Improvement of Recovery Characteristics of REBCO Tape With Several Surface Conditions for Resistive Fault Current Limiter

Superconducting fault current limiters (SFCLs) are required to return to the superconducting state within the proper time (recovery time) after limiting a fault current according to a relay operation scheme in a power system. In order to apply SFCLs to power systems, the recovery time is important property and deeply depends on the heat transfer property of the heated surface of the superconducting tape (normal conducting state) to liquid nitrogen. It has been confirmed that REBCO tapes with various shaped fins or PTFE coating improved cooling property. In this paper, to clear the mechanism of cooling property improvement of fins or PTFE coating, boiling phenomena on REBCO tapes with some types of fins or PTFE coating was observed by use of a high-speed video camera. The influence on the cooling improvement property of cooling fins and PTFE coating was discussed according to the photographical view of the boiling phenomenon.