. 



APPENDIX C 



289 



The extent' to which the power-factor at the power-house bus 

 is affected by the over-excitation of the synchronous motors is best 

 shown by a vector diagram. 



This was figured from simultaneous readings on the turbo- 

 generators at the power-house, and the synchronous motors at the 

 substations. The average power-factor of the turbo-generators with 

 a load of 31,100 KW., under normal running conditions, is about 

 95 per cent, lagging. The reactive component of this is 9750 K.V.A., 

 lagging. The total load taken by the synchronous motors is 10,735 



12100 K.W.-Hailway and Lighting Load 



18474-Probable Total Of 

 Reactive K.V.A. Without, 

 Syuchronoua Motors 



KW. with a power-factor varying from 50 to 95 per cent leading, 

 and the summation of all its reactive components at the various 

 power-factors is 8724 K.W.A. This leading component counteracts 

 an equal lagging one, leaving a resultant reactive lagging component of 

 9750 K.V.A. on the whole system, corresponding to a power-factor of 

 95 per cent. Without this leading component the lagging component 

 would be 18,474 K.V.A., which would mean a power-factor of 85 

 per cent. Hence it is seen that a 10 per cent rise in power-factor 

 is obtained by over-excitation of the synchronous motors in our 

 substations. 



Regarding the overrating of the motor-ends of the motor- 

 generator sets, the following two examples of rating might be 

 mentioned: 



