Degradation characteristics of dielectric film under nanosecond pulse current and the mechanism based on PIC-MCC simulation

The peaking capacitor is a crucial component in the high-altitude electromagnetic pulse device. One of the significant challenges faced by the peaking capacitor is the reduction in the flashover tolerance strength of the dielectric film. This paper simulates the electromagnetic environment of dielectric film and carries out flashover experiments to study the degradation characteristics of polypropylene (PP) and polyethylene terephthalate (PET) films under nanosecond pulse current injection. The effects of damage type and degree on the flashing process are analysed by PIC-MCC method. The results show that the deformation characteristics of the film surface under nanosecond pulse current have a key influence on the flashing tolerance strength. Specifically, the raised and folded deformation of the PP film can increase the electron emission coefficient of the surface and expand the ionization range of the gas, which significantly enhances the number of electrons and reduces the flashover voltage. The microporous deformation of PET film increases the area of electron collision, but the pitted deformation restricts the diffusion of low-energy electrons. As a result, the number of electrons remains balanced, leading to a more stable flashover strength. The simulation can predict the flashover voltage of dielectric films and highly consistent with the experiments, revealing the deterioration mechanism of the film’s flashover tolerance under the action of multiple flashovers. This provides analytical methods and a theoretical basis for improving the flashover tolerance strength of dielectric films.