Shunt-assisted simultaneous quenches in series-connected resistive SFCL components

We investigated shunt-assisted quenches in resistive superconducting fault current limiter (SFCL) components based on YBCO thin films when they are connected in series. Slight differences in Ic between the components induces significant power imbalance, which causes uneven quenches between the components. The extremely fast superconductor-normal transition causes the uneven quenches. Therefore, an appropriate quench delay is needed for synchronized switching of all components. In addition to the currently practised ways, an alternative way was demonstrated for simultaneous activation of components (or units) connected in series, the shunt-assisted quench. The shunts of equal resistance across individual components are to increase the current over Ic to each of the superconducting components. This design successfully produced simultaneous quenches, resulting in equal voltages over all components, while the YBCO films were protected from excessive heating. The shunts are found to be somewhat insensitive to differences in Ic. This design provides a wide selection of shunt resistance and film uniformity, allowing practicality, particularly in engineering application.