SUPERCONDUCTING FAULT CURRENT LIMITERS

50-60 Hz electrical engineering represents a considerable potential market for superconductors. Fault current limitation will probably be the first among the possible applications, to find an industrial opening. Exploited features are very specific of the superconductors, namely the large contrast existing between an on-state with high current density and an off-state with high electrical resistivity, obtained as soon as the current reaches a specified level. It thus becomes possible to warrant the grid from any current excursion over a specified value, with considerable impact on the protection and dimensions of conductors and devices, and increased possibilities of interconnexion. The current limiter technology is rather complex ; different structures have been proposed and tested ; they are resistive or inductive, based on low-T(c) or high-T(c) superconductors. The most advanced candidate to date is a resistive structure, using conductors made of ultra-fine niobium-titanium filaments in a coppernickel matrix, whose essential features are described hereunder.