Development of Superconducting Fault Current Limiters

Somewhere in a power utility system, a mishap may cause a short- circuit. The sudden reduction in the power grid's impedance will lead to a surge of current, termed fault current. Sometimes, fault currents can create disasters to power generators, distributors, and consumers. Today, options available for utility companies to handle faults are very limited and compromise the efficiency and increase the cost of the power system. People have been attempting better solutions for fault current control with the application of superconductors. Superconducting fault current limiter (SFCL) is currently the only short-circuit current limiting device capable of associating a low impedance at normal operation to a large impedance at short-circuit conditions, although the SFCL technology still requires further development and techno-economic studies. We started our saturated iron core reactive type SFCL development program in 2002. We fabricated and tested a single phase concept-proof model and a three phase lab testing model in 2004 and 2005 respectively. A 35 kV/100 MVA prototype will be developed in 2006 and will be live -grid tested in 2007. We believe SFCL will address fundamental challenges in power system design. In this paper, we will report the technical data and testing results of the three phase laboratory test model. Some key design parameters of the 35 kV/100 MVA machine will also be presented.