22 CONSTANT-VOLTAGE TRANSMISSION 



in the lines of the city net-work. Accordingly, if the 

 transmission-line voltage at the city end has too great a 

 variation for the capacity of the potential regulators, 

 there will be variation in the voltage actually supplied to 

 customers, and this will entail all the disadvantages in the 

 use of electric power described above. Power companies 

 depend, for increasing their power load, on keeping cus- 

 tomers satisfied by giving them good service. Allowing 

 noticeable variations in the voltage supply is one of the 

 surest ways of making a power-user dissatisfied with the 

 service of the supply company in particular, and with 

 electric power in general. Moreover, as is often pointed 

 out, allowing the voltage to fall by a certain percentage 

 at peak load produces twice as great a percentage de- 

 crease in the power consumed by both lamps and motors. 

 This is annoying to a customer, since he wishes full 

 power and is willing to pay for it, but it is a direct money 

 loss to the power company, whose income is based on 

 the amount of energy registered by the meters. 



In a great many power-transmission systems, energy 

 must be sold for application close to the generating 

 plant, and voltage variation at the end of the transmis- 

 sion line next the power plant has the same disadvan- 

 tages as variation at the city end of the line. There are 

 cases where there are no customers close to the gener- 

 ating station, and as far as the sale of power is con- 

 cerned, the only place where steady voltage is desired is 

 at the receiver end of the transmission line. The volt- 

 age of the generators may, therefore, be varied through 

 a large range in order to compensate for drop in the line. 

 What, then, is the limit to the voltage variation allowed 

 at the generating end? It is found as a result of practi- 



