Analysis of quench propagation characteristics of the YBCO coated conductor

Abstract

Hot spot may emerge in a local region if the critical current is not uniform along the high temperature superconducting (HTS) tape, and the hot spot will cause serious damage to the HTS tape in some cases. However, under the present processing techniques, it is hard to make a long-length YBCO tape with uniform critical current density. Therefore, examining the thermal stability characteristic of the YBCO tape for the quench protection is very important. In this paper, the quench propagation velocities of YBCO tapes with insulating sheath materials were measured in liquid nitrogen (77K) immersion. A heater is installed at the center of the tape to produce a normal zone to examine the propagation characteristics of the normal zone in the longitudinal direction. The quench characteristics were obtained by measuring the voltages between two nodes at different locations. Two different YBCO tapes produced by SuperPower Inc. and American Superconductor Corporation (AMSC) were tested under different currents respectively. The velocities both of them are under 3cm/s and the results are discussed in detail. Based on the results, special attentions concerning the problems of stability in the power applications were discussed.