PROTECTIVE GEAR FOR INSULATED-NEUTRAL LINE Russian patent published in 2001 - IPC

FIELD: selective disconnection of double ground faults, single-phase ground faults, and all kinds of interphase short circuits in radial systems. SUBSTANCE: protective gear designed to selectively respond to double ground faults and to other kinds of short circuits has interphase shorts protective unit; zero-sequence current and voltage sensors, zero-sequence power direction relay, time relay, OR gate, and output gate, all connected to line under protection. Introduced in addition are two pulse shapers, inverter, threshold element, AND gate, one-shot multivibrator, and INHIBIT gate. Input of first pulse shaper is connected to that of power direction relay and output, to input of inverter whose output is connected to first input of AND gate; input of threshold element is connected to output of zero-sequence voltage sensor and output, to input of second pulse shaper whose output is connected to second input of AND gate whose output is connected to input of one-shot multivibrator; direct input of INHIBIT gate is connected to output of OR gate, inverted input, to output of one-shot multivibrator, and output, to input of output gate. EFFECT: enlarged functional capabilities. 2 dwg