Study On Contamination And Electric Field Characteristics Of Cantilever Composite Insulator In High Pollution Environment

Catenary cantilever insulator is an important parts to keep electrical insulation between electrified body and grounding body in electrified railway traction network.Its performance directly affects the safe and reliable operation of traction power supply system.Contamination characteristics and electric field characteristics,which are two important indexes to measure the performance of insulators,can be used to predict the contamination degree of insulators and judge their insulation state under different meteorological conditions.In order to solve the pollution flashover problem of catenary insulators under high pollution environment,this thesis takes the catenary cantilever composite insulator in the Salt-lake wind area of Lanzhou-Xinjiang Railway as the research object.The research is carried out from five aspects:electric field distribution characteristics of clean insulators,natural contamination characteristics on the surface of operating insulators in the target area,contamination distribution characteristics of insulators,electric field distribution characteristics of contaminated insulators and design of new type insulators.The main work and achievements are as follows:Firstly,the equal scale geometric model of cantilever insulator is constructed,and the electric field calculation mathematical model of clean insulator is established based on the electric quasi-static field theory.According to the electric field control equation,the potential and electric field distribution characteristics of insulators with different shed structures in clean state are analyzed by finite element method.The results show that the sheds structure has no obvious influence on the potential and electric field distribution along the insulator surface when the sheds spacing,sheds angle and sheds number are the same.The distribution of potential and electric field on the surface of a single shed has a circular symmetry,and the potential and electric field strength gradually decrease from the root to the edge of the shed.Secondly,natural contamination samples on the surface of cantilever composite insulator in the Salt-lake wind area of Dabancheng-Urumqi section of Lanzhou-Xinjiang Railway were collected,and the micro morphology and element composition of contamination were analyzed by SEM and EDS.The main anions and cations in the contaminated soluble salt were analyzed by inductively coupled plasma mass spectrometry(ICP-MS)and ion chromatography(IC).The main components of insoluble pollutants were analyzed by X-ray diffractometer.With the help of laser particle size analyzer,the particle size distribution characteristics of cantilever insulator under two special arrangements of horizontal and oblique are analyzed for the first time.Analysis shows that most of the pollution particles are irregular in shape,only a small amount of pollution particles are spherical.The main component of soluble pollution is divalent salt Ca SO₄.The main component of the crystal in the insoluble substance is Si O₂.Under the horizontal installation mode,the particle size is concentrated in 8?32?m.Under the oblique installation mode,the particle size is concentrated in 8?25?m.Thirdly,Eulerian-Lagrangian method is used to describe the pollution accumulation process of insulator,and the particle trajectory mathematical model of single phase coupling of electric field,flow field and particle tracking field is established.Based on the characteristics of pollutants in the Salt-lake wind area,a numerical simulation model of wind tunnel contamination of cantilever composite insulator is built on the COMSOL Multiphysics software platform.The influence of wind speed,wind direction and particle size on the contamination characteristics of insulator is analyzed under horizontal and oblique mode.The collision coefficient is used to characterize the maximum contamination degree of insulators.The larger the particle size or the wind speed or the airflow angle[0°,±30°],the more obvious the influence of the layout on the collision coefficient is.Fourthly,there are two kinds of contamination states:separated water droplets and wet contamination layer.The effects of static contact angle,position and spacing of water droplets on the potential and electric field distribution of insulators are analyzed.A new electric field calculation method is proposed for insulators with uniform wet pollution layer.The influence of the thickness and conductivity of the pollution layer on the electric field distribution is analyzed.By comparing and analyzing the electric field characteristics of insulators under clean,separated water droplets and with wet pollution layer,the evolution law of electric field characteristics of insulator surface is revealed.Finally,a new type of insulator structure is designed from the point of view of constant height of insulator structure,maximum effective creepage distance of insulator and minimum average electric field strength between sheds.By combining numerical simulation with natural contamination test,the anti-pollution effectiveness of the new sheds structure insulator is analyzed.The results show that:the new sheds structure insulator can effectively improve the pollution accumulation capacity of the insulator under different wind directions.As an active anti-pollution measure,it can reduce the pollution flashover accident rate from the source and improve the reliability of traction power supply system.