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

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.

Comparative Analysis of Partial Discharge Detection Features Using a UHF Antenna and Conventional HFCT Sensor

“…More references about the PRPD for surface discharge including surface discharge on Epoxy Resin, the solid insulation used in this paper, can be found in literature, e.g. [37], [38], [39], [40], [41], [42], [43], [44], [45], [46]. Indeed, by increasing the applied voltage, the discharge number and discharge amplitude in both positive and negative half-cycles will increase accordingly for both antenna and HFCT sensor.…”

Largely Enhanced High-Frequency Insulation Performances of Polyimide by Incorporating Siloxane-Based Fillers

“…Polyimide (PI) film is commonly used as the main insulation and interturn insulation material for high-frequency power electronic transformers due to its excellent insulation property, high-temperature resistance, and film formation ability . Different from the conventional power frequency operation environment, the sharp rise of the operation frequency, voltage, and temperature of high frequency power electronic transformers can accelerate the insulation deterioration of PI films and consequently lead to early breakdown of PI films, which is attributed to the long-term damages of strong high-frequency electric stress and electric–thermal coupling . Therefore, it is essential to increase the breakdown field strength of insulating polymer materials under high-frequency stress to ensure the safe and reliable operation of high-frequency power electronic transformers.…”