Improvement on the power capacity of the transformer-type SFCL with neutral lines between secondary windings

Application of the superconducting fault current limiter (SFCL) to the power system requires connection of superconducting elements in parallel and series. The uneven critical property of the superconducting element, however, causes unbalanced quenching. This brings the increase in power burden to a specific superconducting element. To solve this problem, a transformer-type SFCL with neutral lines was studied. In this paper, the fault current-limiting characteristics and consumption power of the superconducting element were analyzed. As a method to increase the power capacity of the transformer-type SFCL, the number of secondary circuits of the transformer was also increased. As a result, we found that the voltage and current of the superconducting elements were efficiently controlled by turn ratios of the transformer. This structure resulted in minimized consumption power. The transformer-type SFCL with neutral lines induced the simultaneous quenching between superconducting elements. This enabled us to increase the number of secondary circuits. Therefore, it induced the increase in its power capacity in the transformer-type SFCL. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.