Authors: OKAN ÖZGÖNENEL, DAVID THOMAS
Abstract: In recent years, environmental awareness has been a great concern, and even governments have sometimes been under pressure to comply with bilateral agreements. Mineral oil/epoxy cast resins are one of the most harmful soil pollutants. Of course, they provide a good insulation material in (distribution/power) transformers, but they present some disadvantages, such as low ignition point, additional insulation costs, requirement for an extinguishing apparatus, long clearance distance, toxicity, costly decontamination, and explosion risk. For this reason, gas-insulated transformers have nowadays been put into specifications. % This paper investigates SF6-gas-insulated transformer (GIT) designs for the complex distribution transformer model, i.e. 2.5 MVA open-air type. The model has 34.5/0.4 kV, 50 Hz ratings. SF6 GITs present more reliable working conditions due to the inherited specs of SF6 because it has nonflammable insulation and an explosion-proof design. Therefore, the proposed transformer design is mostly suitable for security risk environments, such as submarines, mines, and nuclear power plants. Apart from these advantages, the new SF6 GIT design is compact in design and lighter than the oil-type or the epoxy cast resin type.
Keywords: Distribution transformer, SF6 insulation, epoxy cast resin, transformer oil
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