Preventing Space-Charge-Induced Breakdown Using Electrets at Various Temperatures

In medium voltage direct current (MVDC) systems, charge carriers gradually inject into the bulk of a dielectric, leading to space charge accumulation. As more charge carriers inject and accumulate, the effective thickness of a dielectric decreases, reducing the breakdown voltage. This phenomenon intensifies at high temperatures. Our previous research has demonstrated the effectiveness of electrets in mitigating space charge accumulation and space-charge-induced breakdown in dielectric materials via electric field neutralization. However, the impacts of high temperatures have yet to be investigated. This study employs the electret-based electric field neutralization approach to prevent space-charge-induced breakdown at higher temperatures. We performed numerical analysis using bipolar charge transport models at various temperatures to estimate the effects of using electrets. Then, we performed experiments, including instantaneous and delayed breakdown measurements at three different temperatures: 25 °C, 50 °C, and 75 °C. The results of this study demonstrate that electrets effectively prevent charge carrier injection and space-charge-induced breakdown at elevated temperatures.