The MGFR series of ground fault relays are microprocessor based relays that measure the ground fault current from the secondary of a zero sequence current sensor connected to the relay. When a ground fault occurs, the relay computes the RMS value of thefault current. If the fault current is above the level of the pick-up setting of the relay, the trip unit operates to open a circuit breaker in accordance with a set of programmable time current characteristics.
The MGFR series has five basic models each with eight discrete pick-up and time settings. The range of the pick-up settings varies from model to model. The entire series covers the range from 10 mA to 1200 Amps.