Distribution network single-phase earth fault line selection method based on negative sequence impedance angles

Abstract

A distribution network single-phase earth fault line selection method based on negative sequence impedance angles belongs to the technical field of power system relay protection. The method is characterized by comprising the following steps of: first, synchronously sampling the three-phase currents of the near power ends of all lines in a distribution network and the three-phase voltage of a system; calculating the negative sequence voltage fault component phase angle of the system and the negative sequence current fault component phase angles of the near power ends of all the lines according to a sampling result, and furthermore, obtaining the fault component negative sequence impedance angles of the near power ends of all the lines; and if the fault component negative sequence impedance angle of the near power end of a certain line is between minus 80 degrees and minus 190 degrees and the negative sequence impedance angles of the near power ends of all the lines which are connected with a far power end of the line are between minus 10 degrees and 100 degrees, determining the line to be a fault line, and otherwise, determining the line to be a normal line. The single-phase earth fault calculation of a typical 35kV multi-branch complicated distribution network shows that the method provided by the invention can accurately and flexibly select the fault line, moreover, a line selection principle is not influenced by an arc suppression coil, and the method can be applied to the distribution networks with various earthing modes.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a single-phase ground fault line selection method applied to a power distribution network. Background technique [0002] Single-phase grounding is the most likely fault in distribution network, accounting for about 80% of all faults, but the selection of single-phase grounding fault line in distribution network has always been a technical problem that plagues people. Because the fault current is small and the fault characteristics are not obvious, it is more difficult to select the fault line of the distribution network whose neutral point is grounded through the arc suppressing coil. [0003] In recent years, scholars have proposed many line selection methods and developed a series of line selection devices, and there are many invention patents related to this technology. The line selection method based on the fault transient electrica...

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Problems solved by technology

When the grounding resistance is high, the single-phase grounding fault has very little influence on the power flow in the system, and this method will be useless

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