Temperature Instability in High-Tc Superconducting Wire Exposed to Thermal Disturbance

High-Tc superconductor wires/ conductors of longer lengths have emerged as one of the most promising candidates for several useful applications such as in utilities and in current lead powering large magnet system. These conductors are liquid nitrogen cooled and are much cheaper to operate. In the event of intrinsic thermal instability or cooling failure, irreversible transition to normal state may occur. These normal zones may propagate rapidly enough to cause transient heating leading to local ‘hot spot’ and resulting in damage to the conductor/ magnet. In this paper, the mathematical formulation to determine the temperature distribution throughout the superconductor wire subjected to such transient disturbance is illustrated. The solution to the problem is achieved by using the method of separation of variables based on physically relevant initial conditions. The results are obtained in the series form in terms of Bessel's functions and are illustrated numerically for a technical yttrium barium copper oxide (YBCO) superconductor wire. Also it is found that even for a steady state heat transfer of 500 W m–2 K–1, the conductor temperature rises above Tc in less than 10 sec of the thermal disturbance.