Electric Field Assist on Enhancing the Electrical Breakdown Strength of Cross-Linked Polyethylene for Power Cable Insulation

The electrical breakdown strength of cross-linked polyethylene (XLPE) used for high-voltage power cables is closely related to its morphology. The electric field assist is widely used to regulate the morphology, but its effect on the breakdown strength is still unknown. In this paper, XLPE was prepared under different assisted electric fields, and its direct current (DC) breakdown strength and conductivity were measured, respectively. With the increase in the assisted electric field, the breakdown strength increases first and then decreases, whereas the conductivity is just the opposite. To reveal the mechanism of the electric field assist, the morphology was characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). It is proven that an appropriately assisted electric field (e.g., 0.3 kV/mm) contributes to the larger amount of smaller spherulites and the larger crystallinity, which introduces more traps to enhance the breakdown strength. This work provides a new way for the development of insulating materials with high breakdown strength.