Development of a 10 m long 1 kA 66/77 kV YBCO HTS cable with low AC loss and a jointwith low electrical resistance

Abstract

We have developed high-Tc superconducting (HTS) cables using YBCO tapes. A 10 mm-wide YBCOtape was divided into five strips using a YAG laser to reduce AC loss. A0.3 m conductor and a 1 m conductor were fabricated achieving AC losses at1 kArms and 50 Hzof 0.054 W m−1 and of 0.048 W m−1, respectively. Based on the successful AC loss reduction in the 0.3 and 1 m conductors, wefabricated a 10 m HTS cable with a three-layer HTS conductor, electrical insulation,and a one-layer HTS shield. The AC loss in this 10 m HTS conductor was 0.090 W m−1 at1 kArms and 50 Hz. An HTS cable joint was designed and fabricated that included athree-layer HTS conductor and a one-layer HTS shield. Joint resistance of 5.2 nΩ for the HTS conductorand that of 10 nΩ for the HTS shield were achieved. The HTS cable joint was compact and had sufficientwithstand voltage properties for 66/77 kV. In addition, we also confirmed the efficiency ofjoint construction. Moreover, a 20 m long HTS cable was successfully constructed andtested in January 2008. This HTS cable consisted of two 10 m HTS cables and the HTScable joint. One 10 m HTS cable using HoBCO was made by Sumitomo, and the HTScable joint and the other 10 m cable using IBAD YBCO were made by Furukawaand Chubu. The electrical resistance of the HTS cable joint was less than 10 nΩ, and the 20 m HTS cable including the joint withstood an over-current of 31.5 kArms whose duration was 2 s.