Space Charge Modulated Electrical Breakdown

TLDR

Electrical breakdown is a key phenomenon in electrical engineering, yet the reason why dc breakdown strength is typically twice that of ac remains unclear. The study investigates how space charge dynamics differ between dc and ac breakdown using a bipolar charge transport model. Using the bipolar model, the authors analyze charge accumulation under dc and ac stresses and estimate breakdown strength modulated by electric‑field distortion from space charge. They find that dc breakdown initiates in the bulk, while ac breakdown starts near the electrode interface, and that lower ac strength and its frequency‑dependent decline are due to space‑charge‑induced field distortion.

Abstract

Abstract Electrical breakdown is one of the most important physical phenomena in electrical and electronic engineering. Since the early 20 th century, many theories and models of electrical breakdown have been proposed, but the origin of one key issue, that the explanation for dc breakdown strength being twice or higher than ac breakdown strength in insulating materials, remains unclear. Here, by employing a bipolar charge transport model, we investigate the space charge dynamics in both dc and ac breakdown processes. We demonstrate the differences in charge accumulations under both dc and ac stresses and estimate the breakdown strength, which is modulated by the electric field distortion induced by space charge. It is concluded that dc breakdown initializes in the bulk whereas ac breakdown initializes in the vicinity of the sample-electrode interface. Compared with dc breakdown, the lower breakdown strength under ac stress and the decreasing breakdown strength with an increase in applied frequency, are both attributed to the electric field distortion induced by space charges located in the vicinity of the electrodes.