A single-phase-to-ground fault location method in distribution network based on line-mode traveling wave mutation

Abstract

The invention discloses a distance measurement method for a power distribution network single-phase earth fault on the basis of aerial mode traveling wave mutation. The method includes the following steps that (1) the same voltage pulse is simultaneously injected to three phases of a head end of a power distribution network, and voltage traveling waves returned from the three phases are detected; (2) the voltage traveling waves of each phase, which are obtained in the step (1), are transformed to modulus by a phase-mode transformation matrix, and further, aerial mode voltage traveling waves are obtained; (3) the aerial mode voltage traveling waves obtained in the step (2) are subjected to difference derivation to obtain first nonzero mutational point time, and thereby, travel time of the traveling waves can be obtained; (4) the travel time obtained in the step (3) is substituted into a distance measurement formula to obtain fault distance. According to the method, high voltage pulse is simultaneously injected to the three phases of the head end to detect aerial mode voltage traveling wave mutation so as to perform fault distance measurement, and thereby, the problem of fake fault points caused by unbalance three-phase loads of the distribution network is solved.

Description

technical field [0001] The invention relates to a traveling wave ranging method, in particular to a method for injecting traveling wave ranging based on a single-phase grounding fault of a distribution network based on a line-mode traveling wave mutation. Background technique [0002] my country's 6~35kV distribution network generally operates in the neutral point non-direct grounding mode. After a single-phase ground fault accounts for 50%~80% of the total faults, the traditional processing method uses manual line inspection to find the fault point, which is time-consuming and laborious. Research on accurate and effective single-phase ground fault location method is of great significance for improving the power supply reliability of distribution network and reducing power failure loss. [0003] At present, there are two main development directions of distribution network fault location methods: the method based on distribution network automation system and the traveling wav...

AI Technical Summary

Problems solved by technology

[0004] For a power distribution network with a complex structure, the signal received by the detection end is the superposition of multiple refraction and reflection waves at the fault point, branch point, and branch end. It is difficult to find the reflected wave at the fault point only by using the waveform obtained after fault phase injection. The following two methods are used to extract the reflected wave of the fault point: one is to inject a high-voltage pulse signal into each phase before the system fails to obtain the non-faulted traveling wave waveform of each phase and store it, and inject the same wave into the faulty phase after the line fails The waveform of the fault condition is obtained by the high-voltage pulse signal, and the two sets of waveform data obtained by the fault phase and the non-fault condition are subtracted to extract the fault information. However, due to the high instability of the distribution network system, the line topology and user load may change at any time. changes, so there is a possibility of misjudgment; the other is to inject high-voltage pulses into the fault phase and the non-fault phase respectively after the fault, and then subtract the obtained waveform data of the fault phase and the non-fault phase, and the first Non-zero mutation point as a fault point reflection information

However, the distribution network has many branches, and the branches are often connected with three-phase unbalanced loads through distribution transformers.

When the length from the unbalanced load to the head end is less than the fault distance, the first difference point may come from the unbalanced load rather than the fault point information, that is, a false fault point appears, resulting in a ranging error

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