Theoretical analysis of current density distribution in superconducting plate of flat type superconducting fault current limiter

We have proposed an inductive (magnetic shielding) type of superconducting fault current limiter which consists of a high Tc superconducting plate in doughnut shape and spiral coil as the primary winding. In this paper, the current density distribution in the superconducting plate was theoretically investigated to understand the fundamental performance of this type of current limiter. For the analysis, we developed the calculation method for the current density. The current density is distributed almost uniformly in the superconducting plate. The impedance of the current limiter changes every moment not only in current limiting operation but also normal operation. That is because the resistance in the superconducting plate and magnetic coupling condition in the current limiter also change with time. Relatively large impedance rapidly appears in the current limiter when the current density in all the area of the superconducting plate attain to the critical current density.