Non destructive quench of bulk YBaCuO in liquid argon

The superconducting fault current limiter (FCL) is particularly attractive since no conventional limiting device exists for high voltage networks and thus corresponds to a real need. YBCO is a good candidate for current limitation due to its large critical current density and its large normal state electric field. This material is, however, very sensitive to hot spots in liquid nitrogen. An operation at higher temperatures decreases the critical current density and consequently reduces local heating (hot spots). Tests in liquid argon (87.3 K) were carried out. The critical current density remained large (about 50 MAm-2, 0 T). For instance the limiting current is much higher (11-15 times) than the critical current but to our knowledge, it is the first time that a cion destructive quench was observed in bulk YBCO mono-domain sample. The power and energy per unit volume developed during the transition reached 75 GWm(-3) and 350 MJm(-3) respectively. These values are large enough to induce an effective current limitation and weak enough to restrict overheating and resulting destruction. In this paper we report measurements and their analysis and show a new and hopeful way to improve YBCO limitation efficiency. (C) 1999 Elsevier Science Ltd. All rights reserved.