RESIBLOC: 50 years of pioneering dry-type transformer technology

Fifty years ago, an innovation was born that would transform the transformer industry. In 1974, Hitachi Energy (former power grids division within ABB) launched the RESIBLOC dry-type transformer, featuring a groundbreaking cast resin insulation system that eliminated the need for oil as a cooling and insulating medium. This pioneering technology, with its unique use of glass fiber, unlocked new possibilities for transformer applications and set the stage for five decades of continued evolution and success.

Today, with over 70,000 units installed in more than 120 countries, RESIBLOC is a symbol of Hitachi Energy's commitment to innovating for a sustainable energy future.

The 1970s: a stroke of genius

In the early 1970s, the energy industry was dominated by traditional oil-filled transformers. While these transformers were effective, they came with inherent limitations. “Oil-filled transformers were reliable and widely used, but there was a growing demand for alternatives that prioritized safety, especially in critical applications such as hospitals, metros, airports, vessels, cruises, heavy industries, and nuclear power plants,” explains Kay Kruse, General Manager at Hitachi Energy's Brilon location in Germany. 

Recognizing the need for a safer, more resilient alternative, a group of forward-thinking engineers embarked on a mission to develop a dry-type transformer that could meet the demand for stricter fire safety requirements. They achieved a key technological breakthrough: a cast resin insulation system with glass fiber. By encapsulating the transformer windings directly in epoxy resin with a high content of glass fiber, Hitachi Energy invented a solid, homogeneous insulation structure that provided superior mechanical strength, thermal stability, and moisture resistance.

“RESIBLOC was a game-changer in what was quite a conservative transformer industry, offering a much safer and more robust solution,” says Kruse. “This innovative design eliminated the need for oil, making RESIBLOC transformers inherently fire-resistant and explosion-proof. The absence of liquid insulation simplified installation and maintenance, opening up new possibilities for transformer placement in buildings, industrial facilities, and challenging environments.”

The 1980s-90s: expanding horizons

Throughout the 1980s and 1990s, RESIBLOC technology continued to evolve, incorporating new materials, design enhancements, and manufacturing processes that further improved its performance and reliability. Hitachi Energy's Research & Development teams worked tirelessly to optimize the cast resin formulation, enhance the thermal dissipation properties, and refine the casting technique. These advancements allowed RESIBLOC transformers to handle higher power ratings, withstand more extreme ambient conditions, and deliver even greater safety and durability.

RESIBLOC transformers gained traction in a wide range of applications where reliability and safety were paramount. “The adoption of RESIBLOC transformers was often driven by critical events, such as fires or accidents, which highlighted the need for a safer solution,” explains Kruse. They became the preferred choice for high-rise buildings, offshore platforms, underground substations, the marine industry, and more. Their unique glass fiber content made them exceptionally robust and suitable for the most extreme of conditions.

In the industrial sector, RESIBLOC transformers proved their mettle in chemical plants, oil refineries, and mining operations, where their ability to withstand vibrations, dust, and extreme temperatures was crucial. In the marine sector, they set a new standard for safety and reliability. “Liquid immersed transformers in marine applications presented specific challenges in case of accidents, which highlighted the need for alternative solutions to enhance environmental protection and safety,” says Kruse. “The marine industry recognized these risks and widely adopted RESIBLOC transformers as a safer alternative. The self-extinguishing properties of the glass fiber ensured that RESIBLOC transformers could neither burn nor leak, providing unparalleled safety and peace of mind on the seas.”

Even under the sea, when TransManche Link began building an undersea rail tunnel to connect the United Kingdom and France, the project required transformers that could operate reliably in the confined, underground environment and ensure the safety of passengers and staff. This made RESIBLOC a natural choice for the Channel Tunnel, meeting all those stringent requirements while providing a dependable supply of power for the tunnel's lighting, ventilation, and signaling systems.

The 2000s: new power for a new millennium

As the world entered the new millennium, it began to place increasing emphasis on sustainability, efficiency, and decarbonization. With its eco-friendly design and energy-efficient performance, RESIBLOC technology was well-positioned to support this transition.

“Since 2000, European Union (EU) regulations have had a significant impact on the transformer market, driving a focus on the full life cycle of products, recyclability, and maintenance-free solutions,” says Kruse. “At Hitachi Energy, we further enhanced RESIBLOC's eco-efficiency by incorporating recyclable materials, optimizing the design for reduced losses, and minimizing the use of consumables.”

As renewable energy gained momentum, there was a growing demand for transformer technology that could handle the variable and intermittent nature of such sources. Hitachi Energy continued to innovate and meet the demands of the market with a new RESIBLOC design that could withstand frequent load cycling. Combined with its proven resilience to harsh outdoor conditions, RESIBLOC emerged as an ideal solution for the rapidly growing challenges of renewable energy integration.

The 2010s: runaway innovation

RESIBLOC transformers reached new heights, quite literally, when they were installed in the Burj Khalifa, the world's tallest building, inaugurated in 2010. The iconic skyscraper in Dubai required a reliable and efficient power supply to meet the extraordinary engineering demands of its extensive electrical infrastructure. Hitachi Energy met this challenge by delivering 72 RESIBLOC transformers for the distribution substation that manages everything from lighting and elevators to ventilation, heating, and air-conditioning systems.

 “In the heat of the desert, and as far off the ground as possible to build, RESIBLOC was still delivering unparalleled safety, reliability, and efficiency,” says Kruse.

Just two years later, Hitachi Energy unveiled the RESIBLOC Rail traction transformer, a groundbreaking leap forward in rail technology. Enhanced in 2021 to support up to 25 kV, it featured an integrated cooling system that eliminated the risk of oil spills and leaks while achieving 99 percent efficiency. The increased efficiency (and consequent decrease in energy consumption) reduces carbon dioxide emissions by 38 tons per train each year, making RESIBLOC Rail a remarkable solution for safety, efficiency, and environmental benefits. Such qualities led Switzerland's Federal Office of Transport to embrace the technology, resulting in substantial energy savings and a notable 10 percent reduction in total energy costs. Today, the RESIBLOC Rail is still the only product in the world that offers a dry-type solution for rolling stock applications.

Continuing to be a pioneering technology leader in the industry, Hitachi Energy launched the TXpert™ digital dry-type transformer in 2019. This technology seamlessly combines the established benefits of RESIBLOC with advanced digital monitoring and analytics capabilities. TXpert enabled distribution transformers, equipped with TXpert ready sensors, collect and analyze data to deliver actionable intelligence, facilitating predictive maintenance, improved asset management, and enhanced operational efficiency. Furthermore, Hitachi Energy’s RESIBLOC transformers with Transient Voltage Protection (TVP®) provide complete protection for electrical systems at every single switching instance, regardless of the network configurations or how often switching operations are performed. These milestones align with the increasing demand for smart and sustainable energy solutions, further solidifying RESIBLOC's position as a pioneering technology in the transformer industry.

The 2020s: the road ahead

In the 2020s, RESIBLOC transformers have been at the forefront of the hydrogen economy. Since 2020, Hitachi Energy has been active in the hydrogen market with RESIBLOC, playing a crucial role in many hydrogen power plants projects in various countries like Denmark, Germany, Africa, and US.

“The robustness and safety features of RESIBLOC make it the ideal choice for the demanding requirements of hydrogen applications like these,” says Kruse.

As RESIBLOC celebrates its 50th anniversary, it stands tall as a symbol of Hitachi Energy's unwavering commitment to pioneering technology and customer success. From its humble beginnings in the 1970s to its current position as the leading dry-type transformer technology, RESIBLOC has consistently pushed the boundaries of innovation, reliability, and sustainability. Looking ahead, RESIBLOC is poised to continue shaping the future of the energy industry. With its proven track record, ongoing technological advancements, and alignment with the global drive toward decarbonization, RESIBLOC is well-equipped to meet the evolving needs of customers and support the transition to a sustainable energy future for all.