A Single Terminal Fault Location Method For Single Phase Fault Of Cable Based On Parameter Identification

At present,most of the fault location methods for the cable are the continuation of the overhead line fault location method,but the cable is different from the overhead line structure.Most of the cable faults are related to the metal protection layer.Only considering the electrical structure parameter model of the cable core may lead to the fault location.Based on this,a single terminal fault location method for single phase fault of cable based on parameter identification is studied.Firstly,the internal structure of the cable,the grounding mode of the metal shielding layer and the electrical characteristics of the cable core parameters are analyzed.According to the different fault location of cable insulation,the single-phase fault of cable is divided into core-shield fault and core-protective layer fault grounding,and the fault characteristics of two kinds of fault are analyzed,which provides a theoretical basis for establishing distance equation.Secondly,a time domain distance measurement equation based on the fault state network and the sampled data of transient fault data is established.The fault location equation of single core cable and three core cable is established by combining the time-domain ranging equation of zero model equivalent circuit with cable type and fault type.At the same time,the method of identifying the type of cable fault is constructed,that is to use the transition resistanceR_f1,R_f2and the ratio of the resistance value identified by the parameters of the core and protective layer fault location equation as the discrimination method of the transition resistance fault identification,as well as the relative error between the zero sequence current and the zero sequence current of the wire path in the metal shield.The identification of zero sequence current fault identification method.Clark phase mode transformation and central difference algorithm are selected to process data,and least squares algorithm is used to identify parameters.Finally,according to the single-phase fault state network and the cable internal structure and electrical parameters,the cable structure line model is set up to simulate the actual situation,and the fault of different types of cable is simulated.The transient information of the voltage and current in the cable core and the protective layer of the cable after the single phase grounding fault of the cable is obtained,and the transient information is entered.In line phase mode transformation,the center difference algorithm is used to derive the derivative.The fault type is identified by using the discrimination method.The fault distance,the transition resistance and the ground capacitance are used as the unknown parameters of the model,and the least squares parameters are identified in the corresponding range equation to get the fault distance.The simulation results show that the single end fault location method using the fault transient information is effective and high precision when the single-phase fault occurs in the cable.