Rossella Beatrice Dalessandro*, Marco Bocchi*, Valerio Rossi*, Luciano Martini* Rivista: IEEE Transactions on applied Superconductivity Vol.17, N.2, Giugno 2007 USA * CESI RICERCA The growth in generation and the increased interconnection of electrical grids lead to higher fault currents and therefore there is a considerable interest in Fault Current Limiter (FCL) devices. In this work, we refer on the results of electrical testing on resistive-type superconducting FCL prototypes made by Ni-sheathed MgB2, developed in the framework of the Italian Project LIMSAT. This is the first time ever that short circuit testing results are reported on MgB2-based FCL prototypes at 27 K, cooled by a liquid neon bath. The time evolution of limited current and voltage across SFCL prototypes are reported and analysed. Critical aspects associated to the fault event such as the steep HTS tape temperature rise and electrical insulation at cryogenic temperature are also discussed. Index Terms—Hysteretic loss, MgB2, Ni-alloy, short-circuit current, superconducting fault current limiter (SFCL).