Streamer discharges in porous dielectrics: effects of pore geometry and surface charge

Abstract

Porous dielectrics significantly affect the development and propagation modes of gas discharges. However, the complex microstructures of realistic pores induce diverse discharge behaviours, and the underlying microscopic mechanisms remain unclear. This study combines streamer simulation based on the Îto-KMC particle model with high-spatiotemporal-resolution optical observations to investigate streamer propagation in porous dielectrics. The simulations are used to analyse the effects of pore geometry and pre-existing surface charge on streamer propagation, while optical observations provide morphological support for the simulated pore-internal micro-discharges and their interaction with external surface streamers. Simulations in randomly generated porous structures reveal two distinct propagation modes: surface-guided streamers and pore-initiated micro-discharges. Statistical results from 60 independent geometries show that increasing porosity and pore diameter enhance internal discharges and electron accumulation inside pores, while ionization in the surrounding gas is suppressed due to local charge trapping. The effects of pre-existing surface charge are further examined. Positive surface charge inhibits primary streamer propagation but promotes localized reverse streamers near pore openings, whereas negative surface charge accelerates surface streamer growth and promotes local discharges within the porous medium. These results provide guidance for the design of porous insulating materials and surface charge management in high-voltage systems.