A protection relay serves a few core functions: Trip the circuit breaker when a fault in the system is detected, preventing further damage. Can differentiate unfaulty operations from actual faults. Allow swift reconnection of supply. Protective Relays - Technical Seminar Nov 2016 - Copyright: IEEE 2 Abstract: Protective relays and devices have been developed over 100 years ago to provide “lastline”of defense for the electrical systems. While this is bad, It's not a. Substations are critical nexus points in the power grid, transforming high-voltage electricity to ensure its safe and efficient delivery from power plants to millions of end-users. This device functions to identify inconsistencies, like overloads or faults, in the electrical circuit operation.