Drop.—In order to determine the drop or volts lost in the line, the following formula may be used

 % loss × volts
drop = —————— × S   (1)
  100

in which the % loss is a percentage of the applied power, that is, the power delivered to the consumer and not a percentage of the power at the alternator. "Volts" is the pressure at the consumer's end of the circuit.

VALUE OF "S" FOR 60 CYCLES
Size of
wire
B. & S.
gauge		Area
in
circular
mils.		.98 power factor.90 power factor
Spacing of
conductors		Spacing of
conductors
1" 3" 6" 12" 24" 1" 3" 6" 12"24"
500,000 500,000 1.211.45 1.61 1.771.92 1.32 1.802.11 2.44 2.75
300,000 300,000 1.15 1.29 1.38 1.48 1.57 1.19 1.47 1.66 1.84 2.02
0,000 211,600 1.121.22 1.28 1.341.41 1.13 1.331.45 1.58 1.63
000 167,800 1.091.18 1.22 1.281.29 1.08 1.231.33 1.44 1.53
00 133,100 1.071.14 1.18 1.211.25 1.03 1.161.24 1.32 1.40
0 105,500 1.051.10 1.14 1.171.20 1.00 1.091.16 1.22 1.28
1 83,690 1.041.08 1.10 1.131.15 1.00 1.051.09 1.14 1.19
2 66,370 1.021.05 1.08 1.101.12 1.00 1.001.04 1.08 1.12
3 52,630 1.021.04 1.06 1.071.09 1.00 1.001.00 1.03 1.06
4} 41,740 1.001.02 1.03 1.041.07 1.00 1.001.00 1.00 1.00
5} 33,100
6} 26,250 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
7"} 20,820
8} 16,510 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
9} 13,090
10} 10,380
Size of
wire
B. & S.
gauge		Area
in
circular
mils.		.80 power factor.70 power factor
Spacing of
conductors		Spacing of
conductors
1" 3" 6" 12" 24" 1" 3" 6" 12"24"
500,000 500,000 1.271.89 2.25 2.643.03 1.14 1.722.12 2.53 2.92
300,000 300,000 1.11 1.46 1.68 1.90 2.12 1.00 1.33 1.56 1.78 2.01
0,000 211,600 1.031.27 1.43 1.581.75 1.00 1.141.29 1.45 1.69
000 167,800 1.001.16 1.28 1.411.53 1.00 1.021.15 1.28 1.50
00 133,100 1.001.07 1.17 1.271.36 1.00 1.001.03 1.13 1.21
0 105,500 1.001.00 1.07 1.151.22 1.00 1.001.00 1.01 1.09
1 83,690 1.001.00 1.00 1.051.11 1.00 1.001.00 1.00 1.00
2 66,370 1.001.00 1.00 1.001.02 1.00 1.001.00 1.00 1.00
3 52,630 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
4} 41,740 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
5} 33,100
6} 26,250 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
7} 20,820
8} 16,510 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
9} 13,090
10} 10,380

The coefficient S has various values as given in the accompanying tables. As will be seen from the table, the value of S to be used depends upon the size of wire, spacing, power factor and frequency.

These values are accurate enough for all practical purposes, and may be used for distances of 20 miles or less and for voltages up to 25,000.

The capacity effect on very long high voltage lines, makes this method of determining the drop somewhat inaccurate beyond the limits above mentioned.

VALUE OF "S" FOR 25 CYCLES
Size of
wire
B. & S.
gauge		Area
in
circular
mils.		.98 power factor.90 power factor
Spacing of
conductors		Spacing of
conductors
1" 3" 6" 12" 24" 1" 3" 6" 12"24"
500,000 500,000 1.011.17 1.23 1.291.36 1.02 1.221.35 1.43 1.61
300,000 300,000 1.04 1.10 1.13 1.18 1.21 1.00 1.08 1.16 1.25 1.31
0,000 211,600 1.031.07 1.09 1.111.14 1.00 1.021.07 1.13 1.15
000 167,800 1.001.05 1.06 1.091.10 1.00 1.001.02 1.07 1.11
00 133,100 1.001.03 1.05 1.061.08 1.00 1.001.00 1.02 1.05
0 105,500 1.001.01 1.02 1.031.04 1.00 1.001.00 1.00 1.00
1 83,690 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
2 66,370
3 52,630
4} 41,740 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
5} 33,100
6} 26,250
7} 20,820 1.001.00 1.00 1.001.00 1.00 1.001.00 1.00 1.00
8} 16,510
9} 13,090
10} 10,380