Current Redistribution in a Superconducting Multi-Strand 35 kA DC Cable Demonstrator

Abstract

High temperature superconductors (HTS) are discussed as energy-efficient solutions for industrial high-current applications beyond 10 kA e.g. bus bar systems in industrial electrolysis plants. In this contribution, the experimental test of a 3.6-meterlong 35 kA DC demonstrator, made from twelve high-current HTS CrossConductor (HTS CroCo) strands in an liquid nitrogen bath at T = 77 K is presented. In this work, a common connector concept of the twelve HTS CroCo strands is proposed. Compared to earlier results without common connector, lead resistances were effectively reduced and current distribution among the individual strands was significantly facilitated. This is confirmed by the observation of increased critical cable current of 37.6 kA compared to 33 kA in previous work without low-resistive common connector. Additionally, the current range, in which all twelve strands reached their critical electric field, was found to be reduced from >7 kA to 2 kA. Results are discussed and assessed with the help of an electric circuit model, from which the solder resistances at the connections could be obtained by fitting.Particular focus was given to the investigation of current redistribution in the demonstrator. Therefore, a heater was installed on one HTS CroCo strand, and activated to raise the temperature on this strand and quench a single strand locally. It is observed that current is redistributed through the common connectors to the other strands.

200 kA DC Busbar Demonstrator DEMO 200 – Conceptual Design of Superconducting 20 kA Busbar Modules Made of HTS CroCo Strands

“…Contact resistances are a key element of DC busbars and cables and were investigated by both modelling and experimental approaches [37]- [40]. In previous works on a 35 kA HTS CroCobased multi-strand cable [41]- [44] of larger HTS CroCo strands made from 6-and 4-mm-wide tapes, contact resistances were both measured and modelled. In [44], a contact resistance variation (sum of both terminations) from 325 n to 548 n among 12 HTS CroCos was determined from a fit to the measured voltage-current-characteristics of a 35 kA demonstrator.…”