Method for judging single-phase grounding fault of low-current grounding system

Abstract

The invention discloses a method for judging a single-phase grounding fault of a low-current grounding system. According to the method, bus zero-sequence voltage, interval three-phase current and zero-sequence current need to be accessed, and whether a grounding fault exists or not is judged according to the zero-sequence voltage; wavelet packet transformation is carried out on the transient three-phase current, the transient zero-sequence current and the transient zero-sequence voltage of the length of the data window of the previous cycle and the latter half cycle of the fault at the grounding occurrence moment; and the directions of the zero-sequence current and the phase current of the characteristic frequency band and the directions of the zero-sequence current and the zero-sequence voltage of the characteristic frequency band, which are obtained after conversion are comprehensively compared so as to identify the grounding fault. The method can be applied to a system of which the neutral point is not grounded and which is grounded through an arc suppression coil.

Description

technical field [0001] The invention relates to the field of relay protection of power systems, in particular to a method for judging single-phase ground faults in small current grounding systems. Background technique [0002] In my country's 3-66kV power supply and distribution network, most of them adopt a small current grounding system. In such a system, when a single-phase ground fault occurs at any point, the entire system will sense zero-sequence current and zero-sequence voltage, and enter failure state. At present, most of the commonly used ground fault judgment methods use the zero-sequence steady-state electrical quantity after the fault. Since the amplitude of the zero-sequence steady-state electric quantity is small when the single-phase is grounded, it is difficult to measure accurately, so it is difficult to apply in practice. The injection method is limited by the capacity of the voltage transformer, and the injection signal is small. When there is a transitio...

AI Technical Summary

Problems solved by technology

At present, most of the commonly used ground fault judgment methods use the zero-sequence steady-state electrical quantity after the fault. Since the amplitude of the zero-sequence steady-state electric quantity is small when the single-phase is grounded, it is difficult to measure accurately, so it is difficult to apply in practice.

The injection method is limited by the capacity of the voltage transformer, and the injection signal is small. When there is a transition resistance grounding, the fault judgment is easy to make mistakes

Transient method requires high sampling rate of equipment, and is easily affected by zero-sequence CT polarity

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