Motor protection relays detect electrical, thermal, and mechanical faults using ANSI codes: 49 (thermal overload), 50/51 (phase overcurrent), 50N/51N (earth fault), 46 (unbalance), 47 (phase failure), 48 (locked rotor).

DG set protection includes electrical (differential, overcurrent, negative sequence, voltage/frequency, reverse power, loss of excitation, V/Hz, lockout) and mechanical (oil pressure, temperature, level, locked rotor, start limits) layers for comprehensive safety.

CTs measure current by stepping down high currents (e.g., 400A to 5A) in series, while PTs measure voltage by stepping down high voltages (e.g., 11kV to 110V) in parallel; both enable safe metering and protection.

The primary protection for the 33 kV transmission line incorporates relays such as 50, 51, 50N, 51N, 67, 67N, 79, 46, 27, and 59, providing overcurrent, ground-fault, directional, auto-reclosing, unbalance, and voltage protection. System stability functions include relays such as 81U (under-frequency), 81O (over-frequency), 81R (rate-of-change-of-frequency), and 78, ensuring frequency and power-angle stability.