Measurement of ac losses of superconducting cable by calorimetric method and development of HTS conductor with low AC losses

To achieve compact and highly efficient HTS power transmission cables, reducing and evaluating AC losses is important. Furukawa is developing conductors with low AC losses of 1 W/m at 3000 Arms for the 66/77 kV class HTS cables as a part of the Super-ACE project. Specifically, we aim to achieve a superconducting conductor with minimum AC losses by optimizing the winding pitches and twisted filaments in the tape. The electrical method is generally used to evaluate AC losses in HTS cables. However, measures of AC losses were uncertain using only the electrical method of evaluation. Therefore, the calorimetric device was developed and was used for determining AC losses. Consequently, results from the two methods almost agreed. Moreover, AC losses in the fabricated HTS conductors were measured at the lowest levels ever achieved.