High impedance fault identification method and system based on zero-sequence current waveform interval slope curve

Abstract

The invention provides a high impedance fault identification method and system based on a zero-sequence current waveform interval slope curve. The method comprises the following steps: receiving zero-sequence current filtering data, describing high impedance fault nonlinear characteristics from the waveform morphological characteristics, computing a slope based on a sampling point extension interval by adopting the least square method, processing the computed slope of the sampling point extension interval by adopting Grubbs criterion, screening out an abnormal value, and determining whether the high impedance fault occurs according to the processed slope curve. The reliable detection on nonlinear characteristics in different degrees in stable arcing or grounding medium breakdown process (weak arc and non-arc) of different fault scenes (neutral point grounding mode, grounding medium and transition resistance of the high impedance fault) can be realized.

Description

technical field [0001] The disclosure belongs to the field of fault diagnosis, and in particular relates to a high-resistance fault identification method and system based on a slope curve of a zero-sequence current waveform interval. Background technique [0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art. [0003] High-impedance faults in distribution networks are a common form of faults, and are mainly single-phase ground faults. Generally, due to line disconnection or tree barriers, the line and high-impedance grounding media such as cement, sand, and trees, etc. touch. Due to its weak fault current, often less than several 10A, or even within 1A, it is difficult for the existing relay protection devices and traditional fault protection algorithms of the distribution network to effectively detect it. In addition, high-resistance faults are often accompanied by arcing,...

AI Technical Summary

Problems solved by technology

Due to its weak fault current, often less than several 10A, or even within 1A, it is difficult for the existing relay protection devices and traditional fault protection algorithms of the distribution network to effectively detect it.

In addition, high-resistance faults are often accompanied by arcing, and its nonlinearity also has a certain impact on fault detection

According to statistics, the detection rate of the relay protection devices installed in the distribution network to arc high-resistance faults is less than 20%, which cannot meet the reliability requirements of fault identification, and poses a huge hidden danger to the stable operation of the system and the safety of personnel and property.

For the transient characteristic quantity, when the grounding resistance reaches a certain value, the transient characteristic quantity basically does not change significantly before and after the fault, so the scope of application of this method to the fault grounding transition resistance is limited; for the high-frequency characteristic signal, due to the high-impedance fault The nonlinearity of the fault comes from the burning of the arc and the breakdown of the grounded solid medium. When the arc burns slightly, the fault nonlinearity is mainly caused by the breakdown of the grounded solid medium. At this time, the fault high-frequency signal features are weak and difficult to detect

In addition, the distribution network is generally in a relatively high noise environment. When a high-impedance fault occurs, the weak fault current makes the transient feature and high-frequency feature very susceptible to noise interference. Therefore, the traditional high-impedance fault detection algorithm It is always difficult to ensure high detection reliability in the actual application environment

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