Study On Pollution Accumulation And Flashover Characteristics Of Anti-tear Roof Silicone Rubber Composite Insulator Of High-speed Train

The high-speed air flow during high-speed train operation may cause the sheath tear of the soft silicone rubber composite insulator installed on the high-speed train roof.Partial insulator sheath tear will shorten the minimum creepage distance.Tearing at sheath the root will expose the mandrel,which is easy to cause moisture intrusion and induce discharge at the interface of the mandrel and the sheath.In serious cases,it will cause insulator flashover and interrupt the power supply of the train.In this thesis,a kind of hard silicone rubber composite insulator is optimized to solve the sheath tear problem.The main research contents and conclusions are as follows:Based on the crack size at the edge of the sheath obtained from the field investigation,long crack and short crack are manually preset,and the influence of the sheath crack on the pollution flashover performance of soft silicone rubber composite insulator is studied.The test results show that the two cracks have no significant effect on the flashover voltage of insulator and the location of the dry area when using continuous boosting test method.However,the arc develops more violently before flashover when the insulator has long sheath crack;The crack size has obvious influence on the development process of leakage current in the constant voltage withstand period,but has no obvious influence on the peak value of leakage current;arc burning marks appeared at the edge of the sheath crack after flashover tests.Based on the fluid-structure coupling method,the influence of sheath parameters on sheath stress and shape change level is analyzed by the means of Finite Element Method.The simulation results show that the structural parameters of the sheath,such as the sheath diameter,the sheath thickness and the the sheath angle are closely related to the shape degree of the insulator sheath;The stress of insulator without sheath skeleton is concentrated at the root of sheath,and the stress of insulator with sheath skeleton is concentrated near the edge of sheath skeleton,and the maximum stress value decreases obviously;Adding sheath ribs to the mandrel can effectively reduce the shape change level of the sheath.Based on the simulation results,a real hard silicone rubber composite insulator is designed and its wind tunnel deformation test is carried out.The test results show that the maximum sheath shape change of the hard silicone rubber composite insulator is less than 0.5mm under the wind speed of0-111m/s,and the insulator sheath is not torn after the test.An open wind speed adjustable wind tunnel with a maximum speed of 80m/s was built,and the maximum test time was set as 8 hours.The influence law of the pollution distribution characteristics of the sheath surface of the new hard silicone rubber insulator under two mass flow rates and two sand particle sizes was obtained.The test and simulation results show that the pollution distribution on the surface of insulator sheath is uneven,the pollution on the leeward area is serious,which is in an splayed distribution,and the pollution density near the two sides of the splayed area is significantly higher than that in other areas;The larger the mass flow rate and the longer the test time,the greater the pollution density on the leeward side becomes;When the air velocity and mass flow rate remain unchanged,the smaller the particle size of pollution particles,the higher the pollution density on the leeward side becomes.Based on the pollution distribution obtained from the pollution accumulation test,the uneven pollution flashover withstand characteristics of rigid silicone rubber composite insulators are obtained by using the solid coating and the constant voltage withstand method.The test results show that the greater the pollution density on the leeward side,the earlier the occurrence time of the leakage current signal characterizing the obvious discharge phenomenon,and the greater the peak value of the leakage current.The results of rain tolerance test show that when the conductivity is less than or equal to 3000μS/cm and the withstand voltage is 32 k V under heavy rain and rainstorm conditions,the new hard silicone rubber composite insulator did not flashover.The new hard silicone rubber composite insulator optimized in this paper can provide a reference for operators to solve the sheath tear problem of train roof insulator on in high-speed environment.