Primary bus protection includes high-speed differential schemes (87B, 87BB, 87Z, 87N, 87ST), restricted earth fault (64REF), and sensitive ground fault (64). Backup protection uses overcurrent (50/51), earth fault (50N/51N/51G), high-set (50HS), negative sequence (46), and directional (67/67N) relays.

Protection relays safeguard generators by preventing damage and ensuring grid stability through reverse power, loss of excitation, unbalanced load, thermal, overcurrent, earth fault, voltage/frequency, and over-fluxing protections.

Differential protection detects faults by comparing input and output currents of equipment; imbalance triggers a trip signal to isolate the fault. It offers high sensitivity and selectivity.

Symmetrical components analyze unbalanced three-phase systems: positive sequence (balanced, normal operation), negative sequence (balanced but reverse rotation, causes motor heating), and zero sequence (in-phase, linked to earth faults).