Fault Section Location Method Of The Distribution Network Based On Wavelet Packet Decomposition And Fault Comprehensive Measure

The medium-voltage distribution network has a variety of structural forms,complicated branch lines,and a high probability of single-phase grounding fault.China's distribution network mostly adopts the operation mode of small current grounding system,which has the advantage of ensuring the reliability of power supply.However,the small single-phase grounding fault current determines the need for highly reliable single-phase grounding protection.If the fault section on the feeder can be located,the fault can be eliminated or isolated in time to improve the reliability of power supply and ensure the safe operation of the system.Firstly,by establishing a single-phase grounding fault model of the resonant grounding system,the characteristics of the transient zero-mode current in the upstream and downstream of the fault point are analyzed in detail based on the zero-mode equivalent network.The waveform in the upstream of the fault point has high similarity and large amplitude,and the transient energy is mainly concentrated in the low frequency band,while the waveform in the downstream of the fault point has high similarity and small amplitude,and the transient energy is mainly concentrated in the high frequency band.It shows that the characteristics of the transient zero-mode current upstream and downstream of the fault point are different,and this feature is not affected by the fault conditions,which provides the theoretical basis for the section location method proposed in the following paper.Secondly,a fault section location method based on wavelet packet decomposition and fault comprehensive measurement is proposed.This method can make full use of fault information and improve the accuracy of fault section location.The transient zero-mode current of T/4 after fault is decomposed by wavelet packet.The fault trust function which can measure the symptom of fault occurrence is constructed by the energy relative entropy.Then the fault comprehensive measurement function which can quantify the fault information from multiple angles is constructed by the singular value Euclidean distance.The section location vector is obtained from the fault comprehensive measurement value of each detection point,and the section corresponding to the maximum value is the fault section.Finally,in order to further verify the effectiveness and applicability of the proposed section location method,a large number of simulations and experimental verifications are conducted by setting different fault conditions.The simulation model of 10kV resonance grounding system and the physical simulation platform of laboratory distribution network,setting different fault conditions for several simulations and simulation experiments have shown the effectiveness of the method.The results show that the method is accurate,reliable,and adaptable to complex fault conditions.