Superconducting fault current limiter operating in liquid nitrogen

Superconductors are known for the ability to carry large electrical currents when cooled to sufficiently low temperature. Due to the highly non-linear current-voltage curve they offer also the possibility to limit transported currents. After trespassing the so-called critical current, I_c, the resistivity of a superconductor quickly increases. This property has been utilized by many groups worldwide in the development of the resistive type of superconducting fault current limiter (SFCL). The most promising solution is based on high-temperature superconductors operating at liquid nitrogen temperature (77 K), prepared in the form of tapes with thin superconductor film deposited onto metallic substrate. The device must contain superconducting tape in the length based on calculation of the resistance necessary to limit the transporting current after entering the limiting regime. Design principles for this element are still under development. In this contribution we present the results of experimental and theoretical study aimed at finding the effect of manufacturing imperfections on the fault current limiter performance.