What is Protective Relay ?Protective Relay DefinitionA protective relay is an automatic device that senses abnormal conditions in electrical circuits and triggers actions to isolate faults.Types of Protective Relays Definite time relays Inverse time relays with definite minimum time(IDMT) Instantaneous relays IDMT with inst Stepped characteristic Programmed switches Voltage restraint over current relayOperating PrinciplesProtective relays operate by detecting abnormal signals, with specific pick