The effect of high-voltage lightning impulses on the core properties of transformers

Results of a preliminary investigation into transformer discharge measurements and core losses under high-voltage impulse conditions are presented. Attention is given to the voltage distribution through the transformer winding for high-voltage impulses, the effects of partial discharges, and the variation in core temperature. It is found that at certain positions in the winding the surge voltage can exceed the initial peak value, which in turn leads to an increase in partial discharge activity at the same monitoring position. It is concluded that there is a possible relationship between voltage distribution, partial discharges, and core losses during surge conditions