KONČAR – D&ST and Nynas supply sustainable transformer technology to Sweden’s first wooden substation
Nynas recently joined KONČAR - Distribution and Special Transformers Inc. (KONČAR – D&ST) in Zagreb for the Factory Acceptance Test (FAT) of a power transformer destined for a truly innovative grid project. The unit will be installed at E.ON’s new transformer station in Karlshammar, southern Sweden – the country’s first power station built primarily in wood.
One of Europe’s largest electricity-network operators, E.ON is creating a next-generation sustainable transformer station in southern Sweden. The Karlshammar station is unique in that it pushes the boundaries of how a substation can be built with reduced climate impact.
“We are using new climate-smart ideas and methods. Building with more sustainable materials and reusing components is an important lesson that will benefit future projects. We also see that this drives innovation and development within the industry," says Mats Tullgren, regional grid manager at E.ON.
The wooden design reduces the station’s carbon footprint by around 17%, while the project also incorporates re-refined oil, reused steel and electrical components, carbon-reduced steel, and climate-improved concrete. Construction practices such as HVO-fuelled machinery and minimal earthworks further lower environmental impact. The result is a substation where performance meets sustainability.
“Over its lifetime, NYTRO® RR 900X can reduce greenhouse gas emissions by more than 70% compared to conventional transformer oil."
KONČAR – D&ST has been selected to design and manufacture the station’s power transformer using a combination of advanced technology and sustainable materials. Widely recognised as a highly innovative manufacturer of power transformers with a strong commitment to the sustainability transition, the company combines deep engineering expertise with a forward-looking approach to grid technology.
“We are constantly working on integrating more energy-efficient designs, advanced materials, and digital monitoring solutions into our transformer portfolio,” says Ivanka Radic, Chemical Engineer at KONČAR – D&ST. “These capabilities make us a key partner for utilities aiming to build more resilient and climate-smart networks.”
Through projects such as this, KONČAR – D&ST continues to demonstrate its role as a trusted partner in the energy transition, delivering innovative and sustainable transformer solutions of modern power systems.
Nynas contributes to the project with NYTRO® RR 900X, a re-refined transformer fluid made entirely from end-of-life insulating oil. Over its lifetime, it can offer a reduction of more than 70% in greenhouse gas emissions compared to a virgin transformer oil.
In January 2026, the 10 MVA transformer manufactured by KONČAR - D&ST for the project and filled with the NYTRO RR 900X underwent a Factory Acceptance Test (FAT) in Zagreb. It successfully passed all specified routine, type, and special tests in accordance with the IEC 60076 standard.
“Results of all performed tests including dielectric tests and temperature rise test were fully in accordance with the calculated values,” explains Vedran Maljković, Quality Control Manager at KONČAR - D&ST. “Additional testing of the insulating liquid was conducted both before and after the temperature rise test, confirming excellent performance, reliability, and compliance with stringent technical and environmental requirements.”
“Thanks to advanced hydrogenation, NYTRO RR 900X is fully equivalent to traditional NYTRO grades,” added Daniele Frustagli, General Manager Italy & the Balkans at Nynas. “It ensures excellent performance and complies with the most demanding quality standards, including IEC 60296.”
This makes the circular insulating fluid an ideal choice for high-power transformers in projects such as the Karlshammar substation where sustainability is a priority. With commissioning planned for late 2026, the station is set to become a reference for sustainable grid development.
