Preparation And Nonlinear Study Of KH560-GNs/EP Anti Corona Paint

With the rapid development of the power industry,the demand for generators has become increasingly stringent.The concentrated electric field at the outlet of the generator stator bar is prone to produce corona phenomenon,which poses a major threat to the safety of large motors and the stability of power systems.To mitigate the impact of corona phenomenon,this thesis successfully developed a highly efficient nonlinear anti-corona coating that can be applied to high voltage generator stator bars.This is of significant importance in ensuring equipment safety and enhancing the reliability of the power system.In this thesis,the anti-corona paint was prepared by using epoxy resin(EP)as matrix,N-N dimethylformamide as solvent,dicyandiamide as curing agent,graphite nanosheets(GNs)and silane coupling agent modified graphite nanosheets(KH560-GNs)as doping fillers.The structure and properties of the anti-corona paint were characterized and tested.The results of the study are as follows: Fourier transform infrared spectroscopy(FT-IR)showed that the powder had a new characteristic peak,indicating that the silane coupling agent KH560 was successfully lapped with the GNs powder,and the KH560-GNs powder was successfully prepared.After comparing the dielectric and breakdown properties of two anti-corona coatings,it was observed that the addition of silane coupling agent improved the compatibility between the powder and the matrix,resulting in enhanced dielectric and insulation properties of the composites.The conductivity characteristic curve of GNs/EP anti-corona paint indicates a positive correlation between conductivity and the doping amount of GNs.Furthermore,as the amount of GNs doping increases,the threshold field strength of GNs/EP anti-corona paint decreases.The lg J-lg E curves of GNs/EP anti-corona paint at different temperatures demonstrate a clear nonlinear trend in the anti-scorching paint,with a first nonlinear coefficient of 1,which corresponds to the ohmic zone.The second nonlinear coefficient,which is greater than 2,is dominated by the space charge limited current theory(SCLC)and is caused by the tunneling effect.The conductivity characteristic curve of KH560-GNs/EP anti-corona paint indicates that the silane coupling agent KH560 improves its dispersibility,and the conductivity of the modified anti-corona paint has been reduced to some extent.The conductivity of KH560-GNs/EP anti-corona paint is positively related to the amount of GNs powder used.The lg J-lg E curves of KH560-GNs/EP anti-corona paint at different temperatures show that conductivity and electric field intensity have a nonlinear relationship,and the first nonlinear coefficient is approximately 1,indicating the ohmic zone.The second nonlinear coefficient is greater than 2,and it is influenced by space charge limited current(SCLC)and tunnel effect.To investigate the improvement of electric field concentration on the surface of the stator bar by the nonlinear anti-corona material,COMSOL Multiphysics software is utilized to simulate a three-dimensional model of the stator bar outlet.The outlet of the stator bar with different anti-corona structures are simulated and analyzed.The potential distribution,electric field intensity and surface loss of stator bars without anti-corona paint,linear anti-corona paint and non-linear anti-corona paint were systematically analyzed.The results indicate that while the linear anti-corona paint can reduce the maximum field strength of the stator bar to a certain extent and help achieve a more uniform electric field,its effect is not particularly significant.Moreover,the potential of the stator bar at the end of the low-resistance layer experiences a sudden increase and has a large potential increase slope,which makes it susceptible to corona discharge.Due to the strong threshold field,Si C/EP nonlinear anti-corona paint failed to play an anti-corona role on the stator bar.The KH560-GNs/EP non-linear anticorona paint prepared in this thesis can make the electric field on the surface of the stator bar evenly distributed,the maximum field strength decreases to 3k V/mm,and the slope of the potential increase on the surface of the stator bar decreases significantly.It is proved that the KH560-GNs/EP anti-corona paint has a good effect on the electric field of the stator bar,which can further ensure the stable operation of the stator bar of the high-voltage motor.