The Basic Dielectric Characteristics of Insulating Materials for HTS DC Cable System

One of the expected systems on the power transmission aspect of high capacity and lower loss is the high-temperature superconducting (HTS) dc cable system. In an HTS dc cable system, the components with insulation system mainly consist of a superconducting power cable, a cable joint, and termination bushing at cryogenic temperature. The superconducting power cable is composed of a former, a superconducting conductor, and polypropylene laminated paper (PPLP) as insulation material impregnated with liquid nitrogen (LN 2 ). The cable joint, which is used to connect cables in joint boxes, has a central copper conductor surrounded by an insulating spacer such as epoxy and PPLP. The cryogenic parts of termination bushings are immersed in LN 2 with glass-fiber reinforced plastic used as insulator. This paper reports basic dielectric characteristics of insulation materials for the HTS dc cable system mainly composed of power cable, cable joint, and termination bushing. These results are studied under dc and lightning impulse voltage.