A nationwide power outage that plunged Spain – and large parts of Portugal and south-west France – into darkness on Monday has exposed the fragility of electrically isolated ‘island’ and peninsular grids, Energy Analyst Jean-Paul Harreman has warned.
The blackout struck just before midday on April 28, halting trains, blacking out traffic lights and forcing airports and hospitals onto emergency power. Spanish system operator Red Eléctrica said a full restoration could take “six to ten hours”, while its Portuguese counterpart REN pointed to “extreme variations” in temperature as a possible trigger. Investigations into the precise cause are ongoing.
Harreman, Director of Montel Analytics, described the event as “an unprecedented incident in modern energy markets”, but not an unexpected one given Spain’s geography.
“Countries that are on the edge of, and more isolated from, the synchronous European grid tend to more easily see grid-frequency deviations,” he said. “In island systems like GB and Ireland, or peninsular systems like Italy and Spain, the AC synchronous interconnectivity with other countries is much lower, leading to a more vulnerable grid as flexibility and resilience has to mostly come from the inside.”
By contrast, core continental nations such as Germany are “surrounded by many other countries and connected with AC connections”, giving system operators access to a broad pool of inertia that helps keep the frequency anchored at 50 Hz when a major generator trips.
Largest grid collapse in a decade
The outage is the worst in Europe since the 2003 Italian blackout and Turkey’s 2015 collapse, Harreman noted, underscoring how quickly a frequency excursion can spiral when there is limited synchronous generation on the bars.
Synchronous machines – chiefly gas, coal and nuclear plants – spin at the same speed as the network and provide the inertia that buys operators precious seconds to react. Variable-speed renewables do not.
Phil Hewitt, also a director at Montel Analytics, added, “Grid disturbances can be ridden out to a degree in regular times but on this occasion, there was a lot of non-synchronous generation on the network which made it more vulnerable.
“Grid operators need to invest in inertia technologies like synchronous condensers to support the drive for more renewables. Investment in fast-acting balancing reserves such as batteries also provides extra resilience as we have seen in markets like GB and Ireland.”
Limited room for new AC links
Although Europe’s integrated market has greatly improved operational cooperation, some parts of the network still “do not completely benefit from the scale of the European market”, Harreman added, pointing out that it is technically and politically difficult to add new AC interconnectors to Spain, Portugal, Great Britain, Ireland, Italy and Denmark.
For Spain, Monday’s blackout is a stark reminder that the energy transition must be matched by investment in inertia, grid-forming equipment and storage – or the lights risk going out again. Thankfully, power was back for many on the peninsula by Monday evening, with Portugal blaming an issue in Spain for the blackout, while Spain pointed the finger at an issue with its interconnection with France – a full investigation is likely to reveal the true nature of the issue.
