Switching and quench propagation in coated conductors for fault current limiters

We address the use of coated conductors for resistive fault current limiters. Fast quench propagation is essential to let the conductor switch on the full length within milliseconds. The ordinary quench propagation mechanism, however, is too slow because of the small heat diffusivity in typical tape substrate materials. Here we present a new mechanism, which is not based on heat diffusion, but on a conductor geometry that leads to current bunching and a rapid spreading of the resistive state. Thus, the conductor develops its full normal resistance, is homogenously warming further up, and self-protecting without the use of thick normal conducting stabilizers that reduce the efficiency. The mechanism was confirmed by a numerical simulation and by experiments on samples of short and medium length. Tape samples up to 50 cm length switched homogenously exhibiting a maximum voltage drop of 2.7 V/cm. (c) 2006 Elsevier B.V. All rights reserved.