Research On Distribution Network Interphase Fault Location Based On Distributed Generation

In recent years,with the development of distributed generation technology,more and more distributed generation(DG)is connected to the distribution network,effectively improving the flexibility and environmental protection of the distribution network.At present,the section positioning of short circuit faults in China’s distribution network mainly relies on overcurrent protection for discrimination.However,due to the connection of DG,the DG will inject current into the fault point after the fault,which has a significant impact on the traditional section positioning technology that uses the amplitude of fault current for discrimination.Therefore,it is very important to reduce the negative impact of DG in locating fault sections in the distribution network.This article focuses on the problem of fault location in medium voltage distribution networks containing DGs.After the distribution line trips due to a short circuit fault and all DGs are out of operation,a certain DG is used to generate transient signals by briefly connecting to the line.Subsequently,various FTU are used to collect signals and perform fault location.The research content of this article mainly includes the following aspects.Based on the analysis of the load equivalent model after power outage,derive the frequency domain description of the equivalent reference inductance and reference capacitance of the line.Conduct accuracy analysis of harmonic impedance measurement,and establish fault property criteria based on parameter identification theory based on the variation trend of reference inductance and capacitance in the frequency domain under transient and permanent faults.Before the line is powered off and closed,it is necessary to determine whether the fault is transient.Based on parameter identification theory,this paper analyzes the equivalent model of the load after power failure and derives the frequency domain expressions of the equivalent reference inductance and reference capacitance of the line using its equivalent model parameters.Verify the accuracy of its harmonic impedance and establish fault property criteria based on the variation trend of their equivalent parameter expressions under transient and permanent faults in the frequency domain.Based on the equivalent model of power outage lines,the expressions of the real and imaginary parts of the equivalent impedance between the fault section and the normal section are derived.The significant differences between the two in the frequency domain are used to describe the degree of their differences,and a fault section orientation criterion characterized by correlation coefficients is constructed.Considering the variation of line parameters,linear fitting is used to describe the variation pattern of line parameters,and the line parameters are set as unknown quantities and brought into the distance measurement equation.Based on the rich frequency domain components of transient signals,multiple sets of distance measurement equations are constructed to solve the fault distance of the signal.This article verifies the accuracy of harmonic impedance,fault property identification,and section orientation algorithms through simulation.Furthermore,simulation experiments were used to further demonstrate the feasibility of identifying fault properties and segment orientation algorithms in practical applications.