98 CONSTANT-VOLTAGE TRANSMISSION 



(n) Efficiency of the Transmission Line. 



E 8 P 8 - (P, 2 + ft 2 ) R 



100 ~ E P ~ per c 



(12) Reactive Kva. of Synchronous Motors Required 

 when Load Power-factor is cos 6. 



The reactive Kva. of the load are equal to the Kw. 

 at receiver end, from (7), multiplied by -. To this 



result, treated as a positive quantity, add the reactive 

 Kva. in the line at the receiver end, from (10), with due 

 regard to the sign. This is a positive quantity when the 

 line power-factor is leading. The sum is the reactive 

 Kva. of synchronous motors required. 



(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, = :=* 



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 X. 



(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. 



