Impact of Accelerated Shock on Partial Discharge Characteristics at the Oil-Paper Insulation Interface of Transformers

The variation in pressure distribution at the oil-paper insulation interface of transformers under shock conditions leads to an enhancement of partial discharge, posing severe challenges to the reliability of transformer oil-paper insulation. In this study, an experimental platform for partial discharge testing at the oil-paper insulation interface under accelerated shock is established to investigate the partial discharge characteristics at different acceleration levels. The experimental results reveal that, compared to the zero-acceleration condition, accelerated shock significantly intensifies partial discharge at the oil-paper interface. With an acceleration of 10 m/s², the average discharge magnitude for the wire-plate electrode increases by 43.2%, while that for the needle-plate electrode increases by 20.0%. Both partial discharge magnitude and discharge frequency are observed to increase markedly with increasing acceleration. Furthermore, based on Comsol Multiphysics, a fluid-structure interaction model of the oil-paper insulation under accelerated shock is constructed. The simulation results indicate that accelerated shock induces fluctuations in the pressure distribution at the oil-paper interface, which alters the microbubble layer formation process and changes the number density of gas molecules at the interface. When the acceleration direction is negative, the pressure of the microbubble layer decreases, the solubility of gas reduces, and the bubble volume expands, resulting in an increased average free path of electrons and thus enhanced partial discharge. During cyclic positive and negative acceleration shocks, negative-direction acceleration is found to play a dominant role in promoting partial discharge at the oil-paper interface, thereby further aggravating the partial discharge process. This study can provide a reference for insulation design and protection of transformers under impact conditions.