Magnetic-shield type superconducting fault current limiter with high T_c superconductors

The continuous development of electric power utilities has led to the increase in the problems concerning fault currents. The use of fault current limiters, which suppress fault currents below a certain level, has been examined in many places. The authors have studied a superconducting fault current limiter that is based on the magnetic shielding characteristics of superconductors. In this paper, three kinds of fault current limiters with high T_c superconductors and their results tested at liquid nitrogen temperature are presented. The experimental results show that the impedances of limiters in the fault condition became higher than those in the normal condition but were lower than the anticipated ones. Next, a numerical calculation model to analyze the experimental results is presented. The calculation results with this model agreed with the above experimental ones very well. From these studies it is concluded that it is necessary for the sudden transition from the superconducting state to the fully resistive state to be caused by the suitable means.