Definition of Protective Relay A protective relay is an automatic device that detects abnormalities in an electrical circuit and closes its contacts. This action completes the circuit breaker's trip coil circuit, causing the breaker to trip and disconnect the faulty section from. Engineering use: Relays are used on feeders, transformers, buses, motors, generators, and transmission lines to protect equipment and improve system reliability. Static Relays: Use electronic components without moving parts.
[pdf] 