De-noising method for ultrasonic testing of high-voltage bushing lead of transformer

Abstract

The invention relates to a de-noising method for ultrasonic testing of a high-voltage bushing lead of a transformer, comprising the following steps: performing wavelet decomposition on an ultrasonic echo signal reflected by the high-voltage bushing lead of the transformer, and performing signal analysis from a detail component and an approximate component; introducing an adaptive threshold methodbased on SURE unbiased estimation, adopting a gradient descent method by the adaptive wavelet threshold estimation, taking the gradient function deltalambda as an objective function, corresponding theminimum value of the gradient function deltalambda to the optimal threshold, introducing the Sigmoid function as a threshold function at the same time, and combining the above variables to obtain a new gradient function deltalambda; combining the grey wolf optimization algorithm with the adaptive threshold method, and optimizing the objective function by using the gray wolf algorithm; de-noisingeach detail wavelet component by using the gray wolf optimization adaptive optimal threshold, and performing wavelet inverse transform signal reconstruction on the de-noised detail component and approximate component, thereby obtaining a de-noised ultrasonic echo signal. Compared with the prior art, the invention has the advantages of improving the accuracy of ultrasonic detection and the like.

Description

technical field [0001] The invention relates to the field of ultrasonic detection of high-voltage bushing leads of transformers, in particular to a denoising method for ultrasonic detection of high-voltage bushing leads of transformers based on a gray wolf optimization wavelet adaptive threshold method. Background technique [0002] With the rapid development of my country's power industry and the continuous expansion of generator unit capacity, the stability of the power grid has put forward higher requirements for the reliability of transformers. In the structure of the transformer, the transformer bushing leads play an important role in connection. Because the bushing lead wire needs to bear the influence of electric force, mechanical force, heat and other factors for a long time during operation, the strength of the lead wire will decrease. If the fault is not eliminated in time, the stable operation of the transformer will be affected. As a non-destructive testing tech...

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Problems solved by technology

As a relatively primitive denoising method, the soft and hard threshold denoising method was proposed by Donoho, and on this basis, a threshold selection method based on SURE was developed, but this threshold denoising method can easily lead to signal distortion

In view of the above deficiencies, some scholars proposed a threshold denoising method based on genetic algorithm, which is used in the denoising of partial discharge signals, which reduces the degree of distortion of the denoising signal, but the calculation of genetic algorithm needs to go through complex coding, crossover , compile, the process is complex

For this reason, a certain scholar introduced the particle swarm optimization algorithm to optimize the threshold function when denoising. When dealing with non-stationary signals, it can better suppress white noise and reduce the degree of signal distortion, but it is easy to fall into a local optimal solution when dealing with discretization problems.

Therefore, some scholars combine the ant colony optimization algorithm with the wavelet threshold method for non-stationary signal denoising, which can quickly sort useful information from the background noise and find the global optimal solution. However, when the method is initialized A large number of ants and iterations are required, and the calculation time is long

In addition, some scholars combine the particle swarm algorithm with the chaos algorithm and optimize the adaptive threshold method to ensure that the particles jump out of the local extreme point, improve the global optimization ability, and use the algorithm in the denoising of partial discharge signals. The denoising effect is obvious, but there are still disadvantages of large amount of calculation, many iterations, and long time

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