Impact of Conductor Inhomogeneity on FCL Transient Performance

The superconducting (SC) fault current limiter (FCL) is a very effective tool to enhance the security and the power quality of electrical grids, two real demands today. This explains the great interest in it throughout the world. Only ReBaCuO coated conductor will be considered. The study of the constraints on the SC element is very important. The three phase clear short-circuit is a rather rare event and does not represent the most severe requirement for the SC element. Impedance faults or single-phase faults are more stringent. We have developed a model to represent the SC element in Matlab/Simulink through a resistance, which depends on the current and the conductor temperature. The temperature is the same across and along the conductor (isothermal block). The conductor is represented by two elements in parallel: the non-SC layers (substrate, shunt, ... ) and the ReBaCuO layer. This model has been validated on small FCL. Impedance short circuits have been investigated. Depending on the conductor, impedance faults may lead to a large temperature excursion for non-homogeneous I_c.