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-distributio n occurs as the current bypasses the normal zone via contact conductan ce between the strands and/or at the ends of the cable. Heat generated in the normal zone also diffuses between strands. A numerical analysi s was performed to investigate stability property of multi-strand cabl es against local disturbances. The influence of the current re-distrib ution and thermal diffusion between strands was studied. The insulatio n of strands affects the current redistribution. When the transport cu rrent is small, removing the insulation of strands substantially incre ases the minimum quench energy against local disturbances. On the cont rary, when the transport current is large, the insulation of strands h as little influence on the minimum quench energy. In this case, curren t re-distribution cannot improve the stability because of little curre nt margin.