FIELD: power engineering; insulated-neutral low-voltage lines. SUBSTANCE: relay has automatic-control, unit for measuring element operation setting that functions to vary setting current as function of neutral bias voltage; mentioned control unit functions, in addition, to disable relay operation in case neutral bias voltage of particular line is lower than preset value. EFFECT: improved reliability of single-phase ground fault detection within comprehensive range of fault resistances; eliminated unwanted relay operation in absence of ground fault. 3 dwg
