Hitachi Energy paves the way for more sustainable and circular transformer solutions
Features | 04.03.2026 | 3 min read
Successfully tests re-refined mineral oil in a large power transformer.
Insulating fluids are vital to the reliable and efficient operation of power transformers, ensuring dielectric insulation and thermal management. Each type of insulating fluid has its advantages, and mineral oil is the most widely used, thanks to its reliability and cost-effectiveness. As more power transformers reach their end of life, larger quantities of used transformer oil become available. As demand for transformers continues to rise rapidly, fueled by unprecedented growth in electricity consumption, it is essential to develop circular material value chains, reducing dependence on virgin materials and advancing the industry's sustainability.
With the successful testing of a large power transformer refilled with re-refined mineral oil at Hitachi Energy’s Córdoba factory in Spain, the company is advancing and celebrating another milestone in its sustainability journey. By testing and confirming the transformer’s performance in its own factory operations, Hitachi Energy is leading the way for wider adoption of this sustainable option.
The re-refined mineral oil is a recently launched solution by Nynas, a leading supplier of long-lasting, high-performance, specialty products, including insulating fluids designed for power transformers. Promoting a circular economy and sustainability, the Nytro RR 900X oil is 100 percent sourced from end-of-life transformer fluids and processed to guarantee traceability and top-tier performance, retaining and matching the dielectric behavior of traditional mineral oils, making it suitable for demanding applications such as high-voltage and high-power transformers.
Environmental credentials
Based on RR 900X’s circularity, this solution creates a true circular material loop as it reduces carbon intensity in oil production by 90 percent compared to European-based production of virgin mineral oil for transformers. The solution lowers the “cradle-to-gate” carbon footprint by approximately eight percent for large transformers and increases recycled content in transformers by over 20 percent.
This re-refined oil is fully compliant with IEC 60296:2020 standards, requiring no design changes. At an industrial scale, it demonstrates that reusing end-of-life transformer oil, rather than downcycling and incinerating, can be a powerful lever for advancing circularity and decarbonization across the transformer value chain.
This advancement reflects Hitachi Energy’s pioneering spirit in driving innovation and collaboration with its extensive global network of suppliers, allowing the company to deliver tangible benefits to customers and the planet.
Sustainable, alternative solutions
Hitachi Energy has taken the lead in validating a wide range of alternative fluids for use in power transformers. This has been achieved through a carefully defined qualification process that includes rigorous testing of dielectric and thermal performance, as well as compatibility with critical transformer components, such as bushings and tap changers. Transformers are expected to operate reliably for over 25 years; ensuring long-term stability and material compatibility is essential. These efforts are opening new paths to transformer design and performance, without compromising on the high standards of performance and safety that the industry demands.
Hitachi Energy continues to lead the expansion of insulating fluid options for power transformers. The company’s goal is to empower customers to make informed decisions based on a clear understanding of the economic, operational, and sustainability benefits of each fluid family. This helps customers choose the most suitable option for their specific application and sustainability priorities, while also strengthening the resilience of our fluids supply chain.
Re-refined cycled mineral oil – ready for the market
Thanks to Hitachi Energy’s comprehensive and credible qualification procedures and advanced testing infrastructure, the company has achieved the necessary level of technical and commercial readiness to offer Nynas’ Nytro RR 900X, a higher-grade fluid option to the market, for power transformers.
