Isolation without side effects TU Braunschweig supports development of climate-friendly circuit breakers

The fluorine gas SF₆ is widely used in electrical circuits. Sulphur hexafluoride, a compound of the elements sulphur and fluorine, is a very inert and electronegative gas. It is therefore particularly suitable as a switching gas in switchgear and controlgear. The catch: the gas is considered a climate killer. In a new industrial project, Technische Universität Braunschweig is researching fluorine gas-free circuit breakers for the high-voltage range.

SF₆ has a lot to offer: The gas combines good electrical extinguishing and insulating properties, chemical inertness, high temperature resistance and non-toxicity. With these properties, it has proven itself in the energy industry. However, it becomes problematic when the gas enters the atmosphere. This is because it has a huge greenhouse gas potential with a CO₂ equivalent of 25,184 – one tonne of SF₆ is equivalent to the climate impact of 25,184 tonnes of CO₂. For comparison: methane has a CO₂ equivalent of 27 (IPCC). Accordingly, it is considered a particularly climate-damaging gas; however, its contribution to the greenhouse effect is comparatively low when compared to carbon dioxide, methane and nitrous oxide (Federal Environment Agency). Nonetheless, there is a need for action: the European Commission expects demand for SF₆ to increase in the coming decades. The reasons are the expected growth of the market for electronic devices and the expansion of the grid to connect renewable energies.

The elenia Institute for High Voltage Technology and Power Systems at TU Braunschweig is developing fluorine gas-free circuit breakers for the high-voltage range in cooperation with the Swiss PFIFFNER Group. The aim is to qualify an alternative medium with a greenhouse gas potential <1. In power engineering, high voltage is defined as a voltage of 36,000 volts or more. The distribution and transmission grid is active in the high-voltage range. Due to the high voltages, correspondingly high demands are also made on the insulating medium within the devices, whereby the market almost exclusively offers devices with fluorine gases, especially in the higher voltage segment. High-voltage technology is used, for example, to supply smaller cities, overhead power lines and to connect larger industrial plants.

Over the next three years, the researchers will accompany the development of a circuit breaker together with Swiss colleagues from the Eastern Switzerland University of Applied Sciences and the University of Applied Sciences and Arts Northwestern Switzerland. “Thanks to elenia’s expertise in the field of switchgear development, we are supporting the PFIFFNER Group in the development of the fluorine gas-free circuit breaker and are carrying out project-accompanying investigations in the institute’s modern test facilities,” says Patrick Vieth, research associate at elenia.

About the greenhouse gas SF₆

A significant area of application for SF₆ is electrical equipment, including switchgear, instrument transformers, gas-insulated lines, high-voltage bushings, capacitors and wind turbines. Other areas of application are soundproof windows, extinguishing agents or etching agents in semiconductor production. The use of the gas is critical on the one hand because of its high greenhouse effect and on the other hand because of its high chemical stability. It decomposes only very slowly in the atmosphere – it remains in the atmosphere for about 3,200 years. The greenhouse gas carbon dioxide, on the other hand, lasts only 120 years.

In April 2022, the European Commission drafted a proposal to amend the European F-Gas Regulation. The goal is to avoid the use of these highly climate-damaging gases and to reduce emissions by 55 per cent by 2030.