Quench in a pancake coil wound with REBCO Roebel cable: Model and validation

Roebel cables assembled with high temperature superconducting tapes are a promising technology for several AC and DC applications. Their mechanical flexibility and compact design, combined with the capability of REBCO tapes to carry high transport currents in intense magnetic fields make them suitable for the application both in power devices and high field magnets. In this paper, an electro-thermal finite-element model developed at the University of Bologna (Italy) is described. The model allows computing the current and heat redistribution between the strands of the cable and from turn to turn inside a winding through non-uniform distributed thermal and electrical resistances between strands. The tape is 'homogenized' so as to create an anisotropic continuum model through a previously developed homogenization technique. The model is validated by comparison with quench tests performed on a well instrumented 7-turn pancake coil wound with a 2 m long Roebel cable composed of 15 REBCO tapes. The experiments were performed at the University of Southampton (UK) in the frame of the R&D activities of the EuCARD-2 project. The quench decision time, the temperature and electric potential evolution, the current and heat redistribution between strands in the event of a quench are analysed and discussed in the present study.