Fact sheet: blackout in Spain and Portugal

Major blackout in Iberian power grid

Earlier this week, the Iberian Peninsula (Spain and Portugal) was hit by a major blackout. The exact cause is still unclear, but an incident on the Spanish grid caused a number of solar farms to go offline. Further investigation is needed to determine the initial cause. Previous reports of an unusual atmospheric phenomenon have been dismissed, but in any case it led to a ‘textbook’ example of a blackout: a cascade of incidents leading to a large-scale blackout.

The first event caused what are known as inter-area oscillations: slow, periodic fluctuations in electrical power and voltage between large regions or countries within an interconnected power grid. Such oscillations occur when groups of generators in one region are out of phase with those in another, for example due to a fault or a sudden change in supply or demand. Although the general grid frequency, such as 50 Hz in Europe, remains ostensibly stable, these inter-area oscillations can occur at much lower frequencies, typically between 0.1 and 1 Hz. In other words, not the base frequency itself is fluctuating, but there are small fluctuations added to it.

The Iberian grid began to fluctuate in a very short time (seconds) compared to the rest of the European high-voltage grid, as far as Latvia. The interconnections between the Iberian Peninsula and France were automatically shut down to prevent further damage. As a result, it is estimated that more than 20 GW of the approximately 26 GW of installed capacity was shut down in a matter of seconds. The effects were also felt in other parts of Europe, although elsewhere the impact remained within normal safety limits and no blackouts were reported. The Belgian grid was not affected.

An exceptional phenomenon, but not unique

While such incidents are rare, they are certainly not unique. Major grid disruptions are more common, often caused by natural phenomena such as hurricanes (think Hurricanes Katrina and Sandy) or wildfires (e.g. California). In addition, technical failures – the simultaneous failure of multiple facilities – or human error can also lead to widespread outages. Two well-known examples are the two-day major blackouts in India in 2012, affecting 400 and 620 million people respectively. Europe itself has experienced a number of “medium-sized” blackouts, such as the 2003 blackout in Italy. Often, a combination of factors leads to a major blackout.

The immediate question is whether such a blackout could happen in Belgium. The last real blackout dates back to August 1982. The concerns about blackouts in the winters of 2014-2015 and 2018-2019 were of a different nature: they were about a possible controlled shutdown of a limited part of the load due to a lack of generation. Due in part to the accelerated phase-out of both coal-fired and nuclear power plants, serious winter electricity shortages were feared, but no actual blackouts occurred.

The Belgian network: strong European integration

Unlike the Iberian Peninsula, Belgium is much more integrated into the European network, with robust connections to neighbouring countries. In contrast, the Iberian Peninsula is less geographically and technically connected to the rest of Europe – partly because of the Pyrenees, which make connections to France difficult. As a result, in the event of major disruptions, it quickly becomes a ‘network island’, exacerbating the situation. In the case of Spain and Portugal, interconnection capacity (the maximum amount of electricity that can be exchanged across borders between countries) is only about 10% of the load, or 2-3% of the total installed capacity. This means that they can only import or export a limited amount to the rest of Europe. By comparison, the European Union has set a target of 15% interconnection capacity by 2030 to increase security of supply between member states and to use renewable energy more efficiently.

Although Belgium is better connected, a major outage is not impossible here either. If a serious incident were to occur in Belgium, there is a real chance that other parts of Europe would be affected because of the interconnectedness of our grids. However, the European electricity grid is extremely stable. Under normal circumstances, the system will continue to operate even if one or more components fail. But there are limits: absolute security against every incident is neither technically nor economically feasible, nor desirable. The focus is therefore increasingly on robustness (resilience): the ability to restart quickly and in a controlled manner, and to limit the impact of faults by zoning the grid.

A blackout and a restart

A blackout such as the one on the Iberian Peninsula shows how dependent society is on electricity. The immediate effects are widespread: loss of elevators, lighting, transport (including traffic lights, trains, the underground and air travel), payment transactions,… and the gradual breakdown of communications. Society grinds to a halt and, in some cases, panic breaks out. Industry is also affected: most industrial processes are disrupted and some may even be damaged. There are also long-term effects, such as the spoilage of (no longer refrigerated) food, sick or elderly people not receiving adequate help, and economic and reputational damage.

There are detailed procedures for restarting the grid. These ensure that the grid is brought back online safely and in stages – first the transmission grid, then the rest. The restart is a step-by-step process, prepared in detail by the grid operator. At each step, it is necessary to decide which combination of load and generation will be switched on, and to do so in sufficiently small steps so as not to lose the fragile reconstruction network again. This process is largely remotely controlled, but in a situation where the exact status of the network is not known and communication is limited or non-existent. It is also not impossible that certain actions may require manual intervention, which is quite time consuming. The majority of users can usually be reconnected within a few hours, but in remote areas or in the event of physical damage, this can take a day or more.

The role of renewables: strength or weakness?

The growing share of renewable energy sources (wind and solar) makes grid management more complex. Renewable generation often consists of many smaller, distributed units that contribute little or nothing to the so-called ‘inertia’ of the grid – an important property that helps keep the grid frequency stable during sudden changes in demand or supply. The lower the inertia, the faster and more violently the frequency will fluctuate during disturbances. So adding more renewable sources to the system means that the grid becomes more sensitive to disturbances.

At the same time, these sources have advantages. Modern renewables can help regulate the frequency (like traditional generators), and there are many more small plants, each of which has a much smaller impact than very large power plants. Some renewables can also (semi-)autonomously help with restarting. However, the energy transition will require major adjustments to the grid and associated grid management systems, and more incidents are likely to occur during this transition period.

Importance of grid stability in interconnected grids with many renewables

Today’s electricity grid is extremely well designed and can withstand a lot. However, it remains important to invest in a stronger and more robust grid. This should include sufficient attention to the necessary stability mechanisms and grid control, but also to the processes for mitigating major incidents and restoring the system as quickly as possible in the event of a failure.

Etch, our recently established Energy Transmission Competence Hub, supported the Flemish government, is conducting pioneering research into future-proof electricity networks.