Just after midday on April 28, operators managing Spain’s electricity system detected an unusual disturbance — what engineers call an “atypical oscillation.” In simple terms, something had unexpectedly jolted the high-voltage transmission network covering Spain and Portugal.
While the official report released this week by the Spanish government did not specify the initial trigger, its consequences were undeniable: a complete collapse of the power grid, leaving more than 50 million people without electricity.
Carlos Gamez, an experienced electrical engineer now based in Perth with Nova Energy Consulting, said the speed of the grid’s failure was striking.
“It only took about half an hour from the first disturbance at 12:03pm until the total collapse,” Mr Gamez explained.
Once the chain reaction began, he noted, there was little that could have stopped it.
“The report essentially concludes that under the system’s existing conditions, no available mitigation measures could have prevented the cascading failure.”
Debate erupts over renewable energy
The blackout immediately sparked heated debate between critics and supporters of renewable energy. At the time of the incident, most of Spain’s power was being supplied by solar and wind sources.
Bloomberg journalist Javier Blas labelled it “the first major blackout of the green electricity era,” while Spanish Environment Minister Sara Aagesen defended renewables, stating that a combination of factors led to the crisis.
“We have a solid narrative of events that will help us reflect and act going forward,” she said.
“We remain committed to the energy transition, which is not ideological but a key pillar of our reindustrialisation strategy.”
Mr Gamez emphasized that blackouts of this magnitude are always complex and rarely have a single cause. He noted that even before April 28, Spain’s grid had been experiencing higher-than-normal voltage instability.
On the day itself, a major oscillation caused nearly five minutes of voltage fluctuations, forcing operators to restrict power transfers between Spain and France. Around that time, a large solar farm in southern Spain reportedly went offline — possibly due to low market prices — triggering further instability.
Voltage surge triggers grid collapse
Shortly after the initial event, another smaller disturbance occurred. Voltage levels across the network then began to surge uncontrollably, forcing power stations to automatically shut down to protect equipment.
“The voltage climbed rapidly, and the grid couldn’t compensate,” Mr Gamez said.
As voltage spiked and system frequency dropped, the grid’s connection with France was cut, leading to a full blackout.
The Spanish government’s report distributed blame among the transmission network operator and electricity providers. Although it stopped short of naming specific companies, it criticized some nuclear and gas plants for failing to stabilise the system when instructed.
“Several plants responsible for voltage regulation did not respond correctly, and some even worsened the situation,” the report stated.
Central to the failure was the management of reactive power, which is crucial for keeping voltage stable.
A warning about growing grid complexity
According to Mr Gamez, the blackout was less about renewable energy itself and more about the system’s inability to handle reactive power surges. He argued it reflected a lack of preparation for such a scenario.
“It wasn’t a shortage of generation capacity. It was the inability to respond correctly to what was happening.”
Mr Gamez said the incident illustrates the increasing challenges of managing modern power grids, which are becoming far more complex than the large, centrally-managed systems of the past.
“The growing complexity is outpacing our current rules, regulations, and technical procedures,” he said.
“This is an example of regulatory and technical systems not keeping up with the rapid changes in grid design.”
He added that while such blackouts remain rare, they often result from a combination of multiple failures.
