Preparation And Structure Optimization Of Anti-corona Material At The End Of Large Generator Stator Bar

When a large generator is running,the end of its stator bar is prone to corona discharge due to the concentrated electric field distribution.This discharge will damage the insulation of the generator bar and shorten its service life.Therefore,the development of anti-corona materials and anti-corona structures at the ends of the stator bar with excellent performance is of great significance to guarantee the safe operation of the generator.This article uses epoxy resin,methyl Nadic anhydride and absolute ethanol as the base material.Silicon carbide and graphite are doped materials to prepare antihalation paint with nonlinear resistivity characteristics.Use the prepared anti-corona paint and alkali-free glass ribbon to make the anti-corona tape used at the end of the generator stator bar,and use a high-power optical microscope to observe the distribution of particles and epoxy matrix in the anti-corona tape.The resistivity test system of the anti-corona belt is used to measure and calculate the resistivity and nonlinear coefficient of the finished anti-corona belt,and the influence of different factors on the resistivity and nonlinear coefficient of the anti-corona belt is studied.The test results show that with the increase of the added silicon carbide content,particle size and graphite content,the resistivity of the anticorona belt decreases and the nonlinear coefficient increases;with the increase of the test temperature,the resistivity of the anti-corona belt decreases.Smaller,the nonlinear coefficient increases.In order to study the electric field distribution at the end of the stator bar of the generator,this paper uses the COMSOL Multiphysics software to establish a threedimensional model of the end of the stator bar of the generator and simulates it according to the actual structure of the end of the stator bar.The distribution of potential,electric field and loss at the end of the stator bar of the motor under the three conditions of anti-corona structure,linear anti-corona structure and non-linear anti-corona structure.The simulation results show that the end of the motor bar is not equipped with an anti-corona structure,and the electric field distribution is highly concentrated at the end of the low resistance layer of the stator bar;the maximum field strength value at the end of the stator bar is significantly reduced after the anticorona structure is added,but due to The sudden change of the resistance value at the junction of each resistance layer causes the electric field to change greatly;when the non-linear anti-corona structure is adopted,the uniformity of the electric field distribution at the end of the stator bar is obviously improved.In order to further improve the electric field distribution at the end of the stator bar of the generator,the length of the anti-corona layer and the resistivity and nonlinear coefficient of the anti-corona layer are changed in this paper,and the anticorona layer at the end of the stator bar of the motor is optimized.After comprehensively considering parameters such as the highest potential at the end of the bar,the highest field strength and the highest loss,the best parameters of each section of the anti-corona layer were obtained through computer optimization.