88 CONSTANT-VOLTAGE TRANSMISSION 



and neglecting capacity effect, as in the attached ex- 

 amples of 200-mile lines, shows that it is possible to 

 transmit about 10 per cent more power over a 2oo-mile 

 line of given maximum voltage, either of varying- 

 voltage or constant-voltage control, than it would be 

 if there were no such thing as line capacity. The effi- 

 ciency of transmission and the generator power-factor 

 are also improved by the line capacity.* 



In connection with one phenomenon of transmission- 

 line operation, the charging current may be considered 

 to be a disadvantage. This occurs when the load is 

 suddenly disconnected, as when the receiver station cir- 

 cuit-breakers open, and the excitation of the generators 

 is, for the time being, unaltered. If there is not a very 

 large number of generators connected, the charging cur- 

 rent will form a heavy leading power-factor load for 

 them. This will help magnetize their fields, so that the 

 sustained line voltage may be as high as twice the 

 normal voltage, as indicated in the attached examples. 

 This might be more harmful, if not prevented, than the 

 transient voltages which also occur on the opening of 

 circuit-breakers. The above phenomenon, however, has 

 not proved to be a very troublesome feature of oper- 

 ation. It can generally be guarded against sufficiently 

 by keeping enough generators on the line to carry the 

 charging current easily and by keeping the generator 

 voltage closely regulated. Although the percentage 

 regulation of a generator between a lagging load and full 

 load of leading power-factor current is large, being much 



" Maximum Loads of Transmission Lines," Electric Journal, 

 September, 1913. 



