60 CONSTANT-VOLTAGE TRANSMISSION 



charging separately for the reactive Kva.-hours, or using 

 the same measurement to calculate the average power- 

 factor, is advisable for cases where the energy-supply 

 company wishes the customer's load to have a leading 

 or a high power-factor at all times of the day, as in the 

 case where the customer is located close to the gener- 

 ating station. This bonus is also applicable where no 

 synchronous motors are installed or are likely to be 

 installed, and where, therefore, power-factor adjustment 

 is not possible. The disadvantage of the above bonus 

 is that it discourages any adjustment of the power- 

 factor, and in many instances it is desirable at times for 

 the sake of the voltage to lower the power-factor by 

 reducing the excitation of the synchronous motors. 

 Some other method than the above of giving the bonus 

 must, therefore, be looked for in a great many cases. 



Where the distance to which the energy is sent is 

 sufficient to make the voltage variation due to line drop 

 noticeable, it is very desirable, as mentioned above, to 

 adjust the synchronous motors continually so as to hold 

 the voltage constant. Since this would require them to 

 be operated lagging part of the time, a bonus for very 

 high power-factor such as has been just described would 

 clearly be inadvisable and would be against the real 

 interests of both customer and supply company. This 

 applies to many cases of the distribution of energy from 

 steam plants in large cities, and to all cases where 

 energy is delivered over transmission lines. It may be 

 said that in the majority of cases adjustable power- 

 factor is of more value than high power-factor, and 

 synchronous motors are more valuable as voltage" reg- 

 ulators than as power-factor correctors, especially be- 



