Resistive fault current limiters with YBCO films - 100 kVA functional model

Within the Siemens current limiter program a 100 kVA functional model has b een realized and tested successfully. According to the modular concept of t he limiter the functional model is assembled of ten switching elements. YBC O-films with a thickness of 250 nm and a critical current density above 2x1 0(6) A/cm(2) are deposited by thermal coevaporation (TU Munich) on 4" sapph ire wafers, To support homogeneous switching the superconducting film is co vered with a 100 nm Au - shunt layer. Good current limiting performance is achieved: The steady limiting current is below the nominal current, the pea k fault current increases up to 3 times the nominal current within an actio n time of one millisecond. The operational recovery time of the limiter, wi thin which the switching elements return to the superconductive state again is about 2 s. Following our limiter program the next step will be a model device with a nominal switching power of 1 MVA.