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Iberian blackout was caused by multiple factors, report says

Published by Global Banking & Finance Review

Posted on March 20, 2026

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· Last updated: April 1, 2026

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Iberian blackout was caused by multiple factors, report says
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By Pietro Lombardi MADRID, March 20 (Reuters) - The massive power outage that hit the Iberian Peninsula in April last year was the result of multiple factors that ultimately led to a voltage surge and

ENTSO-E Report Reveals Causes Behind Major Iberian Peninsula Blackout

By Pietro Lombardi

ENTSO-E Investigation into the Iberian Peninsula Blackout

MADRID, March 20 (Reuters) - The massive power outage that hit the Iberian Peninsula in April last year was the result of multiple factors that ultimately led to a voltage surge and a chain of power-generation loss, a European network of electricity transmission system operators called ENTSO-E said in a report on Friday.

In the organisation's final report into the blackout, it looked at its root causes and offered recommendations to reinforce Europe's power grids and avoid similar incidents in the future using available solutions. The report is not meant to assign blame.

Like previous inquiries, the report confirmed preliminary findings by the organisation, pointing to a surge in voltage as the immediate cause of the April 28 outage - the first of its kind and Europe's most significant blackout in more than two decades, which left large parts of Spain and Portugal without power for up to 16 hours.

Root Causes of the Blackout

ROOT CAUSES

Failures in Conventional Power Plants

The report mentioned several factors as root causes of the blackout. These included conventional power plants - thermal power plants using coal, gas and nuclear - that did not help control voltage as expected by the grid operator based on existing rules. In addition, some network components to control voltage operated manually, taking more time, and settings to disconnect equipment to protect them from a surge of voltage were not in line with existing requirements.

Voltage Control and Network Vulnerabilities

The report also highlighted that the Spanish grid operates at a wider range of voltage than other European countries, meaning that the margin between allowed voltage limits and those triggering disconnections was very small or non-existent.

Moreover, the management of the power links with France could have made the system behaviour worse, it said.

Summary of Key Findings

"The analyses above clearly indicate that the key phenomenon in the incident was the non-effectiveness of voltage control within the Spanish power system," the report's summary said.

Missing Data and Recommendations

MISSING DATA AND RECOMMENDATIONS

Challenges in Data Collection

Experts couldn't establish the reasons for some initial power-generation losses in Spain because the owners of those power plants said they lacked the required data, the report said.

Recommendations for Future Prevention

The report also included some recommendations to avoid similar events in the future. These include improving monitoring of the power system and better coordination and data exchange among players in the power system.

(Reporting by Pietro Lombardi; Editing by David Latona and Thomas Derpinghaus)

Key Takeaways

  • Cascading voltage surges and loss of generation triggered the blackout—multiple interrelated technical failures, not a single fault. Sources cite insufficient reactive and synchronous generation and manual network control delays. (apnews.com)
  • Spain's wider-than-average allowable voltage range left virtually no margin between operational limits and fault-triggering thresholds, exacerbating cascade risk. (cadenaser.com)
  • Lack of data from power plant operators hampered root‑cause clarity. Final recommendations stress improved system monitoring, faster automated voltage control, enhanced data exchange, and better cross-border coordination. (apnews.com)

References

Frequently Asked Questions

What caused the massive power outage in the Iberian Peninsula last year?
According to ENTSO-E, the outage was caused by a voltage surge and loss of power generation due to multiple technical and operational factors.
How long did the April 28 blackout last in Spain and Portugal?
The blackout left large parts of Spain and Portugal without power for up to 16 hours.
What were the main root causes identified in the ENTSO-E report?
Key causes included ineffective voltage control in thermal power plants, manual operation of some grid components, settings not aligned with requirements, and issues with the management of power links with France.
What recommendations did the ENTSO-E report suggest to prevent future blackouts?
Recommendations included improved system monitoring and better coordination and data exchange among power system operators.
Did missing data affect the investigation into the blackout?
Yes, some power plant owners lacked required data, limiting the ability to determine certain initial causes of power-generation loss.

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