Low current neutral grounding system fault route selecting method by wavelet package decompose and correlation analysis

Abstract

The invention uses wavelet packet decomposition and correlation analysis for a small current grounding system fault line selection method, which belongs to the technical field of electric power system relay protection. The method is as follows: when the instantaneous value of the busbar zero-sequence voltage exceeds the limit, the fault line selection device starts immediately and records waves to obtain the transient zero-sequence current of each feeder line; Based on the energy above, the energy of all line transient zero-sequence currents is summed according to the frequency band, and the frequency band where the maximum value and the second maximum value of the energy sum value are located is selected as the characteristic frequency band. The correlation analysis method is applied to the line transient zero-sequence current in the selected characteristic frequency band in turn, and finally the fault point is determined by synthesizing the correlation analysis results of the two frequency bands. This method uses wavelet packet decomposition and correlation analysis method, can more effectively use the information (amplitude, phase) contained in the fault transient process, and can reflect the difference between the fault line and the non-fault line to the maximum extent. Principle analysis and simulation show that the method is accurate and reliable in line selection.

Description

Technical field: [0001] The invention relates to a fault line selection method of a small current grounding system by using wavelet packet decomposition and correlation analysis, and belongs to the technical field of electric power system relay protection. Background technique: [0002] In recent years, my country has done a lot of research on the line selection of small current grounding faults, and achieved certain results, but the problem of accurate and reliable line selection has not been well resolved. Failure to quickly and accurately detect ground fault points not only hinders the development of distribution automation, but also poses a threat to the safe and stable operation of the power grid. [0003] When a single-phase ground fault occurs in a low-current grounding system, zero-sequence voltage will appear in the entire system, and the current flowing through the fault point contains a transient quantity with a high amplitude. Compared with the weaker steady-stat...

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Problems solved by technology

Literature [9-11] selects lines on the basis of multiple frequency bands, but only uses the amplitude or polarity of transient currents, and only uses part of the transient information, which cannot distinguish faulty lines from non-faulty lines to the maximum extent.

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