Electrical properties of commercial sheet insulation materials for cryogenic applications

Dielectric properties of electrical insulation materials are needed for low temperature power applications. Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. In this work we report the dielectric properties of some commercially available materials in sheet form. The selected materials are polypropylene laminated paper from Sumitomo Electric Inc., porous polyethylene (Tyvektrade) from Dupont and polyamide paper (Nomextrade) from Dupont. The dielectric properties are characterized with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 50 K to 300 K. The dielectric breakdown characteristics of the materials are measured in a liquid nitrogen bath at atmospheric pressure.