Heat transfer monitoring between quenched high-temperature superconducting coated conductors and liquid nitrogen

Abstract

High-temperature superconducting coated conductors (HTS-CCs) are good candidates for resistive superconducting fault current limiter (RSFCL) applications. However, the high current density they can carry and their low thermal diffusivity expose them to the risk of thermal instability. In order to find the best compromise between stability and cost, it is important to study the heat transfer between HTS-CCs and the liquid nitrogen (LN 2 ) bath. This paper presents an experimental method to monitor in real-time the temperature of a quenched HTS-CC during a current pulse. The current and the associated voltage are measured, giving a precise knowledge of the amount of energy dissipated in the tape. These values are compared with an adiabatic numerical thermal model which takes into account heat capacity temperature dependence of the stabilizer and substrate. The result is a precise estimation of the heat transfer to the liquid nitrogen bath at each time step. Measurements were taken on a bare tape and have been repeated using increasing Kapton ® insulation layers. The different heat exchange regimes can be clearly identified. This experimental method enables us to characterize the recooling process after a quench. Finally, suggestions are done to reduce the temperature increase of the tape, at a rated current and given limitation time, using different thermal insulation thicknesses.

Composite Heat Sink Material for Superconducting Tape in Fault Current Limiter Applications

“…During the limitation event, the SCFCL experiences electric current and voltage simultaneously and thus a large amount of heat is generated. The conduction of the heat through the interface CC tape/LN2 is very poor, because LN2 evaporates due to a high temperature difference in the solid-liquid interface, and forms a vapour film with thermally insulating properties [5][6][7][8]. Roy et al [9] showed by means of modelling of HTS tapes for resistive type of SCFCL, that the key factor in success to readily attain the thermal stability is the heat capacity instead of thermal conductivity.…”

Thermal and Electromagnetic Design of DC HTS Cables for the Future French Railway Network

“…By varying thpol, the temperature difference between the dissipating parts and the liquid nitrogen during a fault can be adjusted. However, this thickness cannot be increased indefinitely, as this may greatly increase the recovery time tr after the fault is isolated [21].…”

High-speed fluorescent thermal imaging of quench propagation in high temperature superconductor tapes

“…It has been previously shown that a thin layer of insulator between an HTS tape and a cooling bath can influence the heat transfer properties [24,25]. Therefore, the presence of a fluorescent coating may have to be kept in mind when interpreting measurement results about the dynamics of the quench.…”