Hitachi Energy builds the power grid infrastructure for the next generation by delivering its first 460 kV natural ester-filled shunt reactor

Brazil, specifically the state of Sao Paulo, is known for its cultural diversity, its urban and natural landscape and its joyful people. More than 213 million people live in Brazil, making it the 7th largest country in the world. They all rely on safe, reliable and sustainable electricity. To drive the evolution of the energy system, Hitachi Energy delivered its first 460 kV natural ester-filled shunt reactor (4 single phase units) to ISA ENERGIA BRASIL, a leading power transmission utility in the country. It is Hitachi Energy’s largest ever shunt reactor with natural ester oil delivered to a customer to date – it’s the first one in Latin America.

Located at the Bauru Substation, in the state of Sao Paulo, the shunt reactor represents a technological milestone for the power sector, combining innovation, operational safety, and sustainability. The project includes four single-phase shunt reactors with a capacity of 66.67 megavolt-ampere reactive (MVAr) each, with each unit requiring approximately 15,000 liters of natural ester oil. Natural ester significantly enhances environmental safety through improved biodegradability and reduced ecological risk in the event of leakage. The first unit became operational in May 2026, while the remaining units are expected to be installed in August 2026.

Shunt reactors are essential for a reliable electrical system by controlling reactive power, especially in long-distance transmission systems where reactive power must be carefully managed to avoid overvoltage. As a result, these large-scale assets contribute to grid stability, ensuring that electricity reaches consumers safely, efficiently, and within the system’s operational limits.

The Bauru substation is currently undergoing modernization and innovation investments, including the installation of the natural ester-filled shunt reactor and the replacement of other equipment and systems, aiming to increase operational reliability and enhance energy security for Brazil’s National Interconnected System (SIN).

Hitachi Energy is shaping the power network and advancing the transformation of the energy system toward a fully electrified future – secure, affordable, and sustainable – with innovative engineering. Developing a shunt reactor with natural ester fluid at this voltage level requires technology development and know-how combined with highly skilled and experienced engineers. The company conducted specific logistics studies, adapted production processes, established partnerships with strategic suppliers, and deployed specialized equipment to successfully manage this project.

Transformers have traditionally used mineral oil, known for its great electrical properties as an insulation and cooling medium. More recently, transformer technology innovation has advanced the use of alternative fluids, such as natural ester, with additional safety and environmental performance features.

The project marks an important milestone in deploying natural ester insulating fluids for high‑voltage applications, confirming their technical feasibility while enhancing fire safety and reducing environmental risks during operation. While leakages are unlikely, natural ester fluids provide an additional risk‑mitigation layer by significantly limiting environmental consequences should such an event occur, thanks to their up to 100 percent biodegradability within 28 days, as demonstrated for new ester fluids.

By combining Hitachi Energy’s advanced engineering capabilities and proprietary tools with the inherently lower carbon footprint of natural ester – thanks to CO₂ uptake during its production– the new shunt reactor design achieves, in this specific case, a 20 percent reduction in material‑related carbon footprint and an approximately 11 percent reduction in total lifecycle carbon emissions versus a mineral‑oil‑based design.

Hitachi Energy has been supplying natural ester-filled transformers and shunt reactors for over 20 years, with products installed in over 40 countries. With deep expertise in dielectric fluids and a commitment to ongoing research and innovation, Hitachi Energy continuously pursues new alternatives.

The company’s TrafoStar transformer technology platform harmonizes transformer design, manufacturing processes and quality control measures across all Hitachi Energy power transformer factories worldwide, ensuring consistency and excellence in every transformer produced. With more than 30,000 power transformers and shunt reactors produced, the platform incorporates a rigorous quality system and all processes covering material, technical, production, and quality, fostering collaboration, global knowledge sharing, and innovation.