Position of quench initiation in 6 kV-200 A class superconducting fault current limiter

The authors have developed a 6 kV-200 A class superconducting fault current limiter (SC-FCL). The SC-FCL has eight co-axial coils connected in order to minimize total inductance. In the present paper, taking consideration of the self-magnetic field in the SC-FCL, they discussed the position of quench initiation. They calculated spatial profiles of the strength and the direction of the self-magnetic field in the SC-FCL. As a result, the self-magnetic field is applied to sections of the superconducting cable (SC cable) in the transverse direction (maximum value: 6.42/spl times/10/sup -4/ T/A). The connective section between coils, however, suffers a magnetic field with a longitudinal component of 3.34/spl times/10/sup -4/ T/A. In the case of a short sample of the SC cable which was used for the SC-FCL, the quench current levels were found to decrease at the rate of 40 A per 0.1 T in a transverse magnetic field and 100 A per 0.1 T in a longitudinal field. Taking these results into consideration, the authors pointed out that the quench may be initiated in the connective section between coils, where the self-magnetic field is applied in the longitudinal direction.