Ground Fault Circuit Interrupter (GFCI) technology was first introduced in the NEC in 1971, yet four decades later the technology has not been introduced to a great extent outside of the home environment. This thesis introduces the difficulties encountered in low-voltage three phase ground fault current detection, and adopts a previously patented tripping scheme to develop and prototype a digital relay for 3-phase 480 volt systems capable of the sensitivity and speed required for personnel safety. Results demonstrate the feasibility of the concept and suggest commercial development should be pursued. The prototype is capable of mA sensitivity and reliably detects and removes the faulted feeder from the system, without causing false tripping on non-faulted feeders. The prototype system has been tested and responds appropriately for faults over the 1 mA to 1000 A range.