Features of Partial Discharges in Bubbles Irradiated With X-Rays

The effect of X-ray radiation on the possibility and probability of partial discharges (PDs) origin in free-floating helium bubbles in transformer oil under the action of alternating voltage has been experimentally and analytically studied. The interelectrode region, where single helium bubbles floated, was exposed to X-ray pulses. In the absence of absorbing lead screens, radiation initiates PD in all bubbles in which the conditions for PD inception according to Paschen’s law are met. The number of PDs was significantly reduced in the presence of screens with a thickness of 2–5 mm. The dependences of the probability of PD occurrence at various voltages and screen thicknesses were determined and analyzed. It is shown that the initiating electron appears predominantly as a result of the ionization of liquid atoms located near the surface layer of the bubble.