| Hydrophobic coating has been widely used in external insulation of power systems.Operating experience shows that hydrophobic coating can increase the level of external insulation and reduce the risk of flashover.Super-hydrophobic coating is the coating with the most excellent hydrophobicity to date.Its excellent hydrophobicity and self-cleaning properties make it have broad application prospects in the field of anti-pollution flashover,anti-wet flashover,and anti-icing in external insulation of power systems.Comparing the wet flash characteristics of super-hydrophobic coating with RTV,which is the most widely used hydrophobic coating in power systems,is of great significance in guiding the selection and application of hydrophobic coating on external insulation surfaces of power systems.This paper studies the preparation method of super-hydrophobic coating,and systematically compares the physical and chemical characteristics,wet flash characteristics and movement behavior of water droplets on RTV coating and super-hydrophobic coating.The main contents of the paper are as follows:(1)A method for preparing a super-hydrophobic coating that is easy to operate and can be adapted to applications in the engineering field was proposed.Spray the topcoat with super-hydrophobic properties on the formed primer.After drying and molding,obtain a sample of super-hydrophobic material composed of a combination of super-hydrophobic topcoat,primer and substrate.The micromorphology,hydrophobic properties and self-cleaning properties of the prepared superhydrophobic surface were characterized.The results show that the surface of the prepared super-hydrophobic insulating coating has a micro-nano binary rough structure,and has excellent hydrophobicity and good self-cleaning properties.(2)The wet flash characteristics of superhydrophobic coatings and RTV coatings were compared and observed.The development process of wet lightning arc,wet flashover voltage,wet flashover leakage current,hydrophobic recovery of superhydrophobic surface and RTV surface were observed and analyzed.The results show that under different wetting levels,the super-hydrophobic coating’s wet flashover resistance is significantly higher than that of RTV coating and glass,and it has good hydrophobic recovery.A lot of water droplets on the superhydrophobic surface roll off during the flashover process,and the arc along the surface penetrates the poles along the "water droplet-dry zone" channel.The water droplets on the RTV surface coalesce and stretch to form a water belt.The final arc flashover occurs on the "water belt-dry belt" path.(3)The water droplets on the surface of superhydrophobic and RTV materials were analyzed,and the influence of the movement of those water droplets on the development of wet flashover was studied.The phenomenon that the droplet bounce behavior only exists on the superhydrophobic surface but not on the RTV surface was theoretically explained.The super-hydrophobic surface water droplets rolling-off and coalescence-induced jumping behavior under the action of an electric field makes the surface form a large dry area,which is the main reason for its higher wet flash voltage level and lower leakage current.Based on the energy analysis method,a theoretical model of droplet coalescence-induced jumping was established.By comparing and analyzing the energy conversion during coalescence-induced droplet jumping on RTV surface and superhydrophobic surface,the reason that droplet coalescence-induced jumping phenomenon only exists on superhydrophobic surface but not on RTV was found.It shows that compared to the superhydrophobic surface,the RTV surface has an increased viscous force effect during the droplet coalescence process,the surface tension-inertial force effect decreases,and the surface energy released during the droplet coalescence process is dissipated by the internal viscosity and cannot be converted into effective translational kinetic energy. |
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