Effect of Residual Crosslinking By-Products on Thermal Stability of EHVDC Cable Insulation

The extra high-voltage direct current (EHVDC) cable has attracted tremendous attention owing to its high capacity and low loss for long-distance power transmission. Temperature stability has become one of the important issues for EHVDC cable system because of the thick insulation under stringent operational conditions. However, its relationship with cable manufacture and processing, for example, degassing, is still missing. In this article, we investigate the role of residual crosslinking by-product (e.g., cumyl alcohol) on thermal stability of EHVDC cable insulation by proposing a phase field model combined with finite element analysis. Results show that the long-time degassing process eliminates 20% cumyl alcohol from cable insulation, reducing its conductivity, which has negligible impact on the electric field distortion. Further thermal stability simulations suggest that the declined conductivity contributes to a decrease in leakage current and dielectric loss within cable insulation, thus effectively reducing the risk of thermal runaway. This work proposes an effective approach to quantitatively analyze the role of crosslinking by-products and provides a guideline for developing high-reliability EHVDC cable systems.