Who are major manufacturers of oil-filled transformers?

Major oil filled transformer manufacturers include global OEMs such as Hitachi Energy, Siemens Energy, GE Grid Solutions, Schneider Electric, Eaton, and other regional transformer OEMs that build distribution and power transformers for utilities and industry. The „major“ list varies by region and voltage class, and project specs often require approved vendor lists (AVL). When choosing, compare factory test capability, IEC or IEEE compliance, service network, lead times, and reference projects.