Flashover is prone to occur in composite insulation structures such as vacuum‐solid and gas‐solid, which are universally employed in high‐voltage power equipment. In this study, a high flashover strength and superhydrophobic coating were proposed by constructing porous surface morphology. Octadecyl trichlorosilane (OTS) particles were prepared by hydrolysis condensation reaction, and thereafter sprayed onto the substrate surface to form a porous and rough surface structure with hundreds of nanometres of dispersed pores and pits. The coating endowed epoxy resin with maximum 44% flashover voltage increase and the superhydrophobic surface with water contact angle of 158.4°. Since the pore size in OTS coating is close to electron mean free path in atmospheric condition, the collisional ionisation can be effectively hindered, which suppresses the micro‐discharge around the triple junction and improves the flashover strength. The present approach provides a new insight for simultaneously improving flashover strength and superhydrophobic properties of dielectric insulation.

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