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Single-phase high-resistance grounding fault detection method for small-resistance grounding system

A high-resistance grounding fault and low-resistance grounding technology, applied in the fault location, detecting faults according to conductor types, measuring electricity, etc., can solve the problems of low sensitivity of single-phase high-resistance grounding faults, improve safety, stability, and Engineering implementation, increasing the effect of acquisition and processing

Active Publication Date: 2018-05-15
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art. In order to solve the problem of low sensitivity of the existing stage zero-sequence current protection to single-phase high-resistance grounding faults in small-resistance grounding systems, a single-phase instantaneous The single-phase high-resistance grounding fault protection method of small-resistance grounding system based on reactive power theory, which uses the zero-sequence voltage of the busbar and the zero-sequence current of the feeder to calculate the instantaneous active power and instantaneous reactive power according to the single-phase instantaneous reactive power theory, and then Calculate the power factor square value of the feeder, and judge whether a single-phase ground fault has occurred on the line through the power factor square value and its duration, so as to improve the sensitivity of protection to single-phase high-resistance ground faults

Method used

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  • Single-phase high-resistance grounding fault detection method for small-resistance grounding system
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  • Single-phase high-resistance grounding fault detection method for small-resistance grounding system

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Embodiment 1

[0044] A single-phase high-resistance grounding fault detection method for a small-resistance grounding system, the implementation of the feeder zero-sequence protection adopted in this embodiment is as follows:

[0045] S1. Assign the initial value to the zero-sequence voltage mutation start value U 0.set , the minimum value of instantaneous reactive power Q min , protection action setting value Z set And the action duration set value T last ;

[0046] Among them, U 0.set The value of the value needs to consider the size of the zero-sequence voltage when the high resistance is grounded, and the level of the sampling frequency, U 0.set The smaller is, the more sensitive the algorithm is; Q min The value of Z needs to consider the stability of the algorithm, and its value cannot be too high, otherwise the protection will refuse to act; Z set The value of the actual grounding resistance and the zero-sequence impedance of the zigzag transformer should be considered, and it ...

Embodiment 2

[0065] A substation with a 10kV neutral point as a small resistance grounding method is used as the model. The resistance value of the small grounding resistance is 10Ω, the zero-sequence impedance of the zigzag transformer is 10Ω, and the lengths of feeders 1, 2, 3, and 4 are 6km, 9km, 12km, and 15km, respectively. 22 -3*300, the positive sequence parameters are: R1=0.500Ω / km, L1=0.318mH / km, C1=0.376μF / km, and the zero sequence parameters are: R0=0.500Ω / km, L0=6.398mH / km , C0=0.370μF / km. The load rate of the distribution transformer is 60%, and the power factor takes cosθ=0.9.

[0066] In this embodiment, a single-phase ground fault is set at the end of the feeder 3 with a length of 12 km. The fault types are linear transition resistance fault and arc fault respectively, and the fault moment is the moment when the fault point-to-ground voltage is the peak value. The effectiveness of the present invention is verified by taking the protection actions of feeder 3 (faulty line)...

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Abstract

The invention discloses a single-phase high-resistance grounding fault detection method for a small-resistance grounding system. According to the method, according to the single-phase instantaneous reactive power theory, an instantaneous active power and an instantaneous reactive power are calculated by utilizing the zero sequence voltage of a bus and the zero sequence current of a feeder line. After that, the square value of the power factor of the feeder line is calculated. Based on the magnitude of the square value of the power factor and the duration of the square value of the power factor, whether a circuit has a single-phase earth fault or not can be judged. Therefore, the protection sensitivity of a single-phase high-resistance grounding fault is improved.

Description

technical field [0001] The invention relates to the technical field of distribution network relay protection, in particular to a single-phase high-resistance grounding fault detection method for a low-resistance grounding system, which is suitable for feeder protection of a distribution network system whose neutral point adopts a low-resistance grounding method. Background technique [0002] Due to the increasing shortage of urban land, the proportion of cable lines in the distribution network is increasing day by day. The small resistance grounding method has many advantages such as effectively limiting arc grounding overvoltage, eliminating various resonant overvoltages of the system and removing faulty lines in time. It has been widely used in the distribution network of large and medium cities in my country. [0003] Single-phase ground fault is one of the main fault types in distribution network. At present, the main protection configuration scheme is the staged zero-seq...

Claims

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Application Information

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IPC IPC(8): G01R31/02G01R31/08
CPCG01R31/086G01R31/088G01R31/50
Inventor 李海锋陈嘉权蔡东晓
Owner SOUTH CHINA UNIV OF TECH