Safe and environmentally friendly large power transformers with ester successful introduction of ester liquids at the 420 kV transmission level

Power transformers are electrical devices based on concepts and materials developed decades ago. Today it is critical to implement new designs and new materials for these essential pieces of equipment to achieve sustainable, reliable and safe use. For large power transformers, one key area of development where both environmental sustainability and safety can be improved is the insulation liquid. Conventionally, the insulation liquid used in transformers is mineral oil based. However, alternative fluids are currently available, including both synthetic- and plant-based esters. These alternative insulation liquids are far less flammable and much more environmentally friendly than traditional mineral oil. This paper presents experiences from employing alternative insulation liquids at the 420 kV transmission level.