Influence of Temperature on AC Loss in High Tc Superconducting Cable Conductors

The use of high Tc superconducting (HTS) cable is expected to realize compact, highly efficient transmission lines. In order to achieve high efficiency, it is important to reduce AC loss. However, accurately estimating the AC loss of a real cable system is very difficult because the cable length is very long and the operation temperature varies according to condition. The measurement of AC loss using a short sample is simple and possible using liquid nitrogen at the temperature of 77 K, but evaluating temperature dependence is very difficult because a refrigeration system is necessary. Moreover, a simple AC loss estimation method has been established for shield-less cable only, and is therefore not applicable to HTS cable with a shield layer. We have developed AC loss measurement equipment that uses calorimetrics and measured the temperature dependence for both critical current and AC loss of HTS cable with a shield layer. From the results, we propose a new simple estimation method for temperature dependence on AC loss by measuring the temperature dependence of critical current and AC loss at one point.