Spain’s government has concluded the blackout which swept across the peninsula on 28 April was caused by a cocktail of voltage surges, unstable grid behaviour and failing safeguards.
A forensic report delivered to ministers this week concludes the event was a multifactorial collapse, triggered by abnormal frequency oscillations, underperformance by key generators and control systems that simply didn’t kick in.
The system spiralled into full collapse between 12.33.18 and 12.33.30. Just 12 seconds.
At its height, the blackout severed interconnection with France and took the entire mainland system offline .
Vice President and Ecological Transition Minister Sara Aagesen called the investigation “a rigorous and verified diagnosis” and promised a wave of new measures at the next cabinet meeting to prevent a repeat.
“This is a solid foundation we can build on to deliver swift and effective action,” she said.
The committee behind the report analysed more than 300GB of data. It ruled out cyberattack – but revealed that only a handful of synchronous power plants programmed for voltage control were actually operational – and some even worsened the situation by pumping out the wrong type of reactive power.
Key failures include:
- Tension instability in the days before the incident
- A 0.6Hz oscillation that forced emergency grid adjustments
- Disconnections of major generators, some occurring prematurely
Once it began, protection mechanisms failed to stop the surge cascade and in some cases, worsened it.
The power was mostly restored within hours, with 50% of demand covered by 10pm and 99.95% by the following morning, thanks to autonomous hydro generators and interconnectors from France and Morocco.
But despite the quick turnaround, the government isn’t sugar-coating the risk.
Review ordered
The government will now beef up grid supervision, implement stricter obligations on operators and push for greater interconnection with neighbouring countries.
A key technical fix involves enforcing PO 7.4 rules, which allow asynchronous systems to deploy voltage stabilisation tech.
Cyber defences will also be hardened, with new event detection protocols and stricter network segmentation.
Spain’s energy ministry insists this wasn’t a case of lacking resources – just poorly deployed ones.
As new regulations roll out and oversight sharpens, Madrid wants to make sure the lights don’t go out again.
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