Influence of current re-distribution and thermal diffusion among strands on stability of superconducting cables against local disturbances

Quench of multi-strand superconducting cables is often initiated by a local disturbance that produces a normal zone in one or a few strands in the cable. Once the normal zone is produced, current re-distribution occurs as the current bypasses the normal zone via contact conductance between the strands and/or at the ends of the cable. Heat generated in the normal zone also diffuses between strands. A numerical analysis was performed to investigate stability property of multi-strand cables against local disturbances. The influence of the current re-distribution and thermal diffusion between strands was studied. The insulation of strands affects the current re-distribution. When the transport current is small, removing the insulation of strands substantially increases the minimum quench energy against local disturbances. On the contrary, when the transport current is large, the insulation of strands has little influence on the minimum quench energy. In this case, current re-distribution cannot improve the stability because of little current margin