Transforming transformers ~superconducting windings\

Use of high-temperature superconducting (HTS) windings may soon turn power transformers into compact high-performers on good terms with the environment. The potential for HTS transformers is being examined in major design and hardware development programs by several teams of engineers and scientists worldwide. The team to which the authors belong is led by Waukesha Electric Systems. The Waukesha-led team has conducted a series of reference designs concentrating mostly on a 30-MVA, 138-kV/13.8-kV transformer rating. This rating is representative of a medium power transformer class foreseen as comprising about half of all US power transformer sales in the next two decades. Two of these designed are compared with a 30-MVA conventional oil-filled transformer typical of this class. Each uses a different commercially successful and reliable type of refrigeration. Since reliable operation is paramount, both transformers are designed to have a several-day on-board refrigeration reserve that lets them operate continuously with no interruption of service to customers.