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What could cause a Britain-wide blackout?

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In June, virtually all of Argentina, Uruguay, and Paraguay were left without electricity following a massive power failure. Could something similar happen in the UK? Leo Craig of Riello UPS outlines the biggest threats to our power supplies and unveils a new report that investigates the consequences of a nationwide blackout.

On 16 June, nearly 50 million people in South America lost power after problems with two 500 kV transmission lines disrupted the flow of electricity from the Yacyretá hydroelectric plant. 

Suspected design flaws escalated what – in theory – should have been a localised failure into a complete network failure, an incident described by Argentinian President Mauricio Macri as ‘unprecedented’. 

While power was quickly restored within a few hours, focus this side of the Atlantic Ocean centred on whether it could happen here too. 

Our new analysis, the Blackout report, reveals there’s a one-in-200 chance that there will be a complete grid shutdown in the next five years. That’s still highly unlikely, but when you consider you’ve got a one-in-240 shot of dying in a road accident, it’s certainly not beyond the realm of possibility. 

What could cause such a catastrophic power failure? Here are the five biggest threats. 

Extreme weather and climate change

Climate change has seldom been out of the headlines in recent months, what with the exploits of Extinction Rebellion protestors followed by the government’s pledge for the UK to become the first major economy to commit – by law – to net zero carbon emissions by 2050.

In terms of the risk to our power supply though, this could be a case of shutting the stable door after the horse has bolted. 

The 10 hottest years on record in Britain have all taken place since 1990, while the sea levels around our coasts rise by 3mm a year as ice caps melt and warm water expands. 

All trends point to more weather at either extreme end of the spectrum, namely scorching heatwaves, icy cold snaps, torrential rainfall, and ferocious winds. 

All these events threaten serious disruption to our energy grid. Gale and storm-force winds bring down trees that knock out transmission lines. Flooding from downpours damages vital electrical infrastructure and hinders efforts to fix faults. While severe temperature fluctuations produce dangerous spikes in demand as we rely on either air conditioning to keep cool or heaters to warm up. 

Previous examples of extreme weather give us a glimpse of what might be to come:

  • The Great Storm of October 1987 – brought down 15 million trees in south-east England
  • The St Jude Storm of 2013 – left more than 850,000 homes without power
  • The 2015-16 winter floods caused by Storm Desmond – in just three months between November 2015 and January 2016, seven separate storms hit the UK and Ireland
  • Winter 2009-10 – widespread snow building up to 20-30cm in many areas, while temperatures regularly fell to -5oC or even -10oC
  • Summer 2018 – the joint-hottest on record for the UK.

Space weather

This is the collective term to describe a series of phenomena originating from the sun, such as asteroids, meteors, and magnetic fields. 

While we’ve known about solar flares and geomagnetic storms for hundreds of years, our interest has grown over recent decades alongside our increasing dependence on GPS satellite signals. 

Space weather incidents are rare, but their potential impact is devastating. Even relatively weak solar flares are capable of knocking satellites out of action. 

Historically, the largest space weather event recorded on Earth was the ‘Carrington Event’ in 1859, a huge magnetic storm that disrupted telegraph systems and electrical equipment across the world. 

There’s a 1% annual probability there’ll be a reccurrence of such a ‘perfect storm’ today, which would cause devastating disruption to modern electrical and telecoms systems. 

In 1989, a smaller magnetic storm led to the complete collapse of the Hydro-Québec electricity network in Canada, leaving nine million residents without power for nine hours.

Systems failures and accidents

Naturally, there are a lot of potential incidents that fall under this category. They cover everything from component faults and software crashes, through to fires and explosions. 

The impact of most of these events would be restricted to a specific location or service and dealt with locally, although that’s not to downplay the disruption they could cause to significant numbers of people and businesses.

Infrastructure attacks

Of course, the threat of malicious attacks and terrorism is nothing new to the UK. But a global pattern seems to be emerging where a nation’s power supply is increasingly likely to be targeted by both state and non-state actors.

Deliberate strikes using explosives or other physical weapons could be used to knock out essential networks and infrastructure such as substations or transmission lines. 

The 1990s saw numerous attempts to blow-up electric substations, including the IRA attacks in Bishopsgate in 1993 and Docklands in 1996, while in more recent years terrorists have conducted concerted attacks against energy infrastructure in countries such as Algeria and Yemen. 

Earlier this year, anti-government rebels were rumoured to have taken out one of the main hydroelectric plants in Venezuela, which led to a blackout affecting 18 out of 23 states that left 30 million without power.

Cyber attacks

In 2017, the former chief executive, Office of National Grid Steve Holliday warned, “Nowhere else is as worried as the UK about cyber threats. We are just off the scale on our energy system concerns on cyber.”

Hacking today isn’t just the realm of a small band of elite, state-backed actors. The availability of high-grade malware means anyone armed with just a laptop and modicum of knowhow has the power to launch a potentially devastating attack. 

Combine this with our ongoing shift towards renewables-led smart energy grids, plus society’s increasingly internet-driven way of life, and there are far more opportunities for hackers to expose any vulnerabilities.

Many ‘smart’ devices used in both energy tech and our day-to-day lives are plagued by cybersecurity fears. Hacking into a single smart meter or virtual assistant might not have much impact by itself, but what if it’s thousands – or even millions – powering up at the same time?

Compromised appliances could be turned on in the middle of the night when the network isn’t expecting such a power surge. Or they could feed back incorrect information to our smart grids, exaggerating or understating the actual demand for power. 

The most infamous cyberattack on a country’s energy network took place before Christmas 2015 in Ukraine, when malware shut down 30 substations and left 250,000 people without power. 

But did you know the UK’s power grid was compromised by hackers on 7 June 2017, the day the country voted in the General Election? And this spring saw the USA experience its first electricity-related cyber event too, with grids in both California and Wyoming infiltrated.

As well as covering the biggest threats to our power supply, the Blackout report also examines how prepared we are, how long it could take to restart the grid from scratch, and what the ramifications of a complete shutdown would be for society. It can be downloaded at


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