A digital rate-of-change underfrequency protective relay for power systems

A digital relay is described for power systems application which responds both to frequency and to rate of change of frequency. Its application is in the operating situation of load suddenly in excess of generation, either because of sudden unexpected added load or because of generator or other equipment failure; and its function is the initiation of preplanned emergency load shedding. Advantages of the relay are its sensitivity to generation-load imbalance, and its relative simplicity.