| With the development of power system technology and the expansion of power supply scale,users have increasingly higher requirements on the security and reliability of power supply system.3-66 kv power distribution network in our country,the widespread adoption of neutral point grounding or via arc suppression coil grounding operation mode,under this kind of operation mode,single phase ground fault has been one of the problems that affect the power supply security and reliability,many research scientists were analyzed to explore for them,a lot of line selection method is proposed,but there are some limitations.In this paper,a differential line selection method of multi-zero sequence current transformer based on compensation parameters is proposed for single-phase earth fault of neutral point ungrounded system,and the method is analyzed theoretically.By artificially connecting the three-phase balanced reactor and connecting the zero sequence current transformer before and after it and its own circuit respectively,the differential line selection system topology diagram is constructed.Since the zero sequence current measured by the zero sequence current transformer at the first end of the non-fault line is the zero sequence current generated by its own branches,excluding other branches,and the zero sequence current measured by the zero sequence current transformer at the first end of the fault line is the vector sum of the zero sequence current generated by other branches except its own branches.Therefore,the zero sequence current measured by the zero sequence current transformer at the first end of the fault line and the non-fault line is obviously different in nature,and fault line selection can be carried out according to the zero sequence current characteristics shown by different branches.In the whole process of the analysis,the vector graph analysis method was used.The amplitude and phase of the zero sequence current presented by the vector graph in different compensation methods were different.Through the comprehensive analysis of the amplitude and phase relationship,the conclusion of line selection in different compensation methods could be drawn.This paper further studies the influence of compensator parameter setting on safety and reliability.Different compensation parameters under different compensation methods have a great influence on the zero-sequence current at the fault point.Reasonable compensation parameters can not only reduce the risk,but also improve the safety and reliability.MATLAB /SIMULINK was used to verify the simulation experiment,adjust the nature of the compensation device,observe the change trend of the zero sequence current,collect theimage,analyze the image property,and verify the line selection conclusion.Finally,an experimental platform was set up in the laboratory to simulate ground parameters,record data,and analyze and verify the data.The feasibility of this method was comprehensively verified from the simulation and experimental results. |
