Which manufacturers specialize in oil cooled transformers?

Many global power equipment manufacturers produce oil cooled transformers for utility and industrial service, including firms known for distribution and power transformer portfolios, plus numerous regional manufacturers. Specialization often depends on voltage class, MVA range, cooling methods like ONAN, ONAF, OFAF, and standards compliance. When selecting a manufacturer, utilities typically evaluate design type tests, factory quality systems, references in similar networks, after sales support, spare parts, and the vendor’s ability to meet IEC or IEEE requirements.