Electrical and Mechanical Characteristics of Insulating Materials for HTS DC Cable and Cable Joint

A high-temperature superconducting (HTS) dc cable system consists of cable, termination, and cable joint. Polypropylene laminated paper (PPLP) and epoxy have been widely used as insulating material for HTS cable and cable joint. The electrical and mechanical characteristics of insulating materials at cryogenic temperature must be investigated for the long life, stable operation, and compactness of the cable. In order to develop an HTS dc cable and cable joint, it is important to understand the fundamental properties of insulating materials. In this paper, we discuss mainly about the electrical and mechanical characteristics of insulating materials for HTS dc cable and cable joint. We investigate the characteristics of dc and impulse voltage. The flashover and breakdown characteristics of PPLP, epoxy, and composite of epoxy-PPLP are studied. In addition, the mechanical characteristic such as tensile strength of PPLP at 77 and 300 K is discussed.