Dielectric insulation systems at cryogenic temperatures are one of the most critical technologies for the efficient and reliable development of devices based on High-Temperature Superconductors (HTSs), such as cables, transformers, superconducting fault current limiters (SFCL), rotating machines and superconducting magnetic energy storage (SMES). In addition to HTS devices, such studies are also important for accelerators, reactors and medical devices based on Low Temperature Superconductors (LTS). In both cases, the literature highlights the need to study in depth the behavior of dielectric materials and insulation systems at cryogenic temperatures. The Working Group (WG) D1.64 was launched in April 2016 within CIGRE precisely to study in depth the topic of dielectric insulation at low temperatures and Ricerca sul Sistema Energetico – RSE SpA is represented in the group of experts involved in the work.

The goal of the WG is to publish in 2020 a Technical Brochure, of which RSE coordinates Chapter 5 ‘Experience in design of insulation systems and devices’. This report is based on the results of the studies described in the Technical Brochure; however, unlike the CIGRE document, it focuses on the aspects that are of greatest interest to the applied superconducting activities conducted in RSE within the System Research projects. First of all HTS devices, leaving aside here the LTS applications; secondly, among all the HTS devices, most of the space is dedicated to SFCL cables and devices.

After an introduction that outlines the work of WG D1.64 and the structure of the Technical Brochure (Chapter 1), the second chapter is dedicated to the insulation of HTS tapes; Chapter 3 instead takes into consideration HTS cables, both in AC and DC; Chapter 4 presents the peculiarities related to dielectric insulation in SFCL devices; Chapter 5, finally, reports some of the applications of greatest interest in the world and the criteria with which the dielectric criticalities have been resolved. The aim of this work is to constitute a starting point for the development of a research on dielectric insulation in cryogenic environments within RSE, which will be enriched in the future with autonomous theoretical and experimental experiences, starting from the ideas arising from the work within WG D1.64.