Surface discharge characteristics and influencing factors of polyimide insulations under high‐frequency sinusoidal voltages

Abstract

Abstract The high‐frequency power transformer (HFPT) has become a vital component of the power system. For HFPT insulations, surface discharge is a serious problem. Polyimide (PI) is a widely used insulating material for HFPT's. A needle‐plate electrode structure‐based experimental setup was developed to produce and measure the surface discharge. This paper first time used the fluid‐kinetic model by adopting the finite element simulation method to address the micro‐level study of surface discharge. This paper aimed at the discharge phenomenon of the PI under the direct action of high‐frequency sinusoidal voltage and has not considered the overvoltage phenomenon caused by the waveform parameters that is the actual high‐frequency action on the PI material. The development of surface discharge at various stages was analysed. Particle densities and electric field distributions versus discharge time were determined. Frequency, temperature, and air pressure have a significant effect on surface discharge behaviour. As a result, the applied voltage reaches its peak value at high‐frequency, so the flashover time of surface discharge is reduced under the high frequency. The electron density of the streamer development increases as the temperature rises, and the time to flashover the channel becomes shorter. The higher the electron density and the longer the discharge channel develops while the gas pressure is lower. The simulation results have high accuracy and good agreement with experimental data.