Study of partial discharges in bubbles and microsphere in transformer oil

Abstract

Partial discharges in free bubbles floating in transformer oil and in a glass sphere are studied both experimentally and theoretically. Optical, electrical and optoelectronic registration was performed to obtain partial discharge pattern. The time duration of electrical and optoelectronic signals were practically the same and equaled to 50 ns. PDs in bubbles were rare events even at the electric field two times higher than required by Pashen’s law. In the case of rigid sphere the voltage of PD inception was practically the same as the value given by Pashen’s law. Simulations of PD gave the values of “true” and the “apparent” charges close to those measured at the experiments. Simultaneous PDs in bubble and closely situated sphere were not recorded.