Improving flashover strength by constructing microporous structure

Gas-solid composite insulation systems are extensively utilized in high-voltage power equipment. However, the surface flashover will preferentially occur over the interface in composite insulation systems, which seriously threaten the safety operation of high-voltage power equipment. Generally, the surface morphology is considered an important factor influencing the flashover voltages. Inspired by this underlying effect, in this paper, a 3D porous structure with interconnected pores was introduced to enhance the flashover strength. In this paper, microporous materials were prepared by the templating method, in which the sugar granules were used as the porogen. And samples with porosity of $60-75 \%$ and pore size of $95-480 \mathrm{~mm}$ were acquired by controlling the concentration and type of porogen. After that, the influence of porosity and pore size on the flashover strength under different voltage conditions is investigated. The flashover voltages were measured by applying linearly rising voltage across the finger-shaped electrodes. The results show that the porous materials significantly improve both DC and AC flashover voltages. And the flashover voltage increases with porosity, with a maximum increment over $44.9 \%$ and $47.5 \%$ for DC and AC flashover voltages, respectively. At the same time, the small pore size has higher flashover strength. Then, porous structures have been used to investigate how they affect flashover performances by analyzing optical photographs of the surface flashover channel, surface potential decay curve and trap distribution. Experiments demonstrated that surface streamer is attracted into the pore channels in the material and the development process is hindered by the pore wall, which eventually improve flashover strength.