Design improvements on graded insulation of power transformers using transient electric field analysis and visualization technique

This paper deals with design improvements on graded insulation of power tra nsformers using transient electric field analysis and a visualization techn ique. The calculation method for transient electric field analysis inside a power transformer impressed with impulse voltage is presented: Initially, the concentrated electric network for the power transformer is constructed by dividing transformer windings into several blocks and by computing the e lectric circuit parameters. Next, the transient electric field analysis is performed. Using the results of the circuit analysis as boundary conditions , a 2D axisymmetrical electric field finite element analysis is performed. Finally, an animated display technique for the transient voltage, the elect ric field intensity and the tolerance rate of electric field intensity dist ributions is proposed as an extremely useful tool for design on graded insu lation. A successful application of the proposed method for analysis of a m odel transformer for which the computed results agree very well with measur ed results is also presented.