Study On Electric Field Distribution Of Train Top Insulator In Sand Haze Environment And Corona Discharge Microscopic Characteristics

With the continuous development of high-speed railway technology in China,high-speed railway has gradually penetrated into the desert area in Northwest China.Therefore,the roof insulator of the train is faced with the impact of the harsh environment of sandstorm.Moreover,since the occurrence of haze weather is not restricted by the region,the roof insulator will be affected by both the sand and haze weather.Mixed particles such as fog,haze,sand and dust in the air are suspended around the insulator on the roof,which will cause the electric field distortion of the insulator and even cause the insulator flashover.Therefore,the electric field distribution characteristics of roof composite insulators in the sand and haze environment are studied to provide theoretical support for the safe operation of roof insulators operating in the sand and haze environment.Local electric field distortion will cause corona discharge and damage insulator insulation performance,so the influence of environmental factors on the microscopic characteristics of the corona discharge of the insulator on the roof of the train is further explored to provide a theoretical basis for its treatment.Firstly,the distribution of sand and haze mixed particles around insulators in high-speed airflow is studied.The ANSYS simulation model of the roof insulator wind tunnel was built,and the distribution of sand and haze mixed polyphase particles around the insulator in high-speed airflow was simulated and analyzed,and the variation of suspended particle concentration under different wind speeds was studied.It was found that under the action of vortex and pressure gradient,suspended particles would gather in large numbers near the insulator,and the concentration of the suspended particles on the windward side was up to about 20 times that of other areas,while the concentration of suspended particles would decrease slightly with the increase of wind speed.Secondly,the distribution of electric field and potential of the roof insulator in the mixed sand and haze environment is studied.On the basis of the research on the distribution of suspended particles,the three-dimensional electrostatic field model of insulators on the roof,sand particles and haze particles was established by COMSOL software.And simulated and analyzed the electric field potential distribution of insulators on the roof in the sand and haze environment,and the effects of particle charge,charging polarity and particle clustering characteristics on the electric field of insulators were studied.The results show that after the sand and haze mixed particles are charged,the charged sand particles have a great influence on the surface electric field of the insulator on the roof.When the sand particle charge-mass ratio is±304μC/kg,the surface electric field distortion is the most serious,and the electric field distortion of the insulator at+158μC/kg and-104μC/kg is the least.When the sand haze particles are all negatively charged,the distortion of the electric field at the high voltage end is the most serious,while the distortion at the low voltage end is the largest when the sand haze particles are positively charged.The agglomeration of particles near the surface of the insulator skirt will cause more serious distortion of the surface electric field of the insulator skirt.Finally,the influence of the concentration of water molecules in the environment on the microcosmic characteristics of the corona discharge of the roof insulator is further studied.The variation law of electric field intensity,electron temperature,electron density and particle concentration in corona discharge under different water contents were analyzed by two-dimensional numerical simulation.The accuracy of the model was verified by the corona discharge data of insulators in nitrogen and oxygen environment.It was found that with the increase of H₂O concentration,the electron density and the concentration of N₂ and O₂ related positive ions would slightly decrease,while the electric field intensity and electron temperature in the anode area would increase,while the other areas had no obvious change.The concentration of OH^-and·OH in umbrella skirt and hardware of insulator are significantly higher,accelerated the oxidation and corrosion of insulator.And its concentration fluctuated slightly with the concentration of H₂O.