Construction of Complex Threshold and Its Application in UHF Partial Discharge Measurements

In this paper, a new method of de-noising, using complex Daubechies wavelet (CDW) transform, has been proposed and applied to on-site noise rejection for UHF PD measurements. It is a relatively recent enhancement to the real-valued wavelet transform because of the important properties, which are nearly shift-invariant and availability of phase information. Those properties give CDW transform superiority over other real-valued wavelet transform. Based on the real threshold algorithm of real-valued wavelet transform, complex threshold algorithm is devised in this paper. It modifies the real and imaginary parts of complex wavelet coefficients respectively to extract signals with higher peak signal-to-noise ratio (PSNR) and less distortion of original signals.