Fault line selection method of low current grounding system using time-frequency atom decomposition theory

Abstract

The invention provides a fault line selection method of a low current grounding system using a time-frequency atom decomposition theory. The method comprises the following steps of: based on the time-frequency atom decomposition theory, performing sparse decomposition on zero-sequence current data in a Gabor over-complete dictionary, and then obtaining matched attenuation sinusoidal quantity atoms through optimizing and solving relevant parameters. By the time-frequency atom decomposition method, the disturbance characteristics such as start/stop moments, amplitudes, frequencies and change rules of fundamental wave and each subharmonic can be exactly obtained, and interference signals can be effectively filtered. Energy entropies of the atoms decomposed by time-frequency atoms are arranged from large to small; except from the zero-sequence transient current fundamental wave atom, atom phase angles (polarity) similar with zero-sequence current frequency of each line are compared; if the atom phase angle (polarity) similar with the zero-sequence transient frequency of the line is opposite to that of other lines, the line is the fault line; and if the atom phase angle (polarity) of each line is the same, the fault is bus fault, and the fault line is determined by the comparison result of each frequency phase angle.

Description

technical field [0001] The invention relates to a fault line selection method of a small current grounding system of a distribution network, in particular to a method for selecting a fault line of a small current grounding system by applying the time-frequency atomic decomposition theory. Background technique [0002] Most of the distribution networks in my country adopt the neutral point not directly grounded system (NUGS), that is, the small ground current system, which includes the neutral point ungrounded system (NUS), the neutral point through the arc suppression coil grounding system (NES, also Called the resonant grounding system), the neutral point is through the resistance grounding system (NRS). [0003] Our country has done a lot of research on the line selection of small current grounding faults, and proposed a variety of line selection methods, which have achieved certain results, but still can not completely achieve accurate and reliable line selection, which wi...

AI Technical Summary

Problems solved by technology

S transform is the development of continuous wavelet transform and short-time Fourier transform, which has good time-frequency characteristics, but the amount of information after decomposition is too much

At the same time, there is also a line selection method that combines the steady state quantity and the transient state quantity. [10] , such as the neural network algorithm, but this algorithm has local optimum problems, poor convergence, long training time, and relatively low reliability

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