Research On Single-phase Ground Fault Location Method In Distribution Network

With the increasing scale and complexity of distribution network,when singlephase ground fault occurs,the fault point current will increase.If the fault operates for a long time,it may cause the accident to expand.After the fault occurs,it is very important for the safety of distribution network to locate and remove the fault quickly.It can not only reduce the power loss of users,but also improve the power supply reliability of distribution network.After the single-phase ground fault occurs in the distribution network,the fault information contains a large number of characteristic data.In this paper,the fault characteristics of fault line and non fault line are analyzed from two aspects of steady state and transient state.The voltage and current characteristics of fault in steady state and transient process are discussed in detail.In this paper,the fault section location method is based on the transient zero sequence current in the fault line.Through the discussion of the wavelet analysis theory,it is found that the wavelet packet transform can well show the transient characteristics of the fault signal in the time-frequency domain.When analyzing the transient zero sequence current at different acquisition points in the fault line,it is found that the amplitude and frequency of the transient current at the nodes on both sides of the fault point are significantly different from those at other acquisition points.In the line,the current amplitude at the upstream acquisition point of the fault point is large,and the frequency component is mainly low frequency,while the current amplitude at the downstream of the fault point is small and the frequency component is mainly high frequency.Based on the above characteristics,this paper proposes a fault location method for distribution network based on singular similarity,which extracts the reconstruction coefficient of fault signal in a specific frequency band by wavelet packet transform,defines singular similarity by combining singular value decomposition and correlation analysis theory,measures the difference degree of transient zero sequence current at different adjacent nodes by singular similarity,and passes the threshold value set with Compare and judge the fault section.In this paper,through the analysis of the transient traveling wave component characteristics and the traveling wave characteristics of the line after the single-phase ground fault,it is concluded that the reverse traveling wave is conducive to the judgment of the fault distance and location,and the fault location method based on the reverse traveling wave is determined.According to the singularity principle of wavelet transform,we can know that the extreme point of wavelet transform corresponds to the mutation point of transient traveling wave signal,so as to determine the time and polarity of the initial reverse traveling wave and the second reflection wave arriving at the bus,and determine the fault distance according to the formula of reverse traveling wave.For the method of fault section location and fault location in this paper,the simulation analysis is carried out under the condition of changing the initial angle,transition resistance and fault distance of the fault.The simulation results verify the feasibility and applicability of the two methods.