Transformer partial discharge fault diagnosis method based on hierarchical threshold synchrosqueezed wavelet

Abstract

The invention provides a transformer partial discharge fault diagnosis method based on hierarchical threshold synchrosqueezed wavelet. The method is characterized by comprising the following steps of: 1, subjecting a transformer partial discharge signal f(t) to SWT decomposition to obtain an SWT decomposition coefficient S<y><a(i)>(t), wherein the i = 1, 2, L, I; 2, estimating a noise standard deviation [sigma]n by using a formula described in the specification; 3, assigning values to ca(i) step by step at a fixed step length for the ith coefficient of the SWT, calculating the minimum mean square error by a mean square error formula, and determining the optimal value of the ca(i); 4, calculating the hierarchical threshold [gamma]a(i) = ca(i) [sigma]n, and achieving the ith SWT coefficient noise reduction through the ith SWT coefficient formula; 5, using a noise reduction formula to reconstruct de-noised layer coefficients to obtain a de-noised de-noising transformer local discharge signal y(t); and 6, performing feature extraction on the de-noised de-noising transformer local discharge signal y(t), and performing fault diagnosis according to extracted features.

Description

technical field [0001] The invention relates to the field of power system signal processing, in particular to a transformer partial discharge fault diagnosis method based on layered threshold synchronous squeeze wavelet. Background technique [0002] Partial discharge refers to the discharge that only occurs in a local area of ​​an insulating structure under the action of an electric field, rather than a large area or a discharge that runs through the entire conductor. The insulation structure of large-scale power transformers is relatively complicated, and the materials used are various, and the electric field distribution of the entire insulation system is very uneven. Due to the imperfect design or manufacturing process, the insulation system contains air gaps, or the insulation is damp during long-term operation, and the moisture decomposes under the action of an electric field to generate gas and form bubbles. Because the dielectric constant of air is smaller than that...

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Problems solved by technology

[0006] However, the existing research only involves the denoising research of SWT single-layer threshold. For the optimal construction of SWT layered threshold, especially the application of SWT layered threshold denoising to transformer partial discharge fault diagnosis, there are almost no related patents. involves

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