Statnett builds four 420kV transformer stations free of SF6
Image courtesy Statnett
Norwegian TSO Statnett is building four new 420kV stations without the greenhouse gas SF6, calling it a first for Scandinavia.
Statnett is in the process of building the new substations Hyggevatn and Skaidi in Hammerfest municipality, as well as Liåsen and Ulven in Oslo. These four stations are being built with technology fully free of SF6, both in passive and active components, including circuit breakers.
According to the TSO, the four new substations will be the first in Scandinavia to use the SF6-free technology at a voltage level of 420kV.
Said Statnett executive vice president for Technology and Transformation, Ingeborg Øfsthu: “This is a major milestone marking the start of complete SF6-free facilities for 420kV in Statnett.
“Every kilo of SF6 corresponds to 25,000 kilos of CO2 equivalents, and the benefit is therefore significant when using alternatives in such facilities. This will contribute to a significant reduction in Statnett’s long-term carbon footprint.”
Said Statnett’s Guilhem Blanchet, VP for technologies development substation: “It has been a long technology and qualification journey in close collaboration with several high voltage equipment suppliers to find replacements for the greenhouse gas in Statnett’s 145 and 420kV substations.
“We are very proud to be part of this journey at Statnett and instal one of the first 420kV GIS 100% SF6 free 63kA –40C in Scandinavia.”
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Contracts and projects
Hitachi Energy was awarded the contract for the delivery of the tech in Liåsen and Ulven, and GE Vernova for Hyggevatn and Skaidi.
SF6-free technology has been commercially available at lower voltage levels, but it is only now, says Statnett, that the technology is available for the 420kV voltage level.
The construction of Statnett’s new Hamang transformer station in Bærum has been a pilot project where only the passive components of the gas-insulated substation were built without SF6 gas, resulting in a 17% savings.
The station was commissioned in 2024, and based on this experience, new stations are being built entirely without the greenhouse gas for both passive and active components.
Statnett also participates in the European Commission’s research and innovation programme, Horizon Europe, through the project MISSION (eMISsion-free HV and transmisSION switchgear for AC and DC).
In this project, Statnett is developing, designing, and testing a pilot for the world’s first 420 kV air-insulated SF6-free circuit breaker according to Blanchet.
Statnett facilities and SF6
Statnett owns and operates over 200 stations in Norway.
Most of their substations are air-insulated facilities located outdoors, known as AIS facilities (air insulated switchgear), containing little SF6.
Due to their less amounts of SF6, cheaper build and easier operation, the TSO says they are primarily looking to build AIS facilities.
AIS facilities, however, take up more space than gas-insulated facilities (GIS), which are more compact. Therefore, GIS facilities are built where space is limited and it’s impossible to build AIS.
Around 50 of Statnett’s facilities at higher voltage levels are GIS switchgear type. These contain SF6 because the facilities use greenhouse gas as an insulation and extinguishing agent in enclosed facilities and other components.
Statnett thus has a large inventory of SF6 from these facilities, with an estimated annual leakage of between 200-500 kilogrammes of SF6 gas.
Statnett aims for no new facilities to contain SF6 by 2050 and is working to adopt alternative gases through new technology.
Namely, all new 145kV and 420kV GIS substations will be built SF6-free.
The total inventory of SF6 will thus decrease as new facilities are built without SF6 and older facilities containing SF6 are replaced gradually. Statnett is also working on online monitoring to control potential leaks better.
