Current Sharing and Redistribution in Superconducting DC Cable

Uniform current distribution is shown to be an important requirement in superconducting dc cables. The role of nonuniform critical currents of individual tape sections on current sharing in a multistrand cable was investigated using a controlled parallel network of superconducting tapes with deliberately unequal critical current values. It was shown that if there is a significant variation in the critical currents of individual tape sections used for fabricating the cable, there is a potential that the tapes with lowest critical current carry current close to their critical current even when the cable as a whole is operating below its critical current. The results presented suggest that selection of tape sections with equal critical current prevents hotspots and potential catastrophic damage to the cables. The effect of nonuniform current sharing is particularly important in cables cooled with gaseous helium because of the limited cooling capacity.