An investigation by the Spanish government has determined that the blackout affecting the Iberian grid, which supplies both Spain and Portugal, was precipitated by a series of interconnected issues. According to the report, attempts to rectify a minor instability inadvertently exacerbated the situation, culminating in a self-perpetuating cycle where elevated voltages caused power plants to disconnect from the grid, thus further amplifying the voltage.
The report highlights that the grid operator had an alarmingly low number of power plants available to help stabilize the situation, and those that were activated did not respond adequately. Although the complete report is scheduled for release later today, a summary has been shared, detailing the sequence of events that led to the blackout and providing insights into the failures of grid management. It also confirms that a separate investigation found no evidence of a cyberattack.
Prior to the blackout, the Iberian grid faced several days of voltage fluctuations resulting from a supply-demand imbalance, which were managed without serious issues until the afternoon of April 28. Shortly after noon, a rare frequency oscillation was observed, linked to a specific facility on the grid, though the report does not disclose its identity or type, referring to it simply as an “instalación.”
In attempting to address the oscillations, grid operators inadvertently raised the voltages, leading to a subsequent occurrence of a weakened version of the oscillation about 15 minutes later. Eventually, different frequency oscillations unfolded, typical for European grids, provoking further corrective measures that raised the grid’s voltage levels.
While the Iberian grid has the capacity to manage these types of disturbances, the report indicates that only ten power plants were tasked with voltage regulation on that day, marking the lowest commitment for 2025 up to that date. Moreover, several of these plants failed to respond appropriately to the grid operators, with a few exacerbating the voltage surge.