Combined phase and ground distance relaying

A relaying system is described herein providing complete phase and ground distance ??relaying protection for transmission lines, which features a reduction in the necessary equipment over the 6 directional-reactance-distance relay system usually applied where three relays are connected to protect against 3phase, phase-to-phase, and double-phaseto- ground faults, and three relays are connected to protect against single-phase-toground faults. The reduction in equipment is achieved by causing the directional element of the ground-reactance relay to perform the double duty of detecting faults of a phase nature as well as faults of a ground nature. This new system also offers the advantage of providing complete phase and ground protection without the use of objectionable switching arrangements heretofore used to select the faulted-phase current or potential. The combined system is effected by adding to the basic directional-reactancedistance relay for ground fault protection a reactance relay which operates with the directional-fault-detecting element of the ground relay to provide the phase-fault protection.