In 2004, Innopower began the R&D work to develop saturated iron core type SFCL. The initial reasons to choose this technology are to avoid the direct impact by the quench of the superconductor coils during fault current limiting, which results in long recovery time and complicated protection requirement. The saturated iron core type SFCL have been proved to be practical and suitable for utility application from Innopower's almost 10 year R&D practice. A 35kV/90MVA SFCL and a 220kV/300MVA SFCL were successfully manufactured, installed and operated in live grids. Now, a 500kV/1800MVA single phase prototype is under design and manufacturing. Factory tests are planned in early next year. There have been three main stages of Innopower's SFCL R&D. The first was to build several small lab testing models to proof the basic concept and to establish the fundamental design method. The second was to design and manufacture a medium voltage device, a 35kV SFCL. The third was to developing a high voltage device, a 220kV SFCL. Each stage has some important and substantial technical progresses. The next project will be the undergoing 500kV SFCL.