Fault Line Selection And Fault Location Of Distribution Network Based On Traveling Wave Theory

Distribution network is an important part of the power system.As the end of power transmission and power distribution,the distribution network is directly oriented to users.According to the statistical data,90% of the average outage time suffered by users was caused by faults in the distribution network.If the fault line and the fault location can be quickly determine,the fault can be eliminated in time,then the power outage time can be effectively shortened and the reliability of power supply would be enhanced.With the development of communication technologies and signal processing technologies,and the drops of hardware prices,some measures that were not adopted due to economic reasons can be gradually applied to fault location in distribution networks.The layout of monitoring devices such as PMUs in distribution networks is also gradually improving.All these aspects allow us to have more and better choices when dealing with fault location.In this paper,according to the characteristics of distribution network itself,some researches have been done on the problem of distribution line selection and fault location in distribution network.The main research contents of this paper are as follows:This paper first analyzes the propagation characteristics of traveling waves,and analyzes the characteristics of modulant traveling waves and the related properties of traveling waves such as initial traveling wave.The characteristics of the traveling wave after wavelet transformation are analyzed.The simulation model was built in PSCAD/EMTDC to verify the analysis.Finally,the characteristics of wavelet functions are compared by theoretical analysis and simulation,and cubic B-spline wavelet which is suitable for traveling wave processing are selected.Then,the propagation characteristics of traveling wave are analyzed,and the method of fault line selection using amplitude ratio of voltage and current traveling wave amplitude ratio is proposed.In PSCAD/EMTDC,the relevant distribution network models are built,and the fault line selection method is simulated under two grounding types: ungrounded neutral system and arc-suppression-coil-ground neutral system.The simulation results show that this method has higher reliability,selection results are not affected by the grounding types,transition resistance and the fault-inception angle.The theoretical analysis of the suitability of the line selection method in overhead lines and cable mixed system shows that the method are suitable for overhead lines and cable mixed system.At last,combining with the fault indicator in the distribution network,this paper proposes a single-end-based traveling wave fault location strategy.This strategy uses the fault indicators in the distribution network,only need to arrange a single-ended traveling wave measurement device,so the strategy has a high cost performance and practicability.According to the requirement of fault location,the allocation of fault indicator is analyzed,the principle of fault indicator allocation is suggested,and the specific problems such as pseudo fault location and traveling wave head identification are analyzed and solutions are proposed.Finally,some specific examples are given to verify the fault location strategy.