DIFFERENTIAL RELAY Russian patent published in 2003 - IPC

FIELD: short-circuit protective gear for transformers. SUBSTANCE: differential relay has connected in series instrument transformer, rectifier unit, low-frequency filter, and first threshold unit; series-connected pulse counter, second threshold unit, and final member; clock generator; AND gate whose input is connected to HIGHER output of clock generator and output, to pulse counter data input; OR gate; pulse shaper whose input is connected to LOWER output of first threshold unit and output, to first input of OR gate whose output is connected to input of pulse-counter zero-setting input; and monostable multivibrator whose output is connected to second input of OR gate and to trigger input of clock generator. EFFECT: enhanced precision and immunity to noise caused by heavy inrush magnetizing currents when turning on unloaded transformer. 2 cl, 2 dwg