The Excitation Effect of X-Ray on Partial Discharge of Bush-Type Electrical Tree in Epoxy Resin

The partial discharge (PD) signals of bush-type electrical tree defects in epoxy resin are weak, intermittent, and challenging to detect, posing serious threats to insulation performance of power equipment. In response, a PD test method is suggested with X-ray irradiation. To verify its effectiveness, the discharge characteristics of bush-type electrical tree samples at different degradation stages were systematically measured under X-ray irradiation. Experimental results demonstrate that X-ray irradiation exhibits an excitation effect on electrical tree PD at all stages except the first stage (S1). Specifically, during the second stage (S2), X-ray irradiation amplified the maximum discharge magnitude (Q<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sup>) by 17.17 times, and the maximum pulse repetition rate (PRR<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub>) by 2.6 times. For the third stage (S3), X-ray irradiation increases the Q<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> by 4.1 times and the PRR<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> by 2.5 times. For the stage 4.1 (S4.1), X-ray irradiation increased the Q<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> by 3.1 times, and PRR<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> was greatly increased. For the stage 4.2 (S4.2), X-ray irradiation can excite the stopped discharge. X-ray provides initial electrons for PD by ionizing gas in electrical trees to maintain the streamer propagation and reduce the statistical delay of PD. This research can provide a new method for PD detection of epoxy resin electrical tree defects.