Calculation of 3D electric field at the end insulation of transformer

With the increase of voltage level, the operating reliability of transformer has an important effect on the power system. According to statistics, the power transformer fault is mostly due to the insulation breakdown, especially at the end insulation. In order to improve the design quality, a parametric design method is developed in this paper. A real transformer model is created by Pro/E, then the model is imported to FEM software Ansoft Maxwell to calculate the 3D distribution of electric field and voltage at transformer end insulation. This process can be repeated easily until the breakdown criteria is met. Considering the effect of yoke on electric field distribution, two calculation zones that are under yoke area and out of yoke area are chosen. Results show that the maximum electric field of out yoke area is a little greater than that of under the yoke area. The results have some meaning to transformer design.