| The surface pollution of insulators in HV transmission lines will seriously affect the insulation performance of insulators,lead to the occurrence of pollution flashover accidents,and bring a significant impact on the safety and stability of the power system.At present,because of RTV coating’s good economy and ideal application outcome,applying RTV coating has become the main measure to improve the anti-pollution flashover performance of insulators.However,the operation experience indicated that there are some problems in the application of RTV coating,such as decreased hydrophobicity,deterioration of coating aging and surface adhesion during the operation.Compared with RTV coating,the superhydrophobic coating has better hydrophobic performance and unique self-cleaning property,that is,water will remove pollution particles when rolling on the surface of the superhydrophobic coating,which is of great significance for reducing surface contamination and improving anti-pollution flashover performance.Therefore,it has a broad application prospect in electrical equipment such as insulators.However,research on droplet rolling and self-cleaning properties of superhydrophobic coatings in electric field is very scarce.In this paper,the hydrophobicity,hydrophobic material transfer characteristics and insulation performance of hierarchical structured superhydrophobic insulation coating were tested.A droplet electroinduced motion observation experiment platform was built to measure the initial motion field intensities of droplet with different polarity in AC and DC electric fields when the coating was placed horizontally,and the rolling Angle under different electric field intensities.The electroinduced self-cleaning phenomenon of droplet was observed.Then,based on the theory of interface physical mechanics and current mechanics,combined with the simulation results of electrostatic field in COMSOL,the rolling reasons,critical rolling conditions and motion characteristics of droplets on the surface of hierarchical structured superhydrophobic insulation coating in uniform and non-uniform electric fields are studied and discussed,and the self-cleaning phenomenon in the process of electromotion is explained theoretically.Since the expression between rolling Angle and droplet volume has static contact Angle,the relationship between static contact Angle and droplet volume is analyzed theoretically and experimentally at the end of this paper.It is found that the electroinduced motion of the droplet has the following characteristics:the polarity of the droplet in the electric field is not unique,nor is it fixed.The droplet may have positive or negative charge,and the polarity may change during the movement.The initial motion field strength of the positive droplet is lower than that of the negative droplet,and the charge accumulation rate of the positive droplet is faster.The "driving" phenomenon of moving droplets to stationary droplets;Droplet electrokinetic droplet also has self-cleaning ability.With the increase of electric field intensity,the corresponding rolling Angle of electric field decreases gradually.At the same time,the larger the field intensity is,the greater the influence of the field intensity on the rolling Angle is.By Maxwell stress tensor method of COMSOL droplet contour field obtained by simulation calculation,found that electrically induced droplet in the movement for the following reasons: the droplets significantly larger at the bottom of the force,and on the left side of the force at the bottom of the left coating tends to make the droplets,force tends to make the droplets on the right side of the droplets on the coating surface,at the same time super hydrophobic coating and the adhesion force between the droplets is very small,so the droplet in the electric field will be driven rolling.The self-cleaning phenomenon of the superhydrophobic coating was calculated theoretically in the process of electromotion,and the theoretical analysis showed that the surface of the superhydrophobic coating had self-cleaning phenomenon,but the RTV coating did not,because the interface force between the superhydrophobic coating and the pollution was larger and the van der Waals force between the pollution and the coating was smaller.Then,through theoretical calculation,it was obtained that the maximum radius of pollution particles that droplets could carry on the coating surface was about 2.252 mm,and the maximum pollution concentration that droplets could carry was about 13.3%.Current strength analysis was carried out on the electrically induced movement process,found that the droplets from static state,it will get an acceleration that cannot be ignored,on the basis of electrically induced motion critical conditions of the droplets is analyzed,namely the roll Angle and electric field intensity and the theoretical relation between droplet volume,the theoretical value and experimental value in accordance with is better.At the same time,the calculation method of droplet motion in uniform electric field and insulator surface is given,and the expressions of the maximum velocity and maximum acceleration of droplet motion in electric field are given.Finally,this paper using the method of scale separation from the macroscopic scale,microscale and nanoscale micron grade scale from three aspects,build the static contact Angle calculation method considering the influences of droplet volume,experiment and theoretical analysis,found that if the wetting state of droplets in the Cassie state,regardless of the droplets,the volume change caused by the change of the static contact Angle can be ignored.At the same time,the static contact Angle formula of micro-nano superhydrophobic coating neglecting droplet volume is given. |
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