An Underfrequency Relay with Frequency Decay Rate Compensation

The development of a new type of solid-state protective relay which senses both frequency and rate-of-change of frequency is outlined. The design considerations and principles of operation of this relay are explained with respect to modern load reduction concepts. The theory of operation of the device and how it can be applied in an electric power system are discussed. Finally, possible future applications of the philosophy of rate compensated protection are presented.