London Power Tunnels: Supporting National Grid’s SF6-Free future with Hitachi Energy’s GARIP Eco bushings
Customer Story | 4 min read
The London Power Tunnels (LPT) project, led by National Grid, represents a transformative effort to modernize South London's energy infrastructure. By constructing a network of deep underground tunnels, National Grid aims to address the city’s increasing energy needs, ensuring a secure and sustainable power supply for years to come. A central component of this ambitious initiative is the Bengeworth Road substation, a 400kV high-voltage facility designed to provide reliable power to homes and businesses across Central and South London. This substation plays a critical role in stabilizing network voltage and enhancing the capacity to connect future renewable energy sources to the grid.
Challenges
Meeting London’s infrastructure upgrade
National Grid has set a bold target to reduce emissions of SF6 from its network by 50% by 2030, marking a major milestone in its drive toward sustainability. Achieving this vision required more than just replacing legacy equipment; it demanded a new generation of high-performance, eco-efficient technologies.
At the Bengeworth Road substation, the journey began with the deployment of ester-filled transformers and SF₆-free switchgear. Hitachi Energy delivered seven bays of its EconiQ™ 420 kV gas-insulated switchgear (GIS) and 420 kV gas-insulated lines (GIL), enabling long-distance electricity transmission without the use of SF₆.
But innovation didn’t stop there. National Grid sought a direct connection between the eco-efficient transformers and SF₆-free switchgear - a configuration never implemented before. This requirement called for a complete redesign of the transformer bushing, a critical component that enables the safe and reliable transfer of electricity between the transformer and switchgear.
To meet this challenge, Hitachi Energy developed a new bushing design with updated coating and gasket systems, engineered specifically for compatibility with both ester oil and the alternative insulating gas. This advancement ensured not only technical performance and safety but also compliance with strict environmental standards.
Solutions
Innovative bushings to connect eco-friendly systems
To solve this challenge, Hitachi Energy introduced a breakthrough component: GARIP Eco, a next-generation dry-type resin-impregnated paper (RIP) bushing developed specifically for SF₆-free applications. For the Bengeworth project, Hitachi Energy delivered 420 kV and 145 kV GARIP Eco bushings designed to operate reliably between ester-filled transformers and EconiQ™ SF₆-free GIS.
GARIP Eco is a next-generation solution purpose-built for tomorrow’s switchgear. Developed in response to the industry’s growing shift toward eco-efficient gas mixtures like C4-FN blends, GARIP Eco bridges the insulation and mechanical challenges posed by new dielectric conditions, elevated internal pressures, and material compatibility with ester oils.
Developed through close collaboration across transformer and switchgear engineering teams, GARIP Eco represents a complete rethinking of bushing performance, engineered from the ground up to handle the new insulation gases, materials, and pressure demands of a fully eco-efficient system.
Its dry-type design also eliminates the risks associated with oil-filled components, enhancing environmental safety and simplifying maintenance. In doing so, GARIP Eco has proven its role not only as a technical enabler but as a foundational element for future-ready substation design.
This pilot project has successfully validated the seamless interaction between the innovative GARIP Eco bushings and EconiQ™ switchgear, making them ready for deployment in future applications.
Additionally, the extensive research and expertise gained during this project provide a strong foundation for verifying compatibility with other gases upon request.
A key advantage of Hitachi Energy's bushings is also their universal platform applicability to transformers from all OEMs, offering unmatched flexibility and scalability for future projects.
Impact
Empowering sustainability through collaboration
The implementation of Hitachi Energy’s GARIP Eco bushings has delivered transformative benefits, ensured the compatibility of SF6-free systems while enabling a more compact and eco-efficient substation design. By eliminating the need for larger infrastructure, this solution significantly reduces material use and lowers the substation's overall carbon emissions.
The Bengeworth Road substation is set to play a vital role in providing a reliable power supply for London, supporting the integration of more renewable energy sources into the grid, and advancing the UK’s net-zero ambitions. Beyond energy innovation, National Grid’s commitment to sustainability was further demonstrated by planting 27 new trees in Ruskin Park, achieving a 10% net biodiversity gain in the substation area.
In conclusion, the collaboration between Hitachi Energy and National Grid has not only overcome the challenges of transitioning to SF6-free systems but has also set a new benchmark for sustainable energy solutions. By empowering National Grid to meet its sustainability goals, Hitachi Energy has contributed to the creation of a eco-friendly and resilient energy grid for London and beyond, setting a new benchmark for innovation and partnership in building a more resilient, low-carbon energy future.
This key project will deliver a secure and resilient energy supply to the capital, ensuring London’s energy infrastructure is fit for the future. With the contribution from Hitachi Energy, we’ve been able to integrate innovative and sustainable technologies that not only minimize the environmental impact of our operations but also support the UK’s transition to Net Zero. Their expertise and partnership have been instrumental in helping us achieve our goals while setting new standards for sustainability in the energy sector.
