How do you explain that something like this has happened?

‘It is a combination of incidents in the electricity grid. A succession of cascading or joint factors that have caused the collapse of voltages in the grid. It is still too early to know the causes and we will have to wait for official information from Red Eléctrica de España. This type of combination of factors is highly improbable in a grid as strong, as robust and as reliable as the Spanish and European electricity grid, despite the fact that paradoxically today we have had this failure’.

Was it unlikely to happen?

‘The European electricity system, and the Spanish one within it, are enormously robust and a failure like the one that happened today is enormously unlikely. The system works by being prepared for the worst possible failure at all times, so an event like today's must be multifactorial, something caused by many critical events in conjunction. Despite this, the system knows what to do in these cases and the restoration of the system is being carried out as expected’.

Why has this happened on the Spanish mainland, and is it a more vulnerable region in Europe?

‘Spain (or rather the Spain-Portugal peninsular electricity system), due to its low interconnection capacity with the rest of Europe (only a small interconnection with France), is considered in many cases an isolated energy system. This makes it more vulnerable to a combination of events such as the one we have experienced today, despite the fact that an energy zero is highly improbable.

Could it happen again in the next few days, and in the medium term?

‘In the short, medium and long term, this type of event is very unlikely to happen again because of the above. The fact that the system is being properly restored means that the system is under control and we can continue to rely on the very high quality standards of the electricity grid’.

What needs to change so that it doesn't happen again?

‘Without a doubt, analysing the causes of this event will help us to ensure that it does not happen again in the future. For this we must wait for the official report from the system operator (Red Eléctrica de España). From what we are seeing today in the system's replenishment, relying more on renewables, and establishing new grid operation protocols and procedures that include renewables more in the active participation of grid management, is crucial to continue building one of the most reliable and robust grids in the world, as we already are’.

How do you explain that something like this happened?

‘An ‘absolute zero’ is an extremely serious situation in which the power grid completely loses voltage, i.e. the entire system shuts down. It is as if a switch were flicked that suddenly disconnects the entire electricity supply. This widespread blackout on the Iberian peninsula occurred because, in just five seconds, more than half of the electricity generation capacity was lost. The system, unable to balance such a sharp drop between generation and demand, protected itself by automatically disconnecting both internally and from the rest of the European grid. This is a self-protection measure that, paradoxically, implies a total cut-off’.

Was it unlikely to happen?

‘Yes, this type of event is considered highly unlikely. The Spanish electricity grid has multiple safety mechanisms and protocols that act automatically to avoid precisely this type of collapse. However, the speed and magnitude of the loss of generation that occurred today exceeded the usual margins for manoeuvre. Even experts from the system operator itself (Red Eléctrica) had ruled out in the past that there could be an ‘absolute zero’ on the peninsula. This shows that, although the system is prepared for many contingencies, it is not infallible’.

Why did this happen on the Iberian peninsula? Is it a more vulnerable region in Europe?

‘The Iberian peninsula has a peculiar position in the European electricity system because it is poorly connected to the rest of the continent. Its electricity interconnections are limited, so in practice it functions almost like an energy island. This makes it more vulnerable to internal disturbances: if a major failure occurs within the peninsular system, it cannot receive sufficient external support to stabilise itself. In addition, in recent years there has been a large increase in the presence of renewable energies, such as solar and wind, which are variable and weather-dependent. This can make the system more difficult to control in real time, without sufficient backup or storage’.

Can it happen again in the next few days? And in the medium term?

‘In the next few days it is unlikely that an outage of the same magnitude will occur again, especially as the system will now be on high alert. In the short term, the operator will take very strict preventive measures. However, in the medium term, if the exact causes are not well understood and possible structural failures are not corrected, the risk does not disappear completely. It is essential to thoroughly investigate what caused such a rapid loss of generation in order to prevent a recurrence’.

What needs to change so that it doesn't happen again?

‘There are several key lines of improvement The most important is to increase electricity interconnections with France and other European countries, so that the peninsula is no longer so isolated’. It is also necessary to improve the flexibility of the electricity system, incorporating more storage (such as batteries or hydraulic pumping systems) that can compensate for the variability of renewable energy. In addition, control and forecasting systems should be reinforced, and more demanding simulations should be carried out to contemplate extreme scenarios such as the one we experienced today. All this requires investment, planning and a clear strategy for a safe energy transition’.