Current limiting performance by single grained Y-Ba-Cu-O superconducting rings

Abstract

The single-grained YBCO high Tc superconducting (HTS) offer applications in the field of superconducting screening fault current limiters (SSFCL) in electric power networks. The current limiting mechanism is related to the magnetic shielding effect of superconductors. Current limitation can be accomplished by means of the nonlinear impedance of a transformer with the primary winding carrying the power circuit current and the short-circuited secondary winding consisting of rings of single grained Y-Ba-Cu-O (YBCO) material. The latter remains superconductive at normal load level, which act as a magnetic flux shielding device to provide low impedance. If a defined current level is exceeded, a sufficient high magnetic flux is generated to penetrate the HTS ring. The secondary winding turns resistive, and provides a high impedance which limits the prospective fault current. Ring-shaped single grained YBCO disks with different thickness and Jc(H) were produced by the top-seeding melt-textured (TSMT) method. The relationship between the superconducting properties and the current limiting performance are reported.