How one bold idea revolutionized the whole high-voltage industry

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How one bold idea revolutionized the whole high-voltage industry

In an industry known for reliability, one idea dared to disrupt the norm and change everything.

For over half a century, sulfur hexafluoride (SF₆) has been the industry’s trusted insulator in high-voltage switchgear. Its unmatched dielectric strength and arc quenching capabilities made it the cornerstone of reliable grid operation, especially in compact gas-insulated switchgear (GIS) installations. Yet, as the world awakened to the growing urgency of climate change, this “invisible” gas emerged as a very visible liability – one that could no longer be overlooked.

SF₆ has a Global Warming Potential (GWP) of 24,300 times more than CO₂, and its atmospheric lifetime stretches well beyond human time scales.

The question was no longer if SF₆ needed to be replaced – it was how.

What followed was a technical, industrial, and collaborative journey that redefined the boundaries of material science, field performance, and systems engineering. At its heart was one bold idea: to develop a high-voltage alternative that would not only remove SF₆ – but do so without compromise.

Reimagining the foundations of high voltage

To grasp the scale of the challenge, we must first appreciate what SF₆ made possible.

From a technical point of view, the gas was a beautiful innovation. In high-voltage applications – 145 kV and beyond – SF₆’s unparalleled insulating and switching properties enabled equipment to be compact, highly reliable, and virtually maintenance-free.

Replacing it meant more than swapping it out for another gas. It demanded reimagining and redesigning core high-voltage components, rethinking switching behaviour, evaluating long-term materials compatibility, and maintaining or improving overall system performance – all while delivering on sustainability promises and regulatory compliance.

This challenge led to the development of fluoronitrile-based gas mixtures (C4FN) – and the birth of Hitachi Energy’s revolutionary EconiQ® high-voltage portfolio.

Does C4FN really outperform vacuum in high voltage?

Vacuum interrupters have long served the medium-voltage segment with great success, especially in indoor distribution. However, when it comes to high-voltage transmission and GIS, vacuum presents multiple limitations:

1. Transients & over voltages
   Vacuum interrupters generate high-frequency transients during switching, especially under capacitive load conditions. These transients can overstress insulation and damage downstream equipment.
2. Arc quenching limitations
   At higher voltages, controlling and extinguishing arcs in vacuum becomes increasingly difficult without significantly increasing interrupter size.
3. Insulations requirements
   In GIS designs, vacuum interrupters still require an external medium for insulation – bringing the discussion back to the choice of gas.

How do C4FN-based gas mixtures compare? Well, here are just some significant differences in performance:

In rigorous type testing, EconiQ switchgear using C4FN mixtures demonstrated performance parity with traditional SF₆ systems – while achieving a GWP that is less than 1% of SF₆. Discover how the industry is replacing SF₆ in high-voltage solutions in the below insightful infographic.

EconiQ: The journey from lab to field

What started as initial research on alternative solutions evolved into a global mission to advance a more sustainable grid. Our experts lead the charge, applying deep technical expertise across:

• Gas chemistry and environmental science
• Thermal and dielectric simulations
• High-voltage testing under extreme conditions
• Materials aging, compatibility, and arc behavior
• Manufacturing, quality assurance, and digital monitoring

This wasn’t an off-the-shelf type of substitution. Every component – from bushings and seals to current interrupters – had to be requalified. Design tolerances shifted, arc quenching needed new optimization, and factors like thermal properties, mixing ratios, and pressure handling all became integral to the solution.

And perhaps most importantly: field validation was non-negotiable. Utilities around the world partnered to test pilot installations under real operating conditions – many in harsh climates with demanding duty cycles.

Around the world, EconiQ high-voltage technology proved it could handle the job and do it extremely well.

Discover why EconiQ is the top candidate to kick SF₆ out of the grid with its impressive track record in this comprehensive brochure.

One strategic vision that made a real impact

One thing is certain: EconiQ innovation didn’t emerge from a silo. Not at all. It was born from a deliberate, long-term vision to decarbonize the grid without compromising reliability – the most important quality of the energy network.

By introducing a full SF₆-free high-voltage portfolio of switchgear, breakers, and services, the industry could offer utilities a complete and eco-efficient roadmap to amore sustainable energy future. One that fits into global sustainability and decarbonization goals.

Bold ideas need bold teams: What it takes to lead sustainable change

Our EconiQ journey is one I am truly honored to be a part of - one made possible by Hitachi Energy’s incredible and passionate teams – people who believed change to more sustainable solutions was simply essential. It was a collective effort that spanned engineers, product managers, scientists, operators, testers, and business strategists, all working across time zones, cultures, and disciplines.

Taking on the challenge demanded more than expertise; it required:

Each and everyone understood the mission and it was more than just replacing SF₆. It was about rebuilding trust – in our capabilities, our products, our values, and one another.

The future of high voltage is EconiQ

The success of EconiQ proves what’s possible when technical expertise meets environmental responsibility – and when bold vision is matched with decisive action. This was never just a product launch. It marked a true turning point – a catalyst for a global movement that challenged legacy norms, redefined limits, and delivered breakthroughs the entire industry thought was unattainable.

Today, more utilities are demanding SF₆-free solutions. Regulators are setting ambitious targets. And manufacturers are scaling production to meet the challenge head-on.

One bold idea has sparked a transformative journey toward a more sustainable grid, and this is only the beginning. The grid is changing and it’s up to us to keep the momentum going and carry it forward.