Time-frequency characteristics of partial discharge of SF₆ gas in an extremely uneven field under impulse voltage

To investigate the mechanism of partial discharge (PD) of insulation defects in gas-insulated metal-enclosed switchgear (GIS) under impulse voltage, time-frequency characteristics of optical signals and current signals of PD are analyzed with short time Fourier transform (STFT), pseudo Wigner-Ville distribution theory and Gabor distribution theory. The analysis reveals that: 1) The time-frequency characteristics of PD signals can be effectively extracted; 2) Gabor distribution of PD signals is endowed with the best time-frequency aggregation behavior without cross-interference items and reflects the most detailed characteristics of PD signals in time-frequency plane; 3) STFT of PD signals possesses the poorest time-frequency aggregation behavior and 4) Pseudo Wigner-Ville distribution of PD signals includes several inherent cross-interference terms. The time-frequency characteristics of the optical signals and the current signals of PD are different and the rising time of the optical pulse is less than that of the current pulse in time-frequency plane.