Time and Frequency Analysis on Leakage Current Waveforms of Discharges along Hydrophobic and Hydrophilic Surfaces

This paper reported the different leakage current waveforms of discharges on ceramic insulators and RTV coated insulators in the artificial pollution flashover tests. According to the recorded data, the joint time and frequency analysis methods of short-time Fourier transform (STFT) and Gabor transform were used to pick up the characteristics of leakage currents and analyze the development and transition of leakage currents on the hydrophilic and hydrophobic surfaces. Results of STFT and Gabor transform all show that the joint time-frequency distribution of the whole process tested on the hydrophilic surface is different from that on the hydrophobic surface, if they were treated as the non-stationary signals. In addition, the time-frequency distributions of discharges on the hydrophilic surface in different stages are found to differ from those on the hydrophobic surface