has been considered for the wires only, it is necessary in order to find the maxi- mum fibre stress in the pole to recalculate the problem for the pole selected by the above method, including in the calculation the effective wind pressure on the pole. 8 X (34) 2 X (13.7 +2X7) or fin ,u ff Mp = -- =2 --- =3,560 Ib.-ft. M C i= 5,650 Ib.-ft. M C2 = 10,290 Ibs.-ft. M t = 19,500 Ib.-ft. X 34X8 = 234.5 Ibs. = 3321bs. L _ 19,500 _ 19,500 ~234.5+166+332~732^~ Fords =8.46 di-13.7 Find K = 21 (Fig. 322). s = M* = i^M = 928 Ibs. per square inch. K. 2i\ Having determined for the selected pole the maximum fibre stress per square inch (928 pounds) it follows that a certain decrease in ground line diameter may take place due to rotting before the pole will fail. This value is determined as follows : [554] MECHANICAL CALCULATIONS Sec. 8 \ \ v \ *8 ^ * ^ .1 ^ ^ 5 s? [ 555 ] Sec. 8 MECHANICAL CALCULATIONS Assume the bending moment on the pole to be the same when rotted as when new; Mo Then 77=^ = ! M The modulus of rupture of chestnut is 5100 Ibs. per square inch, s 928 therefore, to break the pole must equal ^^- =0.182. So d 3 8.46 Interpolation of the curves in Fig. 323 between ij = 0.1 and 0.2 So shows that the diameter may be rotted to 56% of the original ground line diameter. 56 X 13 7 Rotted diameter = ' =7.66 inches. 20. Dead End Loading. MCI = LI Tut ru M C2 = L 2 Tu 2 n 2 Problem: Find the stress in a 40 ft. chestnut pole, set six feet in the ground, when subjected to the bending moment due to dead ending three No. 00 bare stranded copper wires, one at the top and two, three feet from the top. Assume a 200 f t. span. Solution: Tui= Tu2 = 1,975 Ibs. (From Art. 13, Prob. 1.) m = 1 n 2 = 2 M C i= 34 X 1,975 XI =67,150 Ib.-ft. M C2 = SIX 1,975X2 = 122,300 Ib.-ft. M t = 67,150 + 122,300 = 189,450. Mt 189,450 K = V == T200~- No standard 40-ft. pole will meet this condition. (See Fig. 322.) T , _M t _ 189,450 ? = ~F == 5,100 = This will break a standard 40-ft. pole. Assuming in both cases that the pole does not bend and relieve the wire stress. Such a pole may be used, if guyed as shown in Art. 22. F 556 1 MECHANICAL CALCULATIONS Sec. 8 21. Bends in Line or change in line direction. Assume a 15 angular change in the line. From Fig. 324 T U i equals 26% of the tension in wires. T u i= T u2 = .26Xl,975=5141bs. (Art. 13, Prob. 1.) M C i= 34 X 514X1 = 17,480 Ibs.-ft. M C2 = 3lX514X2 = 31,9001bs.-ft. M t = 49,380 Ibs.-ft. A 15 bend is similar in effect to dead ending, but not to so great an extent. For a 90 bend, however, from Fig. 324. T u = 1.41X1,975 =2,785 Ibs. Mci = 34 X 2,785 X 1 =94,600 Ibs.-ft. M C 2 = 31 X 2,785 X2 = 172,900 Ibs.-ft. M t = 267,500 Ibs.-ft. which is worse than dead end loading. FIG. 325. If it is desired to use pull instead of the curve in Fig. 324. P = pull (Fig. 325). T u = resulting tension on wire supports. T = tension in wires. Then _2PT lu == ~~ 22. GUYING. Mt = total moment on pole. L g = height of point of guy attachment from ground. L'g = distance of guy anchor from base of pole. T g = tension in guy wire. [ 557 ] Sec. MECHANICAL CALCULATIONS POLE M t =T t L Mt FIG. 326. Lg sine a 1 (Fig. 326.) Sine a= r POLE GuySWi L' Mt 9 ' FIG. 327. L g sine a Sine a = ,-= (Fig. 327.) Problem: Assuming the bending moment as determined in Art 21 for a 90 bend. M t = 267,500 lbs.-ft. Guy attached three feet from top of pole. L g = 31 feet; foot of guy 30 ft. from base of pole (Fig. 326). Sine a = 7== = = 0.696 [558] 267,500 MECHANICAL CALCULATIONS Sec. 8 If a factor of safety of three is used the breaking strength of the guy must be 12,400X3=37,200 Ibs. This necessitates the use of two Siemens Martin y% galvanized strands having an ultimate strength of 19,000 Ibs. each. 19,000X2 = 38,000 Ibs. 23. CONCRETE AND STEEL STRUCTURES. It will be noted from the above that the solutions have been confined to wood poles and cross-arms for the reason that the design of steel and concrete structures introduce engineering problems which cover such a num- ber of variables that formulae for their solution would require a treatise on structural design. These problems are essentially structural engineering problems and their solution should be made by men familiar with such work. BIBLIOGRAPHY. N. E. L. A. Overhead Line Committee Report, 1911. U. S. Weather Bureau. Transactions of International Electrical Congress, 1904. A. I. E. E., June, 1911, Mr. P. H. Thomas. Franklin & Esty Electrical Engineering. Mechanics of Materials, Merriman. Overhead Electric Power Transmission, Still. [559] SECTION 9 PRESERVATIVE TREATMENT OF POLES AND CROSS-ARMS PART I GENERAL DATA PART II RECOMMENDED PRACTICE AND SPECIFICATIONS PART III APPENDICES SECTION 9 PRESERVATIVE TREATMENT OF POLES AND CROSS-ARMS PART I GENERAL DATA TABLE OF CONTENTS ARTICLE Introductory 1 Seasoning General 2 Manner of Storing Poles and Cross-arms 3 Spacing 4 Roofing 5 Summary on Seasoning 6 Preservatives General 7 Structure of Wood 8 Sap Wood 9 Decay of Wood 10 Preservative Agents 11 Preservation with Oils 12 Coal Tar Creosote 13 Water Gas Tar Creosote 14 Petroleum Oil 15 Wood Creosote 16 Preservation with Salts 17 Summary 18 Processes General 19 High Artificial Pressure Processes 20 Full Cell Treatment: Bethell 21 Burnett . . 22 Wellhouse 23 Rutgers 24 Card 25 Allardyce 26 Empty Cell Treatment : Riiping 27 Lowry 28 Atmospheric Pressure Processes 29 [563] Sec. 9 WOOD PRESERVATION ARTICLE Full Cell Treatment, Steeping in Cold Preservative .... 30 Hot or Boiling 31 Alternate, Hot and Cold 32 Empty Cell Treatment open tank 33 Low Artificial Pressure Systems, Full or Empty Cell 34 Miscellaneous Treatments, Brush 35 Brush combined with open tank 36 Jacket or Butt setting 37 [564J 1. INTRODUCTORY. The following chapter on preservative treatments consists of extracts from the 1910 and 1911 reports of this Association's Committee on Preservative Treatment of Wood Poles and Cross-arms. The first named report has been condensed in order to present only the sections on seasoning, pre- servatives, and processes. These general descriptions of preserva- tive practises are given not only because they are historically and scientifically interesting, but also to properly introduce the more definite recommendations and specifications presented in Part II. Attention is called to this, as the conclusions regarding the nature of preservatives and methods of treatment given in Part II were intended to supersede the more general conclusions contained in Part I. Much valuable data have necessarily been omitted, particularly the conclusions of the committee on preservative methods con- cerning which they were unable to procure sufficient information to justify recommendation. The reports of this committee are undoubtedly among the most valuable of the association and will be found printed in full in the 1910 and 1911 proceedings. SEASONING 2. General. Whether or not poles or cross-arms are to receive preservative treatment, there can be no doubt that it invariably eiys to season them properly before putting them into service, nder ordinary conditions, the life of a well-seasoned, untreated pole should be at least 30 per cent greater than that of an untreated green pole, and the life of cross-arms is increased in about the same proportion through proper seasoning. For general purposes, air- dried timber should give the best results in regard to the strength after seasoning, decreased moisture content in the wood under aver- age climatic influences, and the increased penetrability afforded to impregnation by preservative fluids. Artificial drying or seasoning methods such as kiln drying, oven drying and steaming are employed for various reasons, but the usual object is to force the drying process. It would seem that where poles and cross-arms are used in limited quantities, and the preserva- tive treatment is to be applied by the pole consumer, there would be no good reason for resorting to artificial means of drymg. It is true, however, that some method of accelerated drying is imperative where the wood is to be treated, and sufficient time cannot be allowed to air-dry it thoroughly. It is astonishing at this late day to learn that in many instances poles and cross-arms are brush-treated while in a green state, whereby the moisture content of the wood is prac- tically sealed within it, so that in a short time, when the superficial coating is worn or torn away fungi are admitted to the interior, and accelerated decay is encouraged. If poles and cross-arms cannot be sufficiently air-dried, or if any form of artificial drying is not resorted to, it is best not to attempt any such treatment before the poles and cross-arms are installed, and if so installed, sufficient time [565] Sec. 9 WOOD PRESERVATION should be allowed to season the arms before treating them. Never- theless, local conditions are apt to govern; as, for instance, poles are often required to be kept painted under franchise or ordinance requirements. 3. Manner of Storing Poles and Cross-arms. In general, whether poles are stored at some distributing point or are distributed along construction routes, the first care should be to keep them clear from the ground. If the bottom tier of a pile of poles is placed at a sufficient height from the ground, say not less than two feet, two necessary things will be accomplished the wood will is farther removed from decay infection and, owing to the freer cir- [ 566 ] WOOD PRESERVATION Sec. 9 culation of air, the seasoning process will be more thoroughly and quickly accomplished. If the poles are to remain for any length of time in one position, the tiers should be separated, and, if possible, the poles should not come in contact. (Figs. 328 and 329.) Forest Circular No. 151 gives some valuable suggestions covering the proper piling and storage of cross-arms: l! 3-2 _M ifS 3 V W) a |-cg a.- ''In addition to natural factors, another of hardly less importance is introduced in the manner of piling the timber. In general com- mercial practice, economy of space and handling are rightly con- sidered of the first importance, and all other considerations are made [567] Sec. 9 WOOD PRESERVATION subservient. Present practice does not secure the best results, but if there were no means by which these could be attained, without the sacrifice of labor and of space economy, no change in the present pile forms would be recommended. However, the adoption of proper methods does not appreciably increase either labor or space. 4. Spacing. "In most seasoning yards, the arms are piled closely together, there being about 28 on each tier. (Fig. 330.) In some cases, however, a partial improvement is made by changing the position of either one arm or two arms at the centre and ends of the tiers, as is shown in Fig. 331. Both of these pile-forms retard the evaporation of the moisture from the wood. In the closest pile the [568] WOOD PRESERVATION Sec. 9 circulation of air is almost entirely shut off, and all evaporation must take place from the ends of the timbers. In case of heavy rain or melting snow the water trickles down over the timber, and the dampness thus promoted, together with even moderate temperatures, stimulates the growth of fungi, while the close contact of the timbers permits a rapid spread of infection. "It often happens, therefore, that where timber is so piled the growth of wood-destroying fungi has reached a serious stage before the timber itself has attained its air-dry condition. Hence it is not uncommon to hear the assertion that the sap-wood of loblolly pine will rot before it can become air-dry. Such an assertion is probably [ 569 ] Sec. 9 WOOD PRESERVATION untrue in every case, and it is certain that loblolly, or any other timber, in a form so well adapted for rapid evaporation of moisture as cross-arms, can be fully seasoned in any part of the country without a risk of deterioration during the seasoning period. By adopting the pile form shown in Fig. 331, a circulation of air is permitted along the sides of the arms. The upper and lower faces are still so closely crowded together than no air current can pass between them. Obviously, the next step is to separate the arms from each other by a space of sufficient size to insure a thorough circulation of the air on all sides of the arms, and yet not so large as to consume unneces- I 570] WOOD PRESERVATION Sec. 9 sary space. When these two requirements are met, the ideal form of pile is attained. "Many experiments have shown that if from 20 to 22 arms are allowed to each tier, and arranged as shown in Fig. 332, most of the desired results will be attained.- This pile, called for convenience the 20-by-20 form, compared with those in general use, gives a sur- prising difference in the rate of seasoning. For example, sap-arms of the July allotment were piled as in Figs. 331 and 332. Those in the 20-by-20 pile dried out to a weight of 34.1 pounds per arm in a little more than six weeks, while more than sixteen weeks elapsed before a like weight was reached by the arms in the figure, or 28-by-28 pile. [571] Sec. 9 WOOD PRESERVATION The only difference in the two piles was in the number of arms to the tier. Had the arms in the 28-by-28 pile been packed closely together, as in Fig. 330, the difference in the rate of seasoning would have been much greater. 5. Roofing. " Under climatic conditions, such as prevail in most r : i parts of the United States throughout the greater portion of the year, it is best to expose the timber directly to the sun and rain. During the Winter months, however, or whenever there is a preva- lence of rain or snow, excellent results will be secured by piling the arms under a roof, without walls, or by constructing a rude roof over [572] WOOD PRESERVATION Sec 9 each pile. This latter method will probably be the cheapest, as it avoids the difficulty of handling the arms in a confined space. If the boards are placed as shown in Fig. 333, the arms below will remain dry during even a heavy rain or snow-storm. Of the two, snow is the more serious, since it generally takes longer to evaporate; and during its slow melting the partially seasoned timber will absorb moisture without giving it off. In all cases, the roofing should extend out over the pile on all sides to protect the ends of the arms, for it is there that the evaporation or absorption of moisture is most rapid. "It is not advisable to attempt to form the roof with the arms [ 573 ] Sec. 9 WOOD PRESERVATION themselves, -as shown in Fig. 334, for three reasons: In the first place, the roof is too short and too narrow to give proper protection to the ends and sides of the pile; in the second place, the exposure of the roof arms to maximum changes of atmospheric condition causes severe checking and warping, with a consequent loss of timber; and, in the third place, considerably more labor is required to handle the greater number of pieces necessary in constructing the roof." Also see Fig. 335 for still another method of cross-arm racking. The length of time necessary to effect sufficient seasoning of either poles or cross-arms decides whether the timber should be cut in the Winter or Spring. Wood that will season to the proper stage in approximately six months can safely be cut in the Spring, while that requiring a longer period should be cut in the Winter so as not to carry the seasoning stock over the late Fall and Winter. This is obvious, as timber cut in the Spring will receive the effect of the hot Summer sun, while the Autumn-cut timber must be held during the Winter months when the seasoning process is at its slowest stage. The United States Forest Service states that no poles should be cut in Summer or early Autumn, as the stumps of poles cut at that time will not give forth vigorous sprouts. Some experiments conducted recently in California by the Government show the following results in regard to seasonal cutting of western yellow pine and western red cedar (Tables 87 and 88). TABLE 87 SEASONING OF WESTERN YELLOW PINE POLES, MADERA COUNTY, CALIFORNIA Month AUTUMN CUT WINTER CUT SPRING CUT SUMMER CUT Weight Cubic Foot Pounds Per Cent of Green Weight Lost Weight per Cubic Foot Pounds Per Cent of Green Weight Lost Weight per Cubic Foot Pounds Per Cent of Green Weight Lost Weight per Cubic Foot Pounds Per Cent of Green Weight Lost October November . December . January. . . February. . March ... . April May June July August September . October.. .. 64.1 54.0 51.3 52.6 54.1 50.4 46.0 41.7 37.6 33.7 30.3 15^8 20.0 17.9 15.6 21.4 28.2 35.0 41.4 47.5 52.7 IM 62.6 56.2 47.7 40.4 36.0 32.8 eio 15.6 28.4 39.3 45.9 50.8 65.2 51.5 44.4 39.8 36.2 32.6 2i!o 31.9 39.0 44.5 50.0 MJ 40.3 33.8 31.8 37i8 47.8 51.0 Average pole "(40 feet) contained 26.1 cubic feet. [574] WOOD PRESERVATION Sec. 9 TABLE 88 SEASONING OF WESTERN RED CEDAR POLES, LOS ANGELES, CALIFORNIA Weight per Cubic Foot Each Month from Time of Cutting.* Month Summer Cut Fall Cut Winter Cut Spring Cut Juiy 42.4f 42Uf ssioj 29.0 26.5 25.5 42.4t S6.12J 28.25 26.30 25.3 42.4t S8.12t 33.0 31.0 29.3 28.0 August October November December 32.5J 31.1 30.0 28.5 26.5 25.0 23.5 23.46 February March April May June July August September October November * The average volume of 300 poles (40 feet 8 inches) was 27.34 cubic feet. tAbsplute green weight. j Weight on arrival at Los Angeles, California, from three to seven months ifter cutting. TABLE 89 RATE OF SEASONING OF CHESTNUT POLES CUT AT DIFFERENT TIMES OF THE YEAR FALL CUT WINTER CUT SPRING CUT SUMMER CUT Time Sea- soned Days Mois- ture Con- tent Per Cent Weight Per Cubic Foot Pounds Mois- ture Con- tent Per Cent Weight Per Cubic Foot Pounds Mois- ture Con- tent Per Cent Weight Per Cubic Foot Pounds Mois- ture Con- tent Per Cent Weight Per Cubic Foot Pounds 30 60 90 120 150 180 210 240 270 300 330 360 85.4 72.0 68.4 66.9 65.8 64.3 62.2 59.2 56.0 53.0 50.8 49.1 47.8 56.4 52.3 51.2 50.7 50.1 49.9 49.3 48.4 47.4 46.5 45.8 45.3 44.9 85.6 77.4 72.6 68.7 64.8 60.6 56.8 53.7 51.2 49.3 56.4 53.9 52.5 51.3 50.1 48.8 47.7 46.7 46.0 45.4 83.0 70.5 64.3 60.0 56.5 53.7 51.7 5.6 51.8 49.9 48.6 47.6 46.7 46.1 84.4 67.9 60.6 57.5 55.9 56.1 51.0 48.8 47.9 47.4 [575] Sec. 9 WOOD PRESERVATION The preceding table taken from Forest Circular No. 147 shows the rate of seasoning of Maryland chestnut poles cut at different times of the year (Table 89). To cover more fully general geographical conditions, the follow- ing, taken from United States Forest Service Circular No. 136 shows the rate of seasoning of Michigan arborvitae poles by seasonal cuts: TABLE 90 WEIGHT AND MOISTURE CONTENT BY SEASONAL CUTS SPRING CUT SUMMER CUT AUTUMN CUT WINTER CUT Mois- Mois- Mois- Mois- ture ture ture ture Time Sea- Con- tent Weight Con- tent Weight Con- tent Weight Con- tent Weight soned Days in Re- lation to Dry Weight Cubic Foot Pounds in Re- lation to Dry Weight per Cubic Foot Pounds in Re- lation to Dry Weight Cubic Foot Pounds in Re- lation to Dry Weight per Cubic Foot Pounds Per Per Per Per Cent Cent Cent Cent 77.4 31.9 81.7 32.7 79.0 32.2 90.0 34.2 30 53.8 27.7 61.4 29.1 79.0 32.2 90.0 34.2 60 49.7 26.9 51.9 27.3 79.0 32.2 90.0 34.2 90 48.4 26. 49.1 26. 79.0 32.2 86.4 33.6 120 48.3 26. 49.0 26. 79.0 32.2 53.0 27.5 150 48.3 26. 49.0 26. 77.2 31.9 42.3 25.6 180 48.3 26. 49.0 26. 43.0 25.7 37.5 24.8 210 48.3 26. 49.0 26. 33.2 24.0 34.3 24.2 240 48.3 26.7 48.0 26.6 29.0 23.2 270 48.3 26.7 40.5 25.3 27.2 22.9 300 48.3 26.7 35.7 24.4 330 44.2 26.0 32.9 23.9 360 36.0 24.5 30.7 23.5 390 33.7 24.1 420 32.3 23.8 The following tables were taken from Forest Service Circular No. 151. They show the green weight according to the season when cut and the comparative rates of seasoning of North Carolina loblolly pine, heart-wood, sap-wood and intermediate grade cross- arms (Tables 91 and 92) : TABJLE 91 COMPARATIVE WEIGHTS OF GREEN NORTH CAROLINA LOBLOLLY PINE WEIGHT PER CUBIC FOOT Portion of Tree Autumn Pounds Spring Pounds Summer Pounds Winter Pounds 42.4 48.8 55.6 42.6 49.9 57.4 45.1 50.2 57.4 45.5 51.1 58.2 Intermediate Sap-wood t 576 ] WOOD PRESERVATION Sec. 9 TABLE 92 COMPARATIVE RATES OF SEASONING OF LOBLOLLY PINE HEART-WOOD, SAPWOOD AND INTERMEDIATE CROSSARMS Days Sea- soned HEART-WOOD SAP-WOOD INTERMEDIATE Weight Per Arm Pounds Weight Per Cubic Foot Pounds Mois- ture Con- tent Per Cent Weight Per Arm Pounds Weight Per Cubic Foot Pounds Mois- ture Con- tent Per Cent Weight Per Arm Pounds Weight Per Cubic Foot Pounds Mois- ture Con- tent "Per Cent 30 60 90 120 150 180 38.8 34.2 33.9 34.3 34.2 33.9 33.6 42.6 37.6 37.3 37.3 37.6 37.3 36.9 51.5 33.4 32.5 33.8 33.7 32.3 31.2 52.7 34.5 32.6 32.6 32.5 32.1 31.6 57.9 37.9 35.8 35.8 35.7 35.3 34.7 105.8 34.8 27.2 27.3 26.9 25.4 23.6 45.8 34.3 33.3 33.4 33.4 33.0 32.5 50.3 37.7 36.6 36.7 36.7 36.3 35.7 79.0 34.0 30.0 30.3 30.3 29.0 26.9 The foregoing Government tests conducted in California on western yellow pine and western red cedar would indicate that the yellow pine should be air-dry and ready for preservative treatment when it had lost 50 per cent of its original weight, and that the red cedar should lose 40 per cent of its original weight before treating. Chestnut poles should be ready to set or to receive brush treatment when they have lost about 15 per cent of their original weight. According to Forest Service Circular No. 136, the air-dry weight of arborvitae should be about 73 per cent of the green weight, or a loss of 27 per cent of its original weight. The above data are given to illustrate the seasoning character- istics of some of the more representative types of wood. The Government tests cited were selected because of their undoubted accuracy. 6. Summary on Seasoning.* 1. Poles should be cut from sound standing timber. , 2. The bark should be well peeled from poles which are to be seasoned, and particularly from those that are to be treated, as the inner bark offers much resistance to the impregnating fluid, and in time this bark peels, leaving the untreated wood exposed to the attack of fungi. 3. Care should be taken in the handling and felling of trees, as those which are split in felling, or are otherwise roughly handled, may afterwards experience serious checking. * For further data, see Bulletin No. 84 of the Forestry Service. 19 [ 577 ] Sec. 9 WOOD PRESERVATION 4. Poles and crossarms should be properly piled and stored, and as soon after cutting as possible. 5. The amount of shrinkage during seasoning is negligible. 6. Poles cut in the Winter or Spring have before them the best period for seasoning, but late Fall and Winter offer the best con- ditions for cutting. 7. Attention should be paid to the value of having wood seasoned where cut, as a material freight-saving may often be made in this way. FIG. 336. Portion of stem of four-j ear-old pine, Pinus Sylvestris, cut in winter, (q) , transverse view ; (1) , radial view ; (t) , tangential view ; (f ) , early wood ; (s) , late wood ; (m) , medulla; (p) , protoxylem ; (1, 2, 3, 4) , the four successive annular rings of the wood; (i) , junction of the wood of successive years; (me, ma', ms'") , medul- lary rays in transverse, radial, and tangential views; (ms") radial view of medullary rays in the bast ; (c) , cambium ting ; (b) , bast ; (h) , resin canals ; (br) , bark. PRESERVATIVES 7. General. In order to understand the physical and chemical action of preservatives in preventing or retarding decay, it will be necessary to consider somewhat the structure of wood, the nature of the phenomena which take place when decay sets in, and the causes underlying the coincident physical and chemical changes in the wood structure resulting finally in its more or less complete destruction. 8. Structure of Wood. From a chemical standpoint, the pre- dominating material which enters into the composition of wood is [ 578 ] WOOD PRESERVATION Sec. 9 cellulose. The other non-cellulose materials present are known as the lignone complex. The latter includes resins, gums, coniferine, tannin, etc. Physically, wood is made up of small organs resembling honeycombs in appearance, but much smaller. (Fig. 339.) These organs are known as wood-cells. They are surrounded by distinct stiff walls and are thus sharply separated from one another. The FIG. 337. Tangential section of the late wood of pine, (t), Bordered pit; (tm), tracheidal medullary ray cells; (sm), medullary ray cells containing starch; (et) , bordered pit only on one side ; (i) , intercellular space in the medullary ray. canals from adjoining cells constantly meet and are sometimes widened at their base into bordered pits (Fig. 337). The most im- portant constituent of these cell-walls is cellulose. It is present in the cell-walls of most plants, except the fungi. The cell-wall is a product of protoplasm, and it never consists of cellulose alone, but contains a considerable amount of other substances which are not of a cellulose character. Lignification (stiffening of the cell-walls) is brought about by the deposition of coneferine, vanillin, and other materials in the cell- wall. After lignification, cell-walls are permeable to water and gases. However, if cutin is subsequently deposited in the cell-walls, [579] Sec. 9 WOOD PRESERVATION which have already been lignified, they are rendered impervious to gases and to water. While the cells of woods vary to some extent, those which are provided with bordered pits and are not sharpened at the ends are spoken of as tracheids (Fig. 338). These contain water, acting as water-carriers for the tree. When they become inactive they are full of air. It must be remembered that these tracheids are extremely small. Tissues result from an intimate union of an aggregation of cells. These cells may fit closely to- FIG. 338. (t), Tracheid having large bordered pits which act as water carrier; (gt), vascular tracheids with similar functions, but with the structure and thickenings of vessels; (ft), fibre tracheids with small luinina and pointed ends, having only small, obliquely elongated bordered pits, and, in extreme cases, exercising merely mechanical functions; (g), tracheae, formed by cell fusion, and provided with all the different forms of thickenings by which they are dis- tinguished as annular, spiral, reticulate, or pitted vessels. All vessels function as water carriers. If they have small lumina and resemble tracheids they may be distinguished as tracheidal vessels. gether, thus leaving no openings or intercellular spaces between them. In case the cells are not so closely fitted together, inter- cellular spaces result (Fig. 337). By reason of variations in climatic conditions, the woody tissue *Figs. 336, 337 and 338 reproduced from "A Textbook of Botany," by Stras- burger and others. fFigs. 339, 340 and 341 taken from Bulletin No. 1 of the Division of Forestry. [580] WOOD PRESERVATION Sec. 9 exhibits variation in size and extent of growth, and it is in conse- quence of such variations that annular rings result (Fig. 336) . During the Spring, when energetic growth takes place, larger trachial ele- . 339. Pinus Palustris, Miller; Long-leaved Pine Transverse Section. [581] Sec. 9 WOOD PRESERVATION ments are developed than during the Fall and Winter season. A difference is therefore noticed between Spring wood, which is made up of very large tracheids, and Autumn wood, which consists of narrow ones. It must be remembered that the tissue, which is " condition, composed content. 9. Sap-wood is composed of cells which go to make the more recent annular rings. These cells are living organisms and act as water-carriers of the tree (Fig. 338). Before these living cells die and enter into the formation of dead tissues they produce certain IiariOW UllcH. J.U IHUBU uc iciiicniucicu. oiiau made up of tracheids, is, in its fully developed of dead-cell cavities devoid of any living conte] suostances, such as gums and tannins, which penetrate the cell-walls and also close, or partly close, the cavities. These tannins are said to prevent the decay of the wood, while the gums are supposed to close the cells and thus end their f unction _as water-carriers. These tissues, composed of dead cells which are impermeable to water, go to make up heart-wood. It will be readily seen why heart-wood is so resistant to decay and why it is almost impossible to penetrate it by means of impregnating materials. Heart-wood can usually be distinguished from sap-wood by its darker color, indicative of the presence of gums or tannins. In some trees, notably the willow, [ 582 ] WOOD PRESERVATION Sec. 9 these protective materials are absent, and the heart of willow trees is, in consequence, usually decayed, finally becoming hollow. 10. Decay is the change which takes place under the influence of certain agents, resulting in the decomposition or breaking-down of complex into simpler bodies. The decay of wood is generally due to the activities of certain low forms of plant life known as fungi. Bacteria are also known to cause decay, but their action is little understood, and in order to illustrate the manner in which these organisms promote decay a description of the fungi will suffice. These plants have their origin in minute spores borne from place 1 1 I I M . 1 hi li M LUIIi FIG. 341. to place by the wind. Those that lodge and find a suitable situation for growth, which may be on living or dead timber, germinate, provided the conditions are favorable, and at once attack the wood, drawing their sustenance partly from the atmosphere and partly from the contents of the wood-cells; and they finally attack the cell-walls, resulting in the breaking up of the complex chemical substances and the liberation of various gases; the result being the reduction of the wood into a mass having little or no resemblance to the original material. [ 583 ] Sec. 9 WOOD PRESERVATION FIG. 342. Tracheid of Pinus sylvestris, decomposed by Trametes Pini. The prkaary cell-wall has been completely dissolved as far as a a. In the lower part the secondary and tertiary layers consist only of the cellulose, in which lime- granules are distinctly visible, b; filamentous mycelia, c, penetrate the walls and make holes as at d and e. [584] WOOD PRESERVATION Sec. 9 The action of the various forms of fungi is quite similar. They grow with great rapidity, sending out numerous threads which penetrate into the wood and attack the contents of the cells the sugars, starches and oils and finally the cell-walls. These thread- like bodies are called hyphae, and aggregations of them form the mycelium. In Fig. 341 will be seen the filamentous mycelia of the Trametes Pini. The gradual decomposition of wood by these fungi is shown in Fig. 342. When sufficient food has been absorbed, the hyphae form a fruiting body (Fig. 343 and Fig. 344) which bears a crop of spores, which in turn again produce the mycelium of decay. Familiar instances of these fruiting bodies are the punks and toad- stools seen on decaying wood. The most favorable conditions for the growth of fungi and other organisms of decay are an abundant food supply, heat, moisture, and air, the amount of each required being dependent upon the kind of organism. A certain amount of moisture must be present or decay cannot set in. Air is also es- sential, and thus may be explained the lasting qualities of wood when kept perfectly dry, and the perfect state of preservation of wood which has been under water for long periods; moisture being lacking in the first case and air in the second. Again, if the wood is rendered unfit for use by an antiseptic* or is protected by a ger- micide, it will not decay. A familiar example, serving well to illustrate the foregoing, is the rotting of fence-posts and telephone, telegraph, and other poles in the zone extending from just below to just above the ground line. At the base of the pole, while moisture id present, air is excluded, while above the ground the pole is generally dry. It is where moisture and air are both present, the former being drawn by capillary attraction from the ground, that decay begins. Before considering the action of preservatives, it may be well to emphasize these axioms: Decay is induced by the action of living organisms. Moisture, air, food, and a certain amount of heat are absolutely necessary for the growth of these organisms. Perfectly dry wood will not decay. Wood kept under water will not decay. Wood saturated with a substance which will act as a germicide will not decay. Wood saturated with a substance which will act as an antiseptic will not decay. 11. PRESERVATIVE AGENTS. A theoretical consideration of the conditions under which decay may start suggests the remedy in the introduction into the wood of some substance which will act as an antiseptic or a germicide, or prevent the entrance of moisture or air. Materials that have been found to possess one or more of these desirable qualities may be classified under two general headings *An antiseptic here is understood to be any substance which will inhibit the growth of fungi, while germicides are understood to be substances which are active poisons to these growths. [ 585 ] Sec. 9 WOOD PRESERVATION oils and salts. The most important of the oils are coal-tar creosote or dead oil of coal-tar, coal-tar anthracene oil, water-gas tar dead oil, and other heavy fractions therefrom, petroleum and petroleum residues, and wood creosote. Of the salts, zinc chloride, mercuric chloride, and copper sulphate are the most extensively used. It is generally believed that all of these substances are capable of insuring one or more of the conditions necessary to prevent decay, provided, always, that the wood remains saturated with the pre- servative. The chief difficulty is encountered when it is required to decide upon the extent of treatment necessary to insure the desired length of life, it being obviously inadvisable to preserve the timber beyond its mechanical life. This consideration, however, is much more important in treating railroad ties than in treating poles and cross-arms, for the reason that the latter are subject to little mechanical wear. Another important consideration is the kind of preservative best suited for a particular situation. Climatic and soil conditions, in some situations, make it inadvisable to use a preservative which, in another situation, would prove perfectly satisfactory. For example, in certain sections of the country where there is a great amount of rainfall, zinc chloride treatments are likely to prove inefficient on account of the lacing out of the soluble zinc chloride. On the other hand, there are many situations where it could be used to advantage both in respect to cheapness and efficiency. These are important economic considerations, and the various processes which have been evolved, some employing antiseptics, others germicides, and still others offering only mechanical protec- tion against the entrance of moisture or air or both, result from the desire to obtain the maximum protection with a minimum expendi- ture of time and money. It may be well here to state that, as a rule, the more of the pre- servative injected per cubic foot the greater the life of the timber is likely to be. It may be, and probably is true, in a great many instances, that the employment of a small amount of preservative, whether by shallow penetration, as in the open tank and brush treatments, or by the withdrawal of a portion of it after it is placed in the wood, as in the empty cell processes, or by its loss by evapora- tion or solution, will furnish a sufficient amount of protection. However, where long protection is of paramount importance, deep full-cell penetrations are undoubtedly the best. 12. Preservation with Oils. Whatever difference of opinion may exist in the minds of those interested in the subject as to the relative merits of other preservatives, one and all agree that coal-tar creosote oil, when properly applied, will protect timber against decay for an indefinite period, usually far in excess of its mechanical life, and it is therefore regarded as the ideal preservative and a standard by which all others must be gauged. The reason for this is due primarily to the fact that time, the all-important factor in the field of wood preservation, has demonstrated its value under most variable and trying conditions. There are numerous 'well-authenticated in- [ 586] WOOD PRESERVATION Sec. 9 stances of timber being preserved by creosote oil for periods of time, in some cases amounting to 30 or even 40 years; a notable example being a Baltic redwood tie removed from the tracks of the Glasgow and Southwestern Railway, in Scotland, in a perfect state of pres- ervation after 42 years of service. There still remained in the tie over 12 pounds of creosote oil per cubic foot. While it is probable that the controlling factor governing the first use of this oil was that it could be obtained in large quantities at a reasonable cost, theoretical considerations to-day, based on our more advanced knowledge of the causes underlying decay, indicate that the chemical and physical characteristics possessed by coal-tar creosote oil make it well worthy of the high esteem in which it is held, and places beyond the bounds of probability any suggestion that the long life of timber treated with this preservative may have been due to other causes. 13. Coal-Tar Creosote. Owing to its importance in timber pres- ervation, as well as to illustrate the relation existing between it and other oils now being used for this purpose, a more or less detailed description of the manner in which it is produced may not be out of place. In the manufacture of illuminating gas, by the destructive dis- tillation of coal in closed vessels, coal-tar is produced as a by-product. It is also produced as a by-product in the operation of retort coke ovens. The difference in the physical characteristics of the tars produced in the two operations is so slight that one may easily be mistaken for the other, and chemically they are identical, containing the same constituents, but in somewhat different proportions. At gas works, the coal is carbonized in externally heated fire-clay retorts capable of working off a charge of from three to four hundred pounds of coal every four hours, while at by-product coke ovens the charge amounts to several tons, and the duration of the carbon- izing period may be from 18 to 30 hours. This difference in method of carbonization has some influence, as stated above, on the quality of the tar, and therefore on the oils distilled therefrom. Bituminous coal containing a considerable amount of volatile matter is used in these operations. That used in the manufacture of gas by the retort method may contain as much as 35 to 40 per cent, while that used in coke ovens usually contains somewhat less. The residue remaining in the retort or oven, as the case may be, constitutes coke. It is from the volatile matter which is driven off that illuminating gas and tar are produced. This volatile matter consists of permanent gases, such as ethylene and its homologues, hydrogen, marsh gas, carbon monoxide, oxygen, nitrogen, etc., which carry in suspension vapors of various other hydrocarbons, whose boiling points cover a considerable temperature range. A slight reduction in the temperature of the carrying gas causes a partial precipitation of the suspended hydrocarbons, and since a gas which will be suitable for illuminating purposes must be permanent under ordinary conditions, it is necessary to free it more [ 587 ] Sec. 9 WOOD PRESERVATION or less completely of suspended matter. The readiness with which the hydrocarbon vapors precipitate upon even a slight reduction in temperature is taken advantage of to free the gas of their presence, the operation being assisted by the use of condensers and scrubbers. The condensed liquid is known as coal-tar. A. chemical examination of coal-tar shows it to be largely made up of hydrocarbons of the closed ring or aromatic series, prominent among them being benzol, toluol, xylol, naphthalene, carbolic acid, anthracene, etc., which have been formed by the high heat to which the coal has been subjected. If the coal is carbonized at a low heat, the character of the hydrocarbons is much changed. In this case, [ 588 ] WOOD PRESERVATION Sec. 9 the paraffin series, such as occur in petroleum oils, will be present in considerable quantities. It should be borne in mind that the hydrocarbons found in coal- tar do not exist in the coal as such, but are formed by breaking down and polymerization of other hydrocarbons, notably of the paraffin series. To quote a well-known authority, "The hydrocarbons produced by the use of a comparatively low temperature are mostly paraffins (hydrocarbons of the methane series) with some defines. At a higher temperature the paraffins, except methane, disappear, and are replaced by olefines ethylene, propylene and butylene. At a still higher temperature acetylene appears, accompanied by [589] Sec. 9 WOOD PRESERVATION benzene, CeHe. These are followed by naphthalene, Cio H 8 , chrysene, pyrene, diphenyl, etc." At one time coal-tar was a waste product, in fact its accumulation created a nuisance with which it was for a long while difficult to cope. The discovery, however, by Sir William Perkin, that some of its, constituents could be used as bases for very valuable dyes opened up a field which has developed along this and other lines to such an extent that tar distillation has become an important industry, and there are at the present time few, if any, compounds obtainable from coal-tar that are not commercially valuable. It is customary in the first distillation of coal-tar, which is carried out in externally fired stills, varying in capacity from a few hundred to several thousand gallons, to make a preliminary more or less crude separation of the volatile portions of the tar into several fractions. The first, or light oil fraction, constitutes the raw material from which are obtained benzol, toluol, and solvent naphtha. This cut is made at about 170 degrees Centigrade (338 degrees Fahren- heit). A second cut at about 230 degrees Centigrade (446 degrees Fahrenheit) includes the middle oils, which contain a large portion of the tar acids and naphthalene. A third cut at 270 degrees Centi- grade (518 degrees Fahrenheit) includes creosote oil. The residue remaining in the still may be hard or soft pitch, depending upon the extent to which the heavier fractions are removed . If the distillation is carried to hard pitch, heavy anthracene oils are recovered after the creosote oils. The accompanying diagram graphically illustrates the position which creosote oil bears to the other products obtainable from coal-tar. Benzol Coal-tar Light oil Middle oil Creosote oil Anthracene oil Pitch Toluol Naphthas Carbolic oils (tar acids) Naphthalene Commercial Creosote Since creosote oil is a mixture of various oils it is not, even under the best conditions, of invariable quality, and under conditions usually met with a uniform grade is difficult to obtain at a price which would not be prohibitive. There are several reasons for this. In the first place, the carbonization of different kinds of coal will affect, to a certain extent, the character of the tar and necessarily, therefore, of the oils distilled therefrom. Then it is the practice of some tar distillers to carry the distillation farther than others, e. g., it is the usual practice abroad to make hard pitch, which means that there will be relatively more of the high-boiling anthracene fractions left in the creosote oil than when soft pitch is made, as is the usual practice of American tar distillers. Another factor operating against uniformity is that creosote oil usually commands the lowest price of the oils produced in a tar distilling plant, and it is customary, [ 590 ] WOOD PRESERVATION Sec. 9 therefore, to extract from the heavy oil fraction the products which, at the time, are more valuable than creosote. It may happen that the demand for naphthalene is slight, and therefore the price which can be obtained for it low. At such times it is usually left in the creosote oil and sold for wood preservation. When the market for naphthalene changes for the better it may be recovered, with the attendant change in the composition of the creosote oil. It is a common practice, also, to run residues and other oils of relatively low value into the creosote oil tank; in other words, it is the re- ceptacle for the low-grade oils produced by the plant. In spite of this, the preservative value of the oil is such that ample protection against decay has been procured when a sufficient quantity of the oil was injected. Owing to the steadily growing progress being made in the art of wood preservation with the increasing knowledge of what constitutes the best grade of creosote oil, large consumers are now purchasing under specifications, with the object in view of eliminating that portion of the oil which will be lost by volatiliza- tion or solution, either during the process of treatment of the timber or after it is placed in service, and of insuring in the oil the amounts of those constituents which they deem most suitable for their par- ticular purpose. Opinions differ greatly as to which are the most important constituents of creosote oil. There are some who main- tain that the tar acids, which are germicides, are the most important constituents. Others contend that naphthalene is the most valu- able, attributing its efficiency to its antiseptic qualities or to its crystallization in the pores of the wood, preventing entrance of moisture and keeping in the lighter portions of the oil. Still others claim that it is the heavy anthracene oil fractions that are of the most value, these oils losing little by volatilization and solution, and effectively excluding moisture and air. Antiseptic powers are also claimed for them by many. Considerable light has recently been thrown on this subject by the Forestry Service.* Some forty specimens of creosoted timber that had successfully resisted decay for from 10 to 40 years were examined, and it was found, in every instance, that the tar acids had either disappeared entirely or been reduced to less than 1 per cent, and that the constituents of the oil which had remained in the timber represented the naphthalene, anthracene, and other high- boiling fractions. The value of such oils is now generally conceded, but their high price restricts their application for full-cell treatments. These high-boiling oils constitute in whole, or in part, many of the well- known high-priced preservatives. When such oils are once gotten into the wood there is little chance of loss by volatilization, and for this reason their value is greater than that of the ordinary grades of coal-tar creosote. Such high gravity oils have their application in brush and dipping treatments referred to in another portion of this report, * Bulletin No. 98. [591] Sec. 9 WOOD PRESERVATION Authorities are now generally agreed that the value of light oils and tar acids is of minor importance compared with the heavy fractions. It is perhaps safe to say that those oils coming off below 205 degrees Centigrade (401 degrees Fahrenheit), when distilled by one or other of the standard methods commonly employed in this country in which the thermometer indicates the temperature of the vapor, will be lost, either during treatment or after the timber is put into service. 14. Water-Gas Tar Creosote. While the value of other oils for wood preservation is not so well established as that of coal-tar creosote, owing to the fact that time alone can furnish absolute proof, theoretical and other considerations point to the fact that oils distilled from water-gas tar may be of equal value. If such is the case, it will do much to relieve the difficulty in securing suitable oils, since two-thirds of the gas used for illuminating purposes in the United States at the present time is water-gas, and about 75,000,000 gallons of tar are made as a by-product of its manufacture. On account of the well-known preservative value of coal-tar creosote and its relatively higher cost, oils of other origin are generally looked upon as adulterants, and while the preservative value of the coal-tar creosote may not have been lessened by the admixture, the practice constitutes a fraud if the material is sold as straight coal-tar creosote. In Bulletin No. 78 of the Forest Service, the following statement is made: "Petroleum-tar creosote is already used in large quantities, most of it being sold not under its own name but as an adulterant of coal-tar creosote. It contains some of the most important constituents of coal-tar creosote as well as those of the paraffin series. Its analysis by fractional distillation is sometimes identical with that of the coal- tar product, and it is probable that after injection into timber it would show no more rapid volatilization." In this Bulletin no distinction is made between water-gas tar creosote and creosote produced from tars formed in the process of making oil-gas as in the Pintsch or the straight oil-gas systems, although the chemical constitution of tars produced in making oil- gas is quite different. Since, however, very little of this tar is made, the reference is undoubtedly to water-gas tar. The manner in which water-gas tar is produced from petroleum, explains its striking similarity to coal-tar. In this process "blue gas, " which consists of a mixture of carbon monoxide and hydrogen, obtained by passing steam through a bed of incandescent coal or coke, is passed into a chamber containing checker brick heated to a high temperature. There it is carburetted by the oil-gas resulting from the cracking up of petroleum oil which is fed into the chamber. Thence the carburetted gas is passed into a second chamber similarly constructed, and there subjected to further heat, which more or less completely finishes the transformation of the paraffin hydrocarbons contained in the petroleum oil into hydrocarbons of the closed ring or aromatic series similar to those found in coal-tar. Naphthalene [592] WOOD PRESERVATION Sec. 9 and all other compounds, except the oxygenated "tar acids," are produced; the production of these latter being prevented probably by the reducing effect of the carbon monoxide and hydrogen present in the "blue gas." If the heat is sufficiently high and the contact with the checker brick sufficiently prolonged, there will be practically no uncracked paraffin oil in the tar, and this is likely to be the case in the best operated works, because the presence there of un- cracked oil means inefficient and uneconomical operation of the machines. Water-gas tar is now employed in the production of benzol, toluol, solvent naphtha, naphthalene, and other similar compounds here- tofore obtained almost exclusively from coal-tar; and exhaustive examinations of the high-boiling fractions reveal the presence of methyl and dimethyl anthracene, phenanthrene, and other con- stituents found in coal-tar. Owing to the absence of tar acids, it is impossible to say, at the present time, whether the oil is a germicide. It is an antiseptic, and there is not the least doubt that there may be procured from it an oil of high gravity which should remain in the wood-cells indefinitely. Such being the case, its value should be equal to that of coal-tar creosote. Owing to the comparatively short time in which this oil has been on the market, the only well-authenticated test is of but three years' duration. In this instance it was placed in comparison with coal-tar creosote and zinc chloride in the Silver Creek Colliery of the Phila- delphia and Reading Coal and Iron Company, being used in protect- ing mine timbers. At the present time there appears to be no difference in the results of the three treatments, all of the timbers being perfectly sound, while the untreated timber was completely destroyed in 15 months. The following statement in a recent article written for the Forest Service is also of interest in connection with this oil: "It is from the distillation of water-gas tar, under certain rather rigid conditions, that consumers of creosote in this country will have to look for increased supplies. Providing that such creosote is distilled from a tar produced in the manufacture of illuminating gas by the Lowe or similar process, and from crude oils containing as- phalt base, and provided that the proper fraction is collected on distillation, it very closely approximates a straight run coal-tar creosote. The main difference is the almost complete absence of phenol, cresols, or homologous 'tar acids.' The naphthalene content of either coal-tar creosote or water-gas dead oil, distilled under similar conditions, is generally about equal, so that where (as some specifications demand) this product is required, and the content of tar acids not considered of importance, either oil is valu- able provided the specific gravity is sufficiently high and distillation results satisfactory." Since no tar acids can be recovered from water-gas tar oils, it is possible to obtain a much more uniform creosote oil from this tar than from coal-tar, and where a distillation is carried to coke, as is sometimes done, straight run oil may be obtained of any gravity [ 593 ] Sec. 9 WOOD PRESERVATION between 1 and 1.12 and within such distillation limits as to preclude the possibility of loss by evaporation. 15. Petroleum Oil. It appears from the success met with on the Gulf, Colorado & Santa Fe Railroad, in using crude petroleum for protecting railroad ties against decay, that this oil may be of great value in wood preservation. A test was started in 1902, and the ties treated with Bakersfield oil, to the extent of 23 to 82 pounds per tie, are still in a good state of preservation. The Santa Fe Railroad is now operating a tie-treating plant using this material. It is probable that the oil has no germicidal action and that its value is dependent upon the protection offered against entrance of moisture. 16. Wood Creosote. The use of wood creosote for timber pres- ervation is very limited, and the results that have been obtained are of uncertain value, owing to the fact that in the majority of cases it was applied by the brush or dipping process and very few records have been kept. A test started in 1905 by the United States Forest Service, in the treatment of telephone poles, employed wood creosote as one of the preservatives. Sufficient time has not elapsed, however, to make any definite statements with reference to its probable value. It is possible, however, that if it is injected into the wood in sufficient quantities it will offer adequate protection. Its high cost, accom- panied with its unknown value as a preservative, will, however, restrict its use. The table on following page will show, at a glance, the chief difference between coal-tar creosote, water-gas tar creosote, wood creosote, petroleum-tar oil and petroleum oil. (Table 93.) 17. Preservation with Salts. The comparatively small use being made of salts in the treatment of poles and cross-arms renders it un- necessary to describe these preservatives at this time, particularly so since, being perfectly definite chemical compounds, a description of them may be obtained from any chemical dictionary or work on inorganic chemistry. 18. Summary on Preservatives. The choice of the proper pre- servative is dependent, in a great measure, upon local conditions. Full-cell treatments, with a high-grade creosote oil, will insure the maximum protection, but it is by no means uncertain that full-cell treatments with petroleum oil or other heavy oils will not offer an equal amount of protection. The chief danger in employing such oil would lie in not using it in quantities sufficient to keep out moisture or air. It would seem that an entirely satisfactory oil, having antiseptic qualities, can be obtained from the distillation of water-gas tar, and as this material may be readily obtained, its general use would do much toward solving the difficulty of obtaining suitable oils at a reasonable cost. While from a theoretical standpoint the use of metallic salts cannot be recommended for poles and cross-arms on account of [594] WOOD PRESERVATION Sec. 9 55 9 ~ . is "8 |g 5 : sr-tslSfl s! lifflNbi' 1 !! !8*ipj'di o o ^ o 02 a ;I^Bliilli!lP s l -S-^<*-C!< O^ +J o3 +J KL'- : '2a>(H -S n 3 n E7*i tL+J '"C^oO.tinlop-y 5 jao-^'-Pcs^Xei . m^-^b^SJ^aj t 595 ] Sec. 9 WOOD PRESERVATION their solubility, still, in view of the exceptional results obtained in Germany by the use of copper sulphate and mercuric chloride, it is impossible to say that these cannot, at times, be used to great advantage. It is recommended, however, when salt treatments are employed, that they be protected against leaching by creosote or some such similar method, and also that due caution be exercised in choosing this method of treatment. Since much of the treating which will be done for the members of the National Electric Light Association is likely to be by the open-tank process, special attention should be paid to specifications covering suitable oils, it being remembered that a large part of the oil distilling under 200 degrees Centigrade is likely to be lost by volatilization during the process of treatment, thus greatly increasing the cost. The oil to be used in the open tank should constitute the higher boiling portions of the tar. PROCESSES 19. General. There are several causes underlying the rapid development which has resulted in the modern, highly efficient processes for impregnating timber with preservatives. The most important, perhaps, was the early recognition of the fact that, however great might be the value of a preservative in retarding or preventing decay, from a theoretical standpoint, its practical ef- ficiency was likely to be largely dependent upon the extent to which it was driven into the timber. For this reason, the early methods of steeping the timber in the cold preservative contained in an open tank or vat was soon almost entirely superseded by processes in- suring deeper penetration. Another important factor underlying this development was the growing demand made upon commercial plants for treated timber, coincident with the recognition of the great economic value of timber preservation and the urgent necessity for husbanding the diminishing supply of timber suitable for rail- road and other purposes. As in other branches of business, increased demand on the part of the consumer resulted in increased effort on the part of the treating plants to turn out a maximum amount of satisfactory work in the shortest possible time, while reducing the cost to a minimum. The greatest aid in the achievement of this end has been the employment of artificial pressure in injecting the fluid, it being found that by its use deep penetration could be gotten in a comparatively short time. Owing to the heavy cost of installing high-pressure systems, however, there are comparatively few privately operated plants in the United States, and for this reason the small consumer of treated timber must either purchase from the large commercial plants, often so remote as to make the cost almost or quite prohibitive, or treat locally by a less costly process. To meet the demands of this class, as well as of those who desire only a moderate protection at a small cost, the United States Forest Service has devoted considerable time to the development of the open-tank or low-pressure system, and has brought its efficiency to such a degree that in many instances [596] WOOD PRESERVATION Sec. 9 it is possible to obtain adequate protection at a very low cost. Such plants can usually be operated by unskilled labor, require no ex- pensive apparatus, and involve a very small initial investment. All processes for treating timber may be considered under three heads high artificial pressure systems, the atmospheric pressure systems, and the low artificial pressure systems; the first including most of the commercial plants, the second and third, the small individual plants. The following table contains a classification of the most important systems, which are described in more or less detail further on. Some of them cannot be recommended for the treatment of poles or cross- arms, but it is felt that the whole field should be reviewed as a matter of general interest: Bethell High Artificial Pressure Systems Atmospheric Pressure Sys- tem . . Low Artificial Systems Pressure Full Cell Empty Cell Full Cell Empty Cell Full Cell Empty Cell Burnett Wellhouse Rutgers Card Allardyce Ruping Lowry Steeping in cold preservatives Steeping in hot preservatives Alternate hot and cold treatments Hot, cold and hot treatments Hot and graded cooling treatment 20. HIGH ARTIFICIAL PRESSURE PROCESSES. High-pres- sure processes may be either full cell or empty cell, depending upon whether or not the full amount of preservative injected into the tim- ber is left in the cells or a portion subsequently withdrawn. The advocates of the full-cell treatments claim that unless the full amount of the preservative is left in the timber, sufficient protection against decay will not be afforded; while the advocates of the empty-cell treatments claim that, provided the penetration is deep, it is only necessary to leave a thin coating of the preservative on the cell- walls. Obviously, empty-cell treatments result in considerable economy of the preservative. The most prominent of the full-cell processes are the Burnett, Card, Allardyce, Wellhouse, and Rutgers. Of the empty-cell processes, the Ruping and Lowry are the best known. 21. Full-cell Treatments. Bethell. The best known of all pre- servative systems is the full-cell Bethell, employing straight creosote as the preservative. In operating the Bethell process, the timber to be treated is loaded upon trucks and run into a cylinder capable of withstanding a high pressure. These cylinders, or retorts, as they are now called, are sometimes as much as nine feet in diameter [597] Sec. 9 WOOD PRESERVATION and 165 feet long. They are made of boiler plate and are provided with doors which may be hermetically sealed and are tight under a high pressure. For light treatment, the timber may be only air seasoned, but when a heavy treatment is desired the timber is steamed after it is put into the cylinder. The method of operation is as follows: After the doors are closed, live steam is admitted and a pressure of about 20 pounds per square inch is maintained for several hours, the exact time depending upon the individual opinion of the operator as well as upon the moisture-content and the size of the timber being treated. In some cases the steam pressure is allowed to go con- [ 598 ] WOOD PRESERVATION Sec. 9 siderably above 20 pounds, but much above this there is constant danger of injuring the timber. When the steam is finally blown put of the cylinder, a vacuum is created and as much of the air as possible is exhausted from the cylinder and from the wood structure. The condensed steam and sap from the wood are drawn off at the same time. The exhaustion period varies with the extent of the treatment. Finally, after a sufficient vacuum is obtained, the creosote oil is run into the cylinder and the pressure pumps are started and continued until the desired amount of preservative fluid has been injected. The remaining oil is then forced back into the storage tanks. The timber is allowed to drip for a few minutes and finally the cylinder [599] Sec. 9 WOOD PRESERVATION doors are opened and the treated timber withdrawn. The whole cycle of operation takes from six to twenty hours, depending upon the condition and kind of timber, size of treating cylinder, quantity of injection, etc. As a rule, it requires about three and one-half hours for steaming, about one hour for vacuum and whatever time it may be necessary to get the required injection. Figs. 345 and 346, show two views of pressure treating cylinders. 22. Burnett. The Burnett process is similar to the Bethell, but, instead of using creosote as the preservative, it employs a two to three per cent solution of zinc chloride, which is injected into the timber under pressure in the same way. The use of zinc chloride, or "Burnettizing," for treating railroad ties dates from 1850. 23. Wellhouse. The users of the Wellhouse process claim to have overcome the chief objection to the Burnett system; namely, the solubility of the zinc chloride and the consequent danger of its being dissolved out of the timber when it is put into use. To pre- vent this the zinc chloride treatment is followed by an injection of glue and tannin, which forms an insoluble "leather" stopping up the wood pores. 24. Rutgers. This is another method of preventing the leaching of the zinc chloride. A mixture of zinc chloride and creosote is em- ployed consisting of from fifteen to twenty per cent creosote and a three to four per cent solution of zinc chloride. The emulsion is forced into the timbers, as in the Burnettizing and Bethell processes* This system is extensively used in Europe, and to some extent in this country. 25. Card. This process substitutes creosote oil for the glue and tannin of the Wellhouse process, it being claimed that the oil is effective in preventing the zinc chloride from being dissolved out. The chief difference between this process and the Rutgers is that dur- ing the time of injecting the liquid into the timber the mixture is kept in continuous circulation by means of a centrifugal pump. It is claimed that this precludes the possibility of a separation of the zinc chloride and creosote, and insures a uniform injection of the preservatives. The following statement is made by the exploiters of the Card system concerning its operation and efficiency : "In the zinc creosote or mixed treatment, as it is sometimes called, the light oils, such as phenols and cresols, to a certain extent, are soluble in hot water and are carried with the zinc chloride into the heart-wood of the timber as well as through the sap-wood. The heavy oils will not penetrate the heart-wood but are deposited in the sap-wood, and as these heavy oils are insoluble in water they prevent the zinc chloride from leaching out of the timber. "The two solutions are kept constantly mixed while under pressure by means of a centrifugal pump attached to the treating cylinder; the suction to this pump is connected to the top of the cylinder, in the middle and at each end, and the discharge from the pump enters the bottom of the cylinder, and is distributed the entire length of [ 600 ] WOOD PRESERVATION Sec. 9 the cylinder through a perforated pipe. The mixing device works under the same pressure that is applied to the treating cylinder. The appliance for mixing the emulsion can be applied to any kind of cylinder, and is inexpensive in its first cost, operating and main- tenance. Since its installation at the several plants now using the zinc creosote process, the contention by some that the creosote and zinc solution cannot be mixed is proven to be without foundation, as all samples drawn from different parts of the retorts, and at all times during the process of treating, show the oil and solution to be in the exact, proportions intended. A water solution of chloride of zinc has greater penetrating powers than creosote oil, and therefore it can easily be injected under pressure throughout the heart-wood of timber." This description serves well to illustrate the principles under- lying the processes employing the zinc chloride and creosote com- bination. All of them are operated under the theory that the creo- sote will serve as a plug to hold in the zinc chloride. 26. Allardyce. The Allardyce process also employs creosote and zinc chloride, but in this method of treatment the zinc chloride is first injected and then followed by a separate treatment of creosote, amounting to about one to three pounds per cubic foot. The advocates of this process claim that inasmuch as the creosote oil follows the zinc chloride, a more effective protection is offered against leaching out of the salt, the creosote acting as a plug. 27. Empty-cell, Treatment. Riiping. The Riiping process aims to secure protection against decay with a comparatively small quantity of creosote. Only thoroughly air-seasoned timber can be used in this process, because its successful operation depends upon compression of the air in the wood-cells. The preliminary steaming and vacuum as carried out in the Bethell process are therefore omitted. After the timber has been placed in the cylinder and the doors are closed, it is subjected to an air pressure of about 75 pounds, which compresses the air contained in the cells. Still holding this pressure, the creosote is forced into the cylinder at a higher pressure, and after the timber has been well covered with the preservative, the pressure is increased to about 225 pounds.. This increased pressure forces the oil into the wood-cells. Then the pressure is released and the expansive force of the compressed air within the wood forces out a part of the oil and leaves merely a coating of the preservative on the cell-walls. The surplus oil is then run back into the storage tank. The expulsion of the surplus oil may be increased by a vacuum in the treating cylinder. 28. Lowry. As in the Riiping process, the timber is seasoned before treatment, but no compressed air is employed in injecting the preser- vative. As soon as the cylinder is closed, the oil is admitted and forced into the timber by pressure. Then the oil is run out of the cylinder, and a high vacuum is quickly drawn. It is claimed that [ 601 ] Sec. 9 WOOD PRESERVATION the sudden expansion of the air, which has been compressed in the wood-cells, drives out the surplus oil, and that a deep penetration but light treatment is thereby given to the timber. 29. ATMOSPHERIC PRESSURE PROCESSES. It is possible by means of some of the modifications of the atmospheric or low- pressure systems to effect full-cell or empty-cell treatment as in the high-pressure systems. Such treatments cannot be given with the same degree of facility or with the same effectiveness as with the high-pressure systems, but in many instances the treatment is adequate. 30. Full-cell Treatments. Steeping in Cold Preservative. The simplest form of non-pressure full-cell treatments, if such a term can be applied to a process usually giving only superficial treatment, is the cold-steeping or soaking process extensively employed in the early days of wood preservation and used to some extent at the present time. The timber to be treated is placed in an open vat and covered with the cold solution, which may be mercuric chloride, zinc chloride, copper sulphate, or creosote oil, as the case may be. In using mercuric chloride, it is necessary to employ non-metallic steeping pits on account of the corrosive action of the mercury. This treat- ment has proven very effective in preserving timber, though in this country its use for line timber has been confined almost entirely to the New England States, where some electric companies use kyanized cross-arms. (In the Appendix will be found a report of the German .Government's Telegraph Department, wherein very favorable mention is made of the mercuric chloride treatment.) 31. Hot or Boiling Treatments. Timber is sometimes treated by simply boiling it in the preservative contained in an open tank or closed retort for varying lengths of time. The preservative most commonly used in this process is a heavy creosote oil. The Forest Service reports that the following method is used on the Pacific coast for Douglas fir, which is an exceedingly difficult wood to treat. The timber, usually green, is placed in a treating cylinder containing creosote heated to a temperature slightly above the boiling point of water. This hot bath is continued for a time varying from several hours to two days or more. The duration of treatment depends upon the size and condition of the timber. During the bath much of the water contained in the sap is driven off together with the volatil- ized light oils. These vapors are caught in a condenser, the water separated, and the oil then run back into the receiving tank to be used over again. Finally, an oil pressure of from 100 to 125 pounds is applied, and at the same time the temperature of the oil is allowed to fall, thus forcing the preservative into the timber. This practice is subject to the general objection that it is unwise to treat timber before it has had time to dry out in the open air. It is evident that the efficiency of the process is much enhanced by the final application of pressure, and that simply boiling in an open tank is very unsatisfactory and inefficient. [ 602 ] WOOD PRESERVATION Sec. 9 [603] Sec. 9 WOOD PRESERVATION FIG. 348. Butt treatment of poles in open tank. [ 604 ] WOOD PRESERVATION Sec. 9 32. Alternate Hot and Cold Treatment. This process is usually carried out in an open tank, and it is the one generally known as the " Open-Tank System." However, in some situations it has been found advisable to employ, in carrying out the process, a low, arti- ficial pressure, which necessitates, of course, a closed tank or retort. The wood is first treated with oil brought to a temperature of from 180 to 220 degrees Fahrenheit, for a sufficient length of time to heat the wood uniformly to the temperature of the preservative. It is then either changed to another bath containing cold preservative or the hot preservative is drawn out and replaced by a charge of cold preservative at or below atmospheric temperature ; or the timber may be allowed to remain in the heated oil, heating being stopped and the oil permitted to cool down. The theory underlying the successful operation of any of these modifications is that the preliminary heating expands the air in the wood-cells, and when the cold oil is introduced the sudden contraction creates a partial vacuum which draws in the oil. In some instances, exceedingly good penetration has been obtained by this method, but it is not applicable to all classes of wood, owing to variations in their penetrability. The simplest equipment for the treatment of poles and cross-arms by the open-tank method consists of a tank, about eight feet deep, set high enough above the ground to permit of a fire beneath it. Facilities should be provided for the convenient handling of the poles. Where steam is available, it may be used to advantage to heat the liquid by means of a coil in the tank, and also to operate a hoisting engine for handling the poles. The liquid may be pumped from the treating tank to make room for the cold oil to be introduced from another tank, or two treating tanks may be employed, one for the hot treatment and one for the cold. In connection with its California experiments, the Forest Service described a pole-treating plant having a capacity of 120 poles per day, which was estimated to cost between four and five thousand dollars; or a plant with a capacity of fifty poles per day, estimated to cost two thousand dollars. The latter equipment was to consist of one 12,000-gallon iron storage tank, two 5 ft. X 5 ft. X 8 ft. treating tanks, one 60-ft. mast with 16-ft. boom derrick, a small hoisting engine, a 20-hp. boiler, steam coils for heating the treating tank, and one steam oil pump, capacity 2,000 gallons per hour. Fig. 347 shows a view of the treating plant of the Philadelphia and Reading Coal and Iron Co., where a closed retort is used for treating mine timber, but which could be utilized for treating poles and cross- arms. In this arrangement, the timber is run into a cylinder on small buggies, and the doors are then closed and sealed as in the high-pressure system. Steam coils heat the preservative to 220 degrees Fahrenheit. After the hot bath, which is continued ac- cording to the condition and size of the wood, the hot preservative is drawn off to the lower tank. Cold oil or zinc chloride is then introduced into the treating cylinder from the storage tank. A small pump is used to pump the oil back to the storage tank and some- times this pump is employed to prcduce a low pressure in the [ 605 ] Sec. 9 WOOD PRESERVATION treating cylinder. Fig. 348 shows a view of a simple open-tank outfit for treating poles; and Fig. 349 gives an extremely simple form of experimental open tank. FIG. 349. A very simple form of experimental open tank. The most interesting and useful data found, regarding open- tank treatments have been obtained from the reports of the Forest Service in connection with its California experiments with western yellow pine and western red cedar. (Part III.) [ 606] WOOD PRESERVATION Sec. 9 33. Empty-cell Treatment. Open Tank. In the full-cell treat- ment with creosote oil, the timber is removed from the tank with a considerable amount of oil on its surface. This is objectionable, not only on account of the waste of oil, but also because of the sub- sequent dripping of the oil from the poles and cross-arms after they have been installed. This difficulty is said to be overcome by taking a third step in the open-tank treatment before described. Before removing the timber, after the cold bath, it is reheated to 200 degrees Fahrenheit, for a period of from two to three hours. The same result FIG. 350. Untreated cedar pole decayed at ground lii and upward about two feet. may be accomplished by taking the timber out of the bath in the second stage of the process, after the creosote has cooled down through a range of 20 degrees Fahrenheit. This causes the contract- ing air in the wood to draw in the free oil from the surface. This method gives about the same penetration as the full-cell open-tank process, but saves a considerable quantity of oil, and, moreover, leaves the surface of the wood dry. 34. LOW ARTIFICIAL PRESSURE SYSTEMS. Full- or Empty- cell Treatments. The Forest Service has recently endeavored to com- [ 607] Sec. 9 WOOD PRESERVATION bine the advantages of both the pressure and non-pressure processes in a low-pressure system. The seasoned timber is first treated in a hot bath, as in the non-pressure treatment, then it is subjected to a cold bath; but, instead of depending entirely upon the atmos- pheric pressure to force the preservative into the wood, some arti- ficial pressure is also applied. The low-pressure process cannot, of course, be used with an open tank, and requires, preferably, a closed cylinder, as in high-pressure work. The advantage claimed FIG. 351. Untreated chestnut pole showing falling off of sap-wood. for this method is that it requires much less time for treatment than in the open tank, and a greater absorption, and a deeper and more uniform penetration are secured. 35. MISCELLANEOUS TREATMENTS. Brush Treatments. Applying the preservative by means of a brush is the most common, but the least efficient, of all treatments. For good results it is essential that the timber be thoroughly seasoned, and that the wood be dry at the time of treatment. The preservative is usually kept heated to about 200 degrees Fahrenheit and is applied to the wood with a suitable brush. Care should be taken to fill all checks, knot-holes, [ 608 ] WOOD PRESERVATION Sec. 9 and abrasions. A second coat should be applied after an interval of not less than twenty-four hours. Besides treating the butt of the pole, the roof of the pole and cross-arm gains should not be over- looked, as such cuts, if left unprotected, expose the interior to decay. Some companies report that they apply the preservative with a spraying machine, claiming it lias decided advantages over the brush method in that it requires less labor and better fills all cracks. FIG. 352. Cedar pole coated with tar. Four year service all sap-wood decayed to the ground. Figs. 350 and 351 illustrate how the sap-wood may scale from poles, leaving the untreated interior exposed to decay. Such scaling, or mechanical injury from various causes, even the spur holes made by linemen's climbing irons, will defeat the object of brush treat- ments. Fig. 352 shows a cedar pole after four years' service, which had been treated with tar. All of the sap-wood is decayed to the ground line and is loose to a height of three-and-a-half feet. Paint- 20 [ 609 1 Sec. 9 WOOD PRESERVATION ing or coating poles with tar is not so generally practiced now on account of the increasing appreciation of its uselessness, though a few years ago it was a very common practice. In contrast to the untreated chestnut pole shown in Fig. 353, the condition of the pole shown in Fig. 354 should be noted. This is a pressure-creosoted pine pole which has been in service near Norfolk, Va., for eighteen years, and there is no sign of decay. Fig. 355 shows a cross section of a well-treated creosoted pine pole. FIG. 353. Untreated chestnut pole decayed at ground line. 36. Brush Combined with Open Tank. A combination of open- tank and brush treatments is made by first treating the timber with zinc chloride in an open tank, then giving it one or more brush applications of creosote or heavy tar oil. 37. Jacket or Butt Settings. Poles are sometimes set in shells of concrete. It is questionable whether this preserves the pole other than in a mechanical way by giving greater stability. When the [610] WOOD PRESERVATION Sec. 9 concrete hardens, it contracts and may leave a space around the pole, where moisture may collect and cause the wood to decay. Some operators surround the pole with a heavy band of pitch or tar. This is not as desirable as the concrete, because it does not add to the mechanical strength of the pole setting, and has been known to create rather than to prevent decay. Mention may be made here of a patented process making use of a jacket of asbestos and asphaltum placed around and at one or two FIG. 354. Pressure creosoted pine pole 18 years' service under southern climatic conditions. No decay to date. inches from the pole near the ground line. The jacket has a cement bottom and is filled with a mixture of hydrated lime, chloride of sodium, copper sulphate and sand. Over the top of the jacket and surrounding the pole a reinforced cement cap is placed. It is claimed, that the chemicals are held in a tight compartment, from which they are slowly dissolved and drawn into the pole. Such descriptions might be continued indefinitely until the simplest [611] Sec. 9 WOOD PRESERVATION form of pole preservation or butt reinforcement were reached, such as the method employed by a large telephone company, which may be described as follows: When the pole butts are found to be in a fairly advanced stage of decay, a stub, having about the same dimensions as the pole butt, is placed in the ground alongside of the pole. This stub is long enough to extend from the bottom end of the pole to a point about two feet above the ground line. It is secured to the pole butt and to the pole above the ground either by wrappings of heavy wire or by through bolts, or a more stable job may be made by combined wrapping and bolting. This plan could [612] WOOD PRESERVATION Sec. 9 scarcely be carried out under city or town conditions, as the unsight- liness of the stub would be a serious objection, but it might be fol- lowed successfully on trunk lines which pass through sparsely settled territory. There seems no reason why the upper part of poles, particularly of the harder species of wood, should not be used in- definitely, provided always that the butt reinforcement is made as strong and reliable as would be the continuous pole. [613] SECTION 9 PRESERVATIVE TREATMENT OF POLES AND CROSS-ARMS PART II RECOMMENDED PRACTICE AND SPECIFICATIONS SECTION 9 PRESERVATIVE TREATMENT OF POLES AND CROSS-ARMS PART II RECOMMENDED PRACTICE AND SPECIFICATIONS TABLE OF CONTENTS ARTICLE General 1 Preservatives General 2 Choice of Preservatives 3 Specifications 4 A Specifications for Coal-Tar Creosote 5 B Specifications for Mixed Oils 6 C Specifications for Water-Gas Tar Creosote 7 Auxiliary Specifications 8 Specifications Covering Oil for Brush Treatments 9 Treatments General 10 Pressure System 11 Creosoted Pine Poles 12 Creosoting of Poles 13 Creosoted Pine Cross-arms 14 Creosoting of Pine Cross-arms ~. 15 Open Tank System 16 Open Tank Treatment of Pole Butts 17 Description of Open Tank Plants . . 18 Brush Treatments . . 19 [617] SPECIFICATIONS FOR PRESERVATIVES AND METHODS OF TREATMENT 1. GENERAL. The following data have been compiled from the 1911 report of the committee on the preservative treatment of poles and cross-arms, and contain only the recommended specifications for preservatives, preservative methods and apparatus. PRESERVATIVES 2. General. The subject matter contained in Part I, while serving well the purpose of describing the nature of preservatives commonly employed in protecting timber from decay and the most common methods of examination, contains little in the way of definite recommendations but is included in order to present to the members of the Association, few of whom have any knowledge of the subject, information of a more or less general nature emanating from recognized authorities, without attempting to reconcile con- flicting views or do more than weed out the obviously bad from the obviously good, so that the final recommendations as contained herein would meet the special needs of the National Electric Light Association. Having the foregoing in mind, radical departures from established methods were found necessary, but the recommendations have been prepared having as their object, to which all else was secondary, the following: a. The choice of the best preservative for the protection of poles and cross-arms obtainable at a cost commensurate with its service. b. Specifications which, while fully covering the requirements of a high-grade preservative, would at the same time be fair to the manufacturer and provide a material no more expensive than the best grades now on the market. c. A method of analysis which would insure compliance with the specifications. 3. Choice of Preservatives. Coal-tar creosote being well-known as a timber preservative, and its value as such being established beyond question, is on this account recommended by the committee as the standard preservative. Under certain circumstances it has been found advisable to use mixtures of coal-tar creosote and various other tar products. The circumstances under which the use of such mixtures are warranted will depend, to a large extent, upon the cost of the various oils and tar products and the conditions under which they are to be used. The admixture of certain tars to coal-tar creosote has been found particularly advisable where the latter is of low gravity, and also where a cheaper preservative could be obtained by using such a mixture than by the use of straight coal-tar creosote. Water-gas [ 619] Sec. 9 WOOD PRESERVATION tar and products obtained by the distillation of water-gas tar nave been used for some years, but records of service of timbers treated with these substances are either not of sufficient duration or of sufficient authenticity to warrant definite conclusions to be drawn as to their value. In view of the fact, however, that considerable quantities of water-gas tar and distillates are available for use as timber preservatives and are being offered commercially, the com- mittee has drawn up specifications covering these latter materials, as well as for coal-tar creosote and for mixed oils. (See Specifications A, B and C.) 4. Specifications. Existing specifications for the purchase of creosote oil, which are in general use, do not fully meet the present requirements, since it is possible, even under the most stringent of them, for unscrupulous manufacturers to adulterate and sell as pure distilled creosote mixtures with other materials. Since such adul- terations are usually made to cheapen the cost of the oil, it renders mutually honest competition impossible and defrauds the purchaser who is entitled to receive what he has ordered and for which he has paid. It is not intended to imply that it is impossible to obtain a pure creosote, and often so-called adulterated oils are knowingly pur- chased and used with the consent of the purchaser of the treated timber, but it is a well-known fact that the protection offered by strict specifications and a method of analysis which will enforce them is at times needed, and, therefore, the specifications drawn up which, while offering no hardship to the honest producer, will insure the receipt of an oil such as was desired by the purchaser. The specifications, which are offered as covering three kinds of creosoting material, have followed, as closely as was deemed ad- visable by the committee, the well-known specifications known as the "American Railway Engineering and Maintenance-of-Way Specifications," the chief difference being the addition of certain tests which would more certainly tend to indicate adulteration, and the adoption of a flask instead of the retort for making the distilla- tion test. The chief reason for this radical step is that it was the general opinion that it would be much easier to enforce the speci- fications when a flask was used than when using the retort, for the reason that retorts of a uniform size and shape are difficult to obtain, and a slight change in the position of the thermometer, which is placed in reference to the surface of the oil, would give widely dif- ferent results, and also on account of the difficulty experienced in placing the thermometer exactly one-half inch above the surface of the oil. It is generally admitted by chemists that the retort is an anti- quated piece of apparatus, and that it would be best to adopt the most scientific methods available. It has been urged by some, who favored the adoption of the retort method of distillation and the maintenance-of-way specifications in their entirety, that any change in method would introduce confusion in the creosoting industry. [620] WOOD PRESERVATION Sec. 9 This argument is not tenable, provided a proper relation is established between the results obtained by the two methods of distillation. The results obtained by the flask method of distillation herein recommended are practically the same as those obtained by the retorted method of distillation. Three specifications for creosote are offered: Specification "A" is designed to insure the furnishing of a high grade of coal-tar creo- sote. Any oil conforming to this specification will include all the qualities that would ordinarily be required in preservative work, and the conditions of the specification enable the manufacturers or agents to make such an oil a commodity as easily available to the purchaser or user as are other grades of creosote. For these reasons such an oil as the standard preservative has been adopted. Where circumstances warrant the admixture of certain tars to coal-tar creosote, Specification "B" is suggested. (See text ac- companying specification for explanation of conditions under which the use of such a preservative might be warranted.) Where water-gas tar creosote is used, Specification "C" is sug- gested. (See text accompanying specification for further remarks concerning this preservative.) 5. "A" SPECIFICATIONS COVERING COAL-TAR CREOSOTE OIL AND METHODS OF ANALYSIS SECTION 1 SPECIFICATION DEFINITION. The material required under these specifications is that commonly known as dead oil of coal tar or coal-tar creosote. More specifically defined it is : (a) A distillate from the tar produced as a by-product in the manufacture of coal gas from bituminous coal by the retort method, or (b) A distillate from the tar produced as a by-product in the manufacture of coke from bituminous coal by the by-product coke- oven process, or (c) A distillate obtained from a mixture of the above mentioned tars, or (d) A product obtained by mixing distillates from the above mentioned tars. It is understood that the presence of any hydrocarbons other than the above, either in the original tars or in the distillates there- from, will, by defeating the purpose of this specification, which is to secure a pure distilled oil from coal gas or coke-oven tar, be looked . upon as an adulteration, which may result in the rejection of the oil. As further defining the material required, the hydrocarbons specif- ically provided against include the following: (e) Raw or partly distilled tars or petroleum oils of any description whatsoever, such as coal tar, coke-oven tar, water-gas tar, oil tar, [621] Sec. 9 WOOD PRESERVATION lignite tar, blast-furnace tar, producer tar, wood tar, and crude petro- leum. (f) Distillates from any of the above mentioned tars or oils, except distillates from coal tar and coke-oven tar (g) Residues from any of the above mentioned tars or oils. (h) Products obtained by nitration of any of the above mentioned tars or oils The purchaser of the treated timber, or his representative, shall have the right to take samples of the oil from the oil tanks or from the treating cylinders at the treating plant and to test such samples whenever or wherever desired. The oil may be refused upon satis- factory evidence that it does not conform to the specifications. In the event of a dispute between the purchaser of the treated timber and the firm treating the same, the matter shall be referred to a referee mutually agreed upon by a representative of the pur- chaser and the manufacturer, and the decision of the referee shall be binding and final. Information, as complete as possible, shall be furnished to the purchaser upon request as to the origin and history of the oil. The oil required under these specifications must, in addition to being of satisfactory origin, possess certain physical and chemical characteristics, and in order to insure that the sample, which is used in determining these characteristics, correctly represents the bulk of the material from which it is taken, the following rules for taking samples must be observed : SAMPLING. A one-gallon sample of the oil shall be taken for analysis, the manner of collecting the same depending upon the nature of storage. The oil must be completely liquid when the sample is taken, and it may therefore be necessary to heat the tank or other receptacle in which it is contained. The following general rules shall be observed when sampling from: (a) Tank Boat. The sample shall be taken from the pumping system while discharging from the boat into the receiving tank as follows: A half -inch cock shall be placed in the line at any convenient point and a continuous stream of oil drawn through this cock during the entire time of emptying the boat. The rate of flow of the stream should be proportionate to the rate of flow of the oil in the pumping line and it should be such that a gallon sample may be collected from each 10,000 gallons of oil passing through the pipe. The bulk sample thus obtained, which may be caught in a barrel or other suitable receptacle provided for the purpose, shall be thoroughly mixed and shall, if necessary, be heated to bring into solution any material which may have crystallized out. A one-gallon sample shall be taken from this for analysis. (b) Storage Tanks less than Twenty Feet in Depth. In sampling from storage tanks of less than twenty feet in depth, a "thief" shall be employed. It shall be made of a length of one-half inch pipe and provided at the lower end with a lever handle cock having an opening of approximately the same size as the interior of the pipe. This cock being open, the "thief" is lowered slowly into the tank and [ 622 ] WOOD PRESERVATION Sec. 9 when it has touched bottom, the cock is closed by means of a chain, wire, or iron rod carried to the top of the pipe. A sufficient num- ber of samples thus procured shall be taken to aggregate one gallon. (c) Storage Tanks over Twenty Feet in Depth. Samples shall be taken from such tanks through one-half inch cocks placed one above the other and one foot apart on the side of the tank. One gallon of oil shall be withdrawn from each level, and the bulk sample thus obtained shall be thoroughly mixed as in (a) and the final sample taken from this. (d) Tank Cars. Drip samples shall be taken from tank cars as in (a). (e) Treating Cylinders. Samples from treating cylinders shall be taken from the charging and discharging line as in (a). PHYSICAL AND CHEMICAL CHARACTERISTICS. The oil under these specifications must have the following characteristics : 1. It shall have a specific gravity of at least one and three-hun- dredths (1.03) and not more than one and eight-hundredths (1.08) at thirty-eight degrees Centigrade (38 C.). If the gravity is taken at a higher temperature, a correction of eight ten-thousandths (.0008 )for each degree Centigrade above thirty-eight (38) shall be made. 2. There shall be not over one per cent (1%) of residue insoluble in hot benzol. 3. The original oil shall contain not over two per cent (2%) of water. 4. The oil shall be miscible in absolute alcohol, volume for volume. 5. The residue remaining upon sulphonating a portion of the total distillate shall not exceed one per cent (1%). 6. The oil shall contain not more than eight per cent (8%) of tar acids. 7. When two hundred (200) grams of the oil are distilled in ac- cordance with the requirements of the specifications for the analysis of coal-tar dead oil or coal-tar creosote hereinafter referred to and results calculated to water-free oil: (a) Not more than five per cent (5%) of oil shall distill off up to two hundred and five degrees Centigrade (205 C.). (b) Not more than thirty-five per cent (35%) of oil shall distill off up to two hundred and thirty-five degrees Centigrade (235 C.). (c) Not more than eighty per cent (80%) shall distill off up to three hundred and fifteen degrees Centigrade (315 C.). (d) The coke residue shall not exceed two per cent (2%). (e) The distillate between two hundred and five (205) degrees Centigrade and two hundred and thirty-five (235) degrees Centi- grade shall deposit naphthalene on cooling to fifteen (15) degrees Centigrade. NOTE. The percentage distilling to two hundred and forty-five (245) and two hundred and seventy (270) degrees Centigrade shall be noted. [ 623 ] Sec. 9 WOOD PRESERVATION SECTION 2. ANALYSIS SPECIFICATIONS. GENERAL. The apparatus employed in making the distillation and other tests required under these specifications shall conform in general to that shown on drawings No. 1 (Fig. 356) and No. 2 (Fig. 357) attached to and forming a part of these specifications, except that a five per cent (5%) variation from the dimensions given is allowed. The distilling apparatus must be assembled as in drawing No. 3 (Fig. 358). As further defining the requirements in this respect, the following description of certain parts and manner of assembling is given: (a) Flask. The flask required is a Lunge side neck distilling flask, provided with a trap (drawing No. 1) (Fig. 356), and having a tubular thirty centimeters (30 cm.) long placed close to the bulb. The flask must have a capacity of three hundred cubic centimeters (300 c.c.) when filled to a height equal to its maximum horizontal diameter. (b) Thermometer. The thermometer must be made of Jena glass and be nitrogen filled and graduated at intervals of one millimeter (1 mm.) in single degrees Centigrade, the scale reading to plus four hundred degrees Centigrade (+400 C.). (c) Receivers. The glass receivers may be of any convenient size and shape; the flask shown on drawing No. 2 (Fig. 357) is, however, recommended. (d) Shield. A shield ten centimeters (10 cm.) in diameter and eight centimeters (8 cm.) high, made of asbestos must be provided (drawing No. 2) (Fig. 357). (e) Support for Flask. The flask must rest on an asbestos board one-half centimeter (.5 cm.) in thickness by fifteen centimeters (15 cm.) in diameter, a hole five centimeters (5 cm.) in diameter being cut in the center of the board. The board shall rest on a ring stand (drawing No. 2) (Fig. 357). ASSEMBLING APPARATUS. The apparatus must be assembled as shown on drawing No. 3 (Fig. 358) . The thermometer passes through a cork in the top of the flask and is so placed that the top of the bulb of the thermometer is on a line with the bottom of the tubular outlet. The asbestos shield is placed around the bulb of the flask and the flask mounted on the asbestos board supported on the ring stand as shown on drawing No. 3 (Fig. 358). DISTILLATION TEST. Two hundred grams of the oil shall be used in the analysis, this amount being weighed on a balance sensitive to one milligram (1 mg.), in the following manner: The flask is first placed on the pan of the balance and weighed, and the weight recorded. Without removing the flask, a two hundred (200) gram weight is placed on the opposite pan of the balance and a sufficient quantity of the oil dropped into the flask through a long stem funnel to bring the pans into equilibrium. The flask is then removed from the balance and set up as in drawing No. 3 (Fig. 358). Care must be taken that the cork stopper carrying the thermometer fits tightly into place. The flask should be heated, preferably by a Bunsen or other standard form of gas burner. The [624] WOOD PRESERVATION Sec. 9 D /STILLING FLASK FIG. 356. National Electric Light Association creosote oil analysis. [ 625] Sec. 9 WOOD PRESERVATION r'^V I 00 tern fern FIQ. 357. National Electric Light Association creosote oil analysis. [626] WOOD PRESERVATION AiR /?A NGrtN T OF D/STILL/NG APPARATUS FIG. 358 National Electric Light Association creosote oil analysis. [627] Sec. 9 WOOD PRESERVATION distillation shall be continuous and at such a rate that two (2) drops of oil per second (5 c.c. per minute) leaves the end of the tubular after the thermometer registers two hundred and five degrees Centigrade (205 C.), or after all of the water has been driven off. The per- centage weights of the following fractions shall be recorded : To 205 degrees Centigrade. To 235 degrees Centigrade. To 245 degrees Centigrade. To 270 degrees Centigrade. To 315 degrees Centigrade. To 360 degrees Centigrade. 6. "B" SPECIFICATIONS COVERING MIXED OILS AND METHODS OF ANALYSIS. SECTION 1. SPECIFICATION DEFINITION. The material required under these specifications is a homogeneous mixture of a distilled product obtained from coal gas tar or coke oven tar and generally known as coal-tar dead oil or coal-tar creosote with certain other hydrocarbons. More specifi- cally defined, the added material, which must constitute not more than forty (40) per cent of the final mixture, may consist of : (a) Raw or partly distilled coal-tar, coke-oven tar, water-gas tar, lignite tar, blast-furnace tar, and producer tar, or (b) Distillates from any of the above mentioned tars, or (c) Products obtained by filtration of any of the above mentioned tars. As further defining the material required, it is understood that the presence in the oil of any of the hydrocarbons given below will, by defeating the purpose of this specification, which is to secure a mixed oil containing certain hydrocarbons, be looked upon as an adulteration and the oil may be rejected. The hydrocarbons provided against are as follows: (d) Petroleum oil or distillates or of residues therefrom. (e) Water gas tar containing over ten per cent (10%) paraffin oil. (f) Oil tar containing over ten per cent (10%) paraffin oil. (g) Distillates or residues from water gas tar or oil tar containing over ten per cent (10%) paraffin oil. CONDITIONS OF PURCHASE. Same as in specifications covering coal-tar creosote oil. SAMPLING. Same as in specifications covering coal tar creosote oil. PHYSICAL AND CHEMICAL CHARACTERISTICS. The oil required under these specifications must have the following characteristics : 1. It shall have a specific gravity of at least one and four-hun- [623] WOOD PRESERVATION Sec. 9 dredths (1.04) and not more than one and ten-hundredths at thirty- eight degrees Centigrade (38 C.). 2. There shall be not over three per cent (3%) of residue insoluble in hot benzol. 3. The oil shall contain not over three per cent (3%) of water. 4. The residue remaining upon sulphonating a portion of the total distillate shall not exceed five per cent (5%). 5. The oil shall contain not less than two per cent (2%) nor more than eight per cent (8%) of tar acids. 6. When two hundred (200) grams of the oil are distilled in ac- cordance with the requirements of the specifications for the analysis of mixed creosoting oil hereinafter referred to and results calculated to water free oil : (a) Not more than three per cent (3%) of oil shall distil off up to two hundred and five degrees Centigrade (205 C.) (b) Not more than twenty-five per cent (25%) of oil shall distil off up to two hundred and thirty-five degrees Centigrade (235 C.). (c) Not more than eighty per cent (80%) shall distil off to three hundred and fifteen degrees Centigrade (315 C.). . (d) The residue above three hundred and sixty degrees Centi- grade (360 C.) shall not exceed thirty-five per cent (35%).* SECTION 2. ANALYSIS SPECIFICATION Same as in Specifications Covering Coal-tar Creosote Oil 7. "C" SPECIFICATIONS COVERING WATER-GAS TAR CREOSOTE OIL AND METHOD OF ANALYSIS. SECTION 1. SPECIFICATION DEFINITION. The material required under these specifications is that known as dead oil of water-gas tar or water-gas tar creosote. More specifically defined, it is: (a) A distillate from the tar produced as a by-product in the manufacture of carburetted water gas from petroleum oil. It is understood that the presence of any other hydro-carbons, either in the original tar or the distillate therefrom, will, by defeating the purpose of this specification, which is to secure a pure distilled oil from water-gas tar, be looked upon as an adulteration, which may result in the rejection of the oil. As further defining the material required, the hydrocarbons specifically provided against, include: (b) Raw or partly distilled tar or petroleum oil of any description, whatsoever, such as coal tar, coke oven tar, water gas tar, oil tar, lignite tar, wood tar, and crude petroleum. *NOTE. The percentage distilling to two hundred and forty-five (245), two hundred and seventy (270) and three hundred and sixty (360) degrees Centigrade shall be noted. [629] Sec. 9 WOOD PRESERVATION (c) Distillates from any of the above mentioned tars or oils, except distillates from water gas tars. (d) Residues from any of the above mentioned tars or oils. (e) Products obtained by filtration of any of the above mentioned tars or oils. CONDITIONS OF PURCHASE. Same as in specifications covering coal tar creosote oil. SAMPLING. Same as in specifications covering coal tar creosote oil. PHYSICAL AND CHEMICAL CHARACTERISTICS. The oil required under these specifications must have the following characteristics: 1. It shall have a specific gravity of at least one and three-hun- dredths (1.03) and not more than one and eight-hundred ths (1.08) at thirty-eight degrees Centigrade (38 C.). 2. There shall be not over one per cent (1%) of residue insoluble in hot benzol. 3. The oil shall contain not over two per cent (2%) of water. 4. The residue remaining upon sulphonating a portion of the total distillate shall not exceed five per cent (5%). 5. When two hundred (200) grams of the oil are distilled in ac- cordance with the requirements of the specifications for the analysis of water gas tar dead oil or water-gas tar creosote hereinafter referred to and results calculated to water free oil: (a) Not more than two per cent (2%) of oil shall distil off up to two hundred and five degrees Centigrade (205 C.). (b) Not more than ten per cent (10%) of oil shall distil off up to two hundred and thirty-five degrees Centigrade (235 C.). (c) Not more than sixty p<*r cent (60%) shall distil off up to three hundred and fifteen degrees Centigrade (315 C.).* (d) The coke residue shall not exceed two per cent (2%). SECTION 2. ANALYSIS SPECIFICATIONS Same as in Specifications Covering Coal Tar Creosote Oil 8. AUXILIARY SPECIFICATIONS. Methods of making free carbon determination, sulphonation test, test for tar acids, and test for coke, as referred to in Specifications "A," "B"and "C." DETERMINATION OF FREE CARBON. The apparatus required is as follows: Knorr Condenser. Knorr Flask. C. S. & S. No. 575 Filter Papers, 15 cm. diameter. Wire for supporting filter papers. Ten grams of the oil should be weighed into a small beaker and digested with C. P. toluol on a steam bath. A cylindrical filter cup is prepared by folding two of the papers around a rod about five- * NOTE. The percentage distilling to two hundred and forty-five (245) and two hundred and seventy (270) degrees Centigrade ehall be noted. L 630 J WOOD PRESERVATION Sec. 9 eighths of an inch (f *) in diameter. The inner paper should be cut to fourteen centimeters (14 cm.) diameter. Prior to using the filter papers, they should have been extracted with benzol to render them fat free. The filter cup is dried at one hundred (100) to one hundred and ten (110) degrees Centigrade and weighed in a weighing bottle. The contents of the beaker are now decanted through the filter cup, and the beaker washed with hot toluol, passing all washings through the cup. The filtrate should be passed through the filter a second time, the residue washed two or three times with hot C. P. benzol and transferred to the extraction apparatus, in which C. P. benzol is used as the solvent, which solvent is vaporized by means of a steam or water bath. The extraction is continued until the filtrate is colorless. The filter cup is then removed, dried and weighed in the weighing bottle. C. P. benzol followed by chloro- form may be used instead of C. P. toluol followed by C. P. benzol. Precautions. In removing filter paper from the extraction ap- paratus see that no particles of mercury find their way into the precipitate. To prevent splashing, the filter paper should be ele- vated as near to the outlet of the condenser as possible. A good precaution is to cover the top of the filter cup with a round cap of filter paper. SULPHONATION TEST. Ten cubic'centimeters (10 c.c.) of the total distillate to three hundred and fifteen degrees Centigrade (315 C.) are placed in a flask and warmed with four (4) to five (5) volumes of concentrated sulphuric acid to sixty degrees Centigrade (60 C.) and the whole transferred to a graduated separatory funnel. (The one shown on drawing No. 4 (Fig. 359) is recommended. The flask is rinsed three times with small quantities of concentrated sulphuric acid and the rinsings added to the contents of the funnel, which is then stoppered and shaken, cautiously at first, afterwards vigorously, for at least fifteen (15) minutes and allowed to Stand over night. The acid is then carefully drawn down into the graduated portion of the funnel to within two cubic centimeters (2 c.c.) of where the unsulphonated residue shows. If no unsulphonated residue is visible the acid should be drawn down to two cubic centimeters (2 c.c.). In either case the test should be carried further as follows: Add about twenty cubic centimeters (20 c.c.) of water and allow to stand for one-half hour. Then draw off the water as close as possible without drawing off any supernatant oil or emulsion, add ten cubic centimeters (10 c.c.) of strong sulphuric acid and allow to stand for from fifteen to twenty (15-20) minutes. Any unsulphon- ated residue will now separate out clear and give a distinct reading. If under two-tenths of a cubic centimeter (.2 c.c.) it should be drawn down into the narrow part of the funnel to just above the stop-cock, where it can be estimated to one one-hundredth of a cubic centi- meter (.01 c.c.) . The volume of residue thus obtained is calculated to the original oil. DETERMINATION OF TAR ACIDS. One hundred cubic centime- ters (100 c.c.) of the total distillate to three hundred and fifteen [631] Sec. 9 WOOD PRESERVATION FIG. 359. National Electric Light Association creosote oil analysis. [632] WOOD PRESERVATION Sec. 9 degrees (315 C.), to which forty cubic centimeters (40 c.c.) of a solution of sodium hydroxide having a specific gravity of one and fifteen hundredths (1.15) is added, is warmed slightly and placed in a separatory funnel. The mixture is vigorously shaken, allowed to stand until the oil and soda solutions separate and the soda solution containing most of the tar acids drawn off. A second and third extraction is then made in the same manner, using thirty (30) and twenty (20) cubic centimeters of the soda solution, respectively. The three alkaline extracts are united in a two hundred cubic centi- meter (200 c.c.) graduated cylinder and acidified with dilute sul- phuric acid. The mixture is then allowed to cool and the volume of tar acids noted. The results shown should be calculated to the original oil. COKE TEST. In making the coke determination, hard glass bulbs similar to the one shown in drawing No. 4 (Fig. 359) are to be used. The test is to be carried out as follows: Warm the bulb slightly to drive off all moisture, cool in a desic- cator and weigh. Again heat the bulb by placing it momentarily in an open Bunsen flame and place the tubular underneath the surface of the oil to be tested and allow the bulb to cool until suffi- cient oil is sucked in to fill the bulb about two-thirds full. Any globules of oil sticking to the inside of the tubular should be drawn into the bulb by shaking or expelled by slightly heating it, and the outer surface should be carefully wiped off and the bulb re- weighed. This procedure will give about one gram of oil. Cut a strip of thin asbestos paper about one-quarter inch wide and about one inch long, place it around the neck of the bulb and catch the two free ends close up to the neck with a pair of crucible tongs. The oil should then be distilled off as in making an ordinary oil distillation, starting with a very low flame and conducting the distillation as fast as can be maintained without spurting. When oil ceases to come over, the heat should be increased until the highest temperature of the Bunsen flame is attained, the whole bulb being heated red hot until evolution of gas ceases and any carbon sticking to the outside of the tubular is completely burned off. The bulb should then be cooled in a desiccator and weighed and the percentage of coke residue cal- culated to water free oil. 9. SPECIFICATION COVERING OIL FOR BRUSH TREAT- MENTS. The material required under these specifications is the same as that called for under specification "A," except that it shall have a gravity of between one and eight-hundredths (1.08) and one and twelve hundredths (1.12) at fifteen degrees Centigrade (15 C.). No oil to distil to two hundred and five degrees Centigrade (205 C.), and not more than ten per cent (10%) to two hundred and thirty- five degrees Centigrade (235 C.). Not more than one-half of one per cent (3/2%) of insoluble matter shall be left upon extraction with hot benzol. [ 633 ] Sec. 9 WOOD PRESERVATION TREATMENTS. 10. General. The following recommended methods are par- ticularly adaptable for the local treatment of line timber with creo- sote. They include standard specifications and descriptions of the actual working plants that would be required by a company in the event of the treating operation being carried out by the company's own employees. The following methods have been given consideration: 1. Bethel or high-pressure system 2. Open-tank or atmospheric pressure system 3. Brush treatments 11. Pressure System. The efficiency of the straight creosote, pressure process, cannot be questioned. Still it should be under- stood, that owing to the heavy cost of installing such a system, it would come within the province of comparatively few operating companies to own an outfit of this kind. At the same time, as the number of creosoting companies increases, a considerable quantity of treated line timber will be purchased, and it is for the purpose of assisting the buyer in obtaining the best, and therefore the most economical timber for the money expended, that the following specifications are offered. 12. CREOSOTED PINE POLES. Creosoting. Unless otherwise ordered, all poles shall be impreg- nated with not less than pounds of ;-. creo- sote per cubic foot of wood, in accordance with the specifications for creosoting timber. The creosote used in impregnating the timber shall conform to the requirements of the specifications for this class of material, hereinafter referred to. Inspection. The quantity of creosote forced into the poles shall be determined by tank measurements, by weighing and by observing the depth of penetration of the oil into the pole. In the case of poles having a growth of sap wood not less than one and one-half (13^) inches in thickness, the depth of penetration shall not be less than one and one-half (1^) inches. In the case of poles having a growth of sap wood less than one and one-half (13^) inches in thickness the creosote shall penetrate through the sap wood and into the heart wood. The depth of penetration shall be determined by boring the pole with a one-inch auger. The right is reserved to bore, for this purpose, two holes at random, about the circumference, one hole five or six (5 or 6) feet from the butt and one hole ten (10) feet from the top. After inspection, each bore hole shall be filled with hot creosote and then with a close-fitting creosoted wooden plug. The inspector may satisfy himself that no portion of the increased weight is due to the presence of water, which may have condensed in the timber in consequence of the steaming process, or in conse- quence of the presence of water in the oil. Subsidiary Specifications. The following specifications and drawing form a part of these specifications: [ 634] WOOD PRESERVATION Sec. 9 Specifications for creosoting timber. Specifications for creosote. Drawing No Framing of Poles. 13. CREOSOTING OF POLES. These specifications cover all directions necessary for the treatment of timber, other than Douglas fir, with creosote. These specifications do not cover the treatment of cross-arms and are not to be used in connection with such treat- ment. General. These specifications describe the processes to be used in impregnating timber, except cross-arms, with creosote and are intended to include all instructions necessary for the proper per- formance of the work. Testing Facilities. The manufacturer shall provide and install such apparatus as is necessary to enable the inspector to determine that the requirements of these specifications are fulfilled. It is suggested that recording temperature and pressure instruments be provided. Workmanship. All material shall be of the best quality unless otherwise specified herein, and all workmanship shall be sound and reliable in character and of the best grade. Timber. The timber subjected to the creosoting treatment shall conform to the requirements of the specifications and drawings furnished by the purchaser. All timber shall be framed, shaped and bored before treatment. The material in each charge shall be in approximately the same condition so far as air seasoning is concerned, and under no circumstances shall green, partially seasoned, or seasoned timber be treated together in the same charge. Species of entirely different characteristics shall not be treated together. When the southern yellow pines are treated, long leaf and Cuban pine shall not be included in charges with short leaf and Loblolly pine. Creosote. The creosote used in impregnating the timber shall conform to the requirements of the purchaser's specifications for creosote. The purchaser shall have the right to take samples of the oil whenever his inspector shall elect. The sample of oil so collected shall be tested wherever the purchaser shall elect. When timber is being treated, the oil may contain not more than five (5) per cent of water. In case more than two (2) per cent of water is present in the oil, the quantity of the preservative added to the timber shall be increased by an amount sufficient to ensure that the required amount of oil computed on a water-free basis has been taken up by the timber. Quantity of Oil. All timber shall be so impregnated with creosote that the average impregnation of the material in each cylinder load shall not be less than the quantity of oil called for in the specifications for the material or in the contract. The volume of timber and the quantity of oil absorbed shall be determined by the inspector. The inspector shall have access to all records of treatment. Excess of oil in one charge shall not be offset against a shortage of oil in another [ 635 ] Sec. 9 WOOD PRESERVATION charge. The treating plant shall be equipped, to the satisfaction of the purchaser, so as to allow a close determination of the amount of oil injected into the timber. The quantity of oil injected into the timber, as determined by the volume of oil withdrawn from the measuring tanks, shall be based on the standard temperature of 100 F. and the quantity increased by an amount equal to 0.00044 of the required volume at 100 F. for each degree of Fahrenheit of oil temperature above the standard temperature of 100 F. General. The treating cylinder shall not be opened during the process of treatment, unless under instructions of inspector. Classification. For the treating process timber shall be classified as heavy or small. Heavy timber shall be understood to include poles and stubs; small timber shall, unless otherwise specified, include all other timber-, except cross-arms, ordered by the purchaser. Steaming and Heating Process. Steam when used shall be maintained at a uniform pressure and temperature in the treating cylinder as indicated in the following table: For heavy timber .... For small timber .... Steam Pressure Not less than Steam Pressure Not greater than Steam Temper- ature Not greater than 17 pounds 12 pounds 20 pounds 15 pounds 259 F. 250 F. The temperature reading shall be taken by means of standard thermometers placed in the treating cylinder so that the bulbs thereof are within the shell. At the beginning of the steaming process the exhaust valve shall be open and shall not be closed until a steady flow of steam escapes through the valve. The duration of the steaming process shall be timed from the closing of the exhaust valve. The exhaust valve shall be opened and the condensation blown off at intervals during the steaming process. The duration of the steaming process shall be as directed by the inspector and shall depend upon the condition and character of the timber, but shall in no case be carried to such an extent as to injure the timber. The timber shall not be steamed in excess of the interval given in the following table: For heavy timber For small timber Green or Very Wet Timber Partially Seasoned Timber Seasoned Timber 8 hours 5 hours 5 hours S hours hours hours Seasoned timber shall not be steamed, but shall be heated in the treating cylinder. The temperature within the cylinder shall [636] WOOD "PRESERVATION Sec. 9 be maintained by means of the closed heating coils at a temperature of about 150 F. For heavy timber for at least 2 hours For small timber ' " 1 hour Exhaustion Process Green and Partially Seasoned Timber. When the steaming process shall have been completed the steam shall be blown off and the treating cylinder exhausted to a vacuum of at least twenty-four (24) inches at or near sea level, or propor- tionately less at higher altitudes. The vacuum shall be maintained at the above minimum for a period. For heavy timber of not less than 2 hours For small timber ' "1 hour and if necessary thereafter until the condenser discharge is clear. During the exhaustion process the temperature within the treating cylinder shall be maintained, by means of saturated steam in the closed heating coils, above that at which water would boil at that degree of vacuum. Exhaustion Process Seasoned Timber. With seasoned timber it is not required that a vacuum shall be drawn after the heating process and before the filling process, provided that the specified amount of creosote is in the timber on its removal from the treating cylinder. Filling Process. After the exhaustion process, the cylinder shall be completely filled, as rapidly as possible, with creosote and in no case shall the flow of oil into the treating cylinder be stopped before the overflow of the cylinder. Pressure shall then be applied until the specified amount of oil has been forced into the timber. The total amount of oil forced into the timber shall be determined from the initial reading on the measuring tanks, and from the readings on the measuring tanks, after the oil in the cylinder at the con- clusion of the pressure process (including all drip from the timber), has been returned to the measuring tanks. The oil at introduction into the cylinder shall have a temperature of not less than 140 degrees Fahrenheit and not more than 175 degrees Fahrenheit. The oil in the measuring tanks shall be main- tained at a uniform temperature during the filling process. Subsidiary Specifications. The following specifications of the purchaser form a part of these specifications: Specification for creosote. Specification for analysis of creosote. 14. CREOSOTED PINE CROSS-ARMS. (Sec. 4, Art. 4.) Inspection. Inspection, unless otherwise arranged, shall be at the creosoting plant before and after treatment. All cross-arms shall be inspected for dimensions and defects outlined under "quality"' before being subjected to the creosoting process. The quantity of creosote forced into the arms shall be determined by tank measure- ments and by noting the depth of penetration of the oil and by [ 637 ] Sec. 9 WOOD PRESERVATION weighing. The right is reserved to select, at random, one arm in each hundred to be sawed for the purpose of determining the pene- tration. All cross-arms not conforming to all requirements of this specification shall be rejected. Sapwood Classification. No limitation is placed on the amount of sap wood which may be contained in any arm. All cross-arms con- taining both sapwood and heartwood shall, however, be shaped so that the sapwood shall be on the top or sides of the cross-arm. All crossarms shall be divided, before treatment, with respect to the amount of sapwood contained by each into three classes as follows: Class " H" not more than twenty-five (25) per cent of sapwood. Class 'S" not less than seventy-five (75) per cent of sapwood. Class "I" not included in classes "H" and "S." Treatment. Each class of cross-arms shall then be separately treated in accordance with the requirements of the "Specification for Creosoting Yellow Pine Cross-arms" hereinafter referred to, with the amounts of creosote shown in the following table : Class "H" cross-arms not less than eight (8) pounds per cubic foot ot timber. Class "S" cross-arms not less than twelve (12) pounds per cubic foot of timber. Class " I " cross-arms not less than ten (10) pounds per cubic foot of timber . The creosote used in treating the cross-arms shall conform to the requirements of the specifications for this class of material, hereinafter referred to. Subsidiary Drawings and Specifications. The following drawing and specifications form a part of these specifications. Drawing No standard cross-arm. Specification for creosoting pine cross-arms. Specification for Creosote. 15. CREOSOTING OF PINE CROSS-ARMS. General. This specification describes the process to be used in impregnating yellow pine cross-arms with creosote and is intended to include instructions necessary for the proper performance of the work. Testing Facilities. The manufacturer shall provide and install such apparatus as is necessary to enable the inspector to determine that the requirements of these specifications are fulfilled. It is suggested that recording temperature and pressure instruments be provided. Workmanship. All workmanship shall be sound and reliable in character and of the best commercial grade. Cro ss-arms. The cross-arms sub j ected to the creosoting treatment shall conform to the requirements of the specifications and drawings furnished. All cross-arms shall be shaped, bored and well seasoned before treatment. Creosote. The creosote used in impregnating the cross-arms shall conform to the requirements of the specifications for creosote here- [ 638 ] WOOD PRESERVATION Sec. 9 inafter referred to. The right is reserved to take samples of the oil at any stage of the creosoting process and to test the samples wherever desired. Water In Oil. The inspector shall frequently take a sample of oil from the treating cylinder and distill it to two hundred and five (205) degrees Centigrade, in order to determine the percentage of water present. If the amount of water is in excess of five (5) per cent, the treatment shall be discontinued until the excess water has been removed from the oil or until oil containing not more than the allowable amount of water can be supplied. In case more than two (2) per cent of water is present in the oil, the quantity of the preservative added to the timber shall be increased by an amount sufficient to insure that the required amount of oil, computed on water-free basis, has been taken up by the timber. Quantity of Oil. All crossarms shall be so impregnated with creosote that the average impregnation of the material in each cylinder load shall not be less than the quantity of oil hereinafter specified. The volume of timber and the quantity of oil absorbed shall be determined by the inspector. The inspector shall have access to all records of treatment. Excess of oil in one charge shall not be offset against a shortage of oil in another charge The treating plant shall be equipped so as to allow a close determination of the amoHnt of oil injected into the timber. The quantity of oil injected into the cross-arms as determined by the volume of oil withdrawn from the measuring and working tanks, shall be based on the standard temperature of one hundred (100) degrees Fahrenheit. The correction to be applied in com- puting the quantity ot the injected oil shall consist in the addition of .00044 of the required volume for each degree Fahrenheit the temperature of the measured oil exceeds the standard temperature of 100 degrees Fahrenheit. Treatment. Gential. The treating cylinder shall not be opened during treatment, unless so ordered by the Inspector. Classification. For the treating process all cross-arms shall be divided, with respect to the amount or sapwood contained by each into three classes as follows : Class H not more than 25 per cent of sapwood. Class S not less than 75 per cent of sapwood. Class I between classes H and S. Each class of cross-arms shall be carried through the entire treat- ing process separately. In no case shall a given cylinder load con- tain more than one class of cross-arms, nor shall it contain cross-arms of different sizes. Heating Process. The seasoned and inspected cross-arms shall be placed in the treating cylinder, the temperature within which shall be maintained by means of the closed heating coils at a tem- perature of about one hundred and fifty (150) degrees Fahrenheit tor at least one (1) hour. [ 639] Sec. 9 WOOD PRESERVATION Exhaustion Process. It is not required that a vacuum shall be drawn after the heating process and before the filling process, pro- vided the specified amount of creosote can be injected into the timber without the previous application of a vacuum. Filling Process. After the heating process or after the exhaustion process in cases where the latter is applied, the cylinder shall be completely filled, as rapidly as possible, with creosote, and in no case shall the flow of oil into the treating cylinder be stopped before the overflow of the cylinder. This shall be determined by means of an overflow valve at the top of the cylinder. All air must be removed from the cylinder before pressure is applied. Pressure shall then be applied until the amount of oil required for each class of cross-arms has been forced into the timber. Each class of cross- arms shall be impregnated with the amounts of creosote shown in the following table: Class H cross-arms not less than 8 pounds per cubic foot of timber. Class S cross-arms not less than 12 pounds per cubic foot of timber. Class I cross-arms not less than 10 pounds per cubic foot of timber. The total amount of oil forced into the cross-arms shall be determined from the initial reading on the measuring and working tanks, and the reading on the measuring and working tanks after the oil in the cylinder at the conclusion of the pressure process, including all drip from the cross-arms, after it has been returned to the measuring tanks. The oil at introduction into the cylinder shall have a temperature of not less than one hundred and forty (140) degrees Fahrenheit and not more than one hundred and seventy-five (175) degrees Fahrenheit maintained at the initial temperature during the whole process of forcing the oil into the cross-arms. Subsidiary Specifications. The following specifications form a part of this specification: Specification creosote. Specification for analysis of creosote. 16. OPEN TANK SYSTEM. The efficacy of treating the butts of poles by the open tank method is now fairly well recognized. It appeals at once to the operating man on account of its simplicity, and as the application of the oil is made at the butts of the poles where they are most susceptible to deterioration, the method is economical. Moreover, the process may be satisfactorily carried out by and under the control of the consumer. General directions are given in the following as a guide for carrying out the open-tank method of treating poles and crossarms. 17. OPEN TANK TREATMENT OF POLE BUTTS. All the inner bark should be thoroughly shaved from the poles in order that the best penetration by the oil may be secured. After cutting, the poles should be piled and stored in layers at least twelve inches above the ground with sufficient space between each pole and each layer to [640] WOOD PRESERVATION Sec. 9 allow for circulation of air, also to prevent the accumulation of snow and moisture, and to facilitate thorough seasoning. All poles should be at least air dried and have not less than three months' seasoning before treatment. Poles of different classifications or different species of wood should not be treated in the same charge. Hot Bath. In the hot bath, the poles should be kept in oil main- tained at a temperature of 200 to 220 degrees Fahrenheit, for from one to three hours. Cold Bath. At the completion of the hot oil treatment, the poles should be placed in the cold oil, or the hot oil changed to cold oil, (oil at the temperature of surrounding atmosphere) for from one to three hours. Time of Treatment. No attempt is made to specify the exact time of either the hot or cold treatment, because this can best be determined by trial. It is understood that a complete penetration of the sap wood should be secured. Control. It should also be explained that where the apparatus is not equipped for both hot and cold baths, it will be necessary to permit the hot bath to cool down to the temperature of the atmos- phere. Penetration. Poles should be examined for depth of penetration of oil by boring samples at about four feet from the butt end. The bored holes should be filled with hot creosote oil immediately after the depth of penetration has been ascertained. The quantity of creosote oil injected should be determined by tank measurements. All tops and gains of poles should be brush-treated with two coats of hot oil. (See Article on Preservatives for specification for oil for brush treatments.) Treatment. The cross-arms should be treated by immersing them for at least thirty minutes in hot oil at from 200 to 220 degrees Fahrenheit, and then leaving them in cold oil for one hour, or more. The necessary duration of each bath is best determined by trial. If complete penetration of sap wood is not obtained, the length of time should be proportionately increased. Specifications have not been provided for a special oil for open tank treatments. It is true that perhaps excessive evaporation will result by using the ordinary oil, but the loss sustained is likely to be less than the extra cost of an especially prepared oil. 18. DESCRIPTION OF OPEN-TANK PLANTS. To meet the different local conditions existing among the member companies, four open-tank plants have been designed and the working plans referred to show the details of their construction: 1. Open-tank plant designated aa "Type A." 2. Open-tank plant designated as "Type B." 3. Open-tank plant designated as "Type C." 4. Open-tank plant designated as "Type D." Types "A," "B" and "C" are intended for the treatment of pole butts, while Type "D" is for the treatment of cross-arms. It has been impossible to include the valuable detail drawings of 21 [ 641 ] Sec. 9 WOOD PRESERVATION the different types of open-tank plants included In the 1911 report, owing to the fact that they could not be reproduced to a sufficiently large scale to be intelligible. For exact detail information, it will be necessary to consult the report as printed in full in the 1911 Pro- ceedings of the National Electric Light Association. The original report should also be consulted for costs of the different types of open-tank plants; also for drawing and details of a portable tank for brush treatments. Open-Tank Plant Type "A." This plant has a capacity of fifty poles per charge, and at least one hundred poles per day. A plant of such ample size is recommended for the use of the larger companies who may find it advisable to construct a permanent ?lant and who use sufficient poles to warrant such an investment, b will be seen from the plan that a steam siding is included and a power-driven derrick, so that heavy manual labor will be reduced as much as possible. Liberal yard room is also provided at one side of the plant for the piling and seasoning of the untreated poles, and at the other for storing the treated poles. The general layout of piping and tanks is so designed that this arrangement affords a plant which is easily controlled and operated. The oil bath in the treating tanks may be quickly changed from hot to cold. The storage tanks are elevated sufficiently above the treating tanks so that the oil will flow by gravity into the treating tanks. A plunger pump, having a capacity of 200 gallons per minute, is connected so that it discharges either from the receiving tank directly into the treating tanks, or into the storage tanks. A turbine drive, three-inch centrifugal pump may be substituted for the plunger pump, and the receiving tank eliminated, if found advisable. The piping shown is of liberal size, so that the time of changing the hot and cold oil will be reduced to a minimum. Steam coils are provided in the storage, receiving and treating tanks, and the area of the treating tank is sufficient, figuring two square feet of surface per pole, to accommodate 25 poles. Each storage tank is 10 feet in diameter, and 20 feet high, giving a capacity of about 11,500 gallons so that oil may be purchased in tank-car lots. The treating tanks contain sufficient heating coils to raise the temperature of the oil from zero to two hundred and twenty (220) degrees Fahrenheit. The coils are separated by 6-inch "I" beams, which have riveted on the top flanges 3^-inch by 2^-inch by 5/16-inch angle irons to support the poles. Angle irons are used instead of flat bars so that when the end of a pole is once placed on the bottom of the tank it will not change its position. The derrick intended for the outfit consists of an 8-inch by 10-inch boom, 4 feet long, two 8-inch by 8-inch stiff legs, each 40 feet long, one 8-inch by 8-inch mast, 30 feet long, and two sills 8 inches by 8 inches, 30 feet long, complete with derrick irons; one 10-foot diameter bull wheel with guide sheaves framed up complete, together with wire rope and clips to connect the bull wheel with the swinging gear. The derrick is equipped with ^-inch, cast steel cable, (hemp center) and with steel blocks having self lubricating bronze bushings. The engine [642] WOOD PRESERVATION Sec. 9 operating the derrick is a double 6%-mch by 8-inch cylinder, tandem, friction drum hoist engine; drums being 14-inch diameter, 16-inch face equipped with ratchet pauls and foot brakes. The boiler is of the vertical locomotive type, 50 horse-power capacity. It should be understood that the equipment may be modified to meet special requirements and a further description will not be dwelt upon, as local conditions governing each installation will have to be given due consideration. For example, in very moist ground, it would probably be advisable to build the plant high, rather than to excavate deep, and again, the capacity of the plant may be increased or diminished by changing the diameter of the treating cylinders, and by substituting a turbine driven centrifugal pump. Likewise a cheap derrick could be used with a steel cable runner, from a drum and engine located in the boiler house. Open-Tank Plant Type "B" has a maximum capacity of 28 poles per day. This outfit is intended for a temporary pole treating plant for a large company, or as a permanent outfit for small concerns. A fairly good control of the oil is secured by the use of a centrifugal pump. The hot oil may be quickly pumped into the top of the storage tank and at the same time the cold oil is filling the treating tank. Hot and cold regulation of oil may also be accomplished without uncovering the poles. The tanks are heated with steam from a small locomotive type, 20 horse-power, vertical boiler, and if found desirable, the derrick may be operated by steam. The design, however, shows it operated by a hand winch. The plant has one 11,500 gallon capacity, storage tank. This is provided so that oil may be purchased in carload lots, thereby giving the consumer the benefit of the lowest price for the preservative. The scheme is flexible; there is no permanent foundation, and the plant may be moved from place to place. Possible modifications of the type "B" open-tank outfit are apparent, as in the case ot type "A." The treating tank shown is 6 feet in diameter. This could be increased to a diameter that would allow a proportionately greater number of poles per charge, thereby increasing the ultimate capacity. In the capacity figured above, (about 24 poles per day) it was estimated that the treating tank would be charged twice and a cycle of operation would be six hours. It would probably be possible to crowd the capacity to at least 36 poles per day. With either the type "A" or type "B" plants the special boiler equipment could be eliminated, if they were located adjacent to a permanent steam plant. Open-Tank Plant Type "C" has a capacity of twelve poles per day. Type "C" plant may be used where the number of poles to be treated is small and the pole treating is to be carried on in an isolated place. This plant is quite elementary. It is apparent that the regulation is poor, it being necessary to heat the oil to, say, 200 degrees Fahrenheit, retaining the temperature at or near that point for three hours, and then after drawing the fire, permit the oil to cool down to atmosphere. This operation gives a heavy treatment, with practically no control. The same outfit may be arranged [ 643 ] Sec. 9 WOOD PRESERVATION without, the fire box, having heating coils in the bottom of the tank, the coils being connected to an independent boiler or to a steam supply from an adjacent plant. Such a modification would give control of the hot treatment, but not of the cold. Open-Tank Plant Type "D" is designed for the treatment of cross-arms, the capacity is approximately 300 cross-arms per day. The cross-arm plant consists of-two^steel tanks, one for the hot and one for the cold oil, each 12 feet long, 3 feet wide and 2 feet high, arranged side by side. The hot oil tank is equipped with four pairs of 1^-inch steam coils, connected to a separate boiler, or to adjacent [644] WOOD PRESERVATION Sec. 9 FIG. 361 [645] Sec. 9 WOOD PRESERVATION WOOD PRESERVATION nj&SiiKVATION o [647] Sec. 9 WOOD PRESERVATION tests show sufficient penetration, the cross-arms should be taken out and piled on the drip table to dry. Figure 360 is from a photograph of an open-tank pole treating FIG. 364. These timbers were supposed to have had the same treatment. Notice erratic results obtained, due to adhering bark and unequal seasoning. plant, in which the cost of handling the poles is reduced to a mini- mum, but this plant has but small capacity, and control of the cold bath is not obtained. Figures 361 and 362 show open-tank pole [ 648 ] WOOD PRESERVATION Sec. 9 treating plants that fairly well represent types "B" and "C." A false bottom for holding poles in position in bottom of treating tank is illustrated in Figure 363. Wide variation in oil penetration resulting from unequal seasoning is illustrated in Figure 364. This shows timber supposed to have had the same treatment. Figure 365 shows a green and a seasoned pole of the same species, both treated by the open-tank method. The effect of seasoning on the efficiency of the treatment is very marked. [649] Sec. 9 WOOD PRESERVATION 19. BRUSH TREATMENT. Much of the line timber treated at present is by the brush method. Although this treatment is less efficient than the pressure or open-tank system, it is recognized as often desirable and is used by many in the absence of more thorough methods. Unless absolutely unavoidable, the timber should not be treated when it is green, wet or frozen. It should be borne in mind that by not properly carrying out the brush treatment it is an easy matter to render the treatment worthless. Coal tar, creosote oil (see specifications for oil for brush treatments, Articles on Preservatives) should be applied with a three or four knot rubberset or wire bound roofing brush, the oil having been heated to a temperature of 200 degrees Fahrenheit. All crevices and shakes should be filled with the oil, using the same liberally for the first coat. The second coat should not be applied until the preceding coat has been fully absorbed. It is best to apply the different coats on different days. Tops and gains of poles should also receive two brush coats of the preservative. A spraying machine may be used for the application of the oil to the butts of poles. It has the advantage of filling up the cracks and season checks, and probably with this method the poles do not have to be handled so much as when the brush is used. However, the advantage of low cost of application is probably lost on account of the oil wasted in spraying the poles. [650] SECTION 9 PRESERVATIVE TREATMENT OF POLES AND CROSS-ARMS PART III APPENDICES SECTION 9 PRESERVATIVE TREATMENT OF POLES AND CROSS-ARMS PART m. APPENDICES Extracts from Report of Forest Service. Open-Tank Experiments on Western Yellow Pine. Open-Tank Experiments on Western Red Cedar. Report of German Government Telegraph Department. Relative Life and Value of Wood Poles. EXTRACT FROM REPORT OF FOREST SERVICE OPEN- TANK EXPERIMENTS ON WESTERN YELLOW PINE AND WESTERN RED CEDAR TABLE 94 POLE TREATMENTS, WESTERN YELLOW PINE Creosote Open Tank Time of Cutting Number Poles Averaged Absorption per Cubic Foot Pounds Penetration Inches Moisture Content; Per Cent, of Green Weight Lost Fall .. 11 15.03 4.3 48.0 Winter 22 11.03 2.7 51.5 Summer 2 1.92 M 55.2 Spring (seasoned) . 3 12.20 3.4 50.1 Spring (nearly sea- soned) 4 11.08 3.03 50.0 42 13.02 3.08 50.5 In the tables throughout the report the absorption is given in pounds per cubic foot of the treated section of the pole. The lower seven feet of the poles contain on an average 6.25 cubic feet. The penetration is given in inches at a point about five feet from the butt of the pole. The following points were brought out : 1. The time of cutting the poles shows a marked influence on absorption. Summer-cut poles are difficult to treat, while the Autumn-cut takes the preservative most readily. 2. Good absorption can be secured without heating the oil to temperatures resulting in evaporation of the creosote. 130 degrees Fahrenheit was used as a maximum temperature with good results. An average absorption of 13 pounds per cubic foot, and a penetra- tion of 3 inches was secured by this treatment. These poles have a heavy treatment. The wood-cells are full of free oil, and as the poles were removed from the cold oil they carried large amounts of it on their surface, much of which is wasted. In an effort to overcome these disadvantages, the next series of treatments were given as the preceding series except that the oil was again heated to about 200 degrees Fahrenheit several hours before the poles were removed. The object of the reheating is to overcome this objection. The results are presented in the following table: (Table 95.) [655] Sec. 9 WOOD PRESERVATION TABLE 95 POLE TREATMENTS, WESTERN YELLOW PINE Creosote Open Tank Time of Cutting Number Poles Averaged Absorption per Cubic Foot (Pounds) Penetration (Inches) Moisture Content; Per Cent of Green Weight Lost Fall Winter. . . . Summer . . . Spring (seasoned) Average . . . 9 14 20 13 56 14.16 5.45 7.10 11.67 8.88 5.25 1.3 2.2 4.3 3.3 54 52 54 54 53 It is apparent that, with the exception of the Summer-cut poles, each cut has taken up less oil per cubic foot. The average penetra- tion is better than in the series in which the poles were not reheated. The average absorption of 8.9 pounds of oil per cubic foot with a penetration of 3.3 inches at the ground line is a satisfactory amount of oil for the result secured. Further, when poles are removed hot from the oil, the outer coating of oil which they carry on their sur- face, is drawn into the pole by the interior contracting air before it reaches the ground from the derrick. Borings in poles treated in this manner show that the outer part of the wood is free from excess oil for a depth up to two inches, while in the lower part of the boring creosote is found free in con- siderable quantity. The third plan tried with a single-tank system consisted in heating the poles in hot creosote several hours and allowing the oil to cool about 20 degrees, which required an hour, and then removing the poles from the partially cooled oil. The 20 degrees fall in temperature draws in a small quantity of oil. The pole being now removed and allowed to cool to air tem- perature the contracting air in the wood draws the free oil in very deep, coating each passageway as it sinks in until no free oil is left in the cells. This secures the greatest protection for the smallest amount of creosote. The treatment is very successful, resulting in as deep a penetration as 3 inches with 5 pounds of oil per cubic foot of wood. The preceding results we're secured by a single bath treatment. Much time can be saved with an equipment permitting two baths of the preservative, one hot and one cold. This may be accomplished by two tanks or an arrangement for changing the oil in the single tank quickly. In this way the effect of the previously described 18-hour treatments can be secured in five hours, or less. In the dry weather of Summer, if the poles are thoroughly seasoned, [ 656 ] WOOD PRESERVATION Sec. 9 penetrations of two to three inches with six pounds of oil per cubic foot can be secured by heating the poles for one hour in oil at 180 degrees Fahrenheit and then plunging them into air-cold oil for from two to five minutes. The poles are removed very hot, the surface oil is immediately drawn in and the poles are dry before they strike the ground. Other variations in the tank treatment are possible. The important conclusions to be drawn from the tank treating experiments with creosote upon western yellow pine are: 1. Poles should be well seasoned before treatment until they have lost 50 per cent of their green weight. 2. Poles should be separated according to season of cutting before treatment if possible. Summer-cut pine poles should not be treated with other poles, as they require a severer treatment. 3. Very old dry poles should not be treated in the same run with timber just seasoned. 4. Seasoned pine can be very successfully treated with creosote with absorptions up to 15 pounds of oil per cubic foot of treated timber and penetrations as deep as five inches. 5. The desirable form of treatment is an empty-cell treatment, which coats the interior of the walls and leaves no excess of oil in the wood. 6. The above treatment can be given with six pounds of oil per cubic foot or with four and one-half gallons to the average 40-ft. 8-in. pole. 7. The quantity of oil used caif be controlled. 8. The time of treatment will" vary according to the moisture condition of the timber as affected by relative humidity and recent rains. 9. Seasoned timber can be very readily treated with creosote in from one to five hours, according to its moisture condition. 10. Green and half -seasoned poles cannot be creosoted successfully. 11. Poles not well seasoned should be treated by heating for several hours at 215 degrees Fahrenheit and plunging into cold oil until the poles are cold. This is a forceful treatment, and the result will depend upon the moisture condition of the poles. 12. The treatment is best applied to seasoned poles as follows: a. By heating the poles for one hour at 180 degrees, cooling the oil to 160 degrees, reheating to 200 degrees, and withdrawing the poles hot. b. By heating the poles for one hour at 180 degrees, plunging them in cold oil for five minutes and removing. c. By heating as above and holding in cold oil until desired ab- sorption is secured and then removing. Tank Treatments with Crude Petroleum. The poles in the table below were heated in crude oil at 200 degrees Fahrenheit for two or three hours and then allowed to cool in the oil over night, making a total time of treatment of 18 hours. The Fall-cut poles show the best absorption. The average ab- sorption of the other cuts is 3.68 pounds per cubic foot with a pene- [ 657] Sec. 9 WOOD PRESERVATION TABLE 96 POLE TREATMENTS, WESTERN YELLOW PINE Crude Petroleum Open Tank Season of Cutting Number Poles Average Absorption per Cubic Foot (Lbs.) Penetration (Inches) Moisture Content ; Per Cent of Green Weight Lost Fall 13 2 2 1 6 11 13.47 2.35 3.94 16.20 2.36 3.68 2.7 1.5 1.5 3.0 1.13 1.4 55.7 53.0 55.0 59.4 50.7 53.0 Winter .... Summer. . . Spring .... (seasoned) Spring (partly seasoned) Average . . . tration of 1.4 inches. A six-hour treatment of Fall-cut poles, con- sisting of heating for three hours at 200 degrees Fahrenheit, cooling in three hours to 160 degrees Fahrenheit, and then removing the poles, gave an average absorption of 9.27 pounds per cubic foot with 1.25 inches penetration. The conclusions respecting tank treatments with crude oil are : 1. Western yellow pine must be thoroughly seasoned, not less than 50 per cent of the original green weight being evaporated before treatment with crude oil. 2. Crude oil is weakly antiseptic, and should therefore be used only on very dry timber and in cell-filling quantities. 3. From three and one-half to 13 pounds of oil per cubic foot of timber, immersed according to the season of cutting, can be forced into seasoned pine with penetrations of from one to three inches. Fall-cut timber treats by far the most easily. 4. The time of treatment will vary from six to eighteen hours. Treatments with Creosote and Crude Petroleum. To secure an antiseptic-treated surface upon poles treated with crude oil, it was proposed to give the hot bath in creosote and the cold bath in crude oil. Six poles treated in this manner gave an average absorption of five pounds of oil per cubic foot of timber with a penetration of 1.7 inches. This treatment is not recommended, for it is difficult to keep the amount of creosote absorbed as low as desired. Further, it is probable that the crude oil mixes with the outer creosote and weakens the strength of the wood-cell coating of creosote. Tank Treatment with Zinc Chloride. The table below shows the result of holding the poles at 170 degrees to 200 degrees Fahrenheit in a zinc chloride solution for two to three hours and allowing the poles to cool with the solution. The treatments were started with a [ 658 ] WOOD PRESERVATION Sec. 9 seven per cent solution of the salt and varied to a point showing a specific gravity of 1.03. (Table 97.) TABLE 97 POLE TREATMENTS, WESTERN YELLOW PINE Zinc Chloride Open Tank Season of Cutting Number of Poles Averaged Absorption per Cubic Foot (Pounds) Moisture Content ; Per Cent of Green Weight Lost 20 6 6 16 48 23.65 17.70 17.70 11.04 17.90 56.2 55.0 MJ Winter Spring Average The zinc chloride solution is the most readily absorbed of any of the preservatives. Borings and chemical analyses proved that pure zinc chloride was present in large quantities at a depth of five inches, and that in many poles a much larger quantity was present than necessary. The use of hot and cold baths shortens the time of treatment. Three hours divided between a bath at 150 degrees Fahrenheit and a cold bath resulted in an absorption of 12.5 pounds of the solution per cubic foot. Merely standing the poles in a cold solution for 15 hours gave an absorption of 9.7 pounds per cubic foot of timber. The conclusions for this treatment are: 1. Pine should be well seasoned (at least 50 per cent of green weight being evaporated) before treatment with zinc chloride. 2. Greener timber can be treated with this preservative than with the oils. 3. Seasoned timber can be treated in from two to six hours. 4. The amount of zinc chloride per cubic foot and the depth of penetration is under control by varying the strength of the solution and the time of treatment. 5. The water of the zinc chloride solution should be dried out before the poles are set in the soil. Two weeks proved sufficient to evaporate this water. 6. There is no difficulty in securing an absorption of one-half pound of pure zinc chlorides per cubic foot, the usual commercial practice. This can be secured with a two per cent to three per cent solution of the salt. Tank Treatments with Creosote and Zinc Chloride. This is a combination treatment designed to secure a narrow creosote-treated belt of wood around an interior full of zinc chloride. The reasons for this treatment lie in the facts that zinc chloride Is inexpensive [659] Sec. 9 WOOD PRESERVATION but soluble in water and so subject to leaching out of the wood, while creosote is insoluble and stable but expensive. In practice the treatment is effected by heating the poles in creo- sote and cooling them in zinc chloride solution, which passes through the creosoted exterior to the interior of the pole. Poles were suc- cessfully treated in this manner. This treatment is not recommended, because of the great difficulty experienced in controlling the amount of creosote absorbed in the hot bath and holding it to a minimum in very dry poles. Summary of Absorption Results. The absorptions tabulated below present the actual results of the successful classes of treat- ment discussed in the preceding pages: (Tables 98, 99, 100.) TABLE 98 AVERAGE ACTUAL RESULTS SECURED Preservative Application Absorption ; Pounds per Cubic Foot Penetration (Inches) Treatment Recommended Pounds per Cubic Foot Creosote .... Creosote .... Carbolineum Carbolineum Creosote .... Creosote Crude oil .... Zinc chloride Brush 1 coat Brush 2 coats Brush 1 coat Brush 2 coats Tank full cell Tank empty cell Tank Tank .4 .6 .5 .8 13.0 8.9 3.5 to 10 17.9 (solution) f I 1 to 3 Complete Same Same Same Same 10 6 6 Ib zinc chloride TABLE 99 WESTERN YELLOW PINE Estimated Annual Service Charge 40-ft. 8-in. Poles Species Treatment COST OP POLES Esti- mated Average Life (Years) Equivalent Annual Charge at 5% Added Life Necessary to Pay for Treatment (Years)t In Yard In Line* Cedar Yellow Pine Yellow Pine Yellow Pine Yellow Pine Yellow Pine Yellow Pine Yellow Pine None None Crude o. Creosote brush Carbolineum brush Zinc chloride Creosote 10 Ibs. Creosote 6 Ibs. $8.00 5.00 5.61 5.19 5.43 5.54 6.82 6.25 $11.00 8.00 8.61 8.19 8.43 8.54 9.82 9.25 10 3 4 5 9 20 20 $1.425 2.94 2.55 2.01 1.20 .78 .74 8 8 a * Including framing, hauling and erecting, but not stepping, shaving or painting, f Estimating the life of untreated pine at three years. [ 660 ] WOOD PRESERVATION Sec. 9 TABLE 100 POLE TREATMENT WESTERN YELLOW PINE COM- PARATIVE COSTS OF TREATMENT, STANDARD 40-FOOT POLE, WEIGHING 800 POUNDS, TREATING 6>i CUBIC FEET QUANTITY COST OF PRE- SERVATIVE Total Handling Cost of Preservative Application Charge Treat- Per Cu. Ft. Lbs. Per Pole Lbs. Per Pound Per Pole per Pole ment per Pole Creosote .... Brush .4 2.50 $0.0235 SO. 06 $0.05 $0.11 1 coat Creosote .... Brush 2 coats .6 3.75 .0235 .09 .10 .19 Carbolineum Brush 1 coat,. .5 3.13 .066 .21 .05 .26 Carbolineum Brush 2 coats .8 5.00 .066 .33 .10 .43 Creosote .... Tank 10.0 62.50 .0235 1.47 .35 1.82 Creosote. . . . Tank 6.0 37.50 .0235 .89 .35 1.24 Crude petro- leum Tank 6.0 37.50 .007 .26 .35 .61 Zinc chloride Tank .5 3.12 .06 .19 .35 .54 Creosote and \ 1.0 6.25 .0235 .15 \ 35 CO zinc chloride /Tank .5 3.12 .06 .19 ) ' 35 .69 WESTERN RED CEDAR Tank Treatments with Creosote. Thoroughly seasoned cedar poles of the Fall and Summer cut, treated after seasoning to 23 pounds per cubic foot, showed an average absorption of seven pounds per cubic foot of timber immersed. The penetrations varied from .2 to 1.5 inches and averaged .7 of an inch at a point corresponding to the ground line of the pole in service. These figures are the average of those obtained by treating 126 poles in a single bath of creosote heated to 200 degrees Fahrenheit to 225 degrees Fahrenheit for from two to six hours, and then allow- ing the poles to cool in the oil until the following morning, making a total time of treatment, including handling, of 24 hours or one run per day. There is no difference in the absorption of Summer-cut and Fall- cut poles as in the case of yellow pine. One reason for this fact is that cedar is all heart-wood except an outer band of sap-wood from one-half to one and one-half inches thick. The heart-wood cannot be penetrated by this process, but the narrow sap-wood band of well-seasoned poles can be completely filled with oil irrespective of the season of cutting. [ 66X] Sec. 9 WOOD PRESERVATION When the heart-wood is protected by a band of sap-wood filled with creosote the pole is exceedingly decay resistant. In order to reduce the time of treatment, experiments on Fall-cut poles seasoned to 23 pounds were tried with hot and cold tanks of oil. The poles were heated from three to six hours in the hot bath and then plunged into the cold bath for a limited period. The results are tabulated below: (Table 101.) TABLE 101 WESTERN RED CEDAR Absorption of Creosote Poles seasoned to 23 pounds per cubic foot HOURS OF TREATMENT Number Poles Averaged Total Absorption (Pounds per Cubic Foot) Penetration (Inches) Hot Cold Bath Bath 8 3 2 1 3.3 .48 4 4 3 1 2.5 .35 4 4 2 2 2.9 .39 6 5 4 1 3.8 .45 4 6 4 2 3.8 .50 126 18 Hot bath cooling to 7.0 .70 air temperature Short runs can apparently be made with success. From the tabulation it cannot be said what period can best be used in practice, but it is safe to say that a six-hour run will result in an absorption of 3.8 pounds per cubic foot and a penetration of one-half inch. Winter-cut poles treated with creosote after seasoning to 25 ^ pounds per cubic foot could not be well treated in short runs. Seven hours in the hot bath followed by one-half hour in the cold bath gave an average absorption of but 1.6 pounds of oil per cubic foot and a penetration of one-eighth inch. These poles were best treated by leaving them in the tank while the oil was heated for about three hours, cooled two hours, reheated two hours, and then permitted to cool over night. The oil absorbed in the first heating and cooling aids in the second heating and cooling. Upon 22 poles this treat- ment resulted in an average absorption of 4.4 pounds of oil per cubic foot arid a penetration of one-third inch. Two and three hours' heating, and allowing the poles to stand over night resulted in three pounds absorption and one-quarter inch penetration. It can be readily seen that poles at 25^ pounds absorb about one-half as much oil as when they are seasoned to 23 pounds. Further, the treatment in the latter case is much shorter. [662] WOOD PRESERVATION Sec. 9 Experiments with the Spring-cut poles proved that poles seasoned to but 28 pounds cannot be successfully creosoted. A few old, dry poles from a pile in the Pacific Electric Company's yards were treated to show the possibilities with thoroughly seasoned poles. The results follow: (Table 102.) 1 FABLE 102 Treatment Absorption Hot Bath (Hours) Cold Bath (Hours) (Pounds per Cubic Foot) (Inches) 4 o 2/3 V* 3 20 minutes 3 H 5 5 " 4 *>/ 1 2 1 1 7 5 i 3 1 5 The important conclusions are: 1. Poles should be seasoned to 25 pounds per cubic foot before creosoting. Better results are secured after seasoning to 23 pounds per cubic foot. 2. The time required for creosoting timber seasoned to 25 pounds per cubic foot will vary from seven to 24 hours according to the result desired. Two runs per day per tank can be made, one giving an absorption of one and one-half pounds per cubic foot, and the second an absorption of three pounds, or one daily run may be made with an absorption of four and one-half pounds per cubic foot. As the poles become dryer the absorptions increase. 3. The best absorption and penetration is secured when the poles are seasoned to a weight of 23 pounds per cubic foot. At this stage the sap-wood can be completely filled with creosote with about five gallons of oil per average pole. 4. Poles seasoned to 23 pounds per cubic foot may be creosoted in six hours and less with an absorption of 3.8 pounds per cubic foot and a penetration of one-half inch. This amounts to about three gallons of oil per pole. 5. The sap-wood of cedar poles seasoned to 23 pounds can be completely filled in a 24-hour single bath treatment with an absorp- tion of seven pounds per cubic foot or approximately five gallons of oil per pole. Tank Treatments with Crude Petroleum. Cedar cannot be suc- cessfully impregnated with crude oil in an open tank. Even with thoroughly seasoned poles but slight absorption and penetration can be obtained barely more than a coating of oil. Tank Treatments with Zinc Chloride. Treatments upon the [ 663 ] Sec. 9 WOOD PRESERVATION partially seasoned poles of the Spring-cut with a water solution of zinc chloride prove that three pounds of solution per cubic foot can be forced into poles seasoned only to a weight of 31 pounds per cubic foot. This required a 24-hour treatment consisting of heating several hours at 210 degrees Fahrenheit and allowing the poles to cool in the solution over night. Poles seasoned to 25 pounds per cubic foot absorbed about four pounds of seven per cent solution per cubic foot in short runs, con- sisting of two hours in each bath or a total of four hours. One hundred and three poles, seasoned to 23 pounds per cubic foot, treated in a zinc chloride solution heated to 210 degrees Fahrenheit for one to four hours and allowed to cool, averaged an absorption of four pounds per cubic foot. This treatment ft unnecessarily long for poles so well seasoned. The same results apparently can be obtained in four hours by hot and cold baths. In these treatments the strength of the solution varied from three per cent to 10 per cent. The conclusions for this preservative are: 1. Greener poles may be treated with zinc chloride solution than with creosote Poles seasoned only to 31 pounds per cubic foot will absorb three pounds of solution per cubic foot in a 24-hour treatment. 2. The strength of the treatment can be controlled by the amount of the zinc chloride in solution. One-half pound of the pure chloride for each cubic foot of timber immersed is sufficient. 3. Poles seasoned to 25 pounds per cubic foot and below can be quickly treated in four hours with four pounds of solution. Tank Treatments with Creosote and Zinc Chloride. This treat- ment should be used only on poles seasoned to at least 25 pounds per cubic foot. At this stage poles held in a bath of creosote at 212 degrees Fahrenheit for one hour or more, and then plunged into a solution of zinc chloride, will absorb about two-thirds pound of creosote per cubic foot in the hot bath and three and one-third pounds of solution in the cold bath. Twelve zinc-treated poles which had evaporated the water of the solution were brush-treated with creosote, absorbing about half- pound of oil per cubic foot in two coats. Poles freshly treated in a zinc solution will not absorb creosote upon being brush treated or plunged into a tank of oil. REPORT OF GERMAN GOVERNMENT TELEGRAPH DEPARTMENT The Relative Life and Value of Wooden Poles BY GEH. OBER-POSTRAT CHRISTIANI, BERLIN 1 The Government telegraph department has in its collection of statistics a rich, but unfortunately undeveloped, field for inquiry as to the life of wooden telegraph poles. All the upper postal direct- ors transmit annually to the head office reports as to the condition at the beginning of the year of the wooden poles standing in the lines, Archiv. fur Post und Telegraphie: Nr. 16 Berlin, August, 1905. [664] WOOD PRESERVATION Sec. 9 likewise the additions due to new construction, change of route, or replacement, and on the other hand, those lost from decay or other causes. These reports which cover the entire territory of the de- partment are comprehensively summarized. These statistics go back for the North-German and even the Prussian telegraph systems to 1852, and thus cover a period of more than 50 years. These statistics are of particular value, because the figures are separated as between untreated and treated poles, and furthermore separated as to the different treatments which have been used, as copper sulphate, zinc chloride, dead oil of coal-tar, and corrosive sublimate. The thought then arises to calculate from this abundant material the average life of the different kind of poles and to draw conclu- sions therefrom as to the economical value of the different treatments. The occasion for doing this in a thorough manner has not previously arisen. Although Archive No. 23 for 1883 contained a paper on "The Average Life of Poles in the Government Telegraph Lines" it is merely a reprint of the statistics collected for the official year 1879-1880 and is without value as a basis for determining the average life. Another paper, by Kohlman, covering the subject matter, is to be found in Archive No. 5 for 1890, under the title, "The Different Processes of Protecting Wood Against Decay With Special Reference to the Conditions Which Are Involved in the Treatment of Telegraph Poles." This noteworthy paper gives a detailed statement of the ordinary methods of treatment under the conditions prevailing at that time, and states among other things that fir (kieferne) poles of the usual dimensions have lives approximately as follows: Untreated poles ................................ 4 to 5 years Poles treated with copper sulphate ............... 10 to 14 " zinc chloride .................. 8 to 12 " dead oil of coal-tar ............ 15 to 20 " corrosive sublimate ............ 9 to 10 This statement, however, is not backed up with adequate figures. We shall see that different average lives follow from Government statistics, the publication of which, together with the data on which they are based, should fill a gap in the literature of the subject. First of all we give an idea of the development of the network of lines upon which these observations have been made by means of the accompanying tabulation of the telegraph poles in the lines at the close of each vear since 1852. (Table 103.) The great proportion of poles treated with copper sulphate is apparent. Expressed as percentage per 100 poles there were at the close of 1903 treated with: Copper sulphate ....................................... 89.9 Zinc chloride .......................................... 0.4 Dead oil of coal-tar ................ . ................... 3.0 Corrosive sublimate .................................... 5.5 Other Methods ...................... .................. 0.1 And Untreated ........................................ 1.1 Total ........................................... 100.0 [665] Sec. 9 WOOD PRESERVATION TABLE 103 CHANGE IN THE NUMBER OF TELEGRAPH POLES FROM 1852 TO 1903 At the POLES WERE STANDING IN THE LINES Close of Treated With the Official Year Copper Sulphate Zinc Chloride Dead Oil of Coal-Tar Corrosive Sublimate Untreated 1852 1,983 1854 1,990 1856 5,751 '942 1857 6,723 2 942 1858 "562 8,185 2 "105 952 1859 3,241 12,318 93 105 952 1860 12,136 18,783 566 105 960 1861 25,048 28,323 2,501 379 1,041 1862 46,246 44,983 3,270 2,072 1,420 1863 65,619 31,973 7,661 2,353 1,462 1864 76,926 50,233 13,268 2,636 2,263 1865 81,702 57,810 20,864 2,893 2,891 1866 80,811 64,005 29,028 2,893 3,574 1867 79,378 71,654 41,117 3,008 6,877 1868 77,308 75,447 70,224 3,425 9,943 1869 75,820 78,847 86,204 4,390 13,165 1870 72,828 81,125 97,704 5,854 15,510 1871 70,545 82,574 116,427 10,924 19,321 1872 69,940 85,089 135,630 12,884 23,535 1873 75,878 92,663 155,073 15,411 28,393 1874 96,767 107,074 159,368 18,803 28,638 1875 137,149 100,411 160,678 26,437 30,930 1876 188,615 88,668 160,016 31,283 29,811 1877 258,221 90,828 163,857 41,995 29,044 1878 350,202 77,679 156,044 67,474 ) 1879 429,834 68,357 148,323 77,571 T 1880 1881 482,878 522,572 56,941 49,519 138,683 134,792 81,111 81,849 1 Uata Missing 1882 566,906 42,551 129,897 80,321 1883 605,504 37,318 128,582 81,616 21,404 1884 613,604 32,317 124,603 85,272 19,277 1885 739,160 27,342 123,976 88,047 16,049 1886 803,493 23,671 119,093 91,393 12,730 1887 833,636 19,560 113,419 94,718 9,957 1888 943,348 17,121 110,678 97,131 7,779 1889 1,018,529 16,723 107,747 95,751 6,259 1890 1,105,656 15,642 103,999 92,278 5,436 1891 1,134,051 14,429 100,326 88,407 4,698 1892 1,26?,842 16,791 96,684 83,845 4,156 1893 1,351,683 16,643 92,099 78,580 16,421 1894 1,439,379 17,296 89,332 74,330 21,962 1895 1,515,234 17,599 85,577 66,957 31,161 1896 1,585,001 17,851 83,640 59,298 42,652 1897 1,670,985 16,949 82,209 52,967 51.300 1898 1,784,312 16,579 81,306 47,392 55,257 1899 1,917,166 15,816 84,505 56,652 60,914 1900 2,111,952 15,089 90,338 74,770 57,332 1901 2,278,021 13,965 88,963 91,035 49,015 1902 2,428,930 13,469 88,254 125,196 39,830 1903 2,560,412 11,689 86,818 156,818 30,895 WOOD PRESERVATION Sec. 9 It might be mentioned here that the administration purchases almost its entire supply of wooden poles green and treats them at its own plants with copper sulphate. Moreover, for about five years, if only as a makeshift, it has provided for the delivery of kyanized poles by outside contractors. The two above-mentioned treatments the cylinder treatments with zinc chloride and with dead oil of coal-tar have on the other hand excepting occasional experiments with tar-impregnated poles been discontinued. In order to obtain the total number of telegraph poles which have served as a basis for our tables, we have added to the poles which were in the lines at the end of 1903, the total number of poles, which, on account of decay and other causes, have been replaced since 1852. These totals are tabulated in the following table: (Table 104.) TABLE 104 TOTAL NUMBER OF POLES UNDER OBSERVATION Treatment Poles Standing in the Line at the End of 1903 NUMBER OF POLES WHICH HAVE BEEN REMOVED BETWEEN 1852-1903 Total No. of Poles Under Obser- vation On Acoount of Decay From Other Causes All To- gether Copper sulphate Zinc chloride 2,590,412 11,689 85,818 156,818 2,108 30,895 663,069 172,822 83,630 113,577 76,813 536,955 33,388 92,049 23,516 15,257 1,200,024 206,210 175,679 137,093 92,070 3,760,436 217,899 262,497 293,911 2,108 122,965 Dead oil coal-tar Corrosive sublimate Other treatments Untreated Total 2,848,740 1,109,911 701,165 1,811,076 4,659,816 During 52 years, 4,659,816 telegraph poles of different kinds have accordingly been under observation. Such a long period of observa- tion and such an extraordinarily large number of observations which have occurred under the most varying local conditions have permitted the calculation of mean lives which can lay claim to general validity. The restriction to a single line or to a shorter period of observation would afford no guarantee for the reliability of the average figures. For, on the one hand, the life of poles depends, for the same kind of treatment, to a large degree on the dimensions as well as on the species, on the age and on the conditions of growth of the tree from which the poles are obtained; on the other hand, on the character of the soil in which they are set and on the climatic influences to which they are exposed. This diversity of conditions could not but make itself felt in a small series of observations; it, however, is [667] Sec. 9 WOOD PRESERVATION feW wh w COH wo Bfe s SB s -g 3^ 85 v* m * to c~ & 1-4 *# r sssgg COCO^tO <=!?>_ ^ ^Tl^eS^i-^iH co^w eutQc*c^ to ****# m o oo co un en N ! g s g s s s s s 8 a 3 e 3 o s ass s i TH" TiT in" t-" en" en" en" in" esT IH" e- 1 1-" o" ^ ^T eo" eo" i-T CO T-l 00 t- IH co 1-1 [668] WOOD PRESERVATION Sec. 9 coH W O nS C^ t-r} rH jaquin^[ jaquin^ "& jaquin^ p9Aora9}j jaquin^j co Tji -^ i-i H e> ^H co *i u> to rHiHiH at oo> o OOv4MMMMM^I2<#MtMkMt10l0<0 ^co^i-j^e^^ eo^ ^SSSS^^ISSSSSSSSSSSSSS !^i 2225^^ SSSSS3 [ 669 1 Sec. 9 WOOD PRESERVATION o ,n S l> cj Cd O H rvi T* Cd *^3 r* ta M S> F ~J rt O <; 53 H a o 15 n "-^ 5 a Sfa J. 9 d> > l^mO>i ^ii |A inches wide to securely fit the cross-arms and shall be Y^ inch deep and spaced 24 inches apart on centers, as shown in Fig. 366. 7. Reverse or Buck-arm Gains. Where reverse or buck-arms are to be placed on a pole, the cross-gains shall be cut at right angles to the line gains. 8. Cross-arm gains, bolt holes and pole tops shall be painted with at least one coat of preservative paint before the pole is set. 9. Painting. Poles that are to be painted in order to improve their appearance, shall be given a priming coat of standard green pole paint before being taken from the yard. After the pole is set and construction line work thereon has been completed, the poles [ 681 1 Sec. 10 LINE CONSTRUCTION FIG. 366. Pole framing. [ 682 ] LINE CONSTRUCTION Sec. 10 shall be given a second or finishing coat of standard green pole paint. Cross-arm braces, pins, switchboxes, pole steps and other fixtures, shall be painted when this finishing coat is applied. 10. Pole Numbering. Every pole belonging to the electric light or power company and every pole that is the joint property of the company, and of some other company, should be numbered. The designating number of the pole shallbe stencilled thereon as soon as possible after the pole has been set. 11. Rights-of-Way. In selecting the route of a pole line, it is important to consider the district through which the line will extend, as well as the probable business that can be connected to such a line. 12. Street Rights-of-Way. Lines should be arranged to follow one side of the thoroughfare as much as possible to reduce the number of crossings to a minimum. In designing a new line, care should be taken to obtain an unobstructed right-of-way, selecting a location which will not conflict with existing pole lines of other companies. It is undesirable to erect pole lines on the same side of the street as existing pole lines. 13. Back Yard Rights-of-Way. It will sometimes be found desir- able to locate poles along the rear lot lines, but unless permanent rights-of-way are secured, such poles shall not be used for carrying important feeders or mains. Poles carrying feeders and mains shall preferably be located on public streets, not only because the rights-of-way are more permanent, but also because poles so located are available for supporting street lamps. 14. Locating Poles on Street. Efforts should be made to select the following locations for poles: (a) At the junctions of all streets or alleys to facilitate the in- stallation of branch lines, feeders and service connections. (b) Poles in all cases should be located so as not to obstruct door- ways, windows, porches, gates, coal holes, runways, etc. (c) At railroad crossings unless physical conditions or municipal requirements prevent the side clearance should be not less than 12 feet from the nearest track rail of main line tracks and 6 feet from the track rail of a siding. 15. Spacing. On straight sections, wood pole lines for distribu- tion work shall have a length of span approximating 125 feet. On curves and corners the spans shall be shortened as given in Table Fig. 367. 16. Street Crossings. When a line must cross from one side of a street to the other, the crossing shall be made with the smallest possible angle of deviation in the line, but the span should not exceed 110 feet. The spans on the straight lines next to and on either side of the crossing, shall also be shortened from the standard pole spacing of 125 feet to 100 feet or less. [ 683 ] Sec. 10 LINE CONSTRUCTION v/) _ Db. i 11! 11 "e3 ill LINE CONSTRUCTION Sec. 10 17. Heavy Poles. The heaviest poles shall be placed at t line terminals, corners, street crossings and other points of exceptional strain; and at such points the depth of pole setting shall be increased at least 6 inches, as specified in the table given in Art. 21. At all such points the length of adjacent spans shall be reduced from the standard pole spacing. 18. Clearing Obstacles. To clear obstacles, such as buildings, railroad gates, foreign pole lines, bridges, etc., poles shall be used of sufficient height and so located that there will be ample clearance between the obstacle and the nearest line wire. 19. Line Level. The length of poles shall be so proportioned to the contour of the country, or to adjacent poles of exceptional height set to clear obstacles, that abrupt changes in the level of the wires will not occur. 20. Curb Line. Poles set along a curb line shall be located so that there is a clear space of about 6 inches between the nearest surface of the pole and the outside edge of the curb. Poles on country roads where the curb line is not laid out should be set as nearly as possible 6 inches inside of the line which the curb will follow, so that when the street is afterwards laid out and curbed, the poles need not be shifted. 21. Pole Setting. Poles shall be set in the ground to a depth not less than that given in the following table. TABLE 110 POLE SETTINGS Depth j n Ground Length Over All in Feet Curves, Corners and Straight Lines Points of Extra Strain 30 5.0 feet 6.0 feet 35 5.5 6.0 40 6.0 6.5 45 6.5 7.0 50 6.5 7.0 55 7.0 7.5 60 7.0 7.5 65 7.5 8.0 70 7.5 8.0 75 8.0 8.5 80- 8.0 8.5 f 685 ] Sec. 10 LINE CONSTRUCTION 22. All holes shall be dug large enough to admit the pole without forcing and shall have the same diameter at the top as at the bottom. 23. Poles shall be set to stand perpendicularly when the line is completed. Exception can be taken to this rule, in that a very slight lean against the strain can be given to poles at line terminals, corners, curves and other points of excessive strain. 24. Poles with a bend or crook shall be so placed in a line that the defect is as unsightly as possible. In general, this result will be obtained by turning the pole bend in the same direction as that followed by the line. 25. After a pole is placed in position, only one shovel shall be used in filling the hole, while three tampers continuously pack in the filling until the hole is completely filled. Crib Braces from 4' to 6* length FIG. 368. Crib bracing. 26. After the hole is completely filled, soil shall be piled up and packed firmly around the pole, and any sod which has been removed to set the pole shall be neatly replaced. New pole settings shall be inspected after they have been subjected to a heavy rainstorm, to make sure that the filling has not sunk and left around the pole a cavity dangerous to the public safety. 27. Crib Bracing. Poles which cannot be strongly guyed, and which must be set in soft ground, may be given additional stability [ 686] LINE CONSTRUCTION Sec. 10 by crib bracing, as shown in Fig. 368. This consists of placing at the point of maximum strain two logs, about five feet long and not less than 8 inches in diameter. The top brace alone, or both braces, can be used according to the amount of additional stability required. 28. Artificial Foundation. When exceptional stability is required of a pole setting, an artificial foundation of concrete may be placed around the base of the pole. This concrete filling shall extend at least one foot from the pole on all sides, be carried above the ground line and bevelled to shed water, and shall consist of one part Port- land cement, three parts sand and six parts broken stone or clean gravel, and mixed wet. 29. Quicksand. When poles are to be set in quicksand or in soft, muddy soil, where the digging is difficult and the setting in- secure, the following method shall be used: As soon as a hole reaches a depth where the sides are continually caving in, place a barrel, without top or bottom, in the hole, digging down from inside of same, and driving down the barrel as the hole progresses. When the required depth has been reached, set the butt of the pole in the barrel, filling the latter with concrete and rock, as specified above for artificial foundation. If much of this work is encountered, the use of a special sheet-iron barrel constructed in two parts, so that the same can be moved from hole to hole, will expedite the work. 30. Poles Located in Rock. When poles are set in rock, the depth of setting may be decreased, depending upon the character of the rock. 31. Protection. Where the use of wood poles as hitching posts for horses cannot be avoided, the pole shall be protected by a sub- stantial metal covering. Where poles are so placed as likely to be damaged by wagon wheels, they should be protected with hub guards. POLE STEPS 32. Poles to be Stepped. All poles carrying branch cutouts, incandescent lamps or other attachments that may require frequent attention, as also all testing poles, shall be stepped to facilitate climbing the same. For the same reason it will be found convenient to step poles carrying transformers. 33. Galvanized Iron Pole Steps. To fit steps to a pole, bore |^-inch holes 4 inches into the pole in locations as hereinafter speci- fied, and drive steps into these holes until they project only 6 inches from the pole, then with a wrench turn the steps so that the foot guard points upward. 34. Location on Pole. The location of pole steps on a pole is shown in Fig. 369. The lowest step shall be 7 feet 4 inches from the ground. It will be necessary to bore the pole with additional holes for steps at the locations specified in Fig. 369, so that linemen [ 687 ] Sec. 10 LINE CONSTRUCTION FIG. 369. Location of steps on pole. [ 688 ] LINE CONSTRUCTION Sec. 10 SOCKET SOCKET iiK :O STEP FIG. 370. Two types of pole step sockets. [ 689 ] Sec. 10 LINE CONSTRUCTION can insert small iron bolts or other form of portable pole steps when climbing the pole. These holes shall be equipped with pole-step sockets, as shown in Fig. 370. 35. Pole steps shall always be placed on a line with the street in which the pole is located. CROSS-ARMS 36. Cross-arms. Owing to the variations in dimensions and pin spacings of cross-arms now in use, it is difficult to specify crossarrns that will suitably conform to, or completely cover, present practice. Whatever arm is used the spacing between the pole pins shall not be less than 20 inches, nor should the spacing between the side pins be less than 10^ inches. The arms covered by specification contained in Sec. 4, Art. 2, are recommended as satisfactory standards. 37. Size Arms to Use. It is recommended that the six-pin arm be adopted for general use. The four-pin arm shall only be used for single-arm suburban lines and for service buck arms. An eight-pin arm may be used for heavy pole lines, especially by com- panies having systems requiring four-wire distribution. 38. Painting and Treating. Cross-arms shall be seasoned for at least three months, and if not to receive a preservative treatment, shall be painted with two coats of standard white lead paint before leaving the yard. The use of cross-arms which have been properly treated with a suitable preservative is recommended, and the treatment should be as provided for in the specifications of the National Electric Light Association Committee on Preservative Treatment of Wood Poles and Cross-arms, (Sec. 9, Part II.) 39. Cross-arm Bracing. Before being placed on a pole, each cross-arm shall be fitted with two braces, the braces shall be attached to the front of the cross-arm by carriage bolts, which shall pass first through a washer, then through the cross-arm and then through the brace with the nut on the brace side. 40. Fitting Cross-arm to Pole. When possible, cross-arms shall be fastened to a pole before the latter is set. Each cross-arm shall be attached to the pole by one f^-inch cross-arm bolt, driven through from the back of the pole. This cross-arm bolt shall be of sufficient length to pass completely through the pole and the cross-arm, and receive its complement of washers and nuts. One washer shall be placed under the head and one under the nut at the end of the bolt . Cross-arm bolts of a proper length for the thickness of the pole shall be used. The back of the pole shall never be cut out to allow the use of a shorter bolt, and projecting ends are not to be left on. 41. Attaching Braces to Pole. Each pair of cross-arm braces shall be attached to the pole by means of one SJ^-inch lag bolt. [ 690 ] LINE CONSTRUCTION Sec. 10 42. Location of Cross-arms. Cross-arms shall invariably be placed either at right angles or parallel to the line of the street on which the pole is set. They shall always be faced on the opposite side of the pole from that on which the maximum strain comes. On straight lines where the spans between poles are equal the cross- arms shall be faced alternately on succeeding poles, first in one direction and then in the other. f Through Bolt --Vertical Brace FIG. 371. Side cross-arm bracing. 43. Side Cross-arms. It is sometimes necessary, in order to avoid obstructions, to use a side or offset arm. In such cases, a special arm of the same dimensions as the standard arm shall be used. This arm shall be bored for pins and bolt holes and installed with angle iron brace and back brace, as shown in Fig. 371. If the pole carries a heavy line, the unbalanced strain should be counteracted by side-guying or by ground braces, if the installation of side guys is impracticable. [ 691] Sec. 10 LINE CONSTRUCTION 44. Double Arms. At line terminals, corners, curves, where the line crosses over from one side of the street to the other and at points where there is an excessive or unbalanced strain on the cross- arms, pins and insulators, the pole should be doubled armed as illustrated in Fig. 372. Two blocks equal in length to the thick- ness of the pole between gains shall be placed between the arms, one at each end between the two outside pins. An y^-inch hole shall be bored at this point through the cross-arms and the inter- vening block. The two cross-arms shall then be bolted together by two 5^-inch bolts of proper length, passing through the cross-arms and the blocks, a washer being placed at both ends of each bolt. [692] LINE CONSTRUCTION Sec. 10 In place of the wooden blocks, described above, spreader bolts may be used, as shown in Fig. 373. When a cross-arm guy is to be attached to the arm, an eye bolt may be substituted for the cross- arm bolt. At line terminals the last pole shall be double-armed as specified, and the cross-arms of the last two poles before the terminal pole faced toward the latter. All poles on which two or more wires are dead ended shall be double-armed. 45. Reverse or Buck Arms. At corners, and where more than two wires branch from the main line, buck arms shall be used. A buck arm is a regulation cross-arm with fittings complete, set at [ 693 J Sec. 10 LINE CONSTRUCTION right angles to the line cross-arm, and 12 inches below it on centers, as previously specified for buck-arm gains. Judgment must be exercised in the use of buck arms, and ample room must be left for Guy n. B M a JUb V it i a/lnf HeoZGuy^ =3 Li? p 1 = C= Head Guy * o y M a V Dead End on this Pole Nofe: Space A should not be less them 0"squdn& /U Branch Line Note; If impossible to install Anchor Guy on Pole 3,~ uy Ho 2 &2tx)3 FIG. 374. Junction pole without double arms. climbing and working on the pole. In all buck-arm construction there shall be one clear space (neglecting the pole area) adjacent to the pole of at least 20 inches square. (Fig. 374.) [ 694] LINE CONSTRUCTION Sec. 10 46. Braces with Buck Arms. On poles equipped with buck arms, the cross-arm braces shall be so attached to both the line arms and the buck arms as to permit their installation without interfering with the arms below. This can be accomplished by using a standard 28-inch brace, and attaching the same to the cross-arms at 23 H inches from the center of the arm, instead of 19 inches, which is the standard distance. The bolt holes in the arms for these braces will be special, and shall be bored in the field. 47. Pins. Before being taken from the yard, each cross-arm shall be fitted complete with pins. Pins shall fit tight into the holes in a cross-ai m, and shall stand perpendicular to the cross-arm when fitted. Wooden pins shall be nailed to the cross-arm with one six- penny nail driven straight from the middle of the side of the cross- arm. INSULATORS 48. Equipping. Insulators shall be placed upon the cross-arrn pins only when the wire is to be immediately attached thereto, and shall be screwed up 'tightly in every case. 49. If a wire be permanently removed from an insulator, and no other is to take its place, the insulator shall also be removed. POLE GUYING 50. When to Use Guys. Guys shall be used whenever they can be located, so as to counteract the strain of the wires attached to the pole and so prevent the same from being pulled from its proper position in the line. The following general instructions cover some of the special cases where guying is required. 51. Straight-Line Guying. Straight-line guying is for the purpose of giving additional stability to a line in case of severe storms. On pole lines carrying more than one cross-arm it is desirable to install guys on straight-line sections at approximately every twen- tieth pole. These storm guys shall consist of head guys extending from the top of the pole to the adjacent poles in the line on either side, and if possible, this same pole shall be side-guyed; that is, guys should extend from the top of the pole on either side at right angles to the line to guy stubs or other supports. 52. Terminal Poles. Line terminal poles should be head-guyed against the strain of the line and on heavy lines ; that is, lines having three arms or more, the two poles next to the terminal pole shall be head-guyed in the same direction to assist the latter in taking the terminal strain. 53. Long Spans. In the case of exceptionally long spans, that is, spans exceeding 150 feet in length, the next adjacent poles on either side of the poles supporting the span shall be head-guyed against the strain, as shown in Fig. 375. [695] Sec. 10 LINE CONSTRUCTION [ 696] LINE CONSTRUCTION Sec. 10 54. Corner Poles. All corner poles, whether the turn is made on one pole or on two poles, shall be head- and side-guyed, as shown in Fig. 376. 55. Curved Lines. On curved lines, side guys shall be installed in line with the radius of the curve, and the pole spacing shall, if possible, be reduced. A convenient table for the location of side guys and for the spacing of poles on curves will be found in Fig. 367. In this table the word "pull" is a convenient expression for describing [ 697 ] Sec. 10 LINE CONSTRUCTION [ G98] LINE CONSTRUCTION v \' \\ Sec, 10 [ 699 ] Sec. 10 LINE CONSTRUCTION [700] LINE CONSTRUCTION Sec. 10 the angle of deviation which the line makes at the pole, the amount of the pull being the distance from the pole to the straight line joining points on the line located 100 feet each side of the pole. All poles carrying two crossarms shall be side-guyed where the pull exceeds five feet. All poles carrying one crossarm shall be side- guyed where the pull exceeds ten feet. 56. Poles on Hills. Poles on steep hills shall be head-guyed to take the down-hill strain of the line on the poles. 57. Details of head- and side-guying are shown in Figs. 377, 378 and 379. 58. Guy Wire. The material used for guying shall be stranded cable, composed of galvanized steel wire in accordance with National Electric Light Association standard specifications. (Sec. 3.) 59. 2300-pound cable may be used for guying light lines; that is, for pole Lines having not more than one crossarm and for guying crossarms 60. 5000-pound cable shall be used for all regular pole guying. 61. Guy Fitting. In connection with stranded guy cable, gal- vanized iron guy clamps and thimbles shall be used. 62. Guy Attachments. All guy wires shall preferably be attached to poles, guy stubs, trees or other ungrounded supports, and when so attached shall not reach within eight feet of the ground. The reason for preferably attaching wires to ungrounded supports is for the purpose of insulating guys as thoroughly as possible from the ground, this protection being in addition to the insertion of strain insulators in the guy itself and having in view the protection of linemen working on a guyed pole from coming in contact with a grounded wire when working on live wires. It is also considered desirable to keep guys, where possible, at least eight feet from the ground, with the idea of keeping them out of reach of persons on the highway. 63. There will, however, be many cases in which it will be necessary to install guys where the conditions stated in Art. 62 cannot be complied with. In such cases, the guy wires may be attached to rocks, stone foundations, iron structures or other grounded supports, or anchor guys may be installed. 64. Stub Guying. When a line cannot be guyed by means of other poles in the vicinity, guy stubs may be set as shown in Figs. 380 and 381. Guy stubs shall be of wood and shall conform to the specifications covering the line poles. They shall be of sufficient length to insure the guys attached to them clearing roadways by not less than eighteen (18) feet, and footways by not less than twelve (12) feet, and also to insure that the guys attached to them shall clear electric wires by at least three feet, as specified in Art. 79. [701] Sec. 10 LINE CONSTRUCTION [702] LINE CONSTRUCTION Sec. 10 703 ] Sec. 10 LINE CONSTRUCTION 65. Anchor Guys. An anchor guy may be employed to guy poles, but must not be installed where it might interfere with surface traffic. It shall be constructed as shown in Fig. 382 and 383. This anchor shall be set in the ground so that the eye of the guy rod will 3"S-5 >, 3 >-s 3 U 3 ^ J S D | 1 S 1 | Y, 1 a Abilene, Tex Albany, N. Y 28 40 39 10 15 42 40 43 41 39 43 39 40 40 43 31 36 27 33 25 40 36 40 40 42 38 39 41 37 17 39 26 36 41 33 17 39 40 33 24 42 26 35 56 31 26 54 39 36 31 58 31 40 33 43 31 27 18 49 56 23 23 38 47 65 48 62 37 49 35 30 39.3 66 38.7 34 47 20 37 54 39 56 33.2 69 41.4 42 17 58 32 26 56 43 36 31 59 33 42 34 44 32 30 22 51 61 25 34 38 50 66 51 64 38 50 38 34 40.3 68 39.7 33 51 24 41 58 43 59 38.0 70 43.0 43 19 68 41 34 68 52 41 38 66 42 52 42 52 41 42 32 63 68 36 38 52 59 67 61 71 45 57 49 46 48.3 74 48.8 43 57 37 51 59 52 68 49.0 77 51.5 56 33 76 55 47 73 62 54 50 72 54 63 54 60 55 59 46 72 71 52 57 65 68 70 71 76 57 65 62 62 60.2 82 60.6 58 62 56 60 62 60 76 59.2 80 63.0 68 55 83 69 59 82 69 66 62 80 65 74 66 69 67 70 57 80 80 64 65 74 78 73 79 83 68 75 70 72 71.5 90 72.9 65 68 68 68 62 68 83 67.5 86 74.4 76 56 89 78 70 88 78 75 72 86 74 82 75 80 76 79 69 87 86 76 74 83 84 78 86 87 77 83 80 81 80.2 100 80.7 76 73 77 79 64 78 90 74.0 89 82.2 85 75 91 82 75 90 88 81 76 88 80 86 79 86 81 84 74 98 88 80 82 87 87 82 89 89 82 87 86 86 84.7 103 84.6 83 81 b2 88 64 51 92 52.9 89 56.5 2 92 80 73 90 86 78 76 87 78 84 77 85 79 82 71 91 88 77 80 86 86 83 88 89 80 84 85 84 S2.2 101 82.6 83 81 80 87 54 79 92 2.2 59 3.8 1 86 73 66 81 76 71 70 83 72 78 72 77 72 74 64 85 85 70 69 79 81 82 32 85 74 79 77 76 76.3 97 76.8 74 74 71 76 58 73 57 71.1 8 7.9 2 76 60 54 75 64 61 58 74 60 66 61 65 60 61 52 74 77 57 58 68 70 77 72 78 63 69 65 64 34.7 35 53.5 61 64 57 63 67 62 77 58.9 82 66.5 70 56 65 46 40 65 52 49 45 66 46 52 47 52 45 44 36 62 69 41 40 53 58 72 60 72 51 59 50 48 5f 30.7 47 54 40 50 61 ft .6 14.4 76 53.9 55 37 56 36 31 54 39 39 36 59 36 43 37 45 35 32 25 52 62 29 33 42 48 67 51 63 41 50 40 36 tl' 1 41.3 40 48 27 39 56 41 58 36.6 70 14.3 45 24 Alpena, Mich Birmingham, Ala Boise, Idaho Boston, Mass . . . Buffalo, N. Y.. Charleston, S. C Chicago, 111. Cincinnati, Ohio Cleveland, Ohio Denver, Colo Detroit, Mich Dubuque, Iowa Duluth, Minn Fort Smith, Ark Galveston, Tex Green Bay, Wis Havre, Mont Kansas City, Mo Knoxville, Tenn Los Angeles, Cal Memphis, Tenn New Orleans, La New York, N. Y Norfolk, Va.. North Platte, Neb Omaha, Neb Philadelphia, Pa Phoenix, Ariz Pittsburg, Pa Rapid City, S. D Roseburg, Ore St. Paul, Minn Salt Lake City, Utah San Francisco, Cal .... Santa Fe, N. M Shreveport, La Spokane, Wash Tampa, Fla Washington, D. C Wichita, Kansas. . . WiUiston, N. D.. [768] METEOROLOGICAL DATA Sec. 11 TABLE 113 MONTHLY MEAN MINIMUM TEMPERATURES. Mean Minimum Monthly Temperature Averaged for the Number of Years Recorded. STATIONS IB o 1 b a c3 1-5 b 1 j3 1 'C a <; jj ^ 1 >-s _>, *9 > \ = < 1 1 t j | I & 1 % 1 Abilene, Tex 28 40 39 10 15 42 40 43 41 39 43 39 40 40 43 31 36 27 33 25 40 36 40 40 42 38 39 41 37 17 39 26 36 41 38 17 39 40 33 24 42 26 35 34 15 12 38 26 20 19 43 17 25 20 17 18 11 1 30 45 8 2 21 30 44 34 45 24 33 11 12 25.7 39 23.6 11 35 3 22 45 19 39 21.1 51 25.8 23 -5 35 15 9 37 27 20 17 44 19 26 20 20 18 13 4 32 50 8 4 21 32 45 36 50 24 34 16 16 25.9 43 24.3 11 36 6 26 47 22 41 23.1 53 26.6 23 -2 45 25 17 48 34 28 25 50 28 35 28 26 26 25 15 42 58 20 16 33 40 47 45 56 31 40 23 27 32.9 47 31.3 20 38 20 33 47 29 49 30.7 58 33.8 34 12 53 37 31 53 39 38 35 57 39 45 39 35 37 39 31 51 62 34 33 46 48 49 53 61 41 48 36 41 42.8 52 41.4 34 41 36 40 49 35 56 37.3 61 43.3 45 31 61 49 41 62 45 48 46 66 49 55 50 44 49 50 40 59 71 45 41 55 56 54 62 68 52 58 47 53 53.5 59 52.4 43 45 48 46 50 43 64 44.5 67 54.0 55 41 68 58 51 68 51 58 57 72 59 65 60 52 58 59 48 67 77 55 50 64 64 56 70 74 61 66 56 62 62.8 69 60.8 53 49 58 55 51 52 70 50.4 71 62.8 64 52 72 63 57 71 58 64 63 75 66 68 64 58 63 64 56 70 79 60 54 69 68 59 73 76 67 71 61 67 68.1 76 65.0 58 53 62 63 52 57 73 55.1 73 67.6 68 54 72 61 55 71 56 62 61 75 65 66 82 57 61 62 57 70 78 58 51 68 66 60 71 76 66 70 60 65 66.5 76 63.0 57 52 60 62 53 56 72 53.6 74 65.7 67 52 65 54 49 66 48 55 55 71 58 60 56 49 55 54 49 63 75 51 43 60 61 57 65 72 60 55 50 54 60.4 68 57.3 48 48 51 52 54 50 67 45.8 72 59.0 60 41 54 43 39 54 40 45 44 60 46 48 45 37 44 42 38 51 68 41 33 48 48 53 54 63 49 54 36 44 49.0 56 45.7 37 43 40 42 53 38 56 37.9 66 47.1 48 31 43 32 29 45 34 35 33 51 33 37 34 26 33 28 23 41 58 27 19 35 38 48 43 54 38 44 23 32 38.7 46 35.7 24 40 24 32 50 28 46 31.2 58 36.6 35 16 36 21 19 37 25 25 24 44 23 29 25 20 24 18 10 33 51 17 12 26 32 46 38 48 28 36 16 19 29.2 38 27.4 18 36 12 25 46 20 11 26.3 52 28.6 26 5 Albany, N. Y Alpena, Mich Birmingham, Ala Boise, Idaho Boston, Mass Buffalo, N. Y Charleston, S. C Chicago, 111 Cincinnati, Ohio Cleveland, Ohio Denver, Colo Detroit, Mich Dubuque Iowa Duluth, Minn Fort Smith, Ark . Galveston, Tex Green Bay, Wis Havre, Mont Kansas City, Mo Knoxville, Tenn Los Angeles, Cal Memphis, Tenn New Orleans, La New York, N. Y Norfolk Va North Platte, Neb Omaha, Neb Philadelphia, Pa Phoenix, Ariz Pittsburg Pa Rapid City, S. D Roseburg, Ore St. Paul, Minn Salt Lake City, Utah San Francisco, Cal. . . Santa Fe, N. M Shreveport, La Spokane, Wash Tampa, Fla Washington, D. C Wichita, Kansas Williston, N. D [769] Sec. 11 METEOROLOGICAL DATA TABLE 114 TOTAL NUMBER OF DAYS WITH MAXIMUM TEMPERATURE 90 OR ABOVE. STATIONS Years record a February I Hi; ~ | i "3 1 September October ' November December Abilene, Tex 27 40 39 10 15 42 43 43 43 39 43 39 40 40 43 31 40 27 30 25 39 36 40 43 42 43 39 41 43 17 39 26 36 25 38 39 37 40 24 24 43 26 32 1 24 1 6 3 4 4 3 1 10 2 3 6 50 2 7 1 2 2 20 3 5 4 4 75 17 4 5 11 4 155 18 7 14 7 10 1 51 11 22 1 9 5 18 45 6 2 11 11 29 22 31 42 9 46 30 23 18 27S 43 5 9 3 5 2 143 4 70 65 25 18 417 53 24 86 46 67 2 233 62 164 14 192 35 113 14 294 120 43 44 132 181 50 337 384 61 180 150 168 126 480 122 65 34 50 103 13 652 30 254 204 195 77 652 135 44 89 223 156 17 417 166 357 37 439 108 248 41 598 236 74 178 264 345 98 553 625 136 400 371 381 242 513 279 169 148 82 472 6 8 904 155 305 417 397 176 635 63 21 123 184 56 6 275 229 20 334 59 148 13 575 223 47 149 266 257 149 424 589 54 226 365 283 100 509 183 181 122 54 371 3 29 871 152 319 233 428 182 291 18 19 65 31 21 1 58 40 102 6 56 23 51 2 296 61 36 24 117 93 100 192 232 24 65 112 124 34 450 79 69 54 31 25 20 11 444 9 196 90 198 33 41 1 1 42 3 4 11 75 6 12 5 2 150 3 1 6 5 58 15 3 8 2 29 5 . Albany N Y Alpena, Mich Birmingham, Ala Boise, Idaho Buffalo, N. Y Charleston S C Chicago, 111 Cleveland, Ohio Denver, Colo Detroit, Mich Dubuque, Iowa Duluth, Minn Fort Smith, Ark Galveston, Tex Green Bay, Wis Havre, Mont Kansas City, Mo Knoxville, Tenn Los Angeles, Cal Memphis, Tenn New Orleans, La New York, N. Y Norfolk, Va North Platte, Neb Omaha, Neb Philadelphia, Pa Phoenix, Ariz Pittsburg, Pa Rapid City, S D Roseburg, Ore St. Paul, Minn Salt Lake City, Utah San Francisco, Cal Santa Fe, N. M Shreveport, La .... Spokane, Wash Tampa, Fla Washington, D. C Wichita, Kansas Williston, N. D [ 770] METEOROLOGICAL DATA Sec. 11 TABLE 115 TOTAL NUMBER OF DAYS WITH MINIMUM TEMPERATURE ZERO OR BELOW. 1 , b 1 1 j STATIONS as c3 3 ^ ^ 1 1 a o3 3 J3 I T, tf 8 >> M p 3 > s 93 1-5 & % ft < tl 3 t-B "3 H^ 3 < I* I I Abilene, Tex . . Albany, N. Y 27 40 3 148 4 150 14 62 Alpena, Mich. Birmingham, Ala Boise\ Idaho 39 10 15 201 11 273 1 5 113 3 41 Boston, Mass Buffalo, N. Y 42 43 48 55 40 86 4 1 24 11 Charleston, S. C 43 Chicago, 111 41 172 121 10 6 67 Cincinnati, Ohio 38 36 27 15 Cleveland, Ohio 43 55 37 5 1 15 Denver, Colo 39 156 114 20 o 22 95 Detroit, Mich 40 Aft 77 Q7A 93 OOA 5 )4 1 10 21 1 1 DUDUQUG, Iowa Duluth, Minn 4U 43 36* 616 ZoU 453 mm 165 11 63 131 321 Fort Smith, Ark 31 11 6 Galveston, Tex 43 Green Bay, Wis Havre, Mont 27 9 238 142 215 104 51 49 1 24 97 61 Kansas City, Mo 25 A1 52 17 51 13 Knoxville, Tenn Los Angeles, Cal 41 38 AF\ H Memphis, Tenn New Orleans, La w 43 New York, N. Y 42 6 7 4 Norfolk, Va 43 North Platte, Neb 39 235 183 42 30 117 Omaha, Neb 41 307 188 16 12 133 Philadelphia, Pa 43 10 11 o 2 Phoenix, Ariz 17 Pittsburg, Pa Rapid City, S. D 39 26 48 212 47 202 71 1 27 14 86 Roseburg, Ore 36 3 St. Paul, Minn 41 553 416 97 63 250 Salt Lake City, Utah 38 20 13 1 3 41 San Francisco, Cal G nn 4rk T? AT AT 39 QfT OC 1Q oanta r e, IN . M Shreveport, La O 1 40 $*) 1" 2 20 Spokane Wash 25 35 22 2 Tampa, Fla 24 Washington, D. C 43 16 8 2 Wichita Kansas 26 37 36 6 Williston, N. D 32 589 494 258 5 1 132 335 [771] Sec. 11 METEOROLOGICAL DATA TABLE 116 HIGHEST WIND VELOCITIES ON RECORD, WITH DIRECTION. (The recorded velocities as given are the greatest maintained for any five minute period.) STATIONS. 1 i j 4 i J2 83 1 8H 4 * < % Abilene. Tex.. . 27 60W 61W 50SW 60SW 66SW Albany, N. Y 40 60NW 70W 54 NW 48NW 41NW Alpena, Mich 39 56SE 52SE 55W 52W 478 Birmingham, Ala 10 50SE 43SE 40SE 45S 44SE Boise, Idaho 15 38NW 33NW 38NW 40SE 42SW Boston, Mass . . . 41 64NE 60E 728 60NE 48E Buffalo, N. Y 42 90SW 76SW 90W 75SW 61SW Charleston, S. C 43 44SW 56SE 55NE 67SE 53NE Chicago, 111 24 66NE 84NE 68NE 72NE 72SW Cincinnati, Ohio 40 48SW 41NW 48SW 44SW 45N Cleveland, Ohio 43 72W 65W 68W 66W 60NW Denver, C clo 41 66 SW 64W 61NW 60NW 68NW Detroit, Mich 43 60W 60SW 86W 72NE 74SW Dubuque, Iowa 40 38NW 36NW 42SW 39NW 34NW Duluth, Minn 43 71NW 60NE 62NE 70NW 60NE Fort Smith, Ark 31 66W 54W 56SW 56SW 54S Galveston, Tex 42 62N 59N 61N 52N 60NW Green Bay, Wis 27 47NE 55N 48NW-SW 46NE 68N Havre, Mont 33 60SW 72NW 60W 63W 63NW Kansas City, Mo 25 74NW 53NW 58SW 56 NW 52NW Knoxville, Tenn 41 58SW 60SW 84S 70W 50SW Los Angeles, Cal Memphis, Tenn 36 40 48NE 64W 42NW 58W 46SW 75SW 42W 64NW 36W 60NW New Orleans, La 41 42NW 52SE 45SW 48N 48NW New York, N. Y 30 86SW 96SW SON 84NW 64NW Norfolk, Va 42 64SW 59NW 58SW 55N 62N Northplatte, Neb 39 58NW 68NW 66NW 96SE 84SE Omaha, Neb 41 66NW 49NW 52NW 52NW 50 Philadelphia, Pa Phoenix, Ariz 43 17 52-ENW SON 48NE-NW 32W 60NW 36SW 50W 34W 60NW 33SW Pittsburg, Pa Rapid City, S. D II 26 66W 51W 58W 52N 67W 66SW 68W 63SW 57NW 56W Roseburg, Ore 36 30SW 36SW 42W 36SW 30SW St. Paul, Minn 25 54N 45NW 60NW 50NW 52SW Salt Lake City, Utah.. San Francisco, Cal.... 38 42 60N 57SE 60N 49S 60NW 60S 60N-SW 42SE 56W 45W Santa Fe.N.M 40 44NW 47W 50E 51SW 51SW Shreveport, N. M 42 40NW-N 39SE 54NW 44W 52SE Spokane, Wash 33 40SW 41SW 44SW 40SW 38SW-W Tampa, Fla 24 40W 49S 41SW 42SW 42SE Washington, D. C 43 48NW 60 50NW 43NW 54SW Wichita, Kansas 26 62NW 49N 60S 54SE 56SW Williston, N. D 32 66NW 72NW 60NW-N 66NW 66E [ 772 ] METEOROLOGICAL DATA Sec. 11 TABLE 116 Continued HIGHEST WIND VELOCITIES ON RECORD, WITH DIRECTION. (The recorded velocities as given are the greatest maintained for any five minute period.) i Jl kj I* 2 3 & J 1 J tc. 9 - * o 55 27 62NE 60SE 48NW 42SW 40NW 48NE 60W 40 48NW 70W 44SE 39SE 70E 52SE 70W-E 39 48W 60SW 41NW 51SE 52E 50NW 46NW 10 393 45SE 58NE 50SE 33SE 39SE 483 15 55SW 41NE 34NE 40W 48NW 43W 38W 41 41E 60SW 483 60N 54NE 65W 60E 42 72NW 66SW 60SW 78W 75SW SOW 78W 43 54E 483 106SE 623 64N 46E 50SE 24 72NW 72W 72SW 72SW 63SE 763 72SW 40 52NW 43SW 50NW 40NW 41SW 48SW 40NW 43 64SW 66NW 58W 66NW 62W 733 613 41 603E 55NE 75NE 51N 553 60NW 56 43 69NW 60W-SW 60NW 68NW 61NW 76SW 56SW 40 60NW 56NW 45NE 42NW 36NW 42 NW 42NW 43 63NE 56NW 51NW 18NE 58NW 70NW 65NW 31 743 49NW 64W 52W 46NW 55NW 43W 42 54SE 68E 53NE 84NE 62NW 54NW 54N 27 59W 59NW 45NW 52NW 52NE 54N-SW 48SW-N 33 76NW 59W 60SW 56SW 60SW 60NW 60NW 25 67N 57NW 55NW 48SW 453 50NW 46NW 41 52W SON 70NW 60SW 36SE 60 54SW 36 34SW 25W 24NE 383 34NE 43NE 38NW 40 60NW 54W 59NW 60NW 72SW 60SW 56SW 41 SON 52E 60E 66SE 54N 42N 48N 30 72NW 72NW 76NW 72SW 76NW 76W 85NW 42 49W 60N 60NE 55SE 60SW 50NW 58NW 39 90SW 84W 66NW 72W 623 62NW 72NW 41 60NW 64NE 54NE 54NE 43NW 51NW 50NW 43 54NW 53N 55NE 58NW 75SE 60E 63SE 17 32NW 48SE 40E 38W 36SE 26W 30SW 41 58NW 52NW 55NW 44SW 60NW 50W 69W 26 59SW 60N 60SW 48NW 46W 60NW 56SW 36 28SW 28SW 41NE 30SW 28SW 30NE-SW 48SW 25 64NW 62N 102NW 55SE 55W 52N 48N-NW 38 54NW 50E 64W 44E 52NE 66NW 50NW 42 48SW 41W 42SW 40W 44NE 64NE 60SE 40 48NW 45W 40E 46N 53SE 51SE 40NE 42 46N 563 43NE 38W 60NW 54NW 52W 33 48SW 52W 39SE-SW 48W 40SW 42SW 48SW 24 44SW 433E 34SE 48NE 48N 363 403 43 51NW 68NE 53N 663E 51NW 54SW 49 26 463 56NW 48NW 47W 483 533 453 32 63NW 54NW-N 67W 60NW 60NW-N 60NW 60NW-W [ 773 ] Sec. 11 METEOROLOGICAL DATA TABLE 117 TOTAL NUMBER OF DAYS WITH MAXIMUM RECORDED VELOCITY OF 40 MILES PER HOUR OR MORE. STATIONS 'H o 6 o> ^ b 03 3 1 >j L c3 1 ^ ^ a < | I-B >. 3 1 M 3 < 1 I 1 | 5 fc 1 QJ & Abilene, Tex 27 33 39 10 15 22 23 24 40 43 22 23 40 43 20 22 27 22 25 22 36 24 21 22 32 39 41 43 17 41 26 36 22 22 20 5 18 1 191 4 92 30 6 15 4 14S 17 107 30 6 26 3 138 11 148 38 1 26 1 25 1 9 1 18 7 7 3 2 9 12 Albany, N. Y Alpena, Mich 7 5 1 3 1 9 2 1 58 12 55 1 42 11 10 1 23 5 7 6 20 4 2 2 5 36 3 7 4 8 1 91 15 85 3 75 16 23 33 3 11 18 12 7 4 8 79 10 14 5 10 10 6 12 9 15 1 182 2 126 2 122 27 39 1 54 6 14 21 19 11 6 2 12 1 110 14 14 7 15 15 19 12 8 16 2 213 5 107 1 99 30 29 1 61 3 25 12 37 10 10 11 4 128 13 6 10 19 28 13 2 14 10 1 2 2 5 2 6 4 38 Birmingham, Ala Boise, Idaho Boston, Mass 62 14 155 No 60 9 116 Da 26 9 61 ta. 39 3 59 40 15 37 3 16 14 4 2 11 6 3 8 12 12 12 10 Buffalo, N Y Charleston, S. C Chicago, 111 Cincinnati, Ohio Cleveland Ohio 124 29 33 72 11 21 18 29 9 11 2 22 113 21 34 60 18 22 19 16 19 15 1 29 111 38 46 2 64 25 16 22 19 28 20 1 28 85 33 52 52 21 21 35 20 27 10 1 30 57 29 26 46 19 20 26 20 22 5 16 39 14 15 2 21 16 8 10 20 13 8 25 46 21 21 2 17 9 3 21 27 14 5 10 Denver, Colo Detroit Mich Dubuque, Iowa Duluth, Minn Fort Smith, Ark Galveston, Tex Green Bay, Wis Havre, Mont Kansas City, Mo Knoxville, Tenn Los Angeles, Cal Memphis, Tenn New Orleans, La New York, N. Y Norfolk, Va North Platte, Neb Omaha, Neb Philadelphia, Pa Phoenix Ariz 133 20 16 12 23 23 23 16 12 173 28 12 14 21 24 20 8 10 163 28 42 20 18 38 18 1 22 11 119 11 63 22 16 30 24 21 14 67 16 34 8 45 9 29 11 51 5 19 6 32 7 9 4 12 12 14 13 18 16 15 9 2 12 7 20 17 3 4 6 1 11 5 3 13 7 8 Pittsburg, Pa Rapid City S D Roseburg, Ore St Paul, Minn Salt Lake City, Utah San Francisco, Cal Santa Fe, N. M Shreveport, La Spokane, Wash 40 42 33 24 27 26 32 2 2 1 2 9 13 44 1 1 Ib 4 1 21 2 1 1 3 1 1 2 3 1 4 16 33 Washington, D. C Wichita, Kansas Williston, N. D 14 12 31 13 27 54 5 38 45 7 16 59 2 14 48 2 7 41 3 6 43 2 5 42 2 7 38 t 774] METEOROLOGICAL DATA Sec. 11 TABLE 118 TOTAL NUMBER OF THUNDERSTORMS. STATIONS TJ 8 2 3 1 e 03 H o? ,n 1 15 'C n 3 >> <5 a> e 3 >-! _>. g NI 1 S 1 2 1 1 3 1 1 1 (5 Abilene, Tex . . . Albany, N Y 27 40 39 10 15 33 43 43 19 27 43 31 43 40 43 31 28 27 32 25 32 36 31 43 30 30 39 41 43 17 28 26 36 25 38 23 38 38 24 24 42 26 31 11 2 10 2 4 6 27 11 8 8 8 5 2 32 34 1 10 9 11 30 56 4 4 1 2 2 11 1 12 17 3 2 19 1 5 6 57 12 22 12 1 12 9 1 42 58 22 33 7 53 77 7 15 7 20 8 11 8 64 13 23 28 15 11 36 82 57 48 40 11 41 51 14 98 64 20 1 67 87 16 106 113 22 40 15 50 41 17 42 3 6 15 24 127 38 46 46 15 16 55 134 109 72 61 36 87 96 40 159 100 43 12 135 104 11 139 116 50 68 75 120 69 12 75 34 9 50 43 185 101 115 75 40 47 149 246 207 161 172 168 203 206 121 209 114 125 71 214 182 155 190 158 114 65 66 176 421 232 193 198 261 241 249 207 234 125 139 183 242 285 144 215 186 133 42 106 226 521 217 169 216 305 262 250 247 206 203 169 157 237 293 135 152 149 123 33 90 170 467 184 155 148 280 185 195 187 205 219 130 134 208 248 77 75 112 71 27 44 81 195 124 79 98 95 108 148 109 110 132 98 44 143 98 49 27 40 11 10 7 47 57 50 26 41 10 53 64 39 63 55 38 57 21 29 7 7 9 3 6 18 40 22 16 11 12 19 4 53 46 8 33 22 2 41 30 9 11 3 14 15 12 5 1 2 6 17 10 3 1 4 26 3 3 1 1 3 13 38 11 8 2 27 75 2 5 5 4 3 4 1 3 Alpena, Mich Birmingham, Ala Boise, Idaho Boston, Mass . Buffalo, N. Y Charleston, S. C. Chicago, 111 Cincinnati, Ohio Cleveland, Ohio Denver, Colo Detroit, Mich Dubuque, Iowa Duluth, Minn Fort Smith, Ark Galveston, Tex. . . . Green Bay, Wis Havre, Mont Kansas Citv t Mo Knoxville, Tenn Memphis, Tenn New Orleans, La New York, N. Y.. 174 209 98 159 183 238 156 19 146 112 27 121 75 216 303 160 183 286 301 197 23 223 242 17 176 96 240 406 07 12 86 65 72 33 38 41 15 53 23 177 61 157 85 20 25 99 68 66 89 15 63 69 85 03 67 52 83 52 81 71 87 52 13 99 61 34 44 21 17 20 72 31 14 22 13 4 37 28 Norfolk, Va North Platte, Neb Omaha, Neb Philadelphia, Pa Phoenix, Ariz Pittsburg, Pa Rapid City, S. D Roseburg, Ore St Paul, Minn Salt Lake City, Utah San Francisco, Cal Santa Fe, N. M Shreveport, La 3 38 2 28 6 4 8 66 33 16 16 25 109 2 54 44 56 1 52 185 12 63 85 123 22 127 203 31 156 191 224 69 167 225 28 314 245 224 175 78 64 49 93 11 26 62 21 98 32 01 06 99 42 24 09 18 10 94 140 59 41 47 4 41 21 70 7 7 39 9 11 14 1 34 10 2 4 Spokane, Wash Tampa, Fla Washington, D. C Wichita, Kansas Williston, N. D [775] Sec. 11 METEOROLOGICAL DATA TABLE 119 TOTAL NUMBER OF DAYS WITH DENSE FOG. (Fog of sufficient density to obscure buildings &c. at a distance of 1000 feet.) STATIONS 1 2 ^ 1 G a >-> 1 1 & 43 1 '1 [ 1-5 | ^ < | | % ce 1 1 1 \ 1 Abilene, Tex Albany, N Y 21 21 39 10 15 23 43 21 19 20 43 31 23 40 43 28 21 27 21 25 32 36 23 43 28 30 39 41 43 17 21 26 36 25 22 23 38 36 21 24 42 26 32 12 41 32 14 47 21 44 86 40 24 21 12 44 46 21 19 132 24 14 44 40 44 33 142 81 41 11 29 56 13 47 8 176 15 39 55 6 24 69 60 74 58 10 10 19 24 6 9 9 31 71 24 22 25 16 18 34 1 6 17 54 62 35 16 32 4 10 47 4 2 20 55 12 25 12 17 2 2 65 1 6 45 15 16 2 3 2 5 38 2 1 10 23 5 11 2 1 1 10 15 1 19 8 2 3 4 27 32 1 22 6 52 43 3 2 32 16 28 19 13 11 10 65 62 3 35 19 39 27 39 14 2 49 40 30 27 15 32 9 23 122 117 11 36 37 36 13 21 41 121 6 49 39 4 13 20 21 58 31 31 10 11 52 33 37 20 40 26 19 25 52 66 20 96 57 41 13 28 50 2 58 14 223 26 5 67 5 19 95 29 83 24 14 11 32 39 5 40 22 32 62 35 25 15 8 49 19 17 14 58 20 19 46 39 45 27 110 65 41 11 47 58 8 37 10 208 16 37 44 6 16 86 25 60 36 10 Alpena, Mich Birmingham, Ala Boise, Idaho Boston, Mass Buffalo, N. Y Charleston, S. C Chicago, 111. . Cincinnati, Ohio Cleveland, Ohio Detroit, Mich 30 13 13 11 90 10 15 18 29 56 33 89 58 37 5 12 34 5 31 30 25 32 10 133 27 10 26 24 86 26 98 81 38 25 27 33 2 26 17 11 52 5 37 15 5 9 14 87 7 6 104 8 2 13 3 7 23 96 4 7 89 10 5 1 14 21 121 3 19 66 5 5 1 13 28 150 30 73 13 28 4 11 76 131 34 30 49 14 22 5 16 67 145 Dubuque, Iowa Duluth, Minn Fort Smith, Ark Galveston, Tex Green Bay, Wis Havre, Mont Kansas City, Mo Knoxville, Tenn Los Angeles, Cal Memphis, Tenn New Orleans, La New York, N. Y Norfolk, Va North Platte, Neb 39 47 9 6 9 12 22 14 60 20 9 10 5 13 12 26 6 16 8 6 18 16 14 4 19 9 7 19 9 8 4 16 12 14 38 7 33 10 39 15 32 73 Omaha, Neb Philadelphia, Pa Phoenix, Ariz Pittsburg, Pa Rapid City, S. D Roseburg, Ore 118 19 11 59 3 15 40 39 39 36 12 74 11 4 29 5 15 19 29 44 25 25 8 16 4 10 1 13 5 16 2 5 5 8 7 13 2 1 4 1 7 44 2 2 2 1 23 61 1 6 5 66 29 46 2 3 10 263 20 1 64 5 11 62 St. Paul, Minn Salt Lake City, Utah San Francisco, Cal Santa Fe, N. M Shreveport, La Spokane, Wash Tampa, Fla Washington, D. C Wichita, Kansas Williston N D 29 10 16 3 11 2 6 9 7 11 10 30 12 21 74 18 10 [ 776 J METEOROLOGICAL DATA Sec. 11 (3) Data on 211 storms show a sleet formation less than J4" for 90 storms (42.65%) ; from %" to Y 2 " for 62 storms (29.39%) ; from W to 1" for 42 storms (19.9%); and greater than I" for 17 storms (8.06%). (4) In three instances the temperature fell below zero after the sleet deposit. (5) The maximum recorded wind velocity during 487 sleet storms occurred simultaneously with the maximum deposit of sleet in 19 instances (3.9%). (6) The map (Fig. 429) is based on the foregoing data and the areas were determined as follows: The total number of damaging storms at each station was divided by the number of years record. The ratio thus obtained was located on the map for the station in question. The areas were then so drawn that they included: 1st. Those stations at which the ratio was approximately 0.2 or greater. This was designated as the area in which sleet storms were frequent. 2nd. Those stations at which the ratio was approximately 0.05 to 0.2. This area was designated as the territory of occasional storms. Some values greater than 0.05 lie outside of the territory indicated, but as they occur in isolated instances, they are not typical of the territory, therefore, the numerical value of the ratio was located rather than indicating the territory with cross-hatching. (7) The tabulated data given are for towns and cities and do not represent the maximum conditions that may be encountered in open country. 15. CORRECTIONS FOR BAROMETRIC PRESSURE b=barometric pressure at height "h" in inches. b barometric pressure at sea level in inches. h -height above sea level in feet at which barometric pressure is desired. t=temperature in degrees F at altitude "h." Let H the height in meters. Let T=the temperature in degrees C., and Let B=the barometric pressure in millimeters. Then, from Dr. William J. Humphreys paper on Barometric Hyp- sometry final equation. H=18,40o(log IO |)(l+i) But rr is a ratio and therefore B and B can be expressed in any D units, provided the same unit is used for both. [777] Sec. 11 METEOROLOGICAL DATA TABLE 120 SLEET DATA LOCATION OF OBSERVING STATIONS T3 1 r" Storm Reports Damaging Storms Most Severe Conditions Reported. Number of Sleet Storms reported for Various Ice Formations Maximum Re- corded Sleet Deposit. Max. Recorded Wind Velocity During Sleet Deposit. h & Accompanying Recorded Wine Velocity a S a li !i >$> <5 Ice Formation a i a S Thickness of Ice Formation. K H 1-1 1" + Abilene, Tex Albany, N.Y Alpena, Mich Amarillo, Tex Atlanta, Ga Atlantic City, N.J.... Birmingham, Ala Bismark.N.D Boston, Mass Buffalo, N.Y Cairo, 111 28 40 39 22 36 14 40 5 20 43 43 10 36 23 10 43 36 29 40 35 22 39 39 43 26 20 25 16 31 36 24 27 25 10 40 33 32 42 25 44 40 4 24 20 36 2 29 4 1 3 3 E 5 4 28 6 4 16 1 14 io 8 2 5 4 10 1 2 9 4 4 g .3* g It' 2 29 g g 8 8 3 17 14 g 3 E 61 g 2a 29a 4a 1 3a 5 4d 28 6f 1 2 Id 3 10 2h li 2 6a 2d 9a 3 4d o 13 o 11 1 3 17a 7 3 .5" .5" 1" .25" .5 g 2.8e 2"e .3" 1" 1"+ .5" .6" .29" t"e 1.62e .5 .3" .5" 4.3e 2.8e 18NW 36 29E 13N 25E 28W 29NE 28 31NE 20NE 14 44 12 40 20 31N 26 42 40W 18 16NE 26NE 23 36W 20 36 12 23 17 31.4 14 30 16 24 10 14 22 23 36 48SW 13N 30ED 56N 45NE 72SW 28 34NE 30W 14 48NE 47 32N 23 27 26 40 31 31 32 48 20E 40W 32 40 48N 26NE 52N 36W 20 36 .25" .5" .25" .5" .03" 2"e .2" .5" 1"+ .5" .29" .75" 1" 4.3e 2.8e 12 29 3 27 8 1 14 28 22 6 24 11 14 22 l 27b 1 1 4 2c 7 c Ic c c c 1 c c c c c c c 5 c c 1 c 32 2 c c 1 1 8 3c 3c 4 3 1 Ic 8 4 2 3 5 2 1 c 6 2 1 1 3 2 1 1 c Charleston, S. C Charlotte, N. C Chattanooga, Tenn Chicago, 111 Cincinnati, Ohio Cleveland, Ohio Columbus, Ohio Concordia, Kansas.... Denver, Colo Des Moines, la Detroit, Mich Dodge City, Kansas... Dubuque, la Duluth, Minn Eastport, Maine Erie, Pa El Paso, Tex Evansville, Ind Fort Smith, Ark Galveston, Tex Grand Haven, Mich. . . Green Bay, Wis Harrisburg, Pa Hartford, Conn Hatteras, N.C Havre, Mont Huron, S. D Indianapolis, Ind Kansas City, Mo Keokuk, Iowa Knoxville, Tenn Lansing, Mich Little Rock, Ark Louisville, Ky Los Angeles, Cal [778] METEOROLOGICAL DATA Sec. 11 TABLE 120 Continued LOCATION OF OBSERVING STATIONS Years record Storm Reports Damaging Storms Most Severe Conditions Reported. Number of Sleet Storms reported for Various Ice Formations. Maximum Re- corded Sleet Deposit. Max Recorded Wind Velocity During Sleet Deposit. Ice Formation Accompanying Recorded Wind Velocity P. 1 .a It Ice Formation a H a Thickness of Ice Formation H I- h 1" + Lynchburg, Va Marquette, Mich Memphis, Tenn Milwaukee, Wis Nantucket, Mass Nashville, Tenn New Orleans, La Norfolk, Va North Platte, Neb... Oklahoma, Okla Omaha, Neb Parkersburg.W.Va.. Philadelphia, Pa Phoenix, Ariz 42 27 40 41 27 39 40 43 39 15 41 25 18 17 23 39 42 27 26 40 36 42 38 37 40 14 16 25 33 35 25 22 12 24 23 26 26 35 20 1 6 7 12 4 7 g 8 4 3 5 1 4 6 18 / 1 g 5 g 2 1 13 9 g 3 g 4 8 3 t" la 6 7 12 3 5 4 1 k 3 3 .38" .9"e 1.5f 1" 1.75 5 .5" 1" 1" 1"! 1.5e .2 !.38 L0.4e 2.5e 15 33 16 37 83NE 37 14 28 28 10NE 30 20N 19 40 29 17 55 JO 30 18NE 36 15 28NW 18 31 10 27 28 29 30 2 8 8 15 33 38 40 83NE 37 54NW 38N 30 17 34NE 36NW 26NE 40 6 9 8 55 8 2S WNE 4 ON .38" .9e 1.75" .5" .75" .75" .5 .2 .38 .25" .4 31 10 27 10 29 2 8 c 1 c c 2 c c c c c c c 2c c c c c 2c c c c c 1 3 1 1 2 2 5 c 2 c 4 1 2 1 3 1 1 2 2 3 1 2 Pierre, S. D Pittsburg.Pa Portland, Me Pueblo, Colo Raleigh, N.C Rapid City, S. D Rochester, N. Y Roseburg, Oregon.... San Francisco, Cal . . . Salt Lake City, Utah. Sandusky, Ohio Santa Fe.N.M Scranton, Pa Shreveport, La Sioux City, la Spokane, Wash Springfield, 111 Springfield, Mo St. Paul, Minn Syracuse, N. Y Tampa, Fla Toledo, Ohio Washington, D. C... . Wichita, Kansas Williston, N. D Wilmington, N.C. . . . (a) Damage to telephone and telegraph wires and poles, (b) Probable thickness ranging from T y to Y' of ice. (c) D?ta incomplete as regards thickness of ice. (d) Damage to telephone, telegraph and electric wires, (e) -This thickness was the ice and snow deposit on the ground and not on wires for which there is no data, (f ) Damage to telephone and telegraph wires, (g) Report practically no sleet damage, (h) 200 telegraph poles down 30 miles southeast of city in one of these storms, (i) One (1) inch of ice formed on telephone wires and 100 poles broken at Miltonvale, 20 miles southeast of station, (j) Estimated, (k) No records. (1) Not government records (obtained by consulting officials of Telephone and Tele- graph Companies. [779] Sec. 11 METEOROLOGICAL DATA JL I *j ~""r3 ~~! i 780 ] METEOROLOGICAL DATA Sec. 11 Therefore, and, TT Iog 10 b=log 10 b 18,400(^1+^ But h=3.28 H, and numerically, T m =5/9 (t, Hence, 32). 3.28 18,400 Iog 10 b=log 10 b Iog 10 b=log 10 bo Problem No. 1. Find the equivalent sea level barometric pressure at an altitude of 6000 feet when the temperature is 60 F. assuming the reading of the barometer is 24.5". 56,422+122.8 t TABLE 121 WIND VELOCITIES, AS INDICATED BY A ROBINSON ANEMOMETER, CORRECTED TO TRUE VELOCITIES. Indicated Velocity. ^0 +1 +2 ^3 + -M +6 +7 +8 +9 5.1 6.0 6.9 7.8 8.7 10 9.6 10.4 11.3 12.1 12.9 13.8 14.6 15.4 16.2 17.0 20 17.8 18.6 19.4 20.2 21.0 21.8 22.6 23.4 24.2 24.9 30 25.7 26.5 27.3 28.0 28.8 29.6 30.3 31.1 31.8 32.6 40 33.3 34.1 34.8 35.6 36.3 37.1 37.8 38.5 39.3 40.0 50 40.8 41.5 42.2 43.0 43.7 44.4 45.1 45.9 46.6 47.3 60 48.0 48.7 49.4 50.2 50.9 51.6 52.3 53.0 53.8 54.5 70 55.2 55.9 56.6 57.3 58.0 58.7 59.4 60.1 60.8 61.5 80 62.2 62.9 63.6 64.3 65.0 65.7 66.4 67.1 67.8 68.5 90 69.2 [ 781 ] Sec. 11 GALVANIZING AND SHERARDIZING Solution: From Table 122 for 6000 feet and 60 F. find the correction factor per 100 feet elevation = 0.084. fiOOO The total correction is~~-X 0.084=5.04". Sea level barometric pressure = 24.5""+ 5.04" = 29.54". Problem No. 2. Find the barometric pressure at an altitude of 6500 feet when the temperature is 50 F. assuming the sea level barometric pressure is 29.92". Solution : From Table 122 for 6500 .feet and 50 F. find the correction factor per 100 feet elevation = 0.085. AC nn The total correction w-rgp X 0.085 = 5.525". The barometric pressure is 29.925.525=24.395". Problem No. 3. Find the barometric pressure at an altitude of 10,000 feet when the temperature is 50 F. assuming a' sea level pressure of 29.92". Solution : Iog 10 b=lo glo b lo glo 29.92 = 1.47596 i u i AVXM 10,000 Iog 10 b = 1.47596 - ^; 422 lo glo b = 1.31612. b = 20.707" 16. HOT GALVANIZING. This process consists in covering wrought iron, cast iron, or steel with a coating of melted zinc. To insure perfect contact bejbween the zinc and the metal it is neces- sary to remove all paint, grease, etc., by the use of benzine or a simi- lar solvent. In preparing cast iron the metal is further cleansed by hydro- fluoric acid to remove the sand. In preparing wrought iron, a pickling solution of sulphuric acid is used, and the surface then scratch-brushed to remove scale. It may sometimes be necessary to remove certain oils with caustic potash. The cleansed material is dipped in muriatic acid and after having been thoroughly dried is dipped in melted zinc at a temperature of about 800 F. When thoroughly coated the articles are withdrawn through clean metal, where the flux has been skimmed back, and then drained and cooled in a tank of running water. The finished surface should be clean, smooth and free from blisters and dross. [782] GALVANIZING AND SHERARDIZING Sec. 11 CM S 8 3 2 sssiiilllliiili 11*11 * 8* 3 3 [ 783 ] g s 3