基于改进EMD的GIS局部放电特高频信号降噪方法研究

Study on noise reduction method for PD ultra-high frequency signal based on the improved EMD

特高频法检测GIS局部放电时往往受到不同类型的噪声干扰,天线采集到微弱的特高频信号容易被噪声淹没,导致局部放电检测不准确甚至检测系统在现场无法正常工作等问题。针对上述问题,提出一种基于改进EMD的GIS局部放电特高频信号降噪方法。该方法利用对偶树复小波(Dual-Tree Complex Wavelet Transform,DTCWT)对经验模态分解(Empirical Mode Decomposition,EMD)降噪法进行改进并对GIS局部放电特高频信号进行降噪。利用EMD法将含噪信号分解为一系列的固有模态函数(IMF)分量,然后利用联合分布模型进行每个IMF分量的DT-CWT降噪的小波系数估计,对每个IMF分量进行降噪。最后将降噪后的IMF分量进行信号重构得到降噪后的信号。GIS局部放电特高频信号降噪试验结果表明了该方法达到很好的噪声与非噪声信号的分离效果,拥有较高信噪比,以及能够保持早期局部放电特高频信号特征。

When the UHF method is used to detect GIS partial discharging, it tends to be different types of noise. The UHF signals which are collected by the antenna are easy to be submerged by the noises, which cannot cause partial discharge detection accurately or system working normally. For above problems, a sort of GIS partial discharge UHF signal noise reduction method based on improved EMD is proposed in this paper. This method uses dual-tree complex wavelet transform and empirical mode decomposition noise reduction method to improve and reduce the GIS partial dis- charge UHF signal noise. The EMD method is used to decompose the noise signals into a series of IMF components, and then, the joint distribution model is used to estimate for each IMF component of DT-CWT noise wavelet coeffi- cient. Finally, the reduced IMF signals are rebuilt to get reduction noise signals. GIS partial discharge UHF signals reduction test results show that this method achieves a good effect to separate noise and non-noise signals. Besides it, the method also has the characteristics which contain high signal-to-noise ratio and can keep early partial discharge UHF signals.