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

Abstract

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-rayinduced 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.

Critical study of partial discharge inception in voids: statistical behavior to stochastic nature

“…The ion drift-diffusion simulation model based on the fluid equation has also been introduced to estimate void PDIE by previous scholars [6,13,14]; their simulation results were in close accordance with theoretical predictions, which suggests that these methods can be used to estimate void PDIE. The PDIE obtained via model experiment under the same void parameters, however, deviates significantly from the results obtained by the above two methods; the measured value may be several times higher than the theoretical value [15]. There are also significant differences in test results among various researchers, even under the same conditions.…”

“…shown that increasing background radiation can significantly raise the probability of PD within the voids [15,30,36]. Figure 10 shows the PDIV of voids with and without x-ray irradiation, where x-ray irradiation did significantly reduce PDIV and its dispersion.…”

“…When the copper plate was removed, the introduction of x-rays gave the PDIV of each test a fixed value of 3.5 kV rms ; that is, the dispersion of PIDV completely disappeared and PDIV th was between 3 and 3.5 kV rms . Physical processes associated with background radiation play a critical role in PD inception in the void, which is generally attributed to the fact that radiation intensifies the bulk ionization process and increases the number of free electrons [15,30].…”