Experimental studies to determine the net dielectric constant of stacked PPLP layers with liquid nitrogen

Abstract

PolyPropylene Laminated Paper (PPLP) is one of the most widely used dielectric materials in cold dielectric based High Temperature Superconducting (HTS) power cables. The PPLP, which is wrapped around the current carrying conductor, has to withstand the rated voltage at cryogenic temperatures. This cold dielectric confines the electric field within itself resulting in electrical insulation of the cable from the cryostat The relative permittivity of PPLP immersed in subcooled Liquid Nitrogen (LN2) for various temperatures (64 to 77 K) and pressures (0 to 0.5 MPa) are of paramount importance and its study becomes crucial for superconducting devices as they operate at extreme conditions. This paper deals with the development of an experimental facility for investigating the dielectric constant of PPLP at cryogenic and ambient temperatures.