GIS Equipment Abnormal Noise Diagnosis Technology Based on Acoustic Imaging and Its Field Application

In order to obtain the acoustic imaging characteristics of typical defects caused by partial discharge and mechanical looseness of GIS equipment, firstly, the typical acoustic imaging characteristic spectrum and characteristic values of 220 kV GIS equipment under normal operation are tested and analyzed, the results indicate that that the main frequency during normal operation is 100 Hz, and frequency energy below 1 kHz can account for over 99%. Secondly, the acoustic imaging characteristic signals under three typical defects on site are analyzed, including the abnormal sound of GIS expansion joint bolt loosening, the abnormal sound of internal discharge breakdown, and the corona discharge outside the bushing, the results indicate that the percentage of 0.5–10 kHz energy in the case of loose bolts increases, the frequency spectrum in the case of breakdown discharge is broadband, and the dominant frequency exceeds 10 kHz. At the same time, the dominant frequency ratio and fundamental frequency ratio is very small, there are a large number of non 50 Hz integer harmonics, for corona discharge, there is a significant 50 Hz odd harmonic component, which ratio is much higher than other cases, and the discharge waveform can be obtained by filtering below 10 kHz. Finally, combined with acoustic imaging testing and electrochemical testing of on-site GIS PT abnormal noise, it is analyzed that the cause of the equipment abnormal noise is internal partial discharge, and the feasibility of using acoustic imaging for partial discharge defect localization and identification is verified through on-site disassembly.