The Shift to SF6-Free Medium Voltage Switchgear

Interest in SF6-free switchgear is growing as utilities, industrial users, and engineering consultants look for alternatives to conventional SF6-insulated equipment. The transition is being driven by environmental regulations, sustainability targets, and advances in insulation and switching technologies.

SF6 has been widely used in medium-voltage switchgear for decades because of its excellent dielectric and arc-quenching properties. Replacing it requires careful consideration of insulation performance, equipment size, reliability, and operating conditions.

This article looks at the role of SF6 in MV switchgear, the technologies available to replace it, and how Toonice approaches SF6-free gas-insulated switchgear design.

Why SF6 Became the Default

SF6 (sulfur hexafluoride) has been widely used in medium-voltage switchgear for decades because of its strong dielectric properties. Its dielectric strength is significantly higher than that of air, allowing conductors and energized components to be placed closer together.

This made it possible to develop compact gas-insulated switchgear (GIS) and ring main units (RMUs) for installations where space is limited, such as substations, commercial buildings, and urban distribution networks.

In sealed switchgear, SF6 provides reliable insulation while protecting internal components from moisture, dust, and other environmental contaminants. It has also been used as an arc-quenching medium in certain switching devices, while many modern MV circuit breakers use vacuum interrupters for current interruption.

The combination of compact dimensions, reliable insulation, and limited maintenance requirements made SF6-based designs well suited to MV distribution. As a result, the technology became widely adopted across utility and industrial networks and remains in service in many installations today.

Why the Industry Is Moving Away from SF6

SF6 offers excellent insulation performance, but its environmental impact has become a major concern. It has a very high global warming potential and a long atmospheric lifetime.

Emissions can occur through leakage, gas handling during servicing, and equipment decommissioning, making lifecycle management an important consideration for SF6-insulated switchgear.

Regulatory requirements are also changing. The EU and other markets are introducing tighter controls on fluorinated greenhouse gases, affecting how SF6-containing equipment is specified, installed, serviced, and eventually replaced.

At the same time, utilities, industrial companies, and project developers are placing greater emphasis on reducing greenhouse gas emissions across their operations and supply chains. These factors are increasing demand for SF6-free alternatives in new MV projects.

There are also practical lifecycle considerations. SF6 equipment requires appropriate procedures for gas handling, leak management, recovery, and end-of-life treatment.

As environmental requirements become stricter, these activities can add cost and complexity over the service life of the equipment. For new installations, evaluating SF6-free technology can therefore reduce both environmental impact and long-term dependence on regulated gases.

SF6-Free Alternatives for MV Switchgear

Manufacturers have responded with several families of alternative technology. Some are commercially available today, while others are still being proven through field experience. Here is a map of the main directions buyers will encounter.

Dry air and clean air insulation

Dry air and so-called clean air are the simplest alternatives. Air has a negligible global warming impact by nature, it is available everywhere, and it does not need to be tracked, reported, or recovered at end of life.

The trade-off is that air has lower dielectric strength than SF6, so an air-insulated design generally needs a larger enclosure or higher gas pressure to reach the same voltage rating.

For many MV applications, especially ring main units and compact distribution switchgear, engineers have learned to design around that limitation, and dry air based units are already a practical choice for buyers who want a low-complexity path away from SF6.

Gas mixtures under development

Another family of alternatives uses fluorinated gases blended with conventional gases to reproduce some of SF6’s dielectric properties. Fluoronitrile blends and fluoroketone blends are the best known directions in this category.

These mixtures can keep enclosures compact while reducing the global warming impact dramatically compared with SF6.

The trade-offs are different: the gases are more complex to handle, the useful temperature range can be narrower, and the long service history simply does not exist yet.

We expect these blends to gain ground as experience accumulates, and we track their development closely for applications where footprint matters most.

Solid-insulated approaches

Solid insulation removes the gas question entirely. Epoxy and other solid dielectrics encapsulate the live parts, so there is nothing to leak and nothing to monitor. Solid-insulated switchgear is compact and quiet, which suits certain indoor and urban installations.

The trade-offs include weight, thermal behavior under heavy load, and the practical difficulty of inspecting or repairing insulation once it is in service. Solid designs have a genuine place in the market, though much of the MV distribution demand still favors gas-insulated solutions for their proven service record and field serviceability.

What Buyers Should Compare in an SF6-Free Unit

When evaluating SF6-free switchgear, the same basic requirements apply as for conventional MV equipment. Key ratings and design features should be checked against the manufacturer’s technical documentation, drawings, and type-test reports.

Electrical ratings should be reviewed first. The rated voltage, normal current, short-time withstand current, and switching or breaking capability must meet the requirements of the network. These values should be supported by the applicable type-test documentation.

Dimensions and installation requirements are also important, particularly when replacing existing SF6 equipment. Depending on the insulation technology, some SF6-free designs may require more space.

Check the overall dimensions, cable interfaces, clearances, and access requirements against the available installation space.

Sealing and service life should be evaluated for sealed gas-insulated designs. Ask the manufacturer about leakage performance, expected service life, pressure monitoring, and procedures for servicing the sealed system where applicable.

Maintenance access varies between designs. Some units use sealed-for-life compartments with limited field access, while others allow inspection or replacement of selected components. The design should match the operator’s maintenance practices and spare-parts strategy.

Finally, review type-test evidence against the applicable IEC 62271 series standards. The documentation should cover the ratings and performance relevant to the specified switchgear, including dielectric performance, temperature rise, short-circuit capability, mechanical operation, and internal arc classification where required.

For SF6-free equipment, any additional performance claims related to the insulation system should also be supported by appropriate test data.

Our Experience Building Eco-Friendly Ring Main Units

At Toonice, we have been building environmentally friendly gas-insulated equipment for exactly this reason. Our NSHBG series is an environmentally friendly gas-insulated ring main unit that covers ratings from 7.2kV up to 40.5kV, which gives utilities, contractors, and OEM partners a practical option when SF6-free requirements are written into the specification.

The series sits within our broader ring main unit program and alongside our medium and high voltage switchgear lines, so project teams can source a complete MV distribution package from a single manufacturer with more than a decade of IEC-oriented production experience.

Conclusion

For specifications, dimensions, ratings, and type-test documentation for the NSHBG Series, contact Toonice with your project requirements. Our engineering team can help evaluate the suitability of our SF6-free gas-insulated ring main units for your network and installation conditions.

Toonice also supports OEM and ODM projects, with configurations available to meet specific technical and application requirements. Send us your single-line diagram or project specifications to discuss the appropriate solution.

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