India’s power transmission sector is evaluating a transition from conventional sulfur hexafluoride (SF₆)-based gas-insulated switchgear (GIS) to environmentally sustainable Green GIS technologies, according to a report by Central Electricity Authority (CEA).

The report recommends a phased transition to Green GIS through regulatory and procurement interventions. It proposes pilot projects starting in 2027–28, focusing on 132 kV systems and retrofitting initiatives, followed by gradual scaling from 2029–30 with around 10% of new GIS projects adopting SF₆-free solutions.

SF₆, widely used in GIS, has a global warming potential (GWP) of 24,300 times that of carbon dioxide, making it one of the most potent greenhouse gases in the power sector.

With India already achieving 50% of its installed electricity capacity from non-fossil sources ahead of its 2030 target, the focus is now shifting toward decarbonizing transmission infrastructure.

However, Green GIS technologies, while reducing environmental impact by up to 99%, currently cost six to eight times as much as conventional systems, largely due to import dependence and limited domestic manufacturing.

Technology Options and Performance

The CEA report evaluates multiple alternatives to SF₆-based GIS, including fluoronitrile-based gas mixtures such as C4-FN blends combined with CO₂ and O₂, clean air systems using nitrogen and oxygen with vacuum interruption, and CO₂-based mixtures.

These technologies are designed to match the dielectric strength, arc-quenching capability, and thermal stability of SF₆ systems. Fluoronitrile-based solutions offer up to 99% lower GWP, while clean air technologies have zero GWP but require a larger physical footprint.

Green GIS technologies have already been proven at lower voltages, such as 132 kV, but remain under development and require further validation at higher voltages, including 220 kV and above.

The report also identifies hybrid GIS configurations that combine air-insulated and gas-insulated systems as an intermediate solution to optimize cost, footprint, and environmental performance.

Cost and Manufacturing Constraints

A major barrier to adoption is the high upfront capital expenditure, with Green GIS systems costing six to eight times more than conventional SF₆-based equipment. Execution timelines are also 20–25% longer due to reliance on imported components and gases.

Domestic production capacity for fluoronitrile is currently around 60 tons annually, expandable to 120 tons, which is sufficient for approximately 3,000 to 3,500 bays of 132 kV GIS.

The manufacturing ecosystem is dominated by global original equipment manufacturers, and India’s dependence on imports creates supply chain vulnerabilities and cost pressures.

In a push for localization, the CEA has identified 73 items used in the power transmission and distribution sector to formulate a comprehensive strategy based on criticality, feasibility, and industry readiness.

Policy Roadmap

Technology development timelines indicate that Green GIS solutions could expand to 550 kV and potentially 800 kV by around 2030–2032, depending on manufacturer advancements.

Policy recommendations include mandatory inventory tracking and reporting of SF₆ usage, environmental evaluation criteria in tenders, and progressive restrictions on SF₆ procurement.

Earlier this year, the CEA directed all state power utilities to strictly follow its prescribed ratings when floating tenders for transformers with a minimum voltage class of 66 kV.