52 CONSTANT-VOLTAGE TRANSMISSION 



erator, then when there is a weak field current in the syn- 

 chronous motor an increase of load on the D. C. machine 

 may cause the motor to drop out of step and open its 

 circuit breaker. Thus automatic voltage regulators 

 must be applied with more caution to synchronous motor 

 generator sets than to synchronous motors running 

 idle. From the above consideration, and from the 

 fact that synchronous motors are usually a small pro- 

 portion of the load of a system, it is probable that the 

 bulk of the reactive Kva. required would be supplied 

 by generators scattered throughout the net-work, and 

 by synchronous phase modifiers running without me- 

 chanical load. 



The cheapening of the design of water-power plants 

 where there is a large power net-work, and the use of 

 scattered generators for voltage control, tend to make 

 smaller water-powers profitable, and to increase the 

 number of water-powers which can be developed. In 

 the same way, a net-work makes it posssible to supply 

 small communities and isolated customers with electric 

 energy which they could not otherwise obtain. 



The growth of high-tension net-works is dependent 

 on the distance separating the power plants and on the 

 economical distance of transmission. If there were a 

 water-power plant every 100 miles throughout the 

 country, it would not be difficult to connect them all 

 into a single net- work, and its operation would probably 

 be safe, judging by some of the large power net-works 

 which already stretch over several hundred miles of ter- 

 ritory. But if the power plants were 400 miles apart, 

 and energy could be economically transmitted only 150 

 miles, the stations could not be interconnected. Now if 



