  We have developed a computer model for the simulation of resistive
superconducting fault current limiters in three dimensions. The program
calculates the electromagnetic and thermal response of a superconductor to a
time-dependent overload voltage, with different possible cooling conditions for
the surfaces, and locally variable superconducting and thermal properties. We
find that the cryogen boil-off parameters critically influence the stability of
a limiter. The recovery time after a fault increases strongly with thickness.
Above a critical thickness, the temperature is unstable even for a small
applied AC voltage. The maximum voltage and maximum current during a short
fault are correlated by a simple exponential law.
