PROTECTIVE RELAY FOR POWER SYSTEM

摘要

A protective relay which generates a signal to protect an object in a power system that is to be protected in response to a differential signal and a suppress signal showing an abnormal condition, which are obtained from electric currents of two separate points in the object. The protective relay is equipped with a logical decision circuit which generates the signal to protect the object only when the differential signal is greater than a predetermined value, and the second harmonic component contained in the differential signal is smaller than a predetermined ratio.