Research On Location Of Single-phase G Rounding Fault Section In Medium-Voltage Distribution Network

The traditional medium-voltage distribution network is prone to single-phase grounding faults due to the complex and diverse line structure.In order to improve the reliability of power supply,The operation mode of resonance grounding has been widely used in China’s medium voltage distribution network,but due to the compensation of the arc suppression coil,the fault characteristics are not obvious,and it is difficult to meet the selection trip requirements of the new distribution network operation regulations.It is necessary to further study the location of small current grounding fault section in distribution network,so as to remove the fault quickly and reliably,and ensure the safe and stable operation of the system.Based on the additional positive sequence real part network model of single-phase to ground fault in resonant grounding system,the characteristics of the additional positive sequence real part network are analyzed theoretically and simulated.The characteristic law of the transient additional positive sequence real currents upstream and downstream of the fault point is analyzed in detail,it is concluded that there are obvious differences in the distribution of transient frequency spectrum between upstream and downstream fault points.Under different fault conditions,the time-domain and frequency-domain characteristics of transient additional positive sequence real part current of each monitoring point on the fault line are simulated.The spectrum difference between upstream and downstream fault points always exists,which provides a theoretical basis for the accurate location of fault section.A segment location method based on transient plus real part current spectrum characteristics is proposed.According to the different spectrum distribution of the upstream and downstream of the fault,single subband reconstruction is used to improve the wavelet packet,and the transient additional positive sequence real current after the fault is decomposed to obtain the wavelet packet energy spectrum distribution of each monitoring point on the fault line in different frequency bands.In order to reduce the pressure of data transmission and feed back the fault location information quickly and accurately,by calculating and comparing the relative entropy of energy spectrum between adjacent detection points,the section location criterion is constructed to determine the fault path and realize the accurate location of fault section.In order to verify the reliability of the fault section location method proposed in this paper,a large number of simulations and experiments are carried out on the fault section location method through computer 10kV simulation model and laboratory 380V distribution network physical simulation system.The results show that the proposed method has a certain anti noise performance,and can effectively and reliably locate the fault section under different operation modes and fault conditions.