Comparative Study of Cryogenic Dielectric and Mechanical Properties of Insulation Materials for Helium Gas Cooled HTS Power Devices

A comparative study of cryogenic dielectric and mechanical characteristics of electrical insulation materials is described. Breakdown strengths and tensile strengths of Cryoflex, Kapton, PPLP, and Teflon were measured at 77 K in liquid nitrogen. Breakdown strengths of Cryoflex, Kapton, PPLP were also measured in gaseous helium at 2 MPa and 77 K. The relative breakdown strengths of Cryoflex and Kapton vary between liquid nitrogen and gaseous helium. Kapton performed better than Cryoflex both for dielectric and mechanical properties. Among the materials studied, Teflon exhibited the least breakdown strength and mechanical properties.