Siemens Energy has developed a prototype 420 kV SF₆-free circuit breaker that will be pilot tested in Norway and France as part of the EU-funded MISSION project, coordinated by SINTEF Energy Research.

"SF₆ gas is very effective for this purpose, but it is also a greenhouse gas that is 24,300 times more potent than CO₂," said Nina Sasaki Støa-Aanensen, senior research scientist at SINTEF. The project aims to replace SF₆-based switchgear with environmentally friendly alternatives without compromising reliability.

The prototype uses vacuum technology and has successfully passed initial tests. According to Maurice Lesser, Head of Product Management at Siemens Energy, "The tests carried out on the prototype proved the technical feasibility of a circuit breaker based on vacuum technology for 420 kV. A fully industrialised solution will be installed by transmission system operators RTE in France and Statnett in Norway in the second half of 2026."

The pilot installations are set for two challenging climates: the Dagali substation in Norway, with temperatures ranging from -50°C to +20°C, and the Marsillon substation in France, where summer temperatures often exceed 30°C.

Guilhem Blanchet, VP for substation technology at Statnett, commented, "Statnett is very proud to host world's first pilot installation of a 420kV AIS SF₆-free circuit-breaker... designed for operation at -50°C."

Minh Nguyen, circuit breaker specialist at RTE, added, "By participating in the project, RTE aims to demonstrate the feasibility of replacing aging SF₆ circuit breakers with SF₆-free technologies - without compromising engineering and maintenance operations."

The MISSION project supports EU regulations requiring SF₆-free switchgear in new installations by 2028 for voltages up to 145 kV and by 2032 for higher voltages, helping reduce greenhouse gas emissions in power transmission.