Research On Location Technology And Device Abnormal Operation Mechanisni Of Single-Phase Grounding Fault In Distribution Network

Single-phase grounding fault is the most common faults in the distribution network,meanwhile,as an significant part of connecting the transmission grid and users,the distribution network is located at the end of the power supply grid,and the decisive link to ensure the quality of power supply for users and reduce personnel electric shock accidents is to protect and control it.When a single-phase grounding fault occurs in the distribution network,the characteristics of the current and voltage are not prominent,and the fault location device exist the abnormal operation problem,which makes the fault location problem of the distribution network not well resolved.Research on the abnormal operation mechanism of the fault location device represented by the fault indicator in this paper,the reason for the abnormal operation of the location device were analyzed and the conclusion that the reliability of the single fault feature utilized to locate is not high was drawn;By analyzing the fault information collected by the distributed terminals of the active distribution network,a location method that integrates the characteristics of multiple faults is proposed to realize the fault section location of the active distribution network.Firstly,the existing mainstream fault location methods and the application of location devices were compared and analyzed in this paper.By comparing characteristics of steady-state and transient-state voltages and currents in the upstream and downstream of the corresponding fault point after a single-phase grounding fault and combining the function of the fault location device and the future development direction of the distribution network,the technology of the fault location with practical value was analyzed,which provides ideas and basis for the next step of the research on the abnormal operation mechanism of the location device.Secondly,aiming at the problem that the action accuracy of the fault location device used in the field cannot reach the expectations.It was focused on the analysis of the abnormal operation of the fault location device represented by the fault indicator when the three phases operate symmetrically.For the sampling error of the acquisition unit and the influence of the external environment on the starting criterion and various location methods,the researches and simulation analysis have been conducted in this paper.The research results show that: the positioning device based on a single fault information is susceptible to external interference,causing the abnormal operation of the device.Finally,in order to improve the problem that inaccurate sampling data and waveform distortion in the line fault information uploaded by the terminal to the master station cause the abnormal operation of the device,a method based on multi-objective weighted gray target decision-making is proposed.By analyzing the influence of distributed generation on the single-phase ground fault current,the normalized equivalent resistance and the fluctuation quantities of the transient zero-mode current in the section、the attenuation speed and the difference of zero-sequence current are selected as the evaluation indexes of the section state.The expected bullseye degree under the sampling data of each section and the three decision results of the preset non-faulty section were calculated,the upstream section of the fault point and the faulty section,according to the size of the three expected bullseye degrees of each section,it is judged whether the section is a fault section.PSCAD/EMTDC simulation results show that the proposed method can integrate multiple fault characteristics,and is suitable for fault section location in radial distribution networks with inverter-type distributed generation under different fault conditions.Theoretical research and simulation results show that the method for using multiple indexes to locate the fault section in the active distribution network is proposed in this paper,which can improve the reliability of the fault location under weak fault conditions in the distribution network and improve the problem that the abnormal operation of the device caused by the influence of uncertain factors including the change of distribution network parameters and the interference of external environmental.