Study on the aging condition of stator bar based on Ultra-wideband PD detection technique

In this paper, the accelerated aging experiment based on the stator bar of 780 kW/6 kV large motor had been conducted in the laboratory in order to simulate the practical aging of large motor or generator in service. The PD of insulation was measured at the end of each aging cycle by using the Ultra-Wide-Band (UWB) PD detection technique. Moreover, the developing characteristics of PD in time-domain and frequency-domain were analyzed by using FFT. The experiment results showed that the high-frequency surge of time-domain wave became more and more severe and the width of PD pulse always shortened with aging time. The high-frequency components in frequency-domain became richer with aging time. In addition, the number of peak in frequency spectrum increased and the main peak of frequency spectrum moved gradually to the high frequency with deterioration of insulation.