Small current grounding fault location method utilizing circuit equivalent parameter identification principle

Abstract

The invention relates to a small current grounding fault location method, particularly to a small current grounding fault location method utilizing the circuit equivalent parameter identification principle. The method is characterized in that changes of a voltage or a current are taken as fault starting conditions; after starting, zero mode voltage or transient state line voltage features detected at detecting points are utilized to determine voltages participating in identifying parameters; then, the scope of selected frequency band is determined; a digital filter is further structured; filtering is performed on the participated voltages and zero mode current signals to obtain components within the selected frequency band; and the participated voltages and zero mode current components in the selected frequency band are then utilized to identify equivalent capacitance of all detecting points so as to further determine the fault section. The small current grounding fault location method simultaneously utilizes transient voltages and current signals, is applicable to fast directional protection of grounding faults of various voltage classes, and can take into consideration of both protection speed and reliability.

Description

technical field [0001] The invention relates to a small current grounding fault location method, in particular to a small current grounding fault location method using the line equivalent parameter identification principle. Background technique [0002] The distribution network is densely covered in urban, rural and mountainous areas, and is outdoors all year round. It is affected by harsh environments such as wind, rain, frost, lightning, and increasingly severe environmental pollution. Coupled with unpredictable human factors, the probability of failure is high, especially for overhead lines. At present, my country's distribution network mostly adopts the operation mode of ungrounded neutral point and grounded through arc suppression coil. After a ground fault occurs, the faulty line can be selected by using the existing line selection device. However, since the distribution network adopts a radial network, The line is long, has many branches, and the structure is complex. ...

AI Technical Summary

Problems solved by technology

This method has been applied to a certain extent, but it has the following disadvantages: when the grounding resistance is large, the distributed capacitance on the line will shunt the injected signal, reducing the detection sensitivity and reliability; it is necessary to design a dedicated large reactive power signal generator, hardware High cost; and cannot detect momentary ground faults

Using the method of transient signal spectrum analysis, it is defined that the distance from a certain traveling wave impedance discontinuity point (including the fault point) to the fault measurement point is inversely proportional to the size of the characteristic frequency, and the fault is calculated by calculating the characteristic frequency of the reaction fault signal The key to distance measurement is the effective determination of the characteristic frequency corresponding to the fault point. This is because when the distribution network has many outlets and branches, there will be many characteristic frequencies, and the close frequencies will alias, resulting in the final fault of the distance measurement. fail

In the distribution automation system, the master station is used to realize the time synchronization of each detection device, and the time synchronization error is at least a few milliseconds, which cannot be applied to the method of comparing the instantaneous value of the transient zero-mode current

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