. Development and electrical distribution of water power . Fig. 53. cuit must be transposed. The transposition for one circuit on apole is that of the middle circuit shown in Fig. 54; that is, two trans-positions in the length of the transmission, one at one-third, theother at two-thirds the distance from the power station. A second Il8 DEVELOPMENT AND DISTRIBUTION OF WATER POWER circuit on the same pole would be transposed like the lowermost cir-cuit shown in Fig. 54; , a transposition at each one-ninth of thetransmission length. A certain tension should be put on the wires in stringing t
. Development and electrical distribution of water power . Fig. 53. cuit must be transposed. The transposition for one circuit on apole is that of the middle circuit shown in Fig. 54; that is, two trans-positions in the length of the transmission, one at one-third, theother at two-thirds the distance from the power station. A second Il8 DEVELOPMENT AND DISTRIBUTION OF WATER POWER circuit on the same pole would be transposed like the lowermost cir-cuit shown in Fig. 54; , a transposition at each one-ninth of thetransmission length. A certain tension should be put on the wires in stringing them 2 3 1 2 Fig. 54. on the poles, and it should be just great enough to give a definiteamount of sag, or dip below the horizontal. The sag is dependent on. Fig. 55. the length between spans and the temperature at the time of good rule is to allow a sag equal to X length between TRANSMISSION CONDUCTORS II9 spans for a temperature of 6o° F. Increase or diminish theamount of sag thus found 7J per cent, for each io° F. aboveor below 6o°. Thus, if spans are 200 feet, the sag would be200 X feet for 6o° F. If the temperature at thetime of erecting were 900 F., the sag would be increased by apercentage = (90 — 60) X 7^ = 22J per cent. 22 J per cent, of = Sag actual = + =, say feet = 3 feet 9\ inches. The spacing apart of wires varies from 36 inches in short spans—say up to 150 feet—to 78 inches in long spans and with highvoltages. Increasing the distance of separation increases the in-ductive drop, thereby increasing the size of generators and theline losses, while if placed too near together, the chance of swayingbringing the wires in contact, or the possibility of sudden
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