Over-Voltage on Transmission Systems Due to Dropping of Load

When a waterwheel-driven generator, or a hydroelectric station, loses all or a large part of its load, the voltage rises more rapidly and to a greater extent than has been generally realized. The purpose of this paper is to show the manner in which the voltage will rise under different conditions, and a method of calculating the voltage rise of a waterwheel-driven generator when load is lost. The results of a large number of tests are given showing the rise in voltage on an 8500-kv-a., 6600-volt waterwheel generator when load was tripped under several different conditions at three different places, namely, at the generator, on the high-voltage side of a transformer bank, and at a substation forty miles away. As it is not considered good practise to subject a transmission system to high over-voltages, consideration is given to methods of checking the voltage rise by use of relays as soon as possible after load has been dropped.