Dielectric Characteristics of Laminated Paper and Polymer Sheets Used for Lapping Dielectric Structure at 77 K

Abstract

110 kV cold dielectric high temperature superconducting (HTS) cable has been developing in China. Generally, the lapped dielectric structure is adapted for cable body, so dielectric characteristics of dielectric sheets are very important. Polyimide, Polypropylene laminated paper (PPLP) and polyimide and poly tetra fluoro ethylene (PTFE) are widespread dielectric sheet materials for HTS equipments with lapped structure. In this paper, the lightning impulse dielectric strengths of three materials under tensile statuses are tested by a special electrode system. The experimental results are processed by method of Weibull plot. As a result, the impulse dielectric strengths of all three materials have good adaptive capacity for tensile stresses in liquid nitrogen. The impulse dielectric strengths of polyimide are highest of three materials under normal using stresses. The AC dielectric strengths of three materials are also concluded from previous papers. Combining experimental results, data in previous papers and design methods related, the multi-layered dielectric thickness and layers of PPLP used for 110 kV cold dielectric HTS cable body are designed.Index Terms-Cold dielectric high temperature superconducting (HTS) cable, dielectric design, impulse dielectric breakdown strength, lapped dielectric structure.

Mechanics of dielectric polyamide/SiO2 nanocomposite coatings for cryogenic service in superconductor systems

“…[8][9][10] Liquid nitrogen (LN 2 )-cooled HTS tapes and cable assemblies traditionally utilize lapped polymer tape dielectric layers of thermally stable materials such as Kapton™ polyimide or polypropylene laminated paper (PPLP). [11][12][13] The lapped tape construction effectively reduces the failure of brittle polymers at cryogenic temperatures by increasing their degrees of freedom inside a dielectric jacket. 3 However, these systems are then required to permit the permeation of the cryogenic coolant into the insulation jacket around superconductors, allowing them to become part of the dielectric media.…”

“…Liquid nitrogen (LN 2 )‐cooled HTS tapes and cable assemblies traditionally utilize lapped polymer tape dielectric layers of thermally stable materials such as Kapton™ polyimide or polypropylene laminated paper (PPLP) 11–13 . The lapped tape construction effectively reduces the failure of brittle polymers at cryogenic temperatures by increasing their degrees of freedom inside a dielectric jacket 3 .…”