Condensation Mechanism Of Droplets On The External Insulation Surface And Induced Surface Discharges In Coastal Power Grid

The doubtful cause flashover of composite insulators in contaminated wetting condition is a serious trouble of power system operation failure.The special environment of high humidity and high salinity in coastal areas poses a certain degree of threat to its transmission lines and external insulation of substations.Very few of studies on effect of contamination and wet conditions on discharge characteristics of insulator surface is carried out.Therefore,the research on the condensation mechanism and discharge characteristics of water droplets on the insulator surface can make the flashover mechanism understood and provide reference for prevention of contamination flashover of power transmission lines and reliable operation of power grid in coastal area.The dynamic behavior of a single droplet deformation and induced electric field distribution are analyzed by using simulation software COMSOL Multiphysics.Obtained results reveal that the droplet parameter(droplet volume and conductivity),the surface tension,the contact angle and the applied voltage affect the spreading coefficient of droplet and the maximum surface field.with the increase of droplet volume and conductivity and applied voltage,the spreading coefficient shows an increasing tendency.The spreading coefficient shows a decreasing tendency with increasing the contact angle and surface tension.With the increase of droplet volume,conductivity and surface tension,the maximum surface field shows an increasing tendency and the contact angle is opposed.Simultaneously,this paper experimentally studies the deformation and flashover characteristic of a single water droplet on the insulator surface.Obtained results reveal that the droplets generate periodic oscillations under the action of the alternating voltage and eventually extend in the direction of the electric field,the degree of deformation shows an increasing tendency with increasing droplet volume and conductivity.The droplet volume,conductivity and contact angle have a certain influence on flashover voltage on the insulator surface.With the increase of droplet volume(10 ?l~50 ?l)and conductivity(1 mS/cm~5 mS/cm),the flashover voltage shows a decreasing tendency and the contact angle is opposed.At last,this paper studies the character distribution of droplets condensation on the insulator surface with different soluble and insoluble salts and effect on the flashover voltage.During the process of experiment,the distribution of droplets is recorded using a high-speed camera by changing the contamination of soluble salts,experimental time,contamination components and the contamination level of insoluble salts.Obtained results reveal that the contamination of soluble salts,experimental time and the contamination level of insoluble salts have certain effects on the droplets condensation and the effect of contamination component on droplet condensation is not obvious,and the different droplet distributions cause different flashover voltages.