Locating method and device for one-phase earth fault of power distribution network based on transient state signal wavelet transformation

Abstract

A distribution network phase-to-earth fault section location method and location device. By terminals mounted in different positions on a line, zero sequence current transient signals of 2 periods before a zero sequence current exceeds a startup value and of 2 periods after exceeding the startup value are accurately caught, and the terminals perform wavelet transformation and reconstruction on the zero sequence current transient signals, and analyse a section where a fault point is located according to the approximation coefficient integral value of a reconstructed precise component.The location device is composed of two parts; terminals and a main station. The terminals are mounted on an aerial line pole or in a cable ring main unit, the input ends of which receive phase current signals of a distribution line CT secondary side which are combined to obtain a zero sequence current signal, and are connected to the main station by optical fibre communication or mobile communication. The main station is mounted in a transformer station or at a scheduling centre, includes an optical fibre communication module and a mobile communication module, and receives signals transmitted from the terminals.

Description

technical field [0001] The invention belongs to the technical field of power system automation, and specifically relates to a section positioning method for a single-phase ground fault in a distribution network and a positioning device based on the positioning method. When a phase-to-ground fault occurs, accurately locate the fault section. Background technique [0002] The 3-60kV distribution network in my country widely adopts the non-effective neutral point grounding method, also known as the small current grounding system, and most of the faults in the small current grounding system are single-phase grounding faults. When a single-phase ground fault occurs, the ground current is very small, and it can continue to run for 1 to 2 hours under the fault condition, but the fault point must be found as soon as possible, which raises the problem of fault location. [0003] The problem of fault location in the distribution network has not been well resolved for a long time, and...

AI Technical Summary

Problems solved by technology

When a single-phase ground fault occurs, the ground current is very small, and it can continue to run for 1 to 2 hours under the fault condition, but the fault point must be found as soon as possible, which raises the problem of fault location

[0003] The problem of fault location in the distribution network has not been well resolved for a long time. The method of manual line inspection is often still used on site. Manual line inspection not only consumes a lot of manpower and material resources, but also prolongs the power outage time and affects the safety of power supply.

At present, there are three methods for automatic positioning on site. The first method is to inject a high-frequency signal from the PT and detect the signal along the line to determine the fault location. However, because the distributed capacitance of the line forms a path for the high-frequency signal, the positioning is not correct when it is grounded through a resistor. precise

The second method is to use the fault indicator. Since the fault indicator can only measure the phase current and cannot measure the zero-sequence current, it is better for short-circuit faults, but the accuracy of single-phase ground fault location is very low.

The third method is to install a smart switch with a built-in CT. Although this method can measure the zero-sequence current, the terminals and master stations operating on the market have simple algorithms that only judge whether the steady-state zero-sequence current exceeds a fixed value. The positioning accuracy of the arc suppression coil grounding system is very low

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