Influence of inter-layer contact resistances on quench propagation in YBa₂Cu₃O_x coated conductors

Superconducting power devices are considered for many applications, including airborne applications. For the devices of interest the operating temperature needs to remain around 70 K in order to minimize the weight and volume of the associated cooling system. The use of YBa₂ Cu ₃ O_x (YBCO) coated conductors allows for operation at fairly high temperature (65-77 K) while maintaining high current carrying capabilities. Unfortunately, when a hot spot is created in a coated conductor wound magnet, the quench propagates so slowly that it cannot be detected using conventional methods and therefore those magnets may remain unprotected. To address this quench detection issue, we must better understand the physics of the quench and the phenomena that drive it so it can be accurately simulated. We have modeled YBCO tapes using Finite Element Analysis to assess the role of the contact resistance between the different layers composing the tape. Indeed, if the temperature rises, the YBCO layer becomes highly resistive and the current redistributes into the stabilization layers. The contact resistance between the YBCO layer and the copper is likely to play a very important role in terms of the current sharing length and voltage difference between the layers. This paper presents a model implemented in COMSOL Multiphysics, simulation results and a discussion.