Flashover is a crucial issue in both high-voltage engineering and surface physics. It not only challenges the existing theories about its dynamic evolution, but also inhibits the clean energy revolution by limiting the accessible voltage rating of power equipment. It is of significance to elucidate the microscopic process along the interface to improve the flashover performance. In the present study, the synergic effect of adsorbed gas and surface charging is investigated, which reveals a long ignored factor for determining the flashover voltage. Depending on the relative amount of adsorbed gas, the flashover voltage varies, which exhibit different behavior from the bulk breakdown of the same gas. The amount of N₂ gas adsorbed on epoxy resin (EP) surface is much larger than that on Al₂O₃ ceramic surface, corresponding to the observed higher flashover voltage on EP. It is proposed that the adsorbed gas molecules not only modify the local surface charging state via their interaction with the trapped charges, but also capture free electrons due to the distortion of their electronic distribution. Both effects suppress the free path length of electrons in the gas-solid interface. This work explores another possibility to improve the surface flashover performance.

To date, breakdown voltage is an underlying risk to the epoxy-based electrical high voltage (HV) equipment. To improve the breakdown strength of epoxy resin and to explore the formation of charge traps, in this study, two types of polyhedral oligomeric silsesquioxane (POSS) fillers are doped into epoxy resin. The breakdown voltage test is performed to investigate the breakdown strength of neat epoxy and epoxy/POSS composites. Electron traps that play an important role in breakdown strength are characterized by thermally stimulated depolarized current (TSDC) measurement. A quantum chemical calculation tool identifies the source of traps. It is found that adding octa-glycidyl POSS (OG-POSS) to epoxy enhances the breakdown strength than that of neat epoxy and epoxycyclohexyl POSS (ECH-POSS) incorporated epoxy. Moreover, side groups of OG-POSS possess higher electron affinity (E_A) and large electronegativity that introduces deep-level traps into epoxy resin and restrain the electron transport. In this work, the origin of traps has been investigated by the simulation method. It is revealed that the functional properties of POSS side group can tailor an extensive network of deep traps in the interfacial region with epoxy and enhance the breakdown strength of the epoxy/POSS nanocomposite.