Are electricity networks doing enough on SF6?

The industry is starting to trial alternatives of sulphur hexafluoride-free switchgear but is this key environmental issue being given enough attention by network operators and the regulator? Utility Week’s Lucinda Dann investigates.

Last week UK Power Networks (UKPN) announced that it has installed its first ‘clean air’ Gas Insulated Switchgear while upgrading a substation in Lewes, East Sussex.

The technology is composed of dehumidified oxygen and nitrogen and has zero global warming potential. Most importantly it is free from Sulphur hexafluoride.

Sulphur hexafluoride, known as SF₆, is the most potent greenhouse gas in existence but it plays a vital, and often irreplaceable, role in insulating switchgear on the electricity network.

Distribution and transmission operators have committed to bringing down leakage rates and like UKPN are exploring the use of alternatives but opinions differ on whether operators are being pushed enough in this area.

Despite there being more than 200,000 pieces of equipment on the distribution system containing the gas, Ofgem has shied away from introducing financial incentives and has rejected plans for more proactive programmes of work.

For both distribution and transmission operators the new price control period appears to bring little in the way of a step-change in activity levels, but if new legislation being brought in on the continent is mirrored here it will bring a firm end to the installation of new SF₆ within a decade.

What is Sulphur hexafluoride?

SF₆ is part of a group of man-made gases known as fluorinated gases, or F-gases. While they used to be found in a huge range of applications such as in double glazing and to keep trainer soles inflated, their use has largely reduced in recent years due to the drive towards net zero. F-gas emission levels were 15 MtCO2e in 2018, accounting for 3% of total UK greenhouse gas emissions. This is 14% down on 1990 levels and 37% below the peak in 1997.

This reduction has largely been brought about by the Kigali Amendment to the UN Montreal Protocol and the European Union’s more ambitious F-gas regulations, with equivalent measures being adopted by the UK on its departure from the EU. However, F-gases are still found in a range of applications where alternatives do not exist, such as within heat pumps, and to insulate electrical switchgear.

For this reason, despite SF₆ being 26,087 times more potent than carbon dioxide on the atmosphere, according to the Committee on Climate Change (CCC), and accounting for 4% of the UK’s total F-gas emissions, it is excluded from any restrictions on use.

However, this does not mean that the electrical industry can keep using it indefinitely.

Science-based targets

While eradication of the gas is the long-term goal, with transmission operator National Grid committing to eliminating all SF₆ from its assets by 2050, leakage is the immediate problem. However, the urgency to tackle the issue both by Ofgem and the companies themselves varies according to voltage level.

By volume, about 85% of SF₆ sits in transmission equipment, with 97% of all leakage at transmission level.

In the RIIO-T2 price control, which runs until 2026, transmission owners are incentivised to reduce their leakage rates, with financial penalties and rewards for over and under achieving against a set science-based target (SBT). They have also produced a SF₆ strategy which covers their approach to asset management, leak repair and how they plan help aid the innovation of SF₆ alternatives through collaboration.

Transmission owners have committed to procuring alternatives where they are available, which in effect means that all new 132kV installations will be SF₆ free. They have also committed to using alternatives at 275kV and 400kV but these are not expected to be commercially available until after 2026.

To this end both National Grid Electricity Transmission (NGET) and SSEN Transmission have begun trialling alternatives across their networks.

Last year National Grid committed to installing an SF₆-free 400kV substation at Lambeth for its London Power Tunnels, with work expected to begin this year. Meanwhile SSEN Transmission has used an alternative gas mixture to insulate a busbar at its New Deer substation in Aberdeenshire, which will help facilitate the connection of the 900MW Moray East offshore windfarm. Using the alternative will reduce the substation’s carbon footprint by the equivalent of more than 117,000 tonnes of carbon dioxide.

Other innovation projects funded by the Network Innovation Competition are looking at reducing leaks while repairs are carried out. NGET is also exploring the possibility of retrofitting SF₆ alternatives into its gas insulated busbars. It has commissioned a project to replace 755kg of SF₆ gas. If successful, NGET has identified another 28 tonnes of gas that could be similarly replaced.

Reputational targets

At distribution voltages leakage levels are much lower, but the size of the asset bank dwarfs that which is found on the transmission network. There are over 200,000 switchgear units containing SF₆ in GB, 97% of which sit at distribution level. The majority of this equipment sits at very low voltages – over two-thirds at 11kV.

Like their counterparts in transmission, distribution network operators’ (DNOs) main focus is on reducing leakage levels. Although DNOs will be able to have a limited impact on overall SF₆ industry leakage rates as most leaks are from transmission equipment, some critics do not believe Ofgem is pushing hard enough for action at distribution level.

Like transmission operators, DNOs must set themselves ‘stretching’ SBTs for leak reduction over the price control period. For example, Scottish and Southern Electric (SSEN) has set itself a target of a 42% reduction against 2020 levels by 2028.

However, think-tank Sustainability First says that the ambition-level of the targets chosen by DNOs seem “modest” and even “level-pegging” compared to ED1 targets set six-years ago, or against their actual performance during the ED1 price control. It adds that it is very difficult to judge what a stretching target would be, or to be able to compare the targets across the companies in any meaningful way.

It called on Ofgem to better understand what a reasonable ‘stretch-target’ against the SF₆ bank and its associated costs would look like before finalising the new price control.

In the current RIIO ED2 price control, which started in April, DNOs were also required to produce an SF₆ strategy for the first time as part of their Environmental Action Plans (EAPs). However, Sustainability First, while welcoming the addition of an SF₆ strategy, said the strategies “vary considerably in quality” from comprehensive to just being on the ‘to-do’ list.

It points out that having a “robust” long-term strategy which considers elements like cost is likely to be crucial to DNOs being able to set ‘stretching’ targets. It believes one reason for the immaturity of several strategies is Ofgem’s decision to rely on reputational regulation for SF₆ rather than introduce financial incentives.

“If left simply to reputational regulation as Ofgem…. a concerted effort by DNOs in the next five years to address their long-run SF­₆ risk cannot be assumed – be that to support cost-efficient outcomes for SF6 asset-management or for net-zero delivery,” it said.

Maxine Frerk, associate at Sustainability First, says that SF₆ did not get the attention it needed in the ED2 price control from Ofgem because it had to compete with net-zero technology like batteries and renewable connections.

“There was a huge amount of work to be done for ED2. We had quite a long battle with Ofgem about whether or not there should be a financial incentive around environmental action plans but in the end the companies were not putting forward anything material in relation to SF₆ to incentivise,” she says.

“SF₆ is covered in that it’s one of the things they have to report on to stakeholders but they will find it quite difficult to judge whether DNOs are doing enough.”

However, she maintains that an “easy win” at distribution level would have been to mirror the financial incentive already in place for transmission operators.

Justifying costs

Although some DNOs appear to be doing the bare minimum on SF₆, for others the need to justify the cost of acting on environmental issues has proven a major limitation.

In its business plan, NGET says the commitments required by Ofgem are not ambitious enough to meet stakeholder and customer expectations. Testing carried out by the company revealed reducing emissions as one of consumers’ top priorities. If cost was not an issue, 60% of consumers want NGET to be a carbon neutral business by 2030 or 2040.

Its externally set science-based target (SBT) is a 50% reduction in scope one emissions by 2050 from a 2018/19 base level, which will require a 33% reduction in SF₆ emissions by 2026. However, NGET says in its business plan that these reductions do not go far enough.

“We believe that to meet our stakeholders’ needs we must be more ambitious than the SBT pathway defined,” it says.

“Our opinion … is that reactive repair alone is not a sustainable solution to SF6 emissions reduction,” it adds.

NGET would like to take a more proactive approach to asset maintenance but struggled to justify the cost to Ofgem due to the cost of carbon and its inability to be able to prove that leaks would not return after being fixed.

It requested £657.19 million to fund a range of ‘flexible’ interventions, but Ofgem said it had not sufficiently demonstrated and justified plans cost-efficient plans, and only allowed £87 million to fund interventions at 10 sites that need immediate work.

Ofgem added that NGET needed to develop an asset intervention plan that focuses on the ultimate goal of reducing the SF₆ inventory in its assets.

DNO SSEN has also pushed to do more on SF­₆. Its business plan it said that it would have to replace its leakiest assets before the end of their expected lifecycle if it was to meet Ofgem’s minimum requirements on SF₆. However, it added that the environmental benefits of early replacements would not outweigh the cost of the work according to traditional cost benefit analysis.

Inevitably its request to do this additional work was initially rejected by Ofgem, although it did accept that the work would need to be carried out in its final determinations.

In its sector summary for F-gases for the sixth carbon budget, the Climate Change Committee (CCC) agrees with SSEN’s cost versus benefit analysis for replacing assets ahead of time.

It says that given the 40-year lifespan of existing assets and the lack of mature alternatives, accelerating asset replacement would be “difficult and expensive”. It expects emissions from switchgear to fall slowly, around 35% from 2017 to 2030 as older SF₆ equipment is replaced.

Frerk says that one of the problems with justifying costs is that Ofgem used an out-of-date cost of carbon while it was setting the new distribution price control.

“One of the things that we were arguing for in ED2 was that Ofgem was using very out of date cost of carbon numbers, so when DNOs tried to show that its worth doing something on environmental grounds Ofgem would say not it’s not.

“Ofgem were using a cost of carbon that was set before the UK committed to net zero. If they had used BEIS’ latest numbers, DNOs could have justified spending more in this area.”

She believes that customers would support more money being spent on environmental issues.

EU Regulations

While the reduction and elimination of SF₆ is not top of the agenda in the UK, the EU is taking a much harder line.

It has recently proposed to bring in bans across all voltage levels on installing new SF₆ equipment by 2031, if alternative technology is available.

Switchgear manufacturer ABB says that alternative solutions containing natural-origin gas for 24kV and 36kV will be available within the proposed EU F-gas timelines.

“Based on our global production footprint, we are already preparing to adjust both our production capacities and our product portfolio in line with the foreseen increasing demand for SF6-free medium-voltage gas insulated switchgear related to regulatory requirements and timelines,” it says.

While the government has committed to maintaining the same percentage reductions as the EU, it does have the ability to set its own rules independently.

However, the CCC supports the UK matching any strengthening of EU rules. It is expected to comment on EU proposals in its annual progress report which will be published at the end of June.

Frerk says that there is a “reasonable possibility” that the UK government will follow suit but even if it does not, the elimination of new SF₆ from the UK market is likely to be a biproduct of any EU regulations as manufacturers won’t produce separate solutions for the UK.

DNOs have been expecting an update to legislation and any ban set to commence during the current price controls would likely lead to a re-opener.

Despite manufacturer ABB’s assertion that it would have product ready for any impending ban, DNOs cite product availability as a key concern if any new regulation does come into effect.

Mark Dunk, head of engineering, Energy Networks Association, said: “The premature replacement of equipment, or the imposition of additional operational restrictions on the electricity network, risks disrupting the UK’s wider net zero transition with serious environmental impacts.

“Commercially available F-Gas free switchgear will not be available in sufficient quantity to meet the required timescales to achieve the government’s decarbonization targets.

“Therefore, it is essential that regulations do not preclude the use of low carbon SF6-free technologies which are already being successfully employed by some UK network operators or preclude new low carbon solutions from being developed.”

Interaction between the supply chain and DNOs is one element that a robust strategy would help to encourage.

For now, it is clear that gaining an understanding of the options, pathways and priorities for managing down SF₆ asset banks over time and the associated costs of asset replacements using alternatives should be a priority for network companies.