Improving Electric Field Distribution in HTS DC Cable Terminals by Nonlinear Conductive Epoxy/ZnO Composites

Nonuniform electric field is a key issue for superconducting cable terminal. This paper tries to uniform the electric field distribution in HTS DC cable terminals by designing nonlinear conductive polymer composites, instead of insulation with a fixed conductivity. The field-dependent conductivities of epoxy/ZnO composites at temperature of -196 □ are fitted, and its effect on electric field distribution in HTS DC power cable terminals is investigated by finite element numerical simulation. The results show that the nonlinear conductive composites can smartly smooth the nonuniform electric field distribution. However, if the nonlinear coefficient is excessively large, the electric field at the polypropylene laminated paper (PPLP) will be excessively large, otherwise the electric field at junction between PPLP and epoxy will be excessively large. It is concluded that the epoxy/ZnO composites with an appropriate nonlinear conductivity can effectively uniform the electric field distribution and improve the reliability of HTS DC cable terminals.