HIGH-TENSION NET- WORKS 51 



Kva. more economically than a synchronous phase 

 modifier, because it can at the same time furnish real 

 power, and the real and reactive power will not be added 

 directly to make up the load of the generator, but only 

 added in quadrature. Thus, 70 per cent of reactive power 

 and 70 per cent of real power make up only 100 per cent 

 load on the generator. There will be small liability of 

 trouble at times of light load when weak field current is 

 used, because at that time the governor setting will be 

 changed, or power will be completely cut off from the 

 prime mover. For this purpose, an operator called a 

 "load despatcher" is found necessary. A local operator 

 can tell from his voltage how much reactive power his 

 generators ought to furnish to the system and what his 

 rheostat settings should be he has merely to adjust for 

 constant voltage, but he has only slight information 

 regarding how much real power he should furnish, and 

 he must be informed as to this by a central operator who 

 watches the load at all parts of the net-work, and who 

 gives orders regarding the setting of governors, the 

 starting and stopping of prime movers, and the connect- 

 ing of transmission lines. The load despatcher has 

 great opportunities of utilizing the water storage and 

 other characteristics of different plants to the best ad- 

 vantage, and of avoiding the operation of machines at 

 low load, and therefore low efficiency. He can also pre- 

 vent the overloading of any connecting link in the net- 

 work. 



A synchronous motor can carry real and reactive 

 loads at the same time in the same way as a generator, 

 but it will not generally be so satisfactory to do this. 

 For example, if the motor is connected to a railway gen- 



