Mechanism of Recovery Performance Improvement With Porous-Stabilized REBCO Tape for Resistive-Type Superconducting Fault Current Limiters

Resistive-type superconducting fault current limiters (R-SFCLs) utilizing rare-earth barium copper oxide (REBCO) tapes have been developed to limit fault currents. To balance recovery and current-limiting performances, a porous-stabilized REBCO tape was proposed. The experimental results showed that using a porous stabilizer with the REBCO tape and insulating epoxy reduced recovery time to 25%. However, the underlying mechanisms of this improvement in recovery performance are not yet clear. The aim of the present study is to understand these mechanisms. To do so, a vapor-film-collapse model was proposed to clarify the impact of the insulating epoxy on vapor film collapse. This model suggests that when liquid nitrogen (LN2) comes into contact with the insulating epoxy, it causes a rapid decrease in the temperature of the insulating epoxy surface, leading to the collapse of the vapor film. Additionally, a liquid-retention model was proposed to investigate the effect of the porous stabilizer. This model indicates that if the porous stabilizer can retain LN2, the equivalent heat flux observed in experiments can be achieved through evaporation of the retained LN2.