Dielectric properties of 500 m long HTS power cable

The 500-m high temperature superconducting (HTS) cable has been constructed in the Yokosuka area, CRIEPI, by CRIEPI, The Furukawa Electric Co. and Super-GM. Its design voltage is 77 kV and the thickness of the electrical insulation layer should be 8 mm made of semi-synthetic paper (polypropylene laminated paper). During cooling, the capacitance and dielectric loss tangent were measured periodically. After cooling, which means that the HTS cable was fully filled with liquid nitrogen (LN₂), the initial voltage withstand test was carried out. This paper describes the design method of the electrical insulation layer including determination of the testing voltage and the result of the initial voltage withstand test, and the permittivity calculated from the capacitance, and dielectric loss tangent.