Initial quench development in uniform Au/Y-Ba-Cu-O thin films [superconducting fault current limiters]

The authors investigated the initial quench development process in resistive superconducting fault current limiters based on YBa₂Cu₃O_7-δ thin films of uniform quench current. The film was coated insitu with a gold layer and patterned into pairs of 1 mm wide and 26 cm long meander lines by photolithography. Voltage taps were mounted along the meander lines to detect quench development. Fabricated limiters were tested with simulated AC fault currents. Upon fault current passing quench current, all sections of the meander line made transitions into the pull flow regime simultaneously with similar flux flow resistivity. Transfer of the generated Joule heat, however, soon changed its distribution. At lower source voltages the center area of the meander line always had the highest resistivity and the edge area the lowest. At higher voltages quench started first and propagated fastest in the area close to the center electrode. But, once quench was completed, the resistivity became the highest in the central area of the meander line. This phenomenon was observed in all uniform samples on which measurements were taken and should be considered in design of fault current limiters made from uniform YBa₂Cu₃O_7-δ thin films. The heat transfer from limiter meander lines to surroundings explains the results