Development of kA-class gas-cooled HTS current lead for superconducting fault current limiter

A current lead with kA capacity and small AC loss is being developed for us e in superconducting current limiting devices cooled with liquid helium. A gas-cooled type current lead using Bi-based oxide superconducting bulk mate rials was examined to clarify the effects of the current lead geometry and the use of multiple current leads. This paper presents the results of exper iments and numerical simulations based on the finite element method taking consideration of non-uniform transport current distribution among multiple current leads connected in parallel. The simulations are performed to inves tigate the relationship between the geometry of current leads and the amoun t of heat flow into a cryostat. In the simulations, the AC loss caused by b oth mutual and self-induced magnetic fields of multiple current leads is ta ken into account. The influence of AC loss, the joule heat generated by the contact resistance at joints of NbTi/CuNi multi-strand cables and the HTS bars, and the return passage for gas on the operating characteristics of th e HTS current leads are evaluated.