FIELD: electrical engineering. SUBSTANCE: relay has operating voltage shaper, three phase voltage shapers, and double-input relay whose first input is connected to output of operating voltage shaper. Newly introduced average-of-three selector unit has its inputs connected to outputs of phase voltage shapers and its output is connected to second input of relay. EFFECT: improved sensitivity of relay to single-phase short circuits occurring at remote distance thereby enlarging its functional capability for automatic reclosure and improving reliability of high-voltage power transmission lines and power system as a whole. 3 cl, 3 dwg
