Blackout was caused by an increase in waterfall voltage. An unprecedented phenomenon in Europe

The blackout had as its most likely cause an increase in waterfall tension. This unprecedented technical phenomenon in Europe takes Experts to admit the need for profound measures to reinforce the defense of the European electrical system.

Unpublished in Europe: The blackout of April 28, 2025 had as a cause increased waterfall voltage.

The conclusion contained in the balance sheet of July 15 of the European Electricity Transport Operators Expert Group (ENTSO-E), which investigates the collapse of the network on April 28 in Portugal and Spain, information released by the Energy Services Regulatory entity (ERSE), which is part of the panel, along with operators and regulators from various European countries.

According to ENTSO-E, the waterfall voltage increases-observed in southern Spain in the final phase of the incident-were followed by Sudden production offspringespecially in renewable facilities, and led to the electrical separation of the Iberian peninsula from the continental system, with Loss of synchronism and collapse of frequency and tension.

This type of disturbance had never been identified as a cause of blackout in No point in the European network.

To confirm this conclusion, it will be necessary “an analysis and investigation by all experts in Entso-e electrical systems”, as well as the adoption of new measures to reinforce resilienceaccording to the report.

Among the measures to be implemented, experts highlight the need to “improve the procedures and capabilities of voltage control management of all active interveners of the electrical system” in order to avoid severe incidents related to future voltage.

The other line of action is to assess whether the defense plans in force are able to protect the European electrical system against “this new type of phenomenon.”

During the incident, automatic response plans were activated in Portugal and Spain, as provided for in European regulations, butthey managed to avoid collapse of the network.

The report still highlights the speed and effectiveness of restoration, with REN concluding the system’s recovery at 00h22 of 29 April and the electrical RED around 4:00 am.

Although the legal deadline for producing the factual report on the incident is October 28, 2025, six months after the incident, the expert panel intends to deliver it first. This will be followed by a final report, with recommendations to the European Commission and the Member States, which should be delivered two to three months later.