Partition and segmentation on-line positioning method for small-current grounding faults

Abstract

Provided is a partition and segmentation on-line positioning method for small-current grounding faults, which comprises first utilizing a pressure measuring unit (PMU) voltage measurement device arranged on a converting station busbar and a plurality of PMU current measurement devices arranged on a circuit to respectively measure zero-sequence voltage of the converting station busbar and zero-sequence currents on each measurement point on the circuit, then determining the upper and lower stream relation between each measurement point and fault points according to the phase-relation between the zero-sequence current of each measurement point on the circuit and the zero-sequence voltage of the busbar of the converting station, and further obtaining a fault interval with the measurement points serving as boundary nodes. The partition and segmentation on-line positioning method for the small-current grounding faults can fast and accurately determine the fault areas and the fault points of small-current grounding under the condition of non-outage, is not influenced by grounding fault types, does not need additional signal devices, is simple to operate, and has high reliability. The partition and segmentation on-line positioning method for the small-current grounding faults can help maintenance personnel to remove faults in time, and is suitable for various fault conditions of metallic grounding, grounding through voltaic arcs, grounding through transition resistors and the like.

Description

technical field [0001] The invention relates to an on-line positioning method for small current grounding faults suitable for neutral point non-effective grounding systems (including the arc suppression coil grounding mode), and belongs to the technical field of detection. Background technique [0002] The 3kV-60kV distribution network widely adopts the neutral point non-effective grounding system, also known as the small current grounding system, and the vast majority of faults in this type of power grid are single-phase grounding faults. When a single-phase ground fault occurs in a non-effectively grounded power grid, the other two phase-to-ground voltages rise to line voltage, which threatens the insulation of the system, especially when intermittent arc grounding occurs, because there is no charge release path at the neutral point, it will cause arcing grounding Overvoltage, and then lead to phase-to-phase short circuit. Therefore, it is necessary to find out the faulty...

AI Technical Summary

Problems solved by technology

[0003] Due to the complex wiring of the medium-voltage power grid, many branches, the efficiency of manual line inspection is low, and it will prolong the power outage time and affect the safety of power supply, so it is necessary to use the line selection device to locate the fault area

There are two fault location methods used by existing line selection devices. One is the signal injection method, including the "S" injection method and the power frequency injection method. This type of method does not use the fault information provided by the fault itself for passive line selection. , but to actively inject a line selection signal, which has three main disadvantages. First, because the power of the injected signal is not large enough, the injected signal converted to the high voltage side is very weak, and it is difficult to measure accurately; secondly, the injected signal will be in The charging current generated in the non-fault line will occupy the capacity of the injected power supply, and when the fault resistance is large, the signal difference between the fault line and the non-fault line is not obvious; third, an additional signal device is required, the operation is more complicated, and the reliability lower

The second method is to locate by measuring the fault current of the line, but this method measures the phase current. Since the single-phase ground current is much smaller than the load current, the fault information cannot be accurately extracted, resulting in inaccurate positioning

In short, neither of the above two methods can realize the interval division of the fault area, and cannot provide accurate information for the isolation of the fault area. It is necessary to study a more accurate fault area location method

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