Normal zone propagation process accompanied by current redistribution in superconducting tripler cables

The normal zone propagation process in multi-strand superconducting cables is often accompanied by current redistribution between strands. This curren t redistribution possibly influences the mode of normal zone propagation an d stability of superconducting cables. In this paper, details of the normal zone propagation accompanied by the current redistribution between strands are revealed in two types of superconducting tripler cables; the strands o f one cable have bare-copper surface, and those of the other cable are plat ed with chrome. Instrumentation includes voltage taps to follow normal zone propagation in each strand and Hall sensors to measure strand currents. Th e contact resistances measured in situ in the setups for quench experiments are 1.7 and 20 mu Omega for in in the cable with bare-copper strands and i n the cable with chrome-plated strands, respectively. In the recovery proce ss assisted by the current redistribution, the current transfers from the h eated strand to the others to improve the stability against local disturban ce. In the quench process, it transfers from the strands carrying more curr ent initially to the strands carrying less current. The contact resistance between strands influences the mode of current redistribution and normal zo ne propagation. In superconducting cables made with chrome-plated strands, the current transfers in the large region along the cable, while it transfe rs near the normal front in superconducting cables made with bare strands. The current redistribution preceding the normal zone propagation in a super conducting cable made with chrome-plated strands is a possible reason for t he increase in the normal zone propagation velocity. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.