The massive blackout that affected Spain last month has put the stability of the electrical system under scrutiny, especially in the context of the transition towards renewable energyAlthough the initial public reaction pointed to the system's low inertia due to its high renewable energy footprint as the main cause of the collapse, over time and with the advancement of research, the discourse has become considerably more sophisticated and nuanced.
For weeks, speculation has swirled about what actually caused the "electricity blackout." As more official data and technical analyses have emerged, a more complex scenario has emerged, where Low inertia was not the direct trigger Although it did play a significant role in worsening the problem once the peninsula was isolated from the continent.
The concept of inertia in the electrical grid
Electrical inertia It is the system's resilience to sudden frequency changes and is traditionally provided by the turbines and generators of conventional power plants (thermal, nuclear, and hydraulic). New renewable sources, when connected through electronic systems, They do not generate inertia naturally, which from the beginning led many experts and public voices to put them in the spotlight of controversy.
Official data have disproved this initial hypothesis. According to Sara Aagesen, Vice President for the Ecological Transition, the inertia level on the day of the blackout was 2,3 seconds, above the minimum of 2 seconds recommended by European operators Entso-E. In fact, Other European countries typically operate with lower inertia, as Joan Groizard, Secretary of State for Energy, explains.
Sequence of oscillations and disconnections
Ongoing investigations have detected anomalous oscillations on the European grid hours before the collapse, some even recorded simultaneously in Spain, France, and Germany. The first significant oscillation occurred around 12:03, and its exact origin is still unknown. About twenty minutes later, another, less intense but widespread oscillation was recorded, reaching countries such as Latvia. All of this generated an unstable environment that was the prelude to the rest of the incidents.
Shortly after, in just twenty seconds, three generation shutdowns (amounting to 2,2 GW) were triggered in Granada, Badajoz, and Seville. This coincidence in time has led experts to rule out mere coincidence and look for a common cause, pointing the finger directly at system surges as the critical element. Several analyses, including that of Professor Luis Badesa, suggest that these prior disturbances in the network may have been the cause of the outcome.
Inertia as an aggravating factor, not as a cause
With the system now isolated from the rest of Europe, the level of inertia became especially important. At that moment, Spain imported a high percentage of renewable energy (around 59% solar and 11% wind). With the loss of support from the continent's major generators, the grid frequency began to fluctuate rapidly. The lack of sufficient inertia caused protection systems to cascade, shutting down plants to prevent further damage and contributing to the blackout.
Technical analyses and official statements agree that the Low inertia was not the cause of the failure, although it did accelerate the collapse. The system's structure wasn't prepared to withstand massive island-like disconnections, leaving the grid at a very vulnerable point.
The consequences for the management and future of the network
Following the event, the presence of synchronous generation in the grid has increased to ensure greater stability. This increase in the proportion of power plants with inertia raised system costs, as less flexible and more expensive technologies must be maintained to ensure supply. This increase in costs is already reflected in the electricity bills of consumers in the regulated market (PVPC) and will likely affect those in the free market when they renew their contracts.
It is evident that the technological adaptation requires new strategies that include storage, microgrids and backup systems, to ensure a supply reliable in a high renewable penetration environmentEnergy transition management must incorporate these aspects to prevent similar incidents in the future, ensuring a more resilient and secure grid.
Authorities expect a full official report in less than three months that will clarify all the technical aspects and responsibilities for the incident. Although questions remain, a growing number of voices are underscoring the importance of strengthening the grid and supporting the integration of renewables through technologies that provide stability and flexibility.
