Overcurrent relay testing is essential to ensure that the relay will correctly operate during fault conditions.

Substations are classified into generating, grid, switching, and secondary types. Generating substations step up voltage for long-distance transmission. Grid substations are located at load centers. Switching stations manage surges, isolate faults, and enable line extensions without voltage reduction. They have more outgoing lines than incoming.

High voltage circuits and transformers use two main protection relays, Main1 and Main2, with identical functions and settings but separate power sources to ensure system reliability. Protection relays from different manufacturers like MiCOM and ABB include instantaneous and time-delayed protections for various fault scenarios.

Bus bar is a set of conductors for different phases at the same voltage. Common schemes include single bus bar with single breaker, double bus bar with single breaker, one and a half circuit breaker, and ring bus bar. Each has specific applications and advantages in power distribution systems.