Research On The Method Of Fault Location For Distribution Network With Distributed Generation

After a short-circuit fault occurs in the distribution network(DN),fast and accurate fault location is beneficial to quickly isolate faults and restore power,which is essential for DN security and improving power supply reliability.Under the background of the development of active distribution network,distributed generation(DG)connecting to the distribution network has become an inevitable trend.DG connection makes the fault characteristics change compared with the traditional DN.It is of great significance to study the fault location method of DN affected by DG connected.In this paper,based on the research and analysis of the existing fault location methods of distribution network grounding,faulty feeder selection and faulty section location methods for single-phase to ground fault of resonant grounding system(RGS)are researched,and faulty section location method for phase to phase fault of distribution networks with DG(DG-DNs)are researched.A method of faulty feeder selection for single-phase to ground fault in RGS based on cross wavelet transform(XWT)is proposed.Firstly,the transient characteristics of zero-sequence current are analyzed.The related concepts and characteristics of continuous wavelet transform(CWT)and XWT are introduced.Secondly,the faulty feeder selection method and flow is proposed according to the phase difference between the main resonating component of the faulty feeder and the sound feeder.The effects of different line types,fault distance,fault initial phase angle and transition resistance are analyzed,and the numerical simulation results verify the accuracy of the proposed method.In addition,considering the influence of harmonics injected from DG,the simulation results show that the proposed method is immune to the influence of injected harmonics.A method of faulty section location for single-phase to ground fault in RGS based on CWT and XWT is proposed.According to the difference of resonance characteristics between the upstream and downstream networks,the frequency band for the main resonant frequency of the current collected by each feeder terminal unit(FTU)are identified.If the frequency band is divided into two categories,the faulty section can be located directly.If the frequency bands are classified into one class,utilizing the XWT to calculate the phase difference between the main resonance components of the current signals collected by adjacent FTUs,then the faulty section can be located.Numerical simulation results verify the effectiveness of the proposed method.In addition,considering the influence of harmonics injected from DG,the simulation results show that the proposed method is immune to the influence of injected harmonics.A method of faulty section location for phase to phase fault of DG-DNs is proposed.Firstly,a switch function based on non-logical operations is constructed,and DG status coefficient is introduced to adapt the change of DG connection status.Then a linear integer programming model for section location is established.Theoretical analysis shows that the proposed method can adapt change of DG connection status and switch status of contact switch with high fault tolerance.Simulation results of different scale indicate that the proposed method is accurate,reliable and suitable for complex DG-DNs with advantage of high speed and good numerical stability,avoiding the problems of too fast convergence and local optimization of intelligent algorithms.