8o 



TRANSMISSION LINE FORMULAS 



other), will have the voltages of the three phases equal at 

 the end of the line. 



The average reactance of an irregularly spaced three- 

 phase line, in which the conductors are transposed at regu- 

 lar intervals, may be calculated as follows: 



Fig. 16. 



*ig. 17. 



Let Fig. 1 6 represent the spacing of the conductors A , B, 

 and C of a transmission line. Let the currents in the con- 

 ductors be represented by the vectors OP, OQ, and OR 

 (Fig. 17). If the power factor is 100%, these vectors may 

 also represent the star voltages, and the line voltages will 

 be represented by the vectors PQ, QR, and RP. 



Let the current in conductor A be 



I A = OP = i .00 7 amperes, 



and let I B = OQ = (- 0.50 + 0.8667) 7 amperes, 

 and I c = OR = (- 0.50 - 0.8667) 7 amperes. 



Let also 



Voltage from neutral to A = i .00 V. 



Voltage from neutral to B = (- 0.50 + 0.8667) V. 



And voltage from neutral to C = (- 0.50 - 0.8667) V. 



Then the measured, or absolute, value of voltage between 

 B and C is 1.732 F, where V is the star voltage of the line. 



