UHF sensor array for partial discharge location in transformers

The application of the ultra-high frequency (UHF) partial discharge (PD) detection method has proven effective in GIS. This method is now also being applied to detect PDs in oil-filled power transformers. In this paper, the localization of the PD source in transformer is discussed. This is achieved by applying an array of four sensors to capture the PD signals at the same time. To determine the PD location, two methods (first peak and cross-correlation) are used to determine the difference in time of arrival between sensor signals and followed by numerical triangulation. The sensor positions and array size influence the PD waveform patterns captured, and thus the accuracy of the PD localization. Experimental results and analysis indicate the first peak method yields better location accuracy than the cross correlation method. However, the traditional external acoustic detection method performs better than the UHF detection method under the same test configurations.