Evolution of bubble in oil-paper insulation and its influence on partial discharge

Abstract

The synergic effects of bubble formation and partial discharge activity in oil-paper insulation are investigated. By controlled lab experiments and Finite Element Computation, the bubble emission rate under various level of partial discharge is studied. The intensification of electric field due to the presence of bubble in oil-paper insulation is calculated. Finally, the partial discharge activity caused by bubbles is tested. The results show that, contrary to our traditional negligence of small partial discharge activity in low field regions, a corona of 50 pC at the bottom of magnet core, for example, may generate enough bubbles to cause flashover at the top insulation layers.