A power system must continuously transport electrical energy while remaining within the thermal, mechanical, and insulation limits of generators, transformers, busbars, transmission lines, cables, motors, and switchgear. When a short circuit, insulation failure, overload, abnormal voltage, frequency disturbance, or equipment malfunction occurs, the affected section must be disconnected quickly. A delay of even a fraction of a second during a severe fault can increase equipment damage, expose personnel to danger, and threaten the stability of the wider electrical network. A protection relay monitors electrical quantities such as current, voltage, frequency, phase angle, impedance, power, and temperature. When measured values meet predefined operating criteria, the relay initiates an alarm, trips a circuit breaker, starts an automatic control action, or blocks an unsafe operation. The three basic duties of a protection relay are: Measure electrical quantities Detect abnormal or fault co...