Major high-power transformer manufacturers include large global OEMs and regional heavy electrical companies capable of producing GSUs, HVDC converter transformers, and large autotransformers. These firms operate specialized plants with large core-handling, vacuum oil-processing, and high-voltage test facilities. They focus on 100 MVA and above, high or extra-high voltage ratings, and custom engineered-to-order designs for utilities, interconnectors, and generation projects across multiple continents.