DEVICE FOR PROTECTION AGAINST FAULT TO GROUND IN A C ELECTRIC SYSTEM Russian patent published in 1995 - IPC

FIELD: electrical engineering. SUBSTANCE: device has current and voltage pickups which outputs are connected to inputs of current and voltage channels correspondingly, voltage starting element and phase-sensitive unit which first and second inputs are linked to first outputs of current and voltage channels accordingly. Device is supplemented with current starting element, logic unit with three inputs and output element unit connected to output of logic unit. Current and voltage channels are provided with second outputs which are coupled through current and voltage starting elements properly to first and second inputs of logic unit which third input is connected to output of phase-sensitive unit. Insertion of current starting element, logic unit with three inputs and their specified connection makes it possible to enhanced reliability of operation and nonoperation of protection with fault to ground within and outside of zone of action of device and to set different times for operation of device and for its return to initial position. EFFECT: enhanced reliability of protection against fault to ground. 5 cl, 4 dwg