‘Blackouts can happen anywhere': how power systems worldwide can collapse

The Guardian

02-05-2025

Europe's biggest blackout in over 20 years on the Iberian peninsula unleashed hours of chaos for people in Spain, Portugal and parts of France earlier this week. But in the aftermath it has raised a common question for governments across the continent: could the same happen here?
Europe's political leaders and energy system operators have given assurances that such blackouts are extraordinarily rare, and that European power grids are some of the most stable in the world.
Yet energy experts have warned that although wide-scale blackouts may be rare, no grid is infallible. Prof Jianzhong Wu, the head of the school of engineering at Cardiff University, told the Guardian blackouts 'can happen anywhere'.
'Despite today's high standards of reliability, low-probability but high-impact blackout events can still happen. These networks are not designed to be completely blackout-free because achieving such a level of reliability would require investment far beyond what is economically feasible,' he said.
Charmalee Jayamaha, a senior manager at the UK government-backed Energy Systems Catapult, said: 'No system can be 100% resilient,' so risks 'need to be balanced with our willingness to pay to reduce them'.
If no power system is bulletproof, then what are the risks that could trigger a catastrophic blackout in any country? Here we look at the top reasons a power system might collapse.
Major power system collapses are frequently due to factors that are difficult to foresee or control.
Extreme weather events and natural disasters present a clear risk because storms, heatwaves and earthquakes can lead to devastating damage to critical national infrastructure. Lightning strikes and solar flares have also been known to damage vital equipment such as substations and power lines, which are crucial to maintaining the stability of the grid.
Early reports suggested that Spain's blackout had been caused by a 'rare atmospheric phenomenon' due to a sudden change in temperature, which may have destabilised the grid. But the grid operator, Red Eléctrica, later dismissed the theory.
Most outages due to natural disasters are easier to identify. In the US state of Texas, a series of three winter storms in early 2021 caused windfarms and gas power plants to freeze over, leaving 4.5m homes and businesses without power, some for several days.
The risk of these events is on the rise as the climate crisis increases the frequency and severity of extreme weather events.
Some blackouts are entirely human-made. Jayamaha said geopolitical factors and cyber-attacks had the potential to cause 'major interruptions' to the grid. Human error could also play a role.
After the Iberian blackout many questioned whether malevolent state actors had taken aim at the grid. However, Red Eléctrica was quick to insist there was no sign of an attack and later ruled the theory out.
Still, the risk of a cyber-attack on power grid infrastructure is 'not science fiction', according to the Dutch cybersecurity expert Dave Maasland. He told the Dutch press that 'attacks on power supplies are possible and have already caused disruptions in the past'. He pointed to Russia's attacks on Ukraine's power system in 2015 and 2016, and a failed attempt after its invasion in 2022.
In the most simple terms, a blackout is caused when the power system stops working: this can be due to an unexpected mechanical glitch involving power lines, substations or other grid infrastructure – or a more complex problem with how the system runs.
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A key concern to emerge after Spain's blackout is the role that renewable energy may have played in the system collapse. Without a clear explanation for the outage it is too soon to comment, experts have said.
What we know so far is that Spain's electricity system suffered two major generation losses in the solar-rich south-west of the country within seconds, which may have destabilised the grid connection between Spain and France, and ultimately led to a full loss of power across the energy system. The initial trigger remains under investigation.
It is true that a renewables-rich grid is more difficult to run than one powered by fossil fuels. This is because the grid was originally designed with big coal, gas and nuclear power plants in mind. These plants feature spinning turbines that create inertia on the system, which helps to maintain the grid's frequency at about 50Hz. Wind and solar farms do not create inertia on the grid, meaning that at times of high renewables output it can be more difficult to keep the frequency steady if there is a sudden loss of power. A significant fluctuation in frequency can cause generators to automatically disconnect, leading to a collapse of the system.
Jayamaha said the shift to renewables would require grid companies to invest in grid-stabilising technologies. 'The electricity grid is undergoing unprecedented change as we reduce our reliance on fossil fuels and move to solutions that are cheaper, better, and cleaner. This creates different resilience challenges that need to be managed,' she said.
'Resilience is no longer just about having enough spare megawatts you can simply switch on – but about the right mix of technologies and system capabilities to operate a grid with a lot more renewables.'
Kate Mulvany, a principal consultant at Cornwall Insight, said that in the UK, a key part of that effort had been the development of new balancing and system management tools, 'particularly the integration of grid-scale batteries, which play a vital role in maintaining stability'.
'The electricity system in GB is among the most reliable in the world. So, while a major blackout will always be possible, the extensive safeguards in place make it extremely unlikely,' she said.
In many cases, the risk factors outlined above can coincide, meaning relatively common or innocuous events can compound to create a cascading failure that leads to catastrophe. These 'black swan' events are nearly impossible to anticipate – meaning grid operators are under pressure to prepare for the unexpected.
In August 2019 the UK suffered its biggest blackout in over a decade, leaving almost 1 million people in England and Wales without electricity and hundreds of people stuck on trains for up to nine hours.
The blackout occurred after a lightning strike hit a transmission circuit north of London and managed to cause two electricity generators more than 100 miles apart to trip off the system within seconds of each other. It was described as an 'extremely rare and unexpected event' by the energy system operator.
Lightning strikes on energy infrastructure are relatively common, as are power plant outages, but the impact of the large double-outage on the grid's stability was severe enough to cause scores of small generators and batteries using incorrect safety settings to trip off the system and make it impossible for the operator to avoid a loss of power.
No single element in the event would cause a large-scale blackout on its own, but the combination proved devastating.