Method for judging magnetizing inrush current of no-load transformer during switching phase reclosing process of circuit breaker

Abstract

The invention discloses a method for judging the magnetizing inrush current of a no-load transformer during the switching phase reclosing process of a circuit breaker, which comprises the following steps: when over current is generated in a switching phase reclosing process of a circuit breaker, an equivalent circuit and a corresponding voltage equation are established based on the switching-on phase number and the switching-on phase current characteristic; calculating the equivalent inductance value of each sampling time according to the voltage and the current sampling values and taking theaverage value; comparing the average equivalent inductance value with a threshold value. When the average equivalent inductance value is greater than or equal to the threshold value, the condition ismagnetizing inrush current. When the average equivalent inductance value is smaller than the threshold value, the condition is short circuit failure. If the average equivalent inductance value is notonly one, when all of the average equivalent inductance values are larger than or equal to the threshold value, the condition is magnetizing inrush current, otherwise, the condition is short circuit failure. The method can accurately identify the magnetizing inrush current of the no-load transformer during the switching phase reclosing process of the circuit breaker, and effectively improve the fault identification accuracy rate and the reclosing success rate.

Description

[0001] Field [0002] The invention relates to a method for discriminating the excitation inrush current of an unloaded transformer during phase selection and reclosing of a circuit breaker, belonging to the field of vacuum circuit breakers. Background technique [0003] Automatic reclosing is widely used in the power system, that is, when the circuit breaker trips, it can automatically reclose the circuit breaker, and when it recloses to a permanent fault, the circuit breaker disconnects the line again. The phase selection control technology can realize the phase-separated closing of the circuit breaker and the closing of the specific phase. When there are no-load transformers in the power system, phase selection reclosing of the circuit breaker may seriously saturate the magnetic circuit of the transformer core, and the excitation current of the transformer increases sharply, resulting in the phenomenon of excitation inrush current. The excitation inrush current may reach s...

AI Technical Summary

Problems solved by technology

Solve the problem that the no-load transformer excitation inrush current is misjudged as a short-circuit fault when the circuit breaker is reclosing with phase selection, resulting in the failure of phase selection reclosure

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