Development of a high-voltage, large-capacity gas-cooled, gas-insulated transformer

Gas-insulated transformers are suited for urban underground substations because of their nonflammable and nonexplosive nature and compact installation space, and their use has been growing in urban areas. However, to meet the demand for large-capacity gas-cooled transformers, cooling difficulty caused by the small heat capacity and thermal conductivity of SF6 gas must be solved. A 275-kV, 300/3-MVA gas-cooled, gas-insulated shell-form transformer has been developed by use of a new cooling structure and is now under a long-term energization test. This paper describes the main features of the transformer as well as the cooling and insulation characteristics obtained by component models of the transformer and from a full-scale model transformer. (C) 1997 Scripta Technica, Inc.