Measurement of critical current of superconducting cable

The critical current of a coaxial cable made of Bi-2223 tapes was investigated to survey underlying problems, especially for the resistive voltage caused by current transfer, for the standardization of test method of the critical current of superconducting AC power cables. Five voltage taps were attached on the copper sheath of 80 mm long, which is used as a part of the current lead, on both ends for the inner conductor layer and outer shield layer. The current transfer was theoretically examined especially for the outer shield layer of a simple structure. The resistive component in the measured voltage was calculated as a function of the position of the voltage tap, and it can be shown that the critical current is correctly obtained using the electric field criterion after subtracting the resistive component, as is usually done in experiments. These results are compared with the observed results.