Research Of Distribution Network Fault Detection And Localization Method

Most of Medium voltage distribution network uses a neutral non-effectivelygrounded running method in our country. Solving the distribution line fault,especially the rapid detecting of single-phase ground fault and accurate positioning,it is not only important to repair the lines and ensure reliable power supply, but alsoimportant to ensure the security, stability and economic operation of the entire powersystem.This paper describes the research status of distribution network fault lineselection, positioning technology in domestic and abroad, analyzes the problemsexisting in fault line selection and positioning, and puts forward some improveprogram in the following areas.First, a single-phase ground fault comprehensive line selection Program, it usessteady-state zero-sequence power as the main criterion, and5th harmonic phase asauxiliary criterion. The program comprehensive uses of the program fault signalpower and phase、fundamental and harmonic, it eliminates the possible judgmentsdead area effectively and improves the accuracy and adaptability in line selection.To measure the zero sequence power and5th harmonic accurately, a kind of slidingdiscrete Fourier transform (DFT) algorithm method is based on the discreterectangular self-convolution window (DRSC) is proposed in this paper. Algorithmusing the spectral characteristics of the DRSC window, which can not only minimizeinter spectrum of fundamental and harmonic leaks effect, to improve the accuracy ofspectral analysis, but also via the recursive algorithm significantly reduce theamount of harmonic real-time analysis and calculation.Second, a new fault line selection method based on transient energy which isproposed in this paper. When failure at the voltage zero crossing and near, theexisting transient energy method of fault line selection in low sensitivity. To solvethis problem, the principle of conservation of energy in the system is used, and thearc suppression coil as a branch in the fault line analysis to avoid the limitations ofonly using of fault slip and non-fault branch circuit transient energy to select faultline. So the accuracy of line selection is important.Finally, to the strengths and weaknesses of the AC positioning method and DC positioning method in fault location, a integrated positioning method is used. Afterresearching the relationship between the positioning reliability and the injectionsignal frequency, analyzing the ground transition resistance and line distributedcapacitance on positioning reliability. The easy detecting of AC method and theAccurate and reliable of DC method are integrated effectively in AC-DC method.The two methods complement each other and the simulation results demonstrate itsfeasibility.