Abstract: An electrical current limiter 1 is provided in which an enclosure 3 combination incorporates an electrical conductor 2 held in effective thermal isolation within an housing 4 having a vacuum 11. In such circumstances known electrical resistivity response of the conductor 2 can be utilised when an electrical fault occurs and therefore the electrical current passing through the limiter 1 increases. The thermal mass of the enclosure 3 combination is designed to limit thermal inertia and therefore an adiabatic temperature response prior to the heating effects of the higher electrical current in the conductor 2 resulting in increased electrical resistivity/impedance and therefore limitation of electrical current.

Abstract: A conductor element for a superconducting FCL has an elongate superconducting element 18 surrounded by bodies 26a, 26b, which form a thermal mass around the element 18. The thermal mass is in thermal connection with a cooling system, such as a cryogenic system. The bodies 26a, 26b are solid, for example copper. The thermal mass maintains even temperature along the element 18, to improve fault response and recovery. Cooling functions are provided externally of the conductor element and may be by means of conventional cryogenic cooling systems. The element is free of cryogens and robust.

Abstract: A fault current limiter comprising: an input node; an output node; a variable impedance element coupled between the input node and the output node; a multi-cycle refrigeration system, comprising a first coolant cycle for cooling the variable impedance element and a second coolant cycle, thermally coupled to the first coolant cycle, for cooling the first coolant, wherein the variable impedance element comprises Magnesium Diboride.