Overview of current distribution and re-distribution in superconducting cables and their influence on stability

Abstract

The stability of multi-strand superconducting cables is substantially influenced by the current distribution among strands. If the current distribution before quench is not uniform, the quench of the strand carrying the largest current may trigger the quench of a whole cable unless its current can transfer to the others quickly. In cables made of insulated strands, slight asymmetric strand transposition and transient changing external magnetic fields affect the current distribution among strands and result in the degradation of the cable quench current. In cables made of non-insulated strands, local current imbalance due to the axial variation of d B/d t can degrade the quench current of cables. When a normal zone is produced by some disturbance, or when a flux–flow voltage appears in a strand carrying the largest current, its current may transfer to the other superconducting strands. The rapidity of this current re-distribution also influences the stability of multi-strand superconducting cables.