Substation becomes more climate-friendly

Hitachi Energy and Tennet have installed a 420 kV circuit breaker with an SF6-free outdoor design in a substation. The first of its kind in the world.

Hitachi Energy and the transmission system operator Tennet have commissioned an SF6-free 420 kV outdoor circuit breaker for the first time at the Oberhaid substation near Bamberg (Bavaria). This is the world's first application of this technology at this voltage level, Hitachi said in a press release.

Circuit-breakers perform a central protective function in the transmission grid. "They detect dangerous short circuits at an early stage and interrupt the flow of electricity within milliseconds - to protect people, systems and infrastructure," it continues. The new system now works without the previously used insulating gas SF6 (sulphur hexafluoride).

SF6 is 25,000 times more harmful to the climate than CO2 and has a very long service life. It remains in the atmosphere for thousands of years. In the energy supply sector, SF6 is mainly used as an insulating and extinguishing gas in high and extra-high voltage systems, such as in circuit breakers and gas-insulated switchgear. Leaking seals or maintenance work can lead to emissions.

Florian Dotzler, Director Supply Chain Management at Tennet: "The switch to SF6-free technologies at the 420 kV level is a milestone for the further development of extra-high voltage technology." The transmission system operator sees the introduction of SF6-free technology as a step towards reducing climate-damaging emissions in grid operation.

The 420 kV level forms the backbone of the European transmission grid. At this voltage level, large amounts of electricity are transported over long distances with comparatively low losses. Up to now, SF6-based switchgear has predominantly been used here. With the "EconiQ" circuit breaker, Hitachi Energy has now opted for an alternative which, according to the company, offers the same reliability, safety and performance.

The project required extensive technical testing in normal and fault operation. In addition, existing substations designed for SF6 technology had to be adapted. Regulatory and normative issues for SF6-free solutions at extra-high voltage level also had to be clarified, according to Hitachi Energy.

Author: Stefan Sagmeister