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.