Posted: 22 February 2015
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Storm in a teacup?

Severe Risk and Resilience Analyst Andrew Richards explains the reality of the threats posed to the UK’s electricity system from solar storms, and outlines what National Grid is doing to minimise any risks.

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Storm in a teacup?

Storm in a teacup?

Artists impression of a Solar Flare

The reality is that if you experience a power cut like this it’s more likely to be caused by mechanical breakdown, or someone drilling through a cable!

National Grid’s Severe Risk and Resilience Analyst Andrew Richards


The biggest solar storm we know of was the Carrington Event in 1859


When we look at it, the sun appears to be constant and unchanging. In fact, it changes an awful lot and we experience these changes in a variety of ways on Earth, including the impressive flashes and bursts – solar flares – we often see reported in the media. These actually have no effect whatsoever on National Grid and pose no threat to the electricity system.

Sometimes, with a very large flare, you get a coronal mass ejection – a big lump of solar energetic particles (100 million tonnes of it) is thrown out into space at a million miles an hour. If it’s thrown in exactly the right direction it can cross space and hit Earth.

By the time it arrives, the temperature isn’t an issue. But this massive burst of solar wind does carry the sun’s magnetic field, which means that if the polarity is the reverse of ours, it is attracted to Earth’s own magnetic field and gets sucked in, dumping energy around the planet.

Imagine hitting Earth’s magnetic field with a giant hammer and ringing it like a bell. This causes electricity currents to flow in the High Voltage electricity networks, but doesn’t affect the Low Voltage networks – those in domestic properties. This means nothing is going into houses and there’s no danger from leaving household items plugged in. All the effects would be in the National Grid transmission lines between pylons.

The sun’s on an 11-year cycle of solar magnetic activity, and during its active period we experience very small solar events several times a month with little or no effect. The very big ejections which we are concerned with don’t follow this solar cycle, but fortunately they are very rare.

There was quite a large coronal mass ejection in 2003, but its magnetic field was the wrong way round so it has no effect on our systems. In 1989, a similar-sized event blacked out Quebec Province in Canada for up to nine hours, and damaged two bits of our equipment in the UK, but that had no effect on the power system or the public here.

The biggest solar storm we know of was the Carrington Event in 1859. We’re certain there will be a repeat of that, and that when it comes there could be some effects on the electricity system, but an event of this magnitude is extremely rare. To put it in perspective, there’s an average one-in-100-year chance it will happen in the coming year, or a 10% chance it will happen in the next 10 years.

But what would the potential effects from such a solar superstorm be on National Grid, and what would the public see and experience?

Our High Voltage transformers, which convert electricity from the very high voltages we use to the lower, less dangerous, voltage used by the public, could overheat and we’d have to turn them off or, in the worst case, the internal insulation might overheat and they would just break. If that were to happen only a National Grid engineer would know, and the public would not be affected at all.

If, however, we were to lose too many transformers at any one site then there’s a chance the people supplied by that electricity station could lose power. Again the chance is exceptionally low – a one-in-10,000 people chance – on top of the fact that the event itself is extremely rare.

There’s another way our machinery could be affected – these solar events can cause fluctuations in the voltage so that, at home, your supply might get lower than 240v. Normally you wouldn’t notice – the lights might become a bit dimmer – but if it goes too low it’s possible we could get a power outage even though National Grid hasn’t lost a transformer.

However, our research has shown such an outage wouldn’t be widespread. It’s really just like a normal terrestrial storm which can knock out power lines leaving a small area of the UK with no power – you can’t see exactly where it will strike, but if it did we’d just reconnect the power supply within between two to 12 hours.

Yes, it’s highly inconvenient to be left without power for any length of time, and connecting people to their energy is central to what we do at National Grid, but the key thing is that it wouldn’t be the Armageddon people may be imagining. It would be localised, not affecting the whole country and National Grid would simply divert power to re-energise the system.

Even in a local blackout there are consequences – to emergency services, traffic lights, the police. However, all critical services in the UK have back-up generation and we have plans in place to get power back on quickly, prioritising vital services such as hospitals, for example.

Everything we can do to minimise the consequences is being done. All the critical services and major agencies are regularly involved in planning and preparedness exercises. And the reality is that if you experience a power cut like this it’s more likely to be caused by mechanical breakdown, or someone drilling through a cable!

I think there are two reasons why people are fearful of solar storms. One is that, in America, people believe their risk is greater. Their transmission system is bigger and uses longer lines as it’s spread out over large distances, while in the UK our system is a highly connected cobweb of shorter, less vulnerable power lines. It’s built differently because we’re a small island and they’re a huge continent.

In the States people talk of the possibility of blackouts lasting months. National Grid were approached by Government to see if that was possible here and, while you can never say anything is impossible, when we worked out the potential effects on the UK, the chance of something like a months-long, UK-wide blackout here is effectively zero.

The second reason is fear of the exotic or unknown. People don’t know much about the sun and fear it could unleash some unimaginable explosion on us – that’s why newspapers love this type of story.

Since the 1989 event we’ve been reinforcing our system based on what we learned. Our High Voltage transformers are of various designs, some much more resistant to these extra currents, and the UK has been gradually replacing transformers with these more resilient types.

We’re bearing the extra costs to put in the new designs that are made of better materials now that, thanks to the big studies made in the 1990s, we understand what the risk is.

Additionally, voltage fluctuations affect the protective relays that are fitted to the electricity system and which are designed to turn off a line if something has gone wrong. Engineers are cautious people so the settings on these have always been at over-sensitive levels. By making the setting slightly less cautious the system can be made more resilient to fluctuations caused by these superstorms with no adverse effects.

We’ve looked at the correct actions to take if we think a storm is on its way so we can batten down the hatches appropriately.

It’s impossible to predict coronal mass ejections – they travel incredibly fast and can reach Earth in as little as 15 hours. That is why we monitor the sun and space weather environment daily, along with the Earth’s magnetic field, to give us advance warning. We use satellite imagery every day to look at sun spots, which are indications of the big build-ups of magnetic energy that can cause these ejections.

If something is going to hit us it has to come from the centre of the sun facing us. So we look at the left-hand side of the sun – which will take four or five days to rotate to the middle – and that gives us enough time to take steps.

If we do find a flare, you have to bear in mind that it might not cause one of these ejections; or might throw it in the wrong direction to hit Earth, or its polarity may not be the right way round to cause problems.

But as a precaution, in the event of a flare, we would make the system as stable as we can to endure fluctuations and ensure that as many of the 8,000km of UK power lines as possible are switched on. The advance warning from the monitoring means we are even able to get lines that are being worked on back in service within three to four days in readiness.

We’d also turn on as much of our High Voltage equipment as we can so they share the burden of the excess current flowing through the system. That way, none of them would become overwhelmed and they’d act as a drain, returning the excess current to earth as quickly as possible.

Several times a year we run control room exercises and training about various risks, including solar storms, to ensure the operational staff who run the system can take the right actions to minimise voltage fluctuation.

The Met Office recently set up a space weather forecasting service which will be critical to our preparedness and we’ve been talking to them about our needs so that what they produce will help National Grid as well as other users.

We aren’t at the stage where we think we have all the answers, but science progresses daily and we’re in close contact with space weather scientists, the academic community, the Government and advisory groups because a major event wouldn’t just affect National Grid.

Although the electricity grid is the biggest thing in terms of size and what’s affected, a major solar weather event would impact other things – airlines and transatlantic flights, atmospheric effects on astronauts, high frequency radio transmissions, and satellites (which could temporarily shut down and affect GPS, and thus things like lorry drivers, emergency services and even cash machines). You can find further reading here.

National Grid is prepared. The effects on our system are very much like those from any other cause. We see solar weather as a risk but alongside the many others we face every day. A rare but important risk we have to manage – and we’re very experienced at managing risks.

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