Surface flashover properties of epoxy based nanocomposites containing functionalized nano-TiO₂

Surface flashover properties should meet stringent requirements for the use in electrical equipment under high voltage DC environments. With the aim of enhancing surface flashover properties and understanding the mechanisms involved at ambient conditions, epoxy nanocomposites with different weight proportions of nano-TiO₂ were prepared. A silane coupling agent was selected to functionalize the TiO₂, the effect of which on nanoparticles dispersion and distribution was perused through scanning electron microscopy and infrared spectroscopy. DC surface flashover measurements in five normally used ambient conditions (N₂, air, CO₂, SF₆ and vacuum) were conducted and results were analyzed relating to loading content, gas parameters, surface trap parameters as well as electrical conductivity of nanocomposites. Outcomes indicate that with low content of nanoparticles, the density of deep traps was increased, showing a positive effect on inhibiting surface flashover. When the nanoparticle content is higher than 1 wt%, the overlapped transitional region reduced the energy level of traps, resulting in a poor display of surface flashover voltages. It was found that the nanoparticle content had a greater influence on surface flashover in vacuum. Electron negativity, ionization coefficient and mean free path of gases were taken into account to explain why surface flashover in SF₆ appeared to be the highest, whereas in N₂, it was the lowest. At last, effects of gas-solid interactions on surface flashover combining surface-trap characteristics, secondary electron-emission contributions and gas molecule impact-ionization characteristics were analyzed.