54 CONSTANT-VOLTAGE TRANSMISSION 



circuit practically only from the neighboring generating 

 stations. 



For example, if a short circuit occurs one hundred 

 miles from a generating station, and the station voltage 

 is held up at 100,000 volts, 60 cycles, a sustained current 

 corresponding only to about 100,000 Kva. will be 

 delivered from the station. This is a small amount 

 compared with that which modern circuit breakers can 

 handle, especially reactance type breakers, which break 

 the current in two steps, or more if necessary. Protective 

 reactance at the station will greatly reduce the above 

 current, so that it may be said that a station one hundred 

 miles away from a short circuit cannot send to it a 

 dangerous amount of current. It is, therefore, evident 

 that the danger from a short circuit is not proportionate 

 to the total power of the net- work, since, when the gener- 

 ators are widely scattered, they are harmless, but the 

 danger is greatest where there are concentrated groups 

 of large ratings in generators. When it is remembered 

 that the i,5oo-mile net-work around San Francisco, 

 stretching over 200 or 300 miles of territory, has a power 

 load of only about 100,000 Kw., while practically 

 concentrated loads of from 100,000 to 150,000 Kw. 

 have been successfully handled at New York, Chicago, 

 and Niagara Falls, it does not seem that the handling of 

 short-circuit currents on an extensive net-work is the 

 most difficult feature of electric-power engineering. 



Stretches of country a few hundred miles across, 

 devoid of any water-power, have seemed an obstacle 

 which a high-tension net-work could not cross. But the 

 principles of constant-voltage transmission allow the 

 net-work to extend economically across such stretches of 



