Proposed flux-based optimization method for determination of minimum superconductor material in shield-type superconducting fault current limiters

Distributed power generation and an ever growing load demand have caused the current level of fault to exceed the nominal rating of power system devices, and fault current limiters are needed even more. The Superconducting Fault Current Limiter, SFCL, forms an efficient category of current limiters. The superconductor part in SFCLs is the most costly part of the device, and minimizing its volume, while maintaining the required characteristics of the device, would be very beneficial. In this work, using a Simulated Annealing optimization algorithm, a method has been proposed to determine minimum required bulk superconductor material in inductive shield-type SFCL structures. The flux linkage balance, generated by the superconductor bulk and copper winding (being the base of the optimization process), has been formulated versus dimensions. The optimum dimensions of the bulk superconductor in a model SFCL, having a limitation current of 3A, are determined using the proposed algorithm. A prototype has been fabricated using determined dimensions, and is tested in an experimental circuit by applying different types of faults. These experimental results demonstrated satisfactory limiting characteristics of the fabricated SFCL. The optimum volume of the bulk superconductor material needed for fabrication of larger scale SFCLs has been calculated and compared with the volume of superconductors employed in worldwide SFCL projects.