94 CONSTANT-VOLTAGE TRANSMISSION 



(10) Power-factor at Generators. 



100 - = per cent. 



E, V P* + Q* 



(n) Reactive Kva. at Generators. 



1,000 



When this quantity is positive, the reactive Kva. and 

 the generator P. F. are leading, and when it is negative, 

 they are lagging. 



(12) Efficiency of the Transmission Line. 



IPO EP 

 E P + (P 2 + (?) R per Cent 



(13) Amperes per Wire. 



As all the expressions for current are in total am- 

 peres, it may be noted that 



total amperes 

 amperes per wire, three-phase, = - r= - 



V3 



total amperes 

 amperes per wire, two-phase, = - - 



and amperes per wire, single-phase = total amperes. 

 For single-phase lines use 2 R and 2 X in place of R 

 and*. 



(14) Allowance for Extra Impedance. 



The resistance and reactance of the transformers 

 and protective coils, referred to high tension, may 

 be added to the resistance and reactance of the line. 

 This involves no error or approximation at all when 

 the electrostatic capacity of the line is not to be 

 considered. 



