  In the equipment of lighting and power plants, the cost of the outside wiring represents a considerable proportion of the total investment, sometimes costing more than the engines, boilers and dynamos. A thorough knowledge of outside wiring is therefore necessary to properly proportion and install the wires so that the system will prove economical and safe. Materials for Outside Conductors.—Copper wire is now considered to be the most suitable material not only for the transmission of current for electric light and power purposes, but also for telegraph and telephone lines, in place of the iron wire formerly employed. Hard drawn copper wire is used in outside construction, because its tensile strength ranges from 60,000 to 70,000 pounds or about twice that of soft copper. This is desirable to withstand the stresses to which the wire is subjected which, in the case of long spans, are considerable. The table on the next page gives the tensile strength, in pounds per square inch of cross section, hard drawn copper wire of various sizes B. & S. gauge.
Pole Lines.—In the majority of cases overhead conductors are supported by wooden poles. In tropical countries, however, such as India, Central America, etc., where wood is rapidly destroyed by the ravages of white ants and other insects, iron poles are almost exclusively used for telegraph, telephone, and other electric transmission lines. The form of iron pole generally adopted consists of tapering shells of sheet iron of convenient length, riveted together at their ends and set into cast iron base plates which are buried in the ground. Figs. 921 to 929.—Pole construction tools. Fig. 921, long handled digging shovel; fig. 922, digging bar; fig. 923, crow and digging bar; fig. 924, tamping and digging bar; fig. 925, wood handle tamping bar; fig. 926, slick digging tool; fig. 927, post hole augur; fig. 928, carrying hook; fig. 929, tamping pick. Wooden Poles.—On account of their size and straightness, various species of northern pine, cedar and cypress are especially suitable for large poles. Chestnut, which can be readily sawed and hewed is a very good material for smaller poles. Sawed redwood is extensively used in California. Preservation of Wooden Poles.—The preservation of wooden poles employed in line work is a matter of importance. Decay of the pole at or near the soil line is caused primarily by various forms of bacteria or fungi, and in some cases by insects. Bacteria and fungi attack either dead or living timber. In the case of dead timber, such as that of poles, they attack the walls of the cells and cause the familiar rot or decay which eventually destroys the usefulness of the pole.
Preservation Processes.—There are several processes which may be successfully employed for the preservation of poles or other exposed timber. The best known of these are the creosoting, burnettizing, kyanizing, carbolizing, and vulcanizing processes.
Figs. 930 to 932.—Pole line construction tools. Fig. 930, split wooden handle post hole auger; fig. 931, cant hook; fig. 932. socket peavey. Methods of Setting Wooden Poles in Unsuitable Soil.—In places where salt is plentiful and cheap, such as the Great Salt Lake region in Utah, it has been found that the liberal use of salt mixed with the dirt filling tamped in around the foot of the pole is very effectual in preventing decay below the soil line. Where poles have to be planted in low, swampy ground, or where the climatic conditions are such that timber decays rapidly, it has been found advantageous to place the poles in concrete settings. This method is extensively employed in various parts of the Southern States, square poles being placed in Reinforced Concrete Poles.—The strongest point in favor of concrete poles is their durability. Untreated wooden telephone and telegraph poles have to be replaced by new poles about every six or seven years, depending on the percentage of moisture in the soil, the drier the soil, the longer being the life of the pole. Concrete poles are not affected by soil conditions, and if properly made will last indefinitely. Figs. 933 to 935.—Glass insulator and insulator pin and bracket. The insulator here shown is of the pony double petticoat type. Insulator pins are used with cross arms, brackets are attached direct to the pole.
Cross Arms.—The familiar cross arms for stringing wires are usually attached to the poles before they are erected. They are commonly made from yellow pine wood, generally 3¼ x 4¼ inches, and are freely coated with good mineral paint as a preservative. Attachment is made to the pole by cutting a gain one inch deep and of sufficient breadth to allow the longest side of the cross arm to fit accurately. It is then secured in place by a lag screw, with a square head, so that it may be driven into place with a wrench. Fig. 936.—Cross arm which carries the insulator pins. The standard cross arm is 3¼ x 4¼ inches, double painted, and bored for 1½ inch pins and two ½ inch bolt holes. Telephone arms are 2¾ x 3¾ inch, bored for 1¼ inch pins and two ½ inch bolts. The cross arm is further secured to the pole with braces. These are flat strips of wrought iron or low carbon steel, 30 inches long, ¼ inch thick and 1¼ inches wide, according to standard specifications. Holes are bored at points one inch from either end, one for attaching to the pole, the other for attaching to the cross arm; two braces forming a triangle with the cross arm for the base and with the apex at the point of connection to the pole. Like all other iron work used on pole lines, the braces are carefully "galvanized," so as to stand three immersions of one minute each in a saturated solution of copper sulphate without showing copper deposits, the color being black at the completion of the test. Before the cross arm is set in place the gain is carefully painted with white lead. As it is important that cross arms on a line of poles, particularly when there are several on each pole, should be at equal distances from the ground as well as being uniformly spaced, it is necessary that some measuring instrument should be used to accomplish this. Such an instrument is the ordinary template, which is a length of board carrying a pointed block at one end, to correspond exactly with the top of the pole, and also cross cleats nailed at precisely the same intervals below it as it is proposed attaching the cross arms. The template, laid upon a pole, shows where to cut the gains. In planting the poles it is customary to so arrange them that the cross arms on alternate poles shall face in opposite directions, for the purpose of equalizing the strain on the line. On curves, however, all cross arms are placed on the side of the pole facing the middle of the curve. Ques. What provision is made for attachment of the wires? Ans. The cross arms are bored with holes for the insertion of the insulator pins, which are made of locust wood and threaded at the upper end to receive the glass insulator.
Ques. How must electric light and power wires be placed when wired on telephone or telegraph poles? Ans. They must not be put on the same cross arm with the telegraph, telephone, or similar wires, and when placed on the same pole with such wires the distance between the two inside pins of each cross arm must not be less than twenty-six inches. Fig. 937.—Portable platform with rigging as used by linemen in wiring and making repairs.
Spacing the Poles.—In general, the spacing of poles, like their dimensions, is regulated by the weight of the lines they are designed to carry—the heavier the lines the greater the number of poles. The spacing of poles also depends on their liability to injury from storms and wind in any given locality, and the nature of the service. Poles for a telephone line may be spaced twenty to fifty to the mile—that is, from about 260 to 100 feet apart. Figs. 938 to 941.—Pole line construction tools. Fig. 938, pike pole; fig. 939, raising fork; fig. 940, mule pole support; fig. 941, jenny pole support. Erecting the Poles.—Since each pole on a properly constructed line is sawed to the right length and carefully shaped before it is finally inserted in the ground, it is necessary that Fig. 942.—Guy anchor log in position. Fig. 943.—Stombaugh guy anchor. It is made of cast iron and can be screwed into the ground like an auger. Wherever required by the nature of the soil, a "grouting" or foundation of loose stones is formed in the bottom of the hole, and, in marshy or springy ground, a base of concrete and cement is laid, with filling of the same material around the pole, when raised. Ques. How are the poles transported to the holes? Ans. They are rolled or carried on hooks similar to those used for carrying blocks of ice, except for a long handle for lifting the load at either side. Fig. 944.—Method of raising a pole. When the pole has been properly placed, it is seized by several linemen. As soon as the top of the pole is raised high enough to permit the pikes to be thrust into the pole, it is then raised to a vertical position. At about 50° the butt end slides into the hole. The earth is then filled in around the pole and firmly tamped down. Eight or ten poles are about as many as can be set by the average gang in a day. Ques. How are the poles raised and placed in the holes? Ans. A piece of timber is inserted in the hole as a slide to prevent crumbling of the earth as the pole is slid into place. The end is raised by hand sufficiently to allow the "dead man," or pole hoist, to be placed beneath, and this is moved along regularly as the pole is lifted with pike poles, until it slides into place through the force of gravity. Fig. 945.—Method of pulling an anchor into place before the guy wire is fastened to the top of the pole, thus obviating the liability of pulling the pole out of plumb.
Guys for Poles.—Where poles are subject to severe strains which might throw them down and break the wires, guy cables are largely employed, these being attached near the top and secured either to the base of the next pole, to a suitable guy stub or post, or to a guy anchor, which is buried about eight feet in the earth and held down by stones and concrete. Ques. Under what conditions is it necessary to guy poles? Ans. They are guyed at corners in order to thoroughly secure the poles so that no strain may come on the cornerwise span. It is also necessary to guy a line where it is to be deflected from a straight path, as when rounding a hill, water course or railway curve, in order to neutralize the pull of the wires, tending to incline the poles toward the center on which the arc is described; also when descending a hill. Figs. 946 to 948.—Methods of guying corner poles. The proper guying of corner and terminal poles is especially important; on corners and curves, the guys should be stronger and more frequent and should be placed on the outer side as shown in the diagrams. Fig. 949.—Head and foot guying of a pole line in descending a hill. Guy Stubs and Anchor Logs.—In guying a line under such conditions, each pole is connected by a suitable cable to a guy post or "stub," or to an anchor log. Standard rules specify stubs between 18 and 25 feet, with exact limits as to circumference measures at the top and at a point 6 feet from the butt, according to the kind of wood used. Figs. 950 to 952.—Lineman's tools. Figs. 950 and 951, Eastern pole climbers, with and without strap for attaching to legs; fig. 952, portable vise with strap for pulling up the slack in splicing.
Wiring the Line.—The erection and guying of the poles of a line as well as the attachment of the cross arms and the screwing on of the insulators are completed before the stringing of the line is begun. It is particularly essential that the pull on poles of a given line be accurately calculated, and that each one be guyed accordingly before the line is strung, in order to avoid the danger of an undue strain upon the wires in attempting to rectify the condition afterward. It is a good working rule that the wires should be subjected to no stress other than the weights of their own spans after they have been attached to the poles. Figs. 953 and 954.—Pay out reels. Fig. 953, type used for telephone or telegraph work; fig. 954, type used for electric light work. Ques. Describe how the wires are strung. Ans. In stringing the lines, either one or the full number of wires may be put up at the same time. When one line only is to be strung, the operation consists simply in reeling the wire and running it off from a hand reel, such as is shown in fig. 953 or 954. At each pole the wire is drawn up to its place, pulled out to the desired tension, and attached to the insulator.
Fig. 955.—One form of "come along." The wire is inserted between jaws and is held fast when tension is applied to the ring. Fig. 956.—An improved form of "come along" or wire stretcher. The jaws which grip the wire are smooth and remain parallel in closing, thus the wire is not scratched or indented, as with circular jaws having teeth. Ques. How much tension must be put upon the wires? Ans. In applying tension to the wires as they are strung on the poles, it is the rule to allow some sag. The amount of sag to be allowed varies with different line hangers.
Fig. 957.—Wireman's "come along" with hook and tackle.
Ques. How is the wire drawn out? Ans. In drawing out the wire, it is customary to use a wire clamp, or "come along." This tool is attached to a block and tackle, or drawn in by hand, and, as soon as the proper force has been applied, the wire is held, while the lineman secures it to the insulator. Fig. 958.—Lineman's block and fall with "come alongs" for stretching wire and holding same when making splices. Figs. 959 and 960.—Approved method of attaching wire to an insulator; elevation and plan of insulator and tie. The line wire is first laid in the groove of the insulator, after which a short piece of the same size of wire is passed entirely around to hold it in place, then it is twisted to the line at either side with pliers.
Ques. How are the wires attached to the insulators? Ans. An approved method is shown in figs. 959 and 960. Standard rules specify that all wires shall be tied to the side of the insulators toward the pole, except on the insulators next to the pole, where they are to be attached on the opposite side. On curves, however, it is required that all wires shall be arranged so that the strain shall be against the insulator and not on the wire. Fig. 961.—American wire joint. This is a simple method of connecting the ends of the sections of wire by tightly twisting the ends around each other for a few turns; it is the standard Western Union wire joint. Figs. 962 and 963.—McIntire sleeve and sleeve joint. An approved method of making the joints of telephone lines is by the use of some form of sleeve, such as is shown in fig. 962. This consists of two copper tubes of the required length, and of sufficient inside diameter, to admit the ends of the wires to be joined, fitting tightly. The tubes are then gripped with a tool, shown in fig. 964, and twisted around one another, so that the wires are securely joined and locked, as shown in fig. 963. Ques. How are the wires spliced? Ans. There are several methods of splicing wires. Fig. 961 shows the American wire joint, and fig. 963 the McIntire sleeve joint. In making a joint, the two ends are gripped by come alongs and drawn up to the proper tension with tackle as shown in fig. 958. The joint is then made as shown in the illustrations. Transpositions.—In some classes of circuit, as for instance telephone lines, the current is often seriously affected by electrostatic induction from other lines, and also from power circuits, owing to the fact that the surfaces of the wires form, as it were, so many charging plates of an electrical condenser, with the intervening air as the insulating layer or dielectric. Fig. 964.—McIntyre's twisting clamp for wires 00 to 16 B. & S. gauge. Fig. 965—Method of making a "transposition." This is usually done by means of transposition insulators, which are either double insulators, one being screwed to the pin above the other, or else such caps as are shown in fig. 967. Such insulators are intended to act as circuit breakers, the particular wire to be transposed being cut and "dead ended," or tied around, on both the upper and lower grooves of the cap. The free end of each length is then passed back and around the insulator and twisted, or sleeve jointed to the other limb of its own circuit. The telephonic current changes the pressure of its own charging surface as frequently as it alternates, and this fact in itself is amply sufficient to account for a vast weakening of the current before it reaches its destination. The only practicable method
Fig. 966.—Telegraph and telephone line glass insulator. Fig. 967.—Type of insulator used in making a transposition. Insulators.—Glass and porcelain are employed almost universally for supporting overhead wires. Insulators made of these materials are superior to those made of other material such as Fig. 968.—Tree insulator. This type of insulator is especially useful in connection with temporary or repair work, or where the wires pass through trees having numerous branches. The illustration shows a Cutler tree insulator lashed to the trunk of a tree. It is made of a single piece of glass, and is provided with a slot which the wire cannot leave accidentally. The back of the device is concave and provided with ribs which prevent sliding. It can be readily slipped over wires already in place, is available for electric light circuit, and will take wires up to ½ inch, in diameter. Figs. 969 and 970.—Overhead cable construction. In some cases, particularly on short lines exposed to inductive disturbances from power and other electrical circuits, it is usual to string the cables on poles such as usually carry the bare conducting wires. It is not necessary, however, to insulate the cable in any way; consequently it is merely hung to a supporting wire rope or cable, called the "messenger wire," being attached either with some form of hanger, such as is shown in figs. 969 and 970, or by loops of tarred marline. The marline is sometimes wound over the cable and messenger wire from a bobbin, but frequently it is merely wound on by hand. Cables used in such overhead construction consist of bundles of wires, the pairs twisted together. The size most often used is No. 19, B. & S., which is about .03589 inch in diameter, weighs 20.7 pounds, and has a specific resistance of about 8 ohms to the mile. Glass insulators are generally used on low tension lines, and porcelain insulators on high tension lines, the latter type being usually stronger and less brittle. Porcelain is more expensive than glass, and its opacity prevents the detection of internal defects which would be readily observed through glass. Fig. 971.—Clark's "antihum;" a device designed to prevent the humming of telegraph wires. Ques. What is a petticoat insulator? Ans. An insulator which has one, two or three deep flanges or "petticoats" around the base for the purpose of increasing the leakage path from the line to the pin.
Service Connections and Loops.—Whenever it is necessary to tap an overhead conductor for service connection, the method of connection will depend upon the character of the circuit. In the case of a parallel circuit, an extra insulator must be placed Fig. 972.—Method of making a series "loop" service connection. Fig. 973.—Parallel service connection. Service wires tapped to the main wires, are run to insulators on an auxiliary cross arm, thence to insulators on the side of the building, and through the drain tube to the service switch. Fig. 974.—Joint pole crossing, showing wires of two lines crossing each other. Four guard wires (shown heavier than the others) extend for one span either side of the joint pole parallel to the wires of the lower circuits and protect them from contact in case of a break in the wires of the upper circuits. These guard wires are insulated. The minimum distance between high and low tension wires should be three feet. Five is better. The end guards, which prevent wires slipping off ends of cross arms and dropping on the lower wires, should extend about six inches above the level of transmission line. Ques. What are service wires? Ans. Wires which enter a building. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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