Time-frequency analysis of RF partial discharge signals using wavelet transforms

One means of determining insulation faults in HV plant is through the measurement and monitoring of partial discharge (PD) activity. This paper concerns the measurement of radiated RF signals by simple broadband antennas from a point-plane PD geometry. To help provide a tool for understanding the nature and characterisation of the radiated PD signals, the time-frequency characteristics of the RF signals are investigated using the Gaussian wavelet via the continuous wavelet transform. The paper demonstrates the experimental results using this tool showing that different frequency characteristics may be identified for the antenna signals based on the inherent antenna response, the location and environment of the antenna and the signals originating from different point-plane gap sizes over positive and negative voltage half cycles.