Quenching behaviour of superconductors in an inductive fault current limiter

Earlier papers introduced a new form of inductive superconducting fault current limiter (FCL) in which the primary and secondary windings were interleaved symmetrically, producing current sharing in the multiplicity of secondary coils. A new FCL which employs similar structure but in a higher rating has been designed and constructed. The new FCL, has eight series connected primary coils interleaving with at least eight isolated secondary superconductor rings around a toroidal iron core. Investigation of this FCL when carrying a different number of superconductor rings has showed the ability to reduce the leakage fields around the windings hence improving the current rating of the FCL by increasing the number of superconductor rings in the FCL. However, being isolated, each superconductor ring has a different switching profile as a result of the development of normal regime resistance at different current values. A new way of characterising this nonuniform quenching behaviour of the superconductors in the FCL as the fault occurs is reported.