Analysis: Increasing electricity demand and growth in renewable generator connections means the Irish grid is running closer to its limits every year
On April 28th last, a massive power outage affected the entire Iberian Peninsula at 12.30pm local time in Spain. This "blackout" shut down the entire national electricity grids of Spain and Portugal, impacting around 60 million people. It was the largest electricity blackout ever in Europe in terms of scale and disruption to everyday life for tens of millions of people.
Spain and Portugal not only lost electrical power but also lost many other essential services. Internet and telecommunications were severely impacted, as well as transport, with rail and metro services and airports all closed. There was chaos on the roads with traffic lights out of service across all the major cities, and banking and card payment services were down. The Madrid Open was stopped. Sadly, there were several reported deaths due to the failure of life-supporting medical equipment.
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From RTÉ Radio 1's Drivetime in April 2025, Dr Paul Deane from UCC on the massive power blackout in Spain and Portugal
What could possibly have caused the electricity grid, the critical infrastructure supporting our entire modern way of life, to collapse suddenly and without warning? In the absence of an immediate explanation of the root cause from official sources, speculation ran wild in the days and weeks following the event.
A cyberattack or other forms of foul play were ruled out early on. Many media outlets across Europe initially attributed the cause to a "rare atmospheric phenomenon", but this explanation was later dismissed by industry experts. Some commentators blamed renewable energy for causing the blackout, since both Spain and Portugal have high levels of wind and solar generation connected to their grids.
So what really caused the blackout?
The electricity grid is a vast interconnected system, with millions of electrical components that all need to work together seamlessly for reliable delivery of power. While faults of individual components in the system are common, a complete failure of the national electricity grid, or "blackout", is very rare. Blackouts are by their nature unexpected and unpredictable. They usually have multiple root causes and are due to "unknown unknowns", factors that could not have been anticipated by grid operators.
From France24, what caused the massive blackout in Spain and Portugal?
To establish the root cause, experts need to sift through billions of data points measured from various parts of the grid. The independent European association ENTSO-e are responsible for establishing the cause of the Iberian Peninsula blackout and recently published their initial findings in a 264-page report.
In short, the blackout was caused by an inability to control voltages on the power transmission system. The voltage in the power grid can be likened to the pressure in a system of water pipes - the force that pushes water through pipes (or electricity through cables in the case of the power grid). In power grids, voltages throughout the system need to be carefully controlled within very tight specifications. If not, generators on the power system will "trip", or disconnect, to avoid equipment damage.
Over a period of several months, experts have pieced together a second-by-second timeline of the events of April 28th and established the root cause based on hard evidence. There were several contributing factors. First, there were "oscillations" observed on the Iberian power grid on the morning before the blackout, caused in part by malfunctioning controllers in two Spanish power plants. Such oscillations are relatively common in power grids and normally would not lead to an emergency.
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From RTÉ Radio 1's Liveline, listeners in Spain and Portugal on the power outage in April
To mitigate these oscillations, control room operators switched on additional transmission lines and changed control settings on the interconnectors from Spain to France. This reduced the oscillations but had unintended consequences that proved to be fatal. These actions increased the voltages in a transmission system which already had elevated voltages due to exporting large amounts of power to France.
Unfortunately, the grid operators were not fully prepared for this scenario and did not have sufficient voltage control resources on the grid to bring voltages back down. In the space of just 20 seconds, voltages on the Spanish and Portuguese transmission grids went from stable levels to dangerously high levels, causing power plants across the peninsula and the interconnectors to France to trip, collapsing the entire grid in an instant.
Could this happen in Ireland?
The learnings from the Iberian blackout will be applied by grid operators across Europe. Improved voltage control schemes will be eventually be implemented in national "grid codes", the rules and specifications for operating each country's electricity grid.
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From RTÉ Radio 1's Morning Ireland in March 2025, Irish electricity demand set to grow 45% between now and 2034
Are we vulnerable to a similar blackout here in Ireland? While our local power distribution networks (especially near Atlantic coasts) are exposed to storm damage, our main transmission grid, the "backbone" of the power system, has been robust. We have never suffered a grid blackout.
However, annual reports from EirGrid warn that we are running our grid harder and closer to its limits each year. We have increasing electricity demand (mostly from data centres) and huge growth in new renewable generator connections. Combined with insufficient investment in our grid infrastructure, this leads us towards an ever more precarious situation.
It is impossible to predict how or when a grid blackout might occur in Ireland, but the events in Spain and Portugal highlight the need to deliver on critical energy infrastructure projects, which in too many cases have been hampered by planning delays and legal challenges.
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The views expressed here are those of the author and do not represent or reflect the views of RTÉ
