AUXILIARY STATIONS 697 



heavy loads on the steam plant during the peaks, thereby requir- 

 ing more boilers and machines in service and, consequently, more 

 fuel and operators. 



" The term * peaks ' is intended to cover heavy load periods 

 of the daily load curve, and not the momentary load fluctuations. 

 Assuming equal governor or speed regulation and equal- fly wheel 

 effects, these momentary load fluctuations are divided between 

 the stations in proportion to the total capacities of the generators 

 operating in each station. The flywheel effect of the steam tur- 

 bine is usually the larger and the steam turbine governor is the 

 more sensitive. The steam turbine station will, therefore, ordi- 

 narily take more of the momentary fluctuation than its propor- 

 tionate capacity in operation. 



" Some fuel can be saved in developments of this kind by 

 carefully observing the rainfall within the drainage area of the 

 stream developed. In case of rainfall within this area the steam 

 plant can be shut down immediately and all the load taken over by 

 the hydraulic plant at the expense of reducing the level of the 

 reservoir. The increased stream-flow will again fill the reservoir. 

 Rainfall at the head waters of a large stream would not materially 

 increase the stream-flow at the development for some time; and, 

 consequently, a considerable saving in fuel would thus be effected. 

 During the dry season, water flowing over the dam means fuel 

 wasted* and, therefore, if enough reliance could be placed in 

 weather forecasts to anticipate rainfalls, the steam plant could be 

 shut down in time, so that the reservoir level would be reduced 

 sufficiently to take care of the increased flow without wasting any 

 more over the dam than necessary." 



Peak-load Stations. The function of the auxiliary plant used 

 to carry the daily peaks of load on the system is similar to that of 

 pondage above the water-power plant, increasing the operating 

 load factor and, consequently, the output from water. In the 

 case of the supplemental plant, the first cost and relative economy 

 of generation must be governed by the proportion of the total 

 output of the system to be carried by the auxiliary plant, i.e., 

 the higher the percentage carried by the auxiliary plant, the 

 more important becomes the economy of generation and the less 

 important the first cost and resulting fixed charges. 



Base-load Stations. Where the conditions are such that the 

 average power demand exceeds the capacity of the hydraulic 



