The scramble to uncover what caused Europe's biggest power outage

Yahoo

28-04-2025

What exactly caused the massive power cuts that swept Spain, Portugal and parts of southern France?
That is the question on the lips of every energy expert in Europe – and theories abound.
Spanish authorities suggested they were investigating the possibility of a cyber attack on grid infrastructure, while some officials in Portugal initially said it was caused by a freak weather phenomenon before backtracking. Both say the exact cause is still unknown.
At the same time, others have warned that Spain's growing reliance on renewable energy, particularly solar power, may also have contributed to the crisis.
With details still thin on the ground, much of this remains speculation, with authorities still scrambling to figure out what went wrong.
But one thing is for certain: The outage on Monday was of nightmare proportions for grid operators.
It was so severe that it took out the national networks of Spain and Portugal, knocking out power for tens of millions of households, and will require a complicated procedure which could take days to put right.
'They need to get the grid up and running again urgently, because major grid outages are really dangerous things,' says Michael Liebreich, an energy consultant.
The outages knocked out traffic lights, electric-powered trains and mobile phone networks, with hospitals and other emergency services forced to switch over to emergency generators.
Such outages are extremely rare in developed countries and are difficult to recover from, due to the need for supply and demand on electricity networks to be finely balanced.
In Spain and Portugal's case, grid operators will now have to carefully restore power across the country in a choreographed fashion.
Simon Gallagher, managing director of the energy consultancy UK Networks Services, says teams will likely split the national grids into sections and start up power stations locally before 'stitching' the network back together in stages.
'It will probably take up to a week or more,' he says. 'It's catastrophically bad and I think people will start to realise that over the next few days.'
That is the priority for now. But experts say the nature of the power outage is concerning for a number of reasons, with no clear information yet provided about the cause.
'This is mature technology, modern power grids are designed to cope with this kind of thing and temperature fluctuations so there is a big question over what's happened here, and it all seems very strange,' adds Gallagher.
Just hours into the outage, Portuguese energy company REN (Rede Eletrica Nacional), the local equivalent of the National Grid, initially claimed the blackouts had been caused by 'extreme temperature variations' in Spain.
It later clarified the statement, with Joao Conceicao, REN board member, saying late Monday that one possible cause was 'very large oscillation in the electrical voltages, first in the Spanish system, which then spread to the Portuguese system'.
But experts believe if the original weather theory holds, it suggests that sudden changes in temperature caused unusual wind activity which may have interfered with high voltage transmission lines – perhaps by blowing them into each other - and caused an electrical fault.
Others said that in high temperature or high humidity conditions, power cables can interact with electric charges in the atmosphere, causing them to vibrate.
Prof Chenghong Gu, an electrical engineering expert at the University of Bath, said: 'This vibration can cause fatigue of conductors … and in very extreme cases, failures of conductors.'
Yet such a fault should be a relatively simple problem to deal with for experienced grid operators.
The mystery is why this one led to cascading failures that spread so catastrophically across Spain and Portugal's entire electricity system.
One possible answer is Spain's growing reliance on solar and wind farms for power.
Electricity systems rely on so-called 'inertia', which is a by-product of power stations that have spinning parts – such as those running on gas, coal or hydropower. Inertia is caused by the natural velocity of the spinning parts, and is a core component of any electrical system.
These plants have turbines that can speed up or slow down to help adjust the power frequency, which must be kept within certain limits at all times for the lights to stay on.
Inertia also helps to protect the system from faults that cause sudden drops in frequency, as it gives grid operators more time to take actions that will stabilise the system.
But solar panels and wind turbines do not generate inertia because they do not have the same spinning parts. And before Monday's power cuts, they were generating almost 80pc of Spain's power, according to transparency data.
There was also less gas-fired power on the system as demand at lunchtime tends to be low, meaning that any sudden drop in frequency – such as one caused by a transmission line fault – would have been harder to deal with than usual.
Kathryn Porter, an independent energy analyst, explains: 'If you have a grid fault, it can cause a frequency imbalance and in a low-inertia environment the frequency can change much faster.
'If you have had a significant grid fault in one area, or a cyber attack, or whatever it may be, the grid operators therefore have less time to react. That can lead to cascading failures if you cannot get it under control quickly enough.'
Duncan Burt, a former British grid operator who is now strategy chief at Reactive Technologies, agrees.
'If you have a very high solar day, like Monday, then your grid is less stable, unless you've taken actions to mitigate that,' he says.
However, he believes low inertia alone was not enough to cause the serious outages seen in Spain and Portugal and that weather conditions on Monday do not appear at first glance to have been particularly unusual.
'In Iberia, it is known they are headed towards a low-inertia situation. But it is quite early to see anything this severe,' he adds. 'There is definitely something deeper going on.'
Tom Smout, an analyst of electricity grids and markets at LCP Delta, contrasted France's resilience to such events with Spain's relative vulnerability.
'France is resilient to these problems because it has a lot of nuclear power plus hydroelectricity which have stable and predictable outputs,' he says.
'Spain has lots of renewable energy and not much storage, so it has a lot of issues with generation levels rising and falling with the weather.
'In European terms Spain and Portugal is also a relatively small and isolated part of the European grid and that makes it more vulnerable to these events.'
Ironically, it also comes just days after the International Energy Agency warned that grid stability was a major issue countries needed to be alive to as they moved towards increasingly electrified energy systems.
Yet what exactly happened remains unclear for now. And the real answer is likely to involve several factors, not just one.
'We're deep in engineering country here,' warns Liebrech. 'It is just really hard to know until they have properly investigated.
'Could it be a cyber attack? Sure. It could also just be that a very weird thing happened that has never happened before.'
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