Insulation Failure Analysis on Power Transformer by Finite Element Method Simulations

Different types of dielectric failure in the insulation system of high voltage power transformers are analyzed using finite element method (FEM) simulations; cases of failure during lightning impulse, switching impulse, applied potential, and induced potential tests are examined. The analysis aims to understand the failure mechanisms involved in each case, comparing the calculation criteria typically used by designers with the defined safety margins used during the design review process, considering aspects like the drying process and manufacturing tolerances. The finite element method is used to calculate electric field distribution to define the expected design safety margins. For safety margin calculations, some known criteria are compared with Weidmann reference curves, manufacturing design rules, and oil volume stress theory. FEM is a numerical technique that enables engineers to analyze complex structures and simulate the behavior of dielectric materials and allows for a detailed and accurate assessment of the electrical performance of insulation structures. This study is intended to help understand the design criteria used in the insulation design review process. Physical analysis of dielectric failures and the application of advanced calculation tools are fundamental to generating criteria to increase the efficiency of design reviews and thus provide greater reliability to electrical equipment.