Characteristics of a Bi-2212 Monofilar Superconducting Fault Current Limiting Element
The Bi-2212 monofilar bulk element was selected as a candidate in developing a 24 kV/630 A class superconducting fault current limiting (SFCL) system. This study investigated the Bi-2212 monofilar element both experimentally and theoretically regarding the DC voltage-current characteristics, AC loss characteristics, inductance, current limiting characteristics and local temperature distribution. It was found that the critical current of the Bi-2212 monofilar element increased 3.3 times as the operation temperature decreased from 77 K to 65 K. Although the arrangement of the Bi-2212 conductor was a coil shape, the measured AC loss was at a level similar to what is calculated from the Norris equation at both the temperatures 77 K and 65 K. The temperatures measured at each section during a fault were in good agreement with the results of the numerical analysis. Moreover, the results showed that the monofilar element was not yet sufficiently homogeneous to be used at its full rated voltage.