Thermal stability of quasi-isotropic strands with different cross-sections and with/without metal sheaths

Abstract

This paper mainly focuses on the thermal stability performance, such as minimum quench energy (MQE) and normal zone propagation velocity (NZPV), of a quasi-isotropic strand (Q-IS) with three different configurations made from 2G high-temperature superconducting (HTS) tapes in the adiabatic approximation. Due to the anisotropic performance of thermal conductivity in 2G HTS tapes, the tensor form of the heat conduction equation was used instead of conventional isotropic forms. We first measured the MQE and NZPV of three strands in the adiabatic approximation. Subsequently, the experimental results were verified by finite element analysis and compared with the values of MQE and NZPV in a liquid nitrogen (LN2) bath. Finally, the effect of a metal sheath on the current distribution and generation of Joule heat during the quench process were analyzed through simulation. The results show that the arc-shaped aluminum filler brings slightly higher thermal stability of Q-IS while the copper sheath largely improves stability. Moreover, compared with the thermal stability of the strand fully exposed to the LN2 bath, for the strand in the adiabatic approximation, the MQE decreases a lot while the maximum of NZPV is increased by 2–3 times.