50 CONSTANT-VOLTAGE TRANSMISSION 



high water. That there is not the slightest doubt of 

 great economies resulting from the formation of large 

 net-works is proved by the fact that in many places 

 competing power companies have made contracts with 

 each other for the interconnection of their net-works 

 and the exchange of power. 



A constant- voltage straight transmission line will re- 

 quire synchronous motors of a total rating equal to 

 about 60 per cent of the total power capacity of the line, 

 as indicated by the examples in Chapter X. A constant- 

 voltage net-work, however, will not require such a large 

 proportion of synchronous motors, unless the generating 

 stations are spaced very far apart. In a net-work, the 

 amount of real power furnished by each generator is not 

 controlled by electrical adjustments, but is determined 

 almost entirely by the setting of the governor of each 

 prime mover. The governor will be set so that there is a 

 certain tendency to increase the frequency of the entire 

 system, which means that the generator is delivering 

 real power to the system. A change in the generator 

 rheostat changes the power-factor at the generator, the 

 amount of reactive power which it delivers to the sys- 

 tem, and indirectly the voltage. Thus a small gener- 

 ator in a net- work provides exactly the same means of 

 maintaining constant voltage where it is located as a 

 synchronous motor in a substation, and so if there are a 

 number of scattered generators in a net-work, the pro- 

 portion of synchronous motors will be expected to be 

 less than 60 per cent, even when the lines are loaded to 

 a maximum degree. 



A small generator connected to a net-work can prob- 

 ably furnish the required leading and lagging reactive 



