Influence of Substrates in HTS Wires on AC Loss Characteristics of Cylindrical Single Layer Conductors

Substrates of high temperature superconductor (HTS) wires can change the magnetic field distribution of the wires, with the consequence that they can affect AC losses of the HTS wires, which is a critical issue in HTS applications. In this study, in order to investigate the effects of the substrates on the AC losses of cylindrical single layer conductors which are usually used in HTS power cables, we first experimentally and numerically evaluated self-field losses of the HTS wires and investigated the influence of the substrates on their self-field losses. Next various HTS cylindrical single layer conductors were prepared using different HTS wires and their AC loss characteristics were discussed from the perspective of magnetic substrate. The main results show that the magnetic materials in HTS wires do affect their losses and the magnetic field distribution. For our pentagonal conductors, magnetic flux does not exist outside of the conductor when the magnetic substrates are located outside. Moreover, the AC losses of the bismuth strontium calcium copper oxide (BSCCO) and yttrium barium copper oxide (YBCO) conductors are quite similar and the AC losses of the NY and YN conductors are larger than the losses of the other two conductors. Especially, the AC loss of the YN conductor is the greatest in the low current region.