APP 3-4 A feasibility study of smart high-temperature superconducting cable to improve stability of KEPCO system *

A resistive type SFCL using REBCO tapes has high potential to limit fault currents quickly and to improve the reliability of a power system for its compactness and rapid increasing of resistance [1]. We have studied the thermal characteristics of a SFCL REBCO coil by numerical analysis using more precise analysis models. Influence of bubbles of boiling nitrogen is also considered in some cases. If bubbles are generated under fault conditions, a rapid local temperature rise may occur and even result in a permanent degradation of JC of REBCO layer. In this paper, we upgrade the previous FEM analysis model [2] for 3D thermal analysis of a REBCO coil in a resistive type SFCL (Fig.). Coupled problems of electromagnetic and thermal fields are solved for studying thermal characteristics of an SFCL REBCO coil immersed in liquid nitrogen. In computation of current distribution in the SFCL coil, a thin-plate approximation is applied to the REBCO tapes and FEM based on current vector potentials T is utilized. Current density J is defined by J=∇×T. The governing electromagnetic equation is given by ∇×(ρ∇×T)=∂B/dt (ρ: electric resistivity; B: magnetic flux density) [2]. In thermal analysis, the 3D structure of SFCL coil is modeled and the temperature rise is calculated under the condition of Joule heating, heat conduction, heat transfer, and cooling characteristics of liquid nitrogen.