Time-delay estimation algorithm of partial discharge ultra high frequency signals based on fractional Hilbert transformation

Time delay estimation is the basis of the localization algorithm for partial discharge (PD) based on time difference in GIS, and it is the key to the accuracy of localization. In this paper, the theory of fractional Hilbert transform for time delay estimation is described. Based on fractional Hilbert transform, a method for estimating the time delay of GIS ultra high frequency partial discharge is proposed, and the numerical implementation steps of the algorithm are given. According to the abnormal partial discharge signals found in the switch gate during the inspection of certain 220kV GIS equipment, high frequency electromagnetic wave is collected by the high speed oscilloscope. According to the time delay of the signal, the space position of the partial discharge source is located from the the disk type insulator pouring hole 1.25 meters. After the disintegration of the switch air chamber, the distance between the discharge source and the pouring hole is 1.3 meters. The error of the partial discharge source localization based on fractional Hilbert algorithm is significantly lower than that of the bi-spectrum and the frequency domain time delay estimation algorithm.