Air

Jun 09, 2023

The chemistry of air as we know it provides the most widely available and sustainable replacement for sulfur hexafluoride (SF6) in electrical MV switchgear.

For our sustainable future, reducing or at a minimum stabilising the concentrations of the greenhouse gases causing global warming in the atmosphere is a top priority best achieved, unless they are directly removable like CO2, by reducing their initial use.

At the top of the list is the SF6 gas, the most powerful greenhouse gas, with the latest data indicating a global warming potential of 25,200, i.e. that 1kg of SF6 has the same global warming impact over a century as 25,200kg of CO2.

As a man-made gas, it has progressively been used over the past 50 years for insulation in high and medium-voltage switchgear, with over 30 million units of secondary gas-insulated switchgear (GIS) alone installed worldwide.

Increased renewable installations mean more switchgear must be installed to manage their grid connections. The same is true for energy users where industries that are replacing fossil fuels with electricity, or transportation like electric buses that now rely on clean electric power.

SF6 and other greenhouse gases are on the radar of authorities and regulators such as the European Commission. The Commission has a proposal currently under review to completely remove it from electric distribution networks or reduce its use in the coming years. Anticipating the critical need to find a sustainable and cleaner alternative, technology providers in the electricity industry have been developing new solutions, and are already making available MV equipment with alternatives that are SF6-free.

One option that has emerged is other fluorine-based gases. However, these require special handling and some health and safety concerns have arisen with their potential use as electrical MV switchgear is commonly located in public areas.

These options present additional challenges for operations and management, particularly at end of life when the risk of leakages of the gas or its by-products being released into the atmosphere is the greatest.

The other main option selected by several technology providers is air as the dielectric medium. It is associated with vacuum breaking technology for the current interruption to achieve electrical performance mandated for use in the grid and building power systems.

Dry air is not an immediately obvious choice as, although a known insulating medium, its properties are not as great as fluorinated gases, but an innovative design approach allows equipment with air to continuously deliver excellent performance (air pressurised at 0.4 bars for 12kV and 1.5 bars for the 24kV switchgear). It also offers several compelling advantages for other key aspects. Sustainable by nature, it is freely and widely available, safe and easy to handle, and suitable for use across a wide range of temperatures. For these reasons, air is trouble-free and can be released into the atmosphere at the end of the equipment's life.

In addition, an important benefit is that the solution can be sized as compactly as the SF6 solution. Consequently, the sustainable installation itself can easily replace a conventional equipment equivalent with SF6.

Overall, the operating mode is identical. The Shunt Vacuum Interruption (SVI) technology comprised of a combination of a vacuum interrupter and a disconnector in air likewise operates similarly to the 3-position switch in SF6.

Industry whitepapers: How SF6 alternatives and digital technologies collaborate to solve energy challengesHow SF6 Alternatives and Digital Technologies Combine to Empower Electricity Decarbonization and Efficiency

With this innovative MV switchgear in use in the field for upwards of 40 years, air replacement provides multiple practical and environmental benefits to utilities and society in general, in both the short and long terms, with otherwise unchanged operating conditions.

Pure air is by nature green with no global warming potential or requiring recycling at the end of life—it's free from any current or future regulatory concerns.

From a practical perspective, pure air switchgear is compact with a footprint identical to or similar to SF6 switchgear. Thus, replacement is eased without the need for modifications of civil engineering in the electrical room. This provides immediate emissions reduction benefits, which companies can account for in their ESG monitoring and reporting.

With restrictions on the use of the SF6 gas imminent, the requirement to achieve net zero by 2050, and any new switchgear now likely to still be in use well past that date, the transition to readily available air-based switchgear is an urgent priority across the globe.

Research by Germany's Fraunhofer Institute on MV SF6 switchgear in Europe has indicated it must be replaced to achieve MV grid carbon neutrality.

With business as usual with grid extension, SF6 volumes will continue to increase dramatically for the next decades. The recently proposed F-gas regulation would enforce and enable systematic reduction of these SF6 emissions to reach 0 in 2050 if SF6 installed base is replaced by that time.

Schneider Electric's award-winning SF6-free AirSeT technology encompasses a range of digital modular air- (AIS) and gas-insulated (GIS) MV switchgear for primary and secondary distribution applications from the smart grid down to individual industries and large buildings.

The technology was recognised for its positive climate impact in the category of ‘High Potential Carbon Handprint Innovation’ by the International Carbon Handprint Awards organized by the Climate Leadership Coalition and Vancouver Economic Commission at the Climate Week NYC 2022. The solution includes patented innovations for current breaking with SVI and for mechanism in composite materials which enables higher mechanical endurance required by increasing penetration of renewable energy in the electrical grid.

The AirSeT Active ranges are also IoT connected by default to form a foundational element of a smart grid architecture with greater visibility and control of their management and operation.

Coupled with the latest wireless sensors and digital tools, additional features available include 24/7 condition monitoring and the potential for new data-based digital services delivered via the cloud.

Some of the electrical distribution networks piloting this green air-based MV switchgear include E.ON in Sweden, the country's largest DSO, the EEC Engie in New Caledonia, the French electricity and gas distributor GreenAlp, and Netze BW in Germany.

In the next editorial in the series, we will delve into some of these in more depth.

Meanwhile, this White Paper offers insights into the potential scenarios around SF6-free technology deployment and how markets perceive the transition away from SF6 and to sustainable alternatives.

The third part of this editorial series will look at a customer case study where Schneider Electric is bringing SF6-free solutions to the market.

Read Part 1 here: Why the energy transition cannot compromise on SF6