FIELD: electrical engineering.
SUBSTANCE: field of application is electrical engineering. Method of differential cut-off of the power transformer, in which the value of the differential cut-off setpoint is corrected at the current time by means of changing the operating mode of the protected power transformer, it differs in the fact that, at this adjustment, the setting value is set at the level, at which the differential cut-off does not work at the peak value of the magnetizing in-rush current and at the peak unbalance current, which is possible at the current position of the switches that connect the power transformer to the load. At the same time, the circuit breaker is considered to be switched on, when simultaneously the circuit-closing auxiliary contact is in the closed position and the circuit-opening auxiliary contact is in the open position, the circuit-breaker is considered to be de-energized, when simultaneously the circuit-closing auxiliary contact is in the open position and the circuit-opening auxiliary contact is in the closed position. If the specified pairs of the auxiliary contacts are latched in the other position without time delay, the differential cut-off setting is set at the level, at which the differential cut-off setting does not actuate at the peak possible value of the magnetizing in-rush current and at the maximum unbalance currents, which are caused by the short circuits outside the protected zone and by the asynchronous stroke in all possible positions of the switches that connect the power transformer to the power systems and the load. After some time that exceeds the time during which the switch was switched from the turned-off position to the turned-on position, the signal is generated that the switch auxiliary contacts are faulty.
EFFECT: increased sensitivity of the differential cutoff to the internal short circuits and simplified method.
1 cl, 1 dwg
