Comparison of fundamental performance of different type of fault current limiters with two air core coils

This paper theoretically investigates the difference in the impedance, initial current in the limiting operation and required volume of high T_c superconductor (HTS) between two types of superconducting fault current limiter with two coaxial air core coils. One of them is a "parallel type" which has been proposed by us and another one is so-called transformer (Tr) type. In the case that the HTS generates the same resistance in each fault current limiter, the larger limiting impedance can be obtained using the Tr type than the parallel type. However, the impedance of the Tr type in the normal operation is also larger than that of the parallel one. In the case that the HTS with the same critical current is used, the initial current in the limiting operation for the parallel type is higher than that for the Tr type. In regard to the HTS volume required to satisfy both of the specified impedance and initial current in the limiting operation, there is no significant difference between the parallel and Tr type.