Influence of mechanical vibration on typical oil–paper insulation partial discharge defects in power transformers

Abstract

Mechanical vibration is a common operating condition of power transformers and may interact with electrical stress, thereby influencing partial discharge (PD) behavior in oil–paper insulation. To investigate this influence, an electro-mechanical coupled experimental platform was developed. Two typical PD defects, namely, needle–plate and floating electrode defects, were studied under various vibration frequencies and acceleration levels. The experimental results indicate that mechanical vibration affects PD characteristics in a defect-dependent manner. For floating defects, vibration significantly reduces the partial discharge inception voltage (PDIV) and average discharge magnitude, while markedly increasing the discharge repetition rate. Under certain conditions, the repetition rate increases by more than one order of magnitude, indicating intensified discharge activity. In contrast, the needle–plate defect exhibits lower sensitivity to vibration. Moderate vibration tends to suppress PD development and slightly increase PDIV, whereas higher vibration levels may promote discharge occurrence. Further analysis suggests that these differences arise from distinct dominant mechanisms. The PD behavior of floating defects is mainly attributed to vibration-induced electric field distortion caused by periodic electrode displacement, while that of needle–plate defects is jointly influenced by electric field variation and bubble dynamics in the oil gap. These findings provide experimental insight into the diagnosis of electro-mechanical coupled faults in power transformers.