Method Of Fault Section Location In Distribution Network Based On Fault Direction Measures

The fault signal of small current neutral grounding system is weak when a single phase-to-earth fault occurs.In addition,the structure of distribution network is very complex.Fault location is a recognized problem,which requires the use of specialized fault detection technology.In the past,the research work mainly focused on the line selection technology,and achieved a lot of research results.In spite of this,it is still very difficult to find fault points.Accurate fault location can help staff easier and more convenient troubleshooting,therefore,the research work in this field has important and far-reaching significance.Based on the development trend of China’s smart grid construction,in order to solve the problem of single phase-to-earth fault location of distribution network,improve the shortcomings of traditional symbolic positioning methods,achieve accurate location of fault points when the fault information is unreliable,save cost of hardware.In this paper,a fault section location method based on fault direction measures for single phase-to-earth fault location in distribution network is proposed.Firstly,constructed the fault direction measures of a single measuring point,indicated the fault direction of a single measuring point and quantitatively evaluate the significance level of the fault features.Analysed the neutral point potential migration after single phase to ground fault in distribution network occurs,established zero sequence equivalent network model,analysed the relationship between zero sequence current of whole system with three-phase load current.The load current is taken as reference,and constructed the direction of zero sequence current,built fault direction measures of the fundamental zero-sequence current.After single phase to ground fault,established phase capacitance transient charging and discharging circuit model.Analysed the characteristics of transient current for each section of fault phase in transient process.Applying the method of phase space reconstruction to construct the fault direction measures of the transient phase current.Secondly,the multi-criteria decision-making model is established for single phase-to-earth fault.Using the multi-criteria decision-making methods describe the problems of single phase-to-earth fault location.The decision criteria is fault direction measures,and the decision variable is the state of system line section.Use historical information and fault feature information as decision knowledge,introduce credibility theory to set priority value,process and comprehensive utilize the fault direction information of each measuring point,establish objective function and then solve it.Finally,simulation and experimental verification are carried out.In the Matlab simulation environment,a single phase to ground fault model of distribution lines is constructed.Combined with the factors affecting the characteristics of single-phase grounding fault such as fault angle,fault location,the size of the transition resistance,the length of the line,etc.Carried out a lot of simulation experiments and data analysis and processing.The static simulation system of distribution network is used to realize functional verification of single phase-to-earth fault location method.The simulation and experimental results show that the fault location methods in this paper can be judged accurately and have fault tolerance ability when the single phase-to-earth fault occurs in the neutral ungrounded power distribution system.