PRACTICAL OPERATION OF DYNAMOS. 



227 



mer demand for current is very considerable even in middle lati- 

 tudes and, as Fig. 142 shows, it is excessively great in Christiania. 

 The sharp maximum of station load, which occurs at 6 P. M. 

 in Christiania in winter time, and usually between 7 and 8 P. M. 

 in middle latitudes in winter time, is called the "peak of the 

 load." The boiler, engine, and generator capacity of a station 

 must be sufficient to meet the excessive demand for current that 

 constitutes the peak of the load, although it is usually permissible, 

 during the short time that the excessive demand lasts, to force 

 the boilers and overload the engines and generators to some 

 extent. 



The actual output of a station in kilowatt-hours during a given 

 period, a month for example, divided by the output that could 

 be obtained during that period by operating the station night and 

 day at its full rated capacity, is called the load factor * of the sta- 

 tion. Thus if the Christiania plant, referred to in Fig. 142, is a 



* The load factor of a station which operates a certain number of hours each day is 

 sometimes defined as the actual output during the day's run divided by the output that 

 would be obtained were the station operated at full-load for the whole time of the run. 



