Influence of Local Inhomogeneities in the REBCO Layer on the Mechanism of Quench Onset in 2G HTS Tapes

Abstract

The Resistive-type of Superconducting Fault Current Limiters (R-SFCL) using the second generation of hightemperature superconductors (2G HTS) are well adapted to power grid protection. Almost electrically invisible in normal operation, it quenches and becomes highly resistive in the event of a fault. The tape operation at the transition from the superconducting state to the resistive state is the basis of a R-SFCL. In this scope, we studied the onset of a quench occurring in 2G HTS tapes using high-speed imaging to record the bubble generation in liquid nitrogen. In the first milliseconds of operation, the bubble generation appears highly inhomogeneous. Dissipation is initiated on multiple spots over the tape surface which first expands in the direction of the width of the tape and then along its length. A detailed analysis of the REBCO layer is performed by means of Scanning Hall Probe Microscopy (SHPM) after the optical study of the tapes is completed. Analysis of the local current density distribution demonstrates that the bubble generation occurs at positions of local inhomogeneities in the REBCO layer. These inhomogeneities, well recognized through SHPM, are not reliably described by the critical current as a function of the position derived magnetically (e.g. by traditional TapeStar® measurements). Similar results were obtained on samples from Superpower and SuperOx.

Current redistribution during inhomogeneous quench of 2G HTS tapes

“…A similar evolution of a dissipation spot was also mentioned in [13]. Furthermore, in [7], it was shown that areas with low superconducting properties in a 2G HTS tape (determined with Scanning Hall Probe Microscopy) matched the positions of the dissipation columns.…”

“…A high-speed Phantom V311 camera able to record one image every 20 µs was used to observe the bubble generation on the surface of the sample. More details are given about the experimental setup in [7].…”

Improved Recovery Time and Voltage Stability for Resistive Superconductor Fault Current Limiters

“…With the breaking capacity of the breakers to be exceeded in the near future, fault-current limiting methods have become indispensable in recent years. One of the modern methods, SFCL, limits the fault current effectively and quickly by using the transition property between the superconducting and resistive regions of the superconducting material (Method, 2019) (Zampa et al, 2022). SFCL limits the fault current level and protects both breakers and other power system components (Ju et al, 2022) (Xiang et al, 2018) (Jiahui Zhu et al, 2019).…”

Limitation Analysis of 1st and 2nd Generation Superconductors used in Resistive Superconductor Fault Current Limiters

“…Elimination of the mentioned disadvantages is possible by using SFCLs, which use the abrupt transition of superconducting material from superconducting to the resistive region at a specific critical current value (Nagarathna et al, 2015) (X. Chen et al, 2022) (Zampa et al, 2022). SFCLs are the best alternative to replace conventional limiting methods thanks to the advantages of superconducting materials (J.…”