A massive power outage that disrupted Spain, Portugal, and parts of France on Monday is still shrouded in mystery, with grid operators ruling out a cyberattack as the cause.
While the exact reason behind the massive blackout remains unclear, experts suggest that a series of failures may have contributed to the incident, raising questions about the vulnerability of interconnected power grids.
Spain’s grid operator, Red Eléctrica, stated that preliminary findings indicated “no kind of interference in the control systems” that would suggest a cyberattack, as confirmed by Eduardo Prieto, the company’s operations director.
This conclusion echoed earlier statements by Portuguese Prime Minister Luís Montenegro. Despite these reassurances, both the Spanish and Portuguese authorities admitted that the cause of the blackout could not yet be definitively determined, and the investigation is ongoing.
On Monday evening, Spanish Prime Minister Pedro Sánchez revealed that 15GW of power, equivalent to 60% of the country’s demand at that time, was “suddenly lost from the system” in just five seconds.
This sudden disruption triggered cascading effects across the Iberian Peninsula and beyond, including parts of France.
According to Prieto, the cut appeared to result from two disconnection events, which occurred in rapid succession in southwestern Spain, a region known for substantial solar power generation.
Sánchez was quick to dismiss claims that renewable energy was the cause of the disruption, emphasizing that there was no failure of supply. In fact, he pointed out that demand for electricity was relatively low leading up to the incident.
Despite this, experts believe the failure could have stemmed from a mismatch between supply and demand, a common issue in power grids.
If the frequency of electricity shifts beyond a certain threshold—particularly in grids that integrate renewable energy—large-scale disconnections can occur to protect infrastructure.
Professor Hannah Christensen from the University of Oxford explained that when multiple companies disconnect to prevent equipment damage due to frequency changes, it can create a “cascading effect” that leads to blackouts.
While renewable power’s intermittent nature can pose challenges, Christensen suggested that Spain’s forecasting system, designed to handle such fluctuations, should have predicted this disruption.
Professor Keith Bell from the University of Strathclyde added that while failures in any energy system—renewable, fossil, or nuclear—are possible, Spain has a long history of managing solar and wind energy with sophisticated forecasting methods.
He speculated that the grid’s failure may have resulted from a series of coincidental failures in the system, akin to the “Swiss cheese model,” where different issues align to create a larger problem.
Another factor that may have contributed to the blackout was Spain’s electrical connection to France. Red Eléctrica suggested that the power loss triggered a trip in the interconnection grid between the two countries.
Spain’s power grid relies on just a few connections through the Pyrenees, making it vulnerable to disruptions. The outage was eventually resolved thanks to backup connections to France, Morocco, and renewable sources, such as gas and hydropower.
In addition, there were initial reports suggesting that a “rare atmospheric event” might have played a role in the disruption. However, Portugal’s grid operator, REN, denied these claims, stating that the blackout was not linked to “induced atmospheric vibration,” a phenomenon previously thought to affect high-voltage transmission lines.
As investigations continue, grid operators and experts will focus on identifying the exact sequence of events leading to the massive power cut.
For now, the incident highlights the complex nature of modern power grids, which rely on intricate networks and the integration of various energy sources to maintain stability.