Diagnostic method for ferromagnetic resonance in neutral non-grounding 10kV system

Abstract

The invention provides a diagnostic method for ferromagnetic resonance in a neutral non-grounding 10kV system. A phase-A voltage to ground, a phase-B voltage to ground, a phase-C voltage to ground, a neutral point voltage and a neutral point frequency are caught when the voltage at the two ends of a PT opening triangle exceeds the set limiting value. Firstly, faults are divided into a frequency division resonance and high frequency resonance class and a fundamental resonance and high frequency resonance class, then, frequency division resonance and high frequency resonance are distinguished according frequencies, the type of fundamental resonance and single-phase ground faults is processed according to an energy method and a loop grounding current method, and the preliminary conclusion is obtained through the energy method and then is checked through the loop grounding current method; when the results obtained through the two methods are the same, it is shown that judgment is correct, and the fundamental resonance and single-phase ground faults are distinguished. The distinguished faults and the obtained non-ferromagnetic resonance and single-phase ground fault conclusions are sent to a terminal to be displayed, and maintainers can process the corresponding faults in time.

Description

technical field [0001] The invention relates to the field of diagnosis of ferromagnetic resonance and single-phase grounding, in particular to a method for diagnosing ferromagnetic resonance in a 10kV system with an ungrounded neutral point. Background technique [0002] In a 10kV power grid where the neutral point is not grounded, in order to measure and protect the three-phase-to-ground voltage, a voltage transformer with (Y / Y / Δ) wiring is often connected to the generator or substation bus, and its high voltage The neutral point of the winding is grounded, so the parameters of the electric network to the ground include the inductance L of the voltage transformer in addition to the capacitance C of the power equipment and the wire. Due to the nonlinearity of the inductance of the electromagnetic voltage transformer, under certain conditions, it is possible to stimulate the ferromagnetic resonance overvoltage. The frequency of the ferromagnetic resonance can be the fundament...

AI Technical Summary

Problems solved by technology

When ferromagnetic resonance occurs in the power grid where the electromagnetic voltage transformer is located, it often leads to burning or explosion of the transformer

When a single-phase ground fault occurs, one phase-to-ground voltage will drop, and the other two phase-to-ground voltages will rise. When the grounding disappears, the transformer will also burn or explode.

Because the phenomenon of single-phase ground fault is similar to the phenomenon of ferromagnetic resonance, it is difficult to distinguish single-phase ground fault and fundamental frequency resonance fault by the traditional single diagnosis method through the magnitude of three-phase voltage and setting zero-sequence voltage threshold, and then use wavelet analysis method and fast Fourier transform method, but due to the singleness of the judgment method, the accuracy rate is not very high, and when the phenomenon difference is not obvious, it is easy to make a wrong judgment

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