Development of a perfluorocarbon liquid immersed prototype large power transformer with compressed SF6 gas insulation

A prototype of a three-phase nonflammable high-power transformer has been developed. It uses nonflammable perfluorocarbon liquid as both a coolant and an insulating material for windings, and compressed SF₆ gas as the insulation from the outer windings to the tank. Using cooling and insulation models, the cooling and insulation characteristics of the disk windings were clarified. Stress analyses and pressure tests on the transformer tank were carried out to evaluate its mechanical characteristics. A prototype of a 275 kV 100 MVA three-phase transformer was developed, and its excellent performance was confirmed