A positioning method and positioning device for a single-phase ground fault section in a distribution network

Abstract

The invention provides an online low-current earth fault positioning method and positioning device based on a BP neural network and by means of a multi-source data fusion algorithm. Due to the fact that terminals arranged on different positions on a circuit accurately catch zero-sequence current transient signals of zero-sequence currents which exceed a starting value before a previous period of a starting value and after four periods of the starting value, signal characteristics of a fault transient signals are extracted by means of a Prony algorithm, a wavelet packet algorithm, an HHT algorithm and a fractal algorithm, the characteristics extracted by the algorithms are analyzed by means of the BP neural network, and a zone where a fault occurs is determined. The positioning device comprises a terminal and a main station, wherein the terminal is arranged on an overhead line tower or in a cable ring main unit, the input end of the terminal receives a zero-sequence current signal synthetized by a phase current signal of a CT secondary side of a power distribution circuit including an overhead line and a cable, the terminal is connected with the main station through optical cable communication or mobile communication, and the main station is arranged in a transformer substation or a dispatch center, comprises an optical cable communication module and a mobile communication module and receives a signal sent by the terminal. The method and the device are mature in technology and high in reliability.

Description

technical field [0001] This application 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, ...

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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