Insulation Characteristics of PPLP in GHe and Design of 10 kV Bipolar Coaxial HTS DC Cable

Electrical insulation is an essential component of high temperature superconducting (HTS) dc cable systems and polypropylene laminated paper (PPLP) and has been widely used as insulation material for cold dielectric (CD) HTS cables due to its excellent dielectric mechanical properties. In this paper, mini-model cables were fabricated to simulate CD-type HTS cables and the insulation tests were carried out. DC and the lightning impulse breakdown strength of the 1% Weibull distribution of PPLP at 0.3 MPa helium gas (GHe) were investigated. Based on these results, the insulation design of a 10-kV bipolar coaxial HTS dc cable was performed. Furthermore, a model cable was manufactured according to the insulation design and tested for dc and impulse withstand voltage, which verified that the insulation design was qualified.