Research On Single-phase Grounding Fault Location Of Small Current Neutral Grounding System In Distribution Network Based On Transient Component

At present,the distribution network of our country widely adopts the neutral point non-effective grounding method,namely small current grounding.According to relevant statistics,the user power failure caused by the fault of distribution network accounts for about 90% of the total power failure accidents of the whole power system.Therefore,when distribution network faults occur,it is of great significance to quickly locate and repair the faults in order to improve the power supply reliability of distribution network,reduce the outage time and improve the satisfaction of users.In recent years,with the continuous upgrading of distribution network,a large number of advanced measurement equipment has been applied to the distribution network,which makes it possible to obtain the fault transient information effectively,and the research on fault location by using the transient quantity has attracted much attention.Based on the transient fault component,this paper mainly studies the fault line selection and location of the small current grounding system in distribution network.In this paper,the fault steady-state characteristics,transient characteristics and the process of fault transient traveling wave generation and propagation are analyzed when single-phase grounding occurs in a small current grounding system.Through analysis,it is found that the transient process after fault occurrence contains abundant fault information,and the characteristics of fault transient information are more reliable than that of fault steady-state information.ICEEMDAN signal decomposition algorithm is introduced to accurately extract fault characteristics in transient components.The advantages of ICEEMDAN decomposition algorithm over other three decomposition methods are verified by simulation examples.In order to solve the problem that the waveform features of transient zerosequence current are damaged due to strong noise interference and the fault feature information is difficult to be extracted,a fault line selection method based on ICEEMDAN-PE denoising and correlation clustering is proposed.Firstly,the improved adaptive noise complete set empirical mode decomposition and permutation entropy principle are combined to denoise the transient zero-sequence current.Then,the feature matrix of the transient zero sequence current is extracted by correlation analysis.Finally,the fault line is selected by K center point clustering algorithm.The simulation results show that the proposed method can still accurately select fault lines under the background of strong noise,and can accurately select fault lines under different fault grounding conditions,which verifies the effectiveness and adaptability of the proposed method.Aiming at the fault location problem of hybrid tree multi-branch lines in distribution network,an improved two-terminal location method based on ICEEMDAN-SDEO is proposed.First,considering the large ranging error caused by inaccurate calibration of wave head,a calibration algorithm of traveling wave head based on ICEEMDAN-SDEO is proposed to calibrate the arrival time of initial traveling wave head.On this basis,a branch discrimination matrix is constructed based on the topology of multi-branch line and the principle of double-ended traveling wave ranging.The fault branches are identified according to the component characteristics of the elements in the branch discrimination matrix,and the accurate location is realized.Considering the uncertainty of traveling wave velocity,redundant traveling wave information is used to correct the traveling wave velocity online,and the ranging accuracy is further improved.Through simulation analysis under different fault conditions,the effectiveness and adaptability of the proposed method are verified.