Numerical Simulation of Converter Transformer's Polarity Reversal Test

Considering the anisotropic and nonlinear conductivity of oil-immersed paper in converter transformer’s insulation,the FEM（finite element method） state equation was obtained by the penalty function method,and the equation was solved by Runge-Kutta method.The transient electric field was calculated of a practical converter transformer under polarity reversal test voltage,and the results showed the electric field of anisotropic nonlinear analysis was very different with that of isotropic linear analysis.Therefore,the anisotropic and nonlinear conductivity of oil-immersed paper should be taken into account for the accurate designing of insulation.