. Journal of electricity, power, and gas . culation of Percentage and Reactance Pres-sures OF Transmission Lines. Let /? ^ resistance of one wire from generator to receiver inohms; Lw^ reactance of one wire from generator to receiver inohms. (For Liu take inductance per mile from (he curve inFig. 7 and multiply by the length of the line in miles.) Let :amperes per wire at non-inductive full load; E^o. m. wires in volts at point of fixed pressure. Then, forthree-phase, percentage resistance pressure ^ 1/3(//?/£) 100;percentage reactance pressure = 1/ 3(LzvI/E)100. F
. Journal of electricity, power, and gas . culation of Percentage and Reactance Pres-sures OF Transmission Lines. Let /? ^ resistance of one wire from generator to receiver inohms; Lw^ reactance of one wire from generator to receiver inohms. (For Liu take inductance per mile from (he curve inFig. 7 and multiply by the length of the line in miles.) Let :amperes per wire at non-inductive full load; E^o. m. wires in volts at point of fixed pressure. Then, forthree-phase, percentage resistance pressure ^ 1/3(//?/£) 100;percentage reactance pressure = 1/ 3(LzvI/E)100. For single-phase or two-phase system replace 1/ 3 in theabove by 2. Example.—Length of line = 15 miles, voltage between wires- - 5000, and full-load current ^60 amperes. From the curve inFig. 7 we find the inductance =^ 10 ohms for 30 between wires. Hence, percentage reactance pressure = 1/3X10X60X100 = 20-75. 5000 For a line ISO miles long, and volts between wires, thepercentage reactance pressure is practically the same. ?\of. Volts Between Wires Fig. 8. Ratio of . Miles of Line Curves give perceiUage reactance at 60 Conditions: Three-phase system. No. 0, B. & S. amperes per wire. For single-phase or two-phase, multiply ordinates by 115, For any other current ? //lOO For any other frequency ? //60 For No. 1 wire, 102. For No. 2 wire, ?? ?• 104. For No. 3 wire, ?? ? 106, etc For wire % in diameter with 12 feet between wires add 4%to curve for No. 0 wire spaced 48. , We see that in the formula for the reactance pressure wealways have the ratio of the voltage between wires and lengtliof line in miles. Assuming a given number of amperes flowingin the line, say 100, we may construct a curve between the per-centage reactance pressure and the ratio of volts to length ofline in miles = £//.. This has been done in Fig. 8, from whichthe percentage reactance pressure for any given case may beciuickly determined. Curves are given for 12, 24, and 48between wire
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