Superconducting fault current limiters based on high Tc superconductors

The worldwide increasing demand for electrical power leads to a growing interconnection of electrical networks. As a consequence, short-circuit currents (I_sc) increase, leading to high mechanical and thermal stresses. All electrical equipment has to be designed to withstand these stresses. It is obvious, from both technical and economical points of view, that a device that reduces the I_sc is needed. All the solutions realized up to now have substantial disadvantages. They fulfil only a few of the characteristics expected of an ideal fault current limiter. The advantages and disadvantages of high temperature superconductors for fault current limiters are briefly mentioned. The authors then discuss the main concepts of superconducting fault limiters, the ABB concept of a shielded iron core, and the construction of a 100 kVA prototype and its testing