Impact of Twisting on Critical Current and n-value of BSCCO and (Re)BCO Tapes for DC Power Cables

The development of high temperature superconducting (HTS) DC power cables requires a detailed information on the impact of the main characteristics of the cable architecture on the electrical parameters of the superconducting tapes. This paper presents the experimental dependence of the critical current and n-value of BSCCO-2223 and (Re)BCO commercial tapes on the cabling twist pitch. DC characterizations were conducted on single tapes twisted around an insulated multistranded Cu former from an actual HTS power cable having a typical diameter of 3 cm. For these characterizations, the twist pitch was varied from 5 to 25 cm. To check that permanent degradation occurred, the critical current Ic and the n-value were measured on a flat sample holder prior to conduct the twist pitch measurements on the former. The results can be used to determine the available range of wire twist pitches to help designing HTS DC power cables.