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SF6-Pilotprojekt Vertragsunterzeichnung 01

For climate protection: TenneT orders the world’s first SF6-free extra-high voltage switchgear

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  • Pilot project to be realised in collaboration with Hitachi Energy

  • Goal: natural gases to gradually replace greenhouse gas SF6

  • Demand: new EU regulation must not delay grid expansion

The transmission system operator TenneT has now placed an order for the construction of the world’s first gas-insulated metal-enclosed switchgear (GIS) at extra-high voltage level. It will operate entirely without the climate-damaging insulating gas sulphur hexafluoride (SF6). The system will be built by the contractor Hitachi Energy at the Erzhausen substation (in Lower Saxony) by 2024 and is part of TenneT’s largest alternating current (AC) grid expansion project ‘Wahle-Mecklar’.

‘By using an alternative gas mixture instead of SF6, the global warming potential of the insulating gas in this new switchgear will be only about one per cent compared to conventional systems’, said TenneT COO Tim Meyerjürgens. ‘Our goal is to gradually transition to using natural gases for insulation in new electrical switchgear systems to reduce this value to almost zero. By 2025, one third of our new orders to service providers should fulfil this criterion for TenneT switchgears, followed by another third by 2030. With this order, we are sending a strong message to the market to develop SF6-free extra-high voltage switchgears.’

The challenges are enormous: natural gases feature less powerful insulating properties. The systems consequently need to be larger and more complex. Therefore, to pave the way for widespread use of SF6-free GIS, experience must be gained through pilot projects in order to safely test the new technologies and optimise them for standard operation.

TenneT, like the other three German transmission system operators (TSOs), is very concerned about current EU plans to trigger excessive time and innovation pressure through regulation. After all, the alternative technologies must have the same high reliability as the current SF6 technology in order to continue to maintain a high level of security of supply. In a joint position paper, the four TSOs demand that all potential alternative technologies must be considered – and, if possible, tested in pilot projects – to ensure that alternative solutions are available for all applications in the transmission system grid in the future.

Typical aspects they regard as important: protection of previously installed SF6 systems, due consideration of technological security and market availability for all technical applications, and assurance of planning security for the energy transition. Otherwise, the four TSOs fear a significant delay and security risk in the expansion of the transmission system grids. After all, trouble-free operation and targeted expansion of the transmission system grids are crucial success factors for decarbonisation of the European economies by 2045/2050. To achieve this goal, large procurement volumes of proven systems and equipment in a broad technical supply range are mandatory prerequisites. It will be several years before these volumes are available.

To accelerate development and ensure that high grid availability remains guaranteed, TenneT is implementing pilot projects such as this SF6-free 420 kV GIS.


SF6 is the strongest known greenhouse gas. According to the United Nations, the SF6 global warming potential is 25,200 (AR6) times that of CO2. In addition, the gas degrades very slowly. Heavy, with high density, non-toxic, chemically inert, non-flammable – for a long time SF6 seemed to be the perfect gas for many applications in the high-voltage sector and appeared to only offer advantages. But since 2007, SF6 applications have been banned in the EU – with one exception: SF6 is still allowed in the electrical industry, because there was no alternative until now. It is mainly used in high-voltage installations, both for insulation and for current interruption. However, SF6 does not have a harmful effect on the climate during normal use in high-voltage installations, but rather only when it escapes into the environment. SF6 emissions cannot be completely prevented because this gas cannot be 100 per cent sealed off in the application. Even though SF6 emissions from TenneT equipment in Germany already make up less than 0.1 per cent today, TenneT’s ‘SF6-free strategy’ envisages that this value will be reduced to zero in the long term through the gradual transition to new switchgears that exclusively use natural gases for insulation.


Media information:

More information on the SF6-EU topic:
BDEW amendment of the European F Gas Regulation

Further information on the SF6 strategy of the four German transmission system operators:
Switch to SF6-free technologies (

In the attached photo from the signing of the contract (from left to right):

Pascal Daleiden, Country Managing Director Austria, Germany and Switzerland, Hitachi Energy; Dr Markus Heimbach, Managing Director High Voltage Products, Hitachi Energy; Sjouke Bootsma, TenneT Director Supply Chain Management; Georg Praehauser, TenneT Director Large Projects Germany; Dr Florian Martin, TenneT Head of Asset Technology - Asset Management



Mathias Fischer

Mathias Fischer

Spokesperson - Grid expansion onshore & offshore, sector coupling, energy policy Northern Germany, flexibility & innovations