HIGH-TENSION NET-WORKS 49 



large part of the year there is more water-power avail- 

 able than can be used. 



The above conditions necessitate a large capital in- 

 vestment in order to supply energy to a certain number of 

 customers, and such conditions are the cause of the un- 

 profitableness of many water-power plants. They can 

 be overcome to a marked degree by allowing the power 

 plants to supply energy into a huge net- work by which 

 electric energy can travel here or there over many miles 

 of country, as the load demands, instead of each plant 

 supplying its own small group of customers. The peak 

 loads of different customers and different towns occur 

 at different times of day. The load curves of a residence 

 city and a factory town are quite unlike, and large dif- 

 ferences also occur where two cities use standard time 

 differing by one hour. The net-work averages up these 

 irregularities in the demands for power, thus making a 

 smaller equipment necessary for a certain number of 

 horse-power of connected load, and, therefore, for a 

 certain income from the sale of energy. This is generally 

 expressed by saying that the load factor of a large net- 

 work is higher than the load factor of a small system, the 

 load factor being the ratio of the average load to the 

 peak load. In the same way, the net-work averages up 

 the irregularities in the water supply of different plants, 

 and minimizes the necessity for water storage and for 

 reserve equipment of all kinds in case of breakdown. 

 Thus each plant may be designed to operate almost stead- 

 ily at its normal load, since the net- work will take energy 

 as the plant finds it convenient to supply it, nor is the 

 net-work inconvenienced if a single plant shuts down. 

 This results also in less power being wasted at times of 



