Degradation diagnosis of large stator winding insulation based on ultra-wide band partial discharge detecting technique

There are two topics that are of particular interest to the workers in the field of partial discharge (PD). One is the impact of a wide variety of statistical tools on the interpretation of discharge data obtained with standard PD detection apparatus according to IEC 270. The other is the study of discharge-induced degradation processes by looking into the physics of the discharge process. Ultra-wide band (UWB) PD detecting technique is introduced to measure the PD pulse of the bar sample during aging. The data obtained are analyzed using joint time-frequency analysis (JTFA) methods, that is, short-time fourier transformation (STFT), Wigner distribution (DWD) and Gabor spectrogram (DGS), and finally Gabor spectrum is selected to analyze the characteristics of single impulse wave in different aging period. The results of analysis indicate that following the increasing of aging time, the high-frequency component of single impulse wave continuously increased, while the energy of discharge alternated from low-frequency long time lag to high-frequency short time lag and high-frequency long time lag.