Fast transients and their effect on transformer insulation: simulation and measurements

An increasing number of unusual transformer failures caused by high frequency overvoltages was reported in medium voltage networks. An investigation was started to get a better understanding of these fast transient phenomena. Two major steps in this research project are described here. First, a numerical model is built to compute the occurring overvoltage phenomena. In the second part, the material behaviour at high-frequencies is investigated, in order to determine the allowable voltages across the internal transformer insulation