Calculation of transient electric field of converter transformer under polarity reversal voltage

A state space finite element method is presented for the calculation of transient electric field in oil-immersed insulation system of converter transformer. Firstly, the state equation is derived based on the quasi-static electric field theory, combined with the given boundary value using the penalty method, which has a clear physical meaning. Secondly, the state equation is solved in a fine integration method. The validation of method is verified by means of a model, in which the analytic solution of transient electric field can be gotten. At last, the transient electric field is calculated of a practical converter transformer under polarity reversal voltage.