Study On The Motion Law Of Water Droplets On The Surface Of Insulators And The Mechanism Of Flashover

With the development and construction of China's smart grid system and the increasing requirements for the safety and reliability of power transmission and transformation,higher requirements are placed on the insulation level of important equipment in power transmission and transformation lines.Silicone rubber composite insulators are widely used in power lines because of their excellent hydrophobicity and wet pollution resistance,which can effectively suppress the occurrence of pollution flashover accidents in power systems.However,under the influence of wet environment such as drizzle,fog and dew,water droplets are easy to adhere to the surface of insulator materials,resulting in the formation of dry and wet areas.Moreover,the water droplets on the insulator surface move and deform regularly under the action of electric field,which seriously distorts the electric field distribution and even causes flashover along the insulator surface.Therefore,it is of great significance to study the motion law of water droplets on the surface of insulators and its influence on flashover along the surface.Firstly,the force analysis of water droplets under static and electric fields is carried out,and the electrical and hydrodynamic problems involved in multiphysics coupling are analyzed separately.Then,the governing equations under different physical fields are derived and the coupling conditions under these two different physical fields are given.Different methods for describing the interface orientation of fluid motion are compared.The phase field method based on Cahn-Hilliard model is selected and the problem of free boundary is described by numerical values.Meanwhile,the multi-physics coupling simulation software COMSOL based on finite element method was used to simulate.The motion mode and shape of water droplets under different electric fields are studied,and the electric field distribution and variation law at different time in the motion process are analyzed.In this paper,a test platform of water droplet movement on insulator surface and a flashover test platform along insulator surface were built.Through the motion test of water droplets on the silicone rubber plate,the motion law of water droplets under different electric field forms was studied.The droplets are affected by the frequency of electric field in AC electric field,and their motion modes are more pluralistic.Under DC electric field,the droplets will undergo sudden deformation under a certain electric field intensity,and the motion mode is relatively simple.In this paper,the motion parameters of water droplets—the elongation rate L_n and the contact angle deformation factor?_n—are defined,and the law of water droplet movement under different factors is summarized.The flashover test results show that the flashover process of water droplets is different under different electric fields,there is no phenomenon of multiple arc extinguishing and reburning under DC electric field.Combined with the movement law of water droplets under different factors,the variation law of flashover voltage is analyzed and summarized,which lays a theoretical and experimental foundation for improving the operation reliability of power equipment with silicone rubber as external insulation.There are 82 pictures,5 tables and 77 references in this paper.