Hitachi Energy has completed testing of a 765 kV / 400 kV, 250 MVA single-phase transformer that uses natural ester insulating fluid instead of traditional mineral oil. According to the company, it is the first transformer at this voltage and power rating to use ester-based fluid, which is both biodegradable and fire-resistant.

Transformers at the 765 kV level are typically used in transmission networks to move large amounts of electricity over long distances. A three-phase unit at this capacity can supply power for a population of approximately 250,000.

The tested unit was designed as part of Hitachi Energy’s TrafoStar platform, which standardizes transformer design and production across its facilities. The unit also includes TXpand™, a casing design the company says is rupture-resistant.

Natural ester has gained attention in recent years as an alternative to mineral oil, due to its higher flash point and biodegradability. The ester used in the new transformer is described as self-extinguishing and up to 100% biodegradable within 28 days. These properties may reduce environmental and fire risks in grid infrastructure, particularly in sensitive locations.

The company stated it has been supplying ester-filled transformers for over two decades, with installations in more than 40 countries. The 765 kV design is applicable to regions where ultra-high-voltage alternating current (AC) transmission is used, including parts of North and South America, Asia, and Africa.

The development comes amid global efforts to modernize grid infrastructure and increase the use of lower-impact insulating fluids in power equipment.

Source: hitachienergy.com