Polyphase Group Distance Relaying by Phase Coincidence Principle

The paper describes a novel method for polyphase ground fault relaying with the help of a simple coincidence principle of the selected input quantities. The general principle of operation, actual design and performance results have been discussed. The relay operates correctly for all single line to ground faults, as well as double line to ground faults with the same reach in each case. For line to line faults and 3-phase faults the relay remains completely inoperative. Like other reported relays of the same category it has the advantages of insensitivity towards balanced overload and power swings in the transmission line. Moreover it has greater tolerance for arcing faults and is less susceptible to transient over-reach or maloperation due to other spurious signals. The relay is also completely directional in nature.