Dielectric breakdown triggered fragmentation in thermally tempered glass

Abstract This paper presents the first in-depth study of the dielectric failure behavior of thermally tempered glass, a critical component in power transmission lines. The research reveals that tempered glass exhibits enhanced dielectric breakdown strength (DBS) and reduced dispersion compared to annealed glass, which is directly attributed to surface compressive stress. The degree of DBS enhancement is positively correlated with the applied stress. However, due to the volume defect effect, the DBS of both glass types progressively decreases with increasing thickness. A significant finding is that increasing surface compressive stress leads to a substantial increase in the number of fragments upon breakdown. From an energy perspective, the tempering strain energy is identified as the primary reason for this high fragmentation, with its contribution far exceeding that of electrostatic energy as thickness increases. While annealed glass samples did not fracture, tempered samples consistently exhibited brittle fracture, with thicker samples undergoing a more catastrophic failure. Fracture surface analysis confirmed these findings, revealing more prominent Wallner lines and secondary cracks in thicker samples, which indicates a more energetic failure process consistent with higher stored elastic potential energy.