Structural features of gas insulated transformers

There has been a rapid increase of gas insulated transformers and reactors in East Asian countries. Plans to construct underground or indoor substations accelerate this trend, because of the difficulty in acquiring spaces for substations in large cities where the electric power demand is concentrated. Requirements of security against fire accidents, compactness and total cost reduction are the key factor for these substations. Total gas insulated substations combining gas insulated switchgears and gas insulated transformers meet these needs. Demand for gas-insulated transformers has been increasing rapidly, particularly in Japan, Hong Kong and China. More than 10,000 units and up to 275 kV-300 MVA class of gas-insulated transformers are currently operating in the field. The first gas-insulated transformer in Japan started operation in 1967. These transformers finished their function satisfactorily in 1990s. These facts indicate that the gas insulated transformer technology has been well matured and proven.