High-Temperature Superconducting Cable Design Based on Individual Insulated Conductors

Peter Cheetham,Woojin Kim,Jose Viquez,Chul H Kim,Lukas Graber,Sastry V Pamidi

doi:10.1155/2018/3637873

Abstract

The idea of insulating individual high-temperature superconducting (HTS) tapes was explored as a dielectric design to reduce the risk and complexity of HTS cable manufacturing. Applying insulation on individual HTS tapes is amenable to continuous manufacturing processes and opens up material choices for the insulation. In this study, heat shrink insulation was selected as the material choice for exploring the possibility of this design philosophy because of its commercial availability in multiple thicknesses. A systematic set of selection criteria was developed for the selection of appropriate heat shrink for given HTS tape dimensions. The cryogenic dielectric characteristics of insulated HTS tapes were evaluated both in liquid nitrogen and gaseous helium environments at 77 K. Dielectric characteristics of tapes with a single layer of thicker insulation were compared with those insulated using multiple layers of thinner insulation to evaluate the relative merits of each method. Several model power cables were fabricated using the PET insulated tapes, and their dielectric behavior was evaluated at 77 K in gaseous helium environment. The results suggest that the explored method is useful for HTS power cables operating at low voltages (<1,000 V) primarily due to the limitation on achieving thick insulation with high quality using heat shrink tubing. The suitable processes of insulating longer lengths of samples with additional dielectric benefits are discussed.

Highlights

Two slightly different high-temperature superconducting (HTS) tapes were used to make two model cables
A comparison of these properties was performed for polytetra uoroethylene (PTFE), uorinated ethylene propylene (FEP), polyether ether ketone (PEEK), and polyethylene terephthalate (PET), with the results shown in Table 1. e data from Table 1 were obtained from commercial suppliers of heat shrink [13, 14]
To characterize the dielectric properties of the heat shrink-insulated HTS cables, AC breakdown and partial discharge (PD) measurements were conducted in a high purity gaseous helium (GHe) environment at 77 K. e model cables were installed within a pressure vessel. e cable was connected to a high voltage bushing installed on the top plate of the pressures vessel

Summary

Introduction

Two slightly different HTS tapes were used to make two model cables. There was excessive friction between the heat shrink and HTS tapes when applying the heat shrink on 1 m samples. Is complicated the process of applying heat shrink and increased the possibility of damaging the HTS tape or the heat shrink. It was decided to use the larger available inner diameter of the heat shrink tubing. Tape 1 used a 4.06 mm inner diameter heat shrink and Tape 2 used a 3.56 mm heat shrink. E shrink ratio for both combinations of HTS tape and heat shrink resulted in a shrink ratio of 25%. As the shrink ratio exceeded the recommended 15% shrink ratio, it was decided to verify the electrical properties of these heat shrinks before beginning fabrication of the model cables. AC and DC breakdown measurements were performed on both types of HTS tape as 4 mm shrink-insulated HTS tapes on the copper former was completed without any damage to the HTS tapes. is demonstrated that the bending properties of the 6x heat shrink are suitable for fabricating the cables

Methods

Results

Discussion

Conclusion