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

Abstract

The invention discloses a method for judging a single-phase grounding fault of a small-current grounding system, which is characterized in that single-phase grounding fault judgment is started according to a sudden change in electric field intensity and a sudden change in phase current, the fault starting time is accurately determined by using a morphological gradient method, and accurate synchronization of three-phase current is realized; filtering is performed on transient current signals so as to determine the duration time of a transient process, and the characteristic frequency of the transient current is calculated by using an autocorrelation method; a grounding fault is positioned according to the correlation of transient current of a fault phase and transient current of a non-fault phase, and detection for a single-phase grounding fault of a small-current grounding system applied to a fault indicator is realized. The method disclosed by the invention is not affected by the operating mode, the grounding site, the grounding resistance or the like, and on-site tuning and debugging are not required compared with a threshold comparison method adopted by the existing fault indicator, so that the fault judgment accuracy can be greatly improved, a problem of low false alarm and alarm omission rate of the existing fault indicator is solved, and the feeder automation level is greatly improved.

Description

technical field [0001] The invention belongs to the technical field of fault location of power system distribution network, and in particular relates to a single-phase ground fault judgment method of a small current grounding system. Background technique [0002] Most distribution networks with a voltage level of 66kV and below in my country adopt the non-effective neutral point grounding method, and this system is often called a small current grounding system. In this mode, when a single-phase grounding fault occurs in the power grid, the fault current is small (especially the grounding system through the arc suppressing coil), although the regulations allow continuous operation for 1 to 2 hours, the voltage of the non-grounded phase after the fault becomes the line voltage, which is harmful to the system. Insulation brings hidden dangers and threats. It is necessary to cut off the faulty line as soon as possible to avoid two-point grounding and short-circuit accidents. Fer...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a method for judging single-phase ground faults in small current grounding systems, aiming to solve the problem of low fault false positives and negative negative rates of existing fault indicators

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