Relay protection refers to

Relay protection is also known as a protective relay or protection relay.Relay protection, in electrical engineering, refers to the system or device designed to detect abnormal conditions in electrical circuits and initiate corrective actions, typically by tripping a circuit breaker to isolate the faulty section from the healthy system (protective relay) . These devices monitor electrical quantities such as current, voltage, frequency, and phase angle, and respond to faults like overcurrent, short circuits, voltage imbalances, or frequency deviations . Protective relays can be classified based on their operating principle—electromechanical, static, or numerical (microprocessor-based)—or by function, such as overcurrent, differential, distance, earth fault, or voltage/frequency relays . They form the backbone of power system protection, ensuring equipment safety, system reliability, and continuity of electrical supply by quickly isolating faulted components while minimizing disruption to the rest of the network . In summary, relay protection and protective relay are interchangeable terms, both describing devices or systems that safeguard electrical power systems by detecting faults and initiating circuit breaker operations.