Predicting the DC pollution flashover voltage on the insulation surfaces with superhydrophobicity

Cleanliness and desiccative are necessary for outdoor insulation surfaces to maintain the voltage withstand capability especially in humid and polluted operation conditions. Once the voltage withstanding capability of insulation coatings is reduced by contaminant electrolyte, flashover accidents would be easier to happen, causing tremendous economy and energy losses. Superhydrophobic coatings, due to their self-cleaning property, are deemed to have great application potential in maintaining outdoor insulation performance, especially in humid and polluted environments. The water patterns on superhydrophobic coating in humid and polluted conditions are obviously different from those on traditional insulation coatings. Flashover voltage is one of the indices for quantifying insulation strength, while to date it is still unclear whether the commonly-used flashover voltage prediction models based on Obenaus's theory are still suitable to be applied in the cases with superhydrophobic surface. Here we proposed a facile and low-cost preparation method of superhydrophobic coating. By analyzing the specific surface condition under humid and polluted conditions, and considering the development of arc path, a novel theoretical model for predicting flashover voltage of superhydrophobic coatings is established from the perspective of electric field. The flashover voltage of the synthesized coating as well as Room Temperature Vulcanized (RTV) silicone rubber coating are tested and compared, for investigating the insulation strength on the synthesized superhydrophobic coating, and verifying the accuracy of the proposed prediction model. It is found the synthesized superhydrophobic coating shows self-cleaning property during the wetting and voltage applying process, the flashover voltage of superhydrophobic coating is higher than that of RTV coating, and is affected less obviously by the change in pollution degree, compared with RTV coating. The established model shows better accuracy in predicting the flashover voltage of superhydrophobic coating than the traditional one, with errors of less than 6%. Based on the proposed model, the flashover voltage of polluted superhydrophobic coating surface is positively and negatively related to the volume and the contact angle of the polluted electrolyte droplet, respectively.