Medium voltage distribution network two-point in-phase earth fault line selection method and system

Abstract

A two-point in-phase earth fault line selection method for a medium-voltage power distribution network comprises the following steps: collecting zero-sequence current of each line and zero-sequence voltage of a neutral point of the power distribution network; judging whether the system breaks down or not according to the real-time break variable and the real-time amplitude of the neutral point zero-sequence voltage; selecting a first fault line by using a wavelet method according to the transient characteristics of the first line when the fault occurs; cutting off the first fault line, and judging whether the fault is a single-phase earth fault or not according to whether the fault disappears or not; if the fault disappears, determining that the fault is a single-phase earth fault and the line selection is correct; if the fault does not disappear, when the first fault line is cut off, the change quantity of the zero-sequence current converted value of one line is far larger than that of the other lines, the two-point same-phase grounding fault is determined, and the line is the second fault line. The method is simple and convenient to operate, does not need to increase extra investment, is high in line selection accuracy, can effectively solve the current situation that the two-point in-phase earth fault line selection of the current power distribution network is difficult, improves the safety and reliability of the power distribution network, and reduces personal injuries.

Description

technical field [0001] The invention belongs to the technical field of power system fault line selection, and in particular relates to a method and system for line selection of two-point in-phase ground faults in a medium-voltage distribution network. Background technique [0002] my country's medium-voltage distribution network generally adopts the low-current grounding method with the neutral point not grounded or grounded through the arc suppression coil, and most of them are concentrated in rural areas and mountainous areas, with long lines, many outgoing lines, and aging insulation. As the structure of distribution lines becomes more and more complex, the probability of two-point in-phase ground faults occurring in the event of severe weather or external force damage is increasing, and it is urgent to solve such fault problems on site. [0003] In the prior art, the fault line selection device has a high accuracy rate for single-phase ground fault line selection, and ca...

AI Technical Summary

Problems solved by technology

Prior art 3 uses the variation of reactive power of each line in two stages and combines the change of zero-sequence voltage to judge the grounding fault of the line, improves the accuracy of line selection, and effectively solves the problem of two phases with the same name. When the points are grounded one after another, it is difficult to ensure the reliability of line selection in the existing fault line selection device

However, existing technology 3 can only perform fault line selection for neutral point ungrounded systems, and cannot perform fault line selection for neutral point grounded systems through arc suppression coils.

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