Performance of a 1-MVA HTS demonstration transformer

We report on test results for a single-phase, 60-Hz, 13.8 kV/6.9 kV, 1-MVA high temperature superconducting (HTS) transformer which was completed in F ebruary, 1998. This transformer models in many ways a full scale section of a 30-MVA HTS commercial transformer design. The transformer windings are c ryocooled in the range of 25K and are made with a low-cost, surface-coated BSCCO-2212 conductor. Heat leaks are reduced using a liquid nitrogen therma l ballast and reservoir. The use of high temperature superconductors can su bstantially reduce transformer losses, weight, size, noise and potential fi re and environmental hazards. Designs promise stable operation through faul ts without thermal degradation, and at temperatures that allow efficient an d reliable refrigeration.