HD Hyundai Electric develops Korea’s first 420-kilovolt SF6-free breaker

A circuit breaker built for high-voltage power grids is now targeting Europe. HD Hyundai Electric says it has developed Korea’s first 420-kilovolt circuit breaker without SF6, the sulfur hexafluoride gas widely used to insulate high-voltage equipment but targeted by tighter European restrictions because of its potent greenhouse gas effect.

The new breaker uses a C4-based insulating gas instead. That substitution was not a simple refill: HD Hyundai Electric says it required an entirely new design to deliver stable, long-term performance under the extreme conditions faced by critical national power grids. The company began its SF6-free circuit-breaker lineup with a 170kV model in 2021, followed by 145kV and 72.5kV products.

The 420kV model is aimed squarely at Europe’s transmission system. The 400kV-class networks where it will be installed account for more than half of the grids operated by Europe’s major transmission system operators. As the European Union tightens restrictions on fluorinated greenhouse gases and grid investment accelerates, HD Hyundai Electric expects the market for SF6-free high-voltage circuit breakers to reach about 3 trillion won ($2.1 billion) by 2030.

The company says it underwent preliminary qualification reviews by European transmission system operators during development. That gives HD Hyundai Electric a route toward supply contracts, but not yet a confirmed deployment. It is pursuing a long-term agreement with a major British power company and aims to secure its first order by the end of this year or early next year.

So what changes in practice? If the design clears customer qualification and enters service, grid operators could install 420kV-class switching equipment without relying on SF6, while keeping the voltage level used by major transmission networks. HD Hyundai Electric also plans to complete SF6-free breakers in the 300kV and 362kV classes within three years, widening the range of equipment it can offer as Europe upgrades its power infrastructure.