Electrical errors inside the transformer may lead to an arc discharge with high energy peaks. These causes pressure shock waves which break the tank open and lead to oil leakage. In order to withstand this overpressure the stresses in the tank wall, especially in welds, must be lower than the tensile strength of steel. To reduce the complexity of dynamic behavior the standard SN 14.1h defines a corresponding static pressure which can be used in a FEM calculation to predict the stresses in the tank. In this paper we compare simulations of a transformer tank under static overpressure with different material models to find a fast solution for validate a design with respect to withstanding the overpressure caused by an arc discharge.

A 3D finite element model is developed to simulate the load noise in order to understand the acoustic and mechanical behavior of power transformers. As we can show, a 3D model is required to get a good correlation between the simulation and measurements, because some resonant modes are not axisymmetric and the phases influence each other. To reduce the complexity of the model we investigated different simplifications of the windings and their effect on the vibration results.