Design and operational testing of a 5/10-MVA HTS utility power transformer

High temperature superconducting transformers offer many economic, operational, and environmental benefits over conventional power transformers for utility applications. To establish the technical and economic feasibility and benefits of HTS transformers of medium-to-large (>10 MVA) ratings, a team that includes Waukesha Electric Systems (transformer manufacturer), SuperPower Inc. (HTS systems manufacturer), Oak Ridge National Lab, and Energy East has designed, built and tested a prototype 5/10 MVA superconducting transformer. The transformer's 4.5-ton cold mass has been successfully maintained at temperatures of 30-50 K for several months, without full-time operator attendance. The transformer has reached its full three-phase operating current, and has been tested to 1.4 times operating current (limited by available power supplies) in single-phase mode. It is now undergoing long-term tests at various current levels, high-voltage tests, and transient overcurrent tests at the Waukesha site. This paper summarizes the manufacturing, cooldown, and the test results achieved to date.