There is nothing particularly new about natural-ester-filled transformers, Hitachi Energy has, for example, been supplying them for over 20 years, with installations in more than 40 countries. However, Hitachi Energy has now successfully tested a 765 kV/400 kV single-phase, 250 MVA natural-ester-filled oil transformer. This “breakthrough innovation makes this transformer the first in the world at this voltage and power level,” says Hitachi Energy, with “the implementation of ester oil providing a biodegradable and safety-by-design option for operators of ultra-high-voltage AC grids.”
The 765 kV/400 kV transformer was designed, manufactured and tested as a further development of Hitachi Energy’s TrafoStar transformer technology platform. TrafoStar aims to harmonise transformer design, manufacturing processes and quality control measures across all Hitachi Energy power transformer factories worldwide (with more than 30 000 power transformers produced
to date).
Transformers have traditionally used mineral oil, well known for its excellent electrical properties, as an insulation and cooling medium. Alternative fluids, such as natural ester, can provide additional safety and environmental performance features.
Natural-ester fluid, as employed in the 765 kV transformer test, has a flash point twice as high as mineral oil and self-extinguishing properties. Combined, these qualities make natural-ester-filled transformers safer than mineral-oil-filled transformers, says Hitachi Energy. In addition, “virgin natural esters are up to 100 percent biodegradable within 28 days,” Hitachi Energy notes, reducing the risk of environmental pollution resulting from insulating fluid leakages. Safety is further enhanced, the company says, thanks to the use of Hitachi Energy’s rupture-resistant TXpandTM technology.
From power generation sites to the end-user, electrical energy passes through an average of four to five transformers, Hitachi Energy notes, observing that 765 kV AC transmission features in power grids in various regions worldwide, including North America, South America, South Africa, and parts of Asia (including China).
