EXPERIMENTS WITH A HIGH-VOLTAGE (40-KV) SUPERCONDUCTING FAULT CURRENTLIMITER

Fault current limiters are devices that restrict fault currents withou t appreciable delay, so that they can protect electrical grids and dev ices more efficiently than classical circuit-breakers, Extremely low r esponse times (a few microseconds) are provided by low-T-c superconduc ting conductors, which combine a high critical current density and a h igh normal-state resistivity, with a vanishing heat capacity. Due to t he risks of dielectric breakdown and overheating, the rated voltages h ave been limited to a few kV up to now. A significant step forward was recently attained with the successful tests of a 40 kV(rms) prototype ; the device accepts rated currents of 315 A(rms), and protects the li ne from any current over 1100 A(peak) (less than one tenth of the ordi nary fault current). Its design and test results are presented here, w ith a tentative extrapolation to higher-rated currents and voltages. ( C) 1996 Elsevier Science Limited