Characteristics of partial discharge induced by continuous X-ray exposure of void defects in insulator

Partial discharge (PD) diagnosis is a part of a routine testing of solid insulating materials to detect void defects. However, the conventional diagnosis is prone to inception delays due to lack of initiatory electron production, especially inside small voids. In this study, we employed continuous irradiation of X-rays to induce and sustain discharge inside the voids. The PD characteristics of void samples under different exposure rates of X-rays were observed. Compared with the conventional diagnosis, this continuous X-ray-induced partial discharge diagnosis enhanced the detection efficiency by eliminating the inception delays and reducing the discharge inception voltage. We focused on the changes in PD characteristics due to varying X-ray exposure rates. As the exposure rates were increased, the number of PD signals per minute increased while the average pulse height of PD signals decreased. Continuous X-ray exposure at rates between 0.5 and 294 mR/s successfully eliminated the inception delays even when the voids were as small as 1.63 mm in diameter of equivalent spherical volume.