Inhomogeneity Effects in HTS Coated Conductors Used as Resistive FCLs in Medium Voltage Grids

For Resistive Fault Current Limiters (RFCLs) based on high temperature superconducting coated conductors (HTS-CCs), inhomogeneity, in terms of critical current and geometrical imperfections such as stabilizer and substrate thicknesses, plays a very important role and it may limit the penetration of such devices into the electrical market. This paper presents an electro-thermal model, developed in SimPowerSystem, able to describe the transient respond of HTS-CC candidates with different degrees of inhomogeneity, both in terms of critical current and of thickness stabilizer. Critical current inhomogeneity has been modeled with Gaussian distributions. Layers thicknesses used in the simulations have been chosen by fitting the temperature dependence of real tape resistances. Our approach considers relative inhomogeneity positions as well as thermal conduction along the HTS-CC length. The model is tuned using experimental measurements made on ReBaCuO coated conductors. A new dynamical thermal calibration of the model is proposed using finite element method calculations. Inhomegeneity effects with different possible faults (e.g. three phases and single phase short-circuit) are presented. Inhomogeneity Effects in HTS-CCs Used as RFCLs in MV Grids 2