Medium voltage distribution network two-point out-of-phase earth fault line selection method and system

Abstract

The invention discloses a two-point out-of-phase earth fault line selection method and system for a medium-voltage power distribution network. The method comprises the following steps: step 1, acquiring neutral point zero-sequence voltage of the power distribution network to judge whether an earth fault exists or not; 2, analyzing the zero-sequence current of each line of the power distribution network by using a wavelet method so as to select a first fault line, and cutting off the first fault line; 3, collecting neutral point zero sequence voltage of the power distribution network to judge whether a grounding fault exists or not; and step 4, extracting a line corresponding to the maximum zero sequence current difference value before and after the first fault line is removed from the rest lines as a second fault line. According to the method, when the grounding fault occurs, the first fault line is judged and cut off, and then the second fault line selection is performed by using the variable quantity of the zero-sequence current amplitude converted value, so that the misjudgment probability of the two-point out-of-phase grounding line selection is reduced, the accuracy of the two-point out-of-phase grounding line selection is improved, and the reliability of the two-point out-of-phase grounding line selection is improved. And the fault characteristics of the two-point out-of-phase grounding fault under all conditions are met.

Description

technical field [0001] The invention belongs to the technical field of power system fault line selection, and in particular relates to a method and system for two-point out-of-phase ground fault line selection in a medium-voltage distribution network. Background technique [0002] The medium-voltage distribution network in my country generally adopts the low-current grounding method, that is, the neutral point is not grounded or the neutral point is grounded through the arc suppression coil. The advantage of this grounding method is that when a single-phase grounding fault occurs in the distribution network, the line voltage remains Unchanged, it can continue to run for 1 to 2 hours according to the regulations, and the reliability of power supply is high. During this period, the fault-to-ground voltage drops, and the non-fault-to-ground voltage rises, up to the line voltage level. If the grounding time is too long, it may lead to ground breakdown at the weak insulation of t...

AI Technical Summary

Problems solved by technology

However, in a two-point out-of-phase ground short circuit, if the transition resistance difference between the two out-of-phase ground points is too large, the zero-sequence current of the non-fault line may be greater than the zero-sequence current of the fault line, and it is difficult to directly pass the zero-sequence current of the fault line. Therefore, the method of judging two out-of-phase ground short circuits in the prior art is not rigorous enough, and there are probability judgment errors

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