Experimental Observations of the Hot-Spot Regime On 2G HTS Coated Conductors

The use of Rare-Earth BaCuO (REBCO) coated conductors is well adapted for Resistive type SFCL (Superconducting Fault Current Limiter) thanks to their high current carrying capability and high resistance per unit length. However, in case of fault currents in the range of the critical current I _c , the dissipation can be highly inhomogeneous along the length, leading to localized temperature elevations in the normal zones. This so-called hot-spot regime is well predicted by simulation tools but was seldom studied experimentally in a non-destructive way. This paper presents two experimental results highlighting the existence of the hot-spot regime. First, localized dissipation on a REBCO tape is observed through high speed recording of nitrogen bubbles synchronized with electric measurements. Second, the maximum temperature at the end of the limitation is studied as a function of the prospective current through measurements carried out on the conductor developed by the European Project FASTGRID. The maximum temperature is found experimentally to be highest for prospective current close to the conductor I _c .