A method for distance measurement of ground fault in distribution network based on zero-mode traveling wave difference

Abstract

A distance measurement method for a power distribution network ground fault based on the zero-mode travelling wave difference comprises the following steps: (A) injecting high voltage pulses into fault phases of the head end of a power distribution network, detecting voltage travelling waves returned by the three phases, and obtaining first zero-mode voltage travelling wave data with the voltage travelling waves returned by the three phases through phase-mode transformation; (B) injecting high voltage pulses consistent with the high voltage pulses in the step (A) into a certain healthy phase of the head end of the power distribution network, detecting travelling waves returned by the three phases, and obtaining second zero-mode voltage travelling wave data with the travelling waves returned by the three phases through phase-mode transformation; (C) conducting subtraction on the first zero-mode voltage travelling wave data obtained in the step (A) and the second zero-mode voltage travelling wave data obtained in the step (B) to obtain difference data; (D) conducting different derivation on the difference data obtained in the step (C) to obtain a first non-zero mutational site moment, and then obtaining propagation time of the travelling waves; (E) substituting the propagation time obtained in the step (D) into a distance measurement formula to obtain a fault distance.

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 zero-mode traveling wave difference. 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...

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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. Therefore, there is a possibility of misjudgment; the other is to inject high-voltage pulses into the fault phase and non-fault phase respectively after the fault, and then directly subtract the obtained waveform data of the fault phase and non-fault phase, and the first non-zero mutation point as the 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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