Investigation of the Stability Behavior of Coated Conductors

Superconducting applications like cables, current leads and high current power lines made with YBCO coated conductors (CC) require a protection of the CC against overheating in case of over currents. One possible protection of the CCs is the application of a highly conductive stabilization layer, such as electroplated Cu. The duration of over currents can vary between microseconds and several seconds depending on the application of the superconductor and the characteristics of the fault current. If liquid Nitrogen (LN₂) is used as coolant, the transient heat transfer into the coolant varies from adiabatic behavior at short term over currents up to a nearly static heat transfer into the coolant at long term over currents. The thermal behavior of CC cooled by LN₂ during over currents was investigated experimentally. The time to reach the transition temperature was calculated analytically and measured for different currents and different stabilizer conditions on the CC. To allow a comparison of the stability for different CCs, a stability number is introduced.