What is a relay? All Questions › Category: Switchgear And Protection › What is a relay? 0 Vote Up Vote Down chetan shidling asked 4 years ago I need short information. 1 Answers 1 Vote Up Vote Down chetan shidling answered 4 years ago The relay is a protective device which will detect the fault and initiate the operation of circuit breaker. It is used for protection in substation, in electronic devices, etc.