A Study On Short Circuit Fault Location In Small Current Grounding System Network

In china, mostly adopted method in the medium voltage power grid is neutralnoneffective grounding, the grounding method can avoid power interruption whensingle-phase earth fault occurs. There are many branches in the kind of grounding fault,due to the weak fault current and arc instability, it is difficult to locate the grounding faultpoint when fault occurs. At present, lacking of reliable fault line selection method anddevice seriously hinders the improvement of the distribution network power supplyreliability and automation level. From this point, accurately locating line fault position canimprove the power supply reliability greatly, therefore, has great significance for smallcurrent grounding system.This paper deeply analyzes the principle of traveling wave and the wave equation oftraveling wave, and summarizes the principle of reflection and refraction of traveling wave,and deduces the reflection and refraction coefficient briefly. The process of traveling wavefault’s occurrence on the three-phase transmission line is studied, firstly, this papersimplifies the fault analysis by adopting the method of phase-mode transformation todecouple the three-phase transmission line, then compares respectively two ways used forfault location: single ended traveling wave method and the double-end traveling wavemethod, for the single ended traveling wave, its advantages are low cost, high accuracy, butthe accurate identification of the reflected wavefront is more difficult, the reliability ofranging is also poor; double-end traveling wave method however, has high reliability torealize fault positioning in the small current grounding fault system, and able to accuratelylocate in the distribution circuit branch, the calculation process is simple and it has highreliability for automatic range by using GPS as the clock of traveling wave fault location,therefore, accurate positioning can be guaranteed, so double-end traveling wave method isadopted in this paper. The transient traveling wave signal is generated at the moment ofline fault, this paper applies the theory of wavelet analysis to detect exact information,because theory of wavelet analysis as a new tool for analyzing has some advantages that others don’t have, the theory of wavelet is used to process the fault signal, and theextraction of fault line selection and fault wavefront by using wavelet transform andmodulus maximum detection method, in this way, the time of arriving at the measurementdevice at both ends of Bus after line fault can be accurately detected, and thus faultlocation can be exactly got.MATLAB software is commonly used in the simulation software, this paper use thesoftware to do fault location simulation, this paper builds the model of the small currentgrounding system by changing different parameters for different ground experiments, useswavelet transform to process the collected signal to get the modulus maximum, and doessingularity analysis on the fault traveling wave signal. The accuracy of this method isverified by the simulation analysis.