Crosslinking-modulated direct-current conductivity of XLPE-PS composite via charge trap characteristics

Low direct-current (DC) conductivity is one of the most desired characteristics for crosslinked polyethylene (XLPE) as a high-voltage DC cable insulation material. In this Letter, a correlation between the DC conductivity and cross-linking characteristics of XLPE-polystyrene (PS) composites at 50 °C was studied. Experimental results show that by adjusting the cross-linking structure, different trap distribution characteristics for XLPE-PS composites were realized. With the increase in the cross-linking agent content, DC conductivities of XLPE-PS composites tend to decrease, and the introduced average trap depth increases correspondingly. An increase of 0.07 eV for average charge trap depth in XLPE-PS composites could be acquired in the test range. It is considered that the increase in the average trap depth reduces the carrier mobility, contributing to the reduction of DC conductivity for XLPE-PS composites. Thus, the DC conductivity and average trap depth of XLPE composites show a strong relevance. The results suggest that the interaction between PS particles and the matrix introduced by cross-linking plays a dominant role in determining the charge conduction for XLPE-PS composites.