Simulation Analysis And Experimental Study On Anti-corona Characteristic Loss Of Large Generator Stator Coil

With the continuous improvement of the rated voltage level of generators,higher requirements for the insulation system of large generators are put forward.It is required that the volume of generators should be reduced as far as possible based on ensuring the excellent electrical and mechanical performances of generators.The electric field distribution at the end of the stator coil of the generator is extremely uneven,corona discharge easily occurs,the loss density at the end of the stator coil is increased,the main insulation of the generator is damaged,the service life of the stator bar is reduced,and the improvement of the capacity of the generator is limited.In this paper,the 3D model of generator stator coil end is established by using PTC Creo 3D modeling software.The simulation software COMSOL Multiphysics is used to simulate the loss of the anti-corona layer at the end of the generator stator coil.The influence of the structure,torsion angle,lap length and nonlinearity coefficient on the anti-corona loss of the stator coil end is systematically studied.The simulation results show that the maximum loss is larger and the average loss is smaller in the anti-corona layer with torsion angle than in the anti-corona layer without torsion angle,and the maximum loss appears at the narrow edge corner of the middle and low resistance lap.Under the same conditions,the maximum and average surface loss of the three-layer anti-corona structure are less than those of the two-layer anti-corona structure.When the torsion angle is 17.5 to 30 degrees,the maximum loss of the anti-corona layer decreases first and then increases with the increase of the torsion angle,the average loss of the anti-corona layer continuously decreases,and when the torsion angle is 22.5 degrees,the surface loss is minimum,and the anti-corona effect is ideal;The overlapping structure can avoid the bad resistance transition of two adjacent anti-corona layers,when the overlapping length is 25 mm,the maximum loss and average loss of the anti-corona layer are small,and the anti-corona process and the effect are the best;The effect of nonlinear coefficient on the loss of anti-corona layer mainly depends on the nonlinear coefficient of the first section of anti-corona layer,if the nonlinear coefficient is too small,anti-corona effect is not ideal,if the nonlinear coefficient is too large,high-resistance terminal easily flashover discharge,anti-corona layer loss increases,when the nonlinear coefficient is 1,anti-corona effect is the best.Based on the simulation analysis of the end loss of the generator stator coil,it is hoped that an ideal nonlinear anti-corona material can be found so that the non-linear coefficient of the anti-corona material satisfies the anti-corona condition and the end loss of the stator coil can be reduced.In this paper,silicon carbide/epoxy resin nonlinear anti-blooming paint and silicon carbide-organic montmorillonite/epoxy resin non-linear anti-blooming paint were prepared by melt blending method with pure epoxy resin and organic montmorillonite/epoxy resin as base paint and silicon carbide with the number of 400 mesh as filler.The effects of silicon carbide content and montmorillonite content on the anti-blooming parameters of silicon carbide nonlinear anti-blooming paint were studied experimentally.The results show that the resistivity of anti-corona paint decreases and the nonlinear coefficient increases with the increase of silicon carbide content.The increase of organic montmorillonite content can improve the non-linear coefficient of anti-blooming paint,and has little effect on the resistivity of anti-blooming paint.