SUBSTATIONS. 109 
® 
conditions on which they depend. 'These are obviously 
different in the different classes, but in all we have to deal 
with the same general circumstances. 
The time comes in the growth of a great urban street 
railway system or the development of long interurban 
lines, when the cost of transmission of the necessary power 
becomes very burdensome on account of the long distances. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
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Street Railway Journal 
BIG. 62; 
Something has to be done, but to define the particular 
thing which is best under the circumstances is generally 
far from an easy task. ’The operation of substations of 
any kind means usually an increased cost of power de- 
livered at the station switchboard, incurred in order to 
save a heavy expense in power distribution. 
Minimum total cost of power is the thing to be sought. 
If generated in a single central station it can be delivered 
at the switchboard cheaply, but the total cost per kilowatt 
actually used may be quite high. On the other hand if 
the power is generated in separate substations the cost of