Is it the End of the Road for SF6?

Is it the End of the Road for SF6?

Sulphur hexafluoride – SF6 – is widely used in the electricity distribution industry in medium- and high-voltage installations such as substations, transformers and power stations. It is an odourless, colourless, non-flammable gas that acts as an insulator and prevents explosions and fires brought about by short circuits.

These qualities have made it the most common gas insulator for HV switchgear and use is increasing as a greater number of smaller generators come onto the grid. However, concern has been raised about the global warming potential of SF6 as use increases, perversely driven by increased demand for renewable energy.

Why is SF6 a Problem?

Carbon emissions are correctly cited as the principal cause of global warming but a number of other pollutants have a powerful global warming effect. Global warming potential (GWP) measures how polluting a unit of any given gas is compared to carbon dioxide and SF6 has a GWP of 23,500 meaning that every kilo that is released will be the equivalent of 23.5 tonnes of carbon dioxide.

Given that every wind turbine contains up to 5kg of SF6, the potential for harmful emissions is huge. Additionally, SF6 is a synthetic gas that does not break down naturally and can stay in the atmosphere for up to 1000 years so will remain a problem for longer than other greenhouse gases such as methane.

How Much is Used at the Moment?

According to Cardiff University, the use of sulphur hexafluoride is increasing by about 30-40 tonnes every year across transmission and distribution networks. The UK network currently holds around 1000 tonnes of SF6 and rises in emissions across the EU in 2017 contributed the equivalent of 1.3 million extra cars on the road for a year.

One of the paradoxical issues surrounding SF6 is that demand is increasing, fuelled by more green electricity generators being connected to the grid. The smaller, more fragmented grid has required more switchgear and, as nothing comes close the same effectiveness as SF6, this has led to emissions rising by 8.1% across the EU in 2017.

Are there any Solutions?

Leakage of SF6 from electricity distribution networks is the principal means by which the gas leaks into the atmosphere so one of the clear solutions is to improve the maintenance of insulation in the equipment. Newer switchgear has much better rates than older equipment but replacing switchgear across the whole grid would be extremely costly and does not solve the underlying problem.

As far as alternatives go, medium-voltage installations including transformers can be insulated by insulating oil which does not pose the same risk of leaking into the atmosphere as it is a liquid rather than a gas. (We stock a number of instruments capable of testing insulating oil in laboratories and in the field.) Other gases can also be used on medium voltage switchgear.

As far as HV installations are concerned, however, there are no viable alternatives that offer the same insulating, low maintenance properties as SF6. A European Union review is due next year and similar exercises have had positive impacts in other sectors, for example in automotive air conditioning, but sulphur hexafluoride is set to stay for many years to come.

A Price Worth Paying?

For all of the damaging effects of SF6 on the environment, its outstanding properties should not be overlooked. It has led to safer electricity distribution for workers and those living near HV equipment and is remarkably unreactive and safe. Furthermore, it has been an important factor in making the entire grid greener as it facilitates the connection of more and more renewable generators.

Although EU emissions were the equivalent of 1.43 million extra cars on the road in 2017, that is still a tiny fraction of the more than 300 million vehicles in the bloc and if these emissions can be negated by more green energy and electric cars, SF6’s benefits may outweigh its costs until an alternative is found.

We stock a range of detectors for SF6 gas. Click here for more.