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Scientists comment on power outages across Iberian Peninsula, possibly caused by induced atmospheric vibration.
Prof Keith Bell, Professor of Electronic and Electrical Engineering, University of Strathclyde, said:
“As of Tuesday morning, it’s very good to see that almost all demand for electricity in Spain and Portugal has now been restored.
“It’s not yet clear to me what happened to cause this very large outage.
“Events of this scale have happened in many places around the world over the years, in power systems using fossil fuels, nuclear, hydro or variable renewables. It doesn’t matter where you are getting the energy from, you’ve got to get the engineering right in order to ensure resilient supplies of electricity. Thanks to the design of power systems and well-established system operation protocols, major power outages like this are mercifully rare. However, it is impossible to guarantee that something of this scale will never happen. System operators and providers of critical services need to be prepared for what to do if and when they do.
“System operators and equipment owners try to ensure that such major events don’t happen and to learn lessons when they do, sharing those lessons internationally once investigations have been completed.”
Prof Jianzhong Wu, Professor of Multi-Vector Energy Systems, University of Cardiff, said:
“Large-scale power outages, such as the ongoing event in Spain and Portugal, have occurred throughout the history of modern interconnected power networks. These networks are not designed to be completely blackout-free because achieving such a level of reliability would require investment far beyond what is economically feasible. Despite today’s high standards of reliability, low-probability but high-impact blackout events can still happen. In history, each blackout has had its own cause.
“Some early media reports said that the widespread power outages in Spain and Portugal could have been triggered by a rare phenomenon called ‘induced atmospheric vibration,’ where extreme temperature variations caused oscillations in high-voltage transmission lines. This may have disrupted the synchronisation needed across interconnected electricity grids, leading to cascading failures. However, due to the complexity of the interconnected power system, a proper investigation will take time, and the explanation of ‘induced atmospheric vibration’ still needs to be verified. The real cause could be very different. We must wait for detailed professional analysis.
“Although Europe’s interconnected grids generally enhance reliability, they can also allow disturbances to spread quickly. Full restoration will likely take several hours, depending on the extent of system separation. A detailed technical investigation could take days, weeks, or even months to complete.
What could have caused the outages?
“Large-scale power blackouts can be caused by various reasons, often in combination. Common causes include extreme weather events (such as storms, heatwaves, or lightning strikes), equipment failures in critical components like transformers or generators, and system instability when parts of the grid fall out of synchronisation. Human error during operations, cyberattacks on control systems, and natural disasters such as wildfires or earthquakes can also trigger widespread outages. In some cases, high demand exceeding available supply or insufficient grid redundancy can lead to system collapses. Very rare environmental phenomena, such as rapid atmospheric changes causing physical oscillations in transmission lines, as reported in the current Spain-Portugal incident, can also disrupt large interconnected networks. However, I am not aware of extreme weather conditions in Spain today (my daughter is on a School trip in Spain and she told me the weather was really nice there), so I am not sure whether this is the real cause. Typically, blackouts arise when several small disturbances interact and cascade across the grid, rather than from a single isolated fault.
Why has this affected such a large area?
“Spain and Portugal’s electricity grids are highly interconnected with each other and with the wider European system. This interconnectedness provides resilience under normal conditions but can also allow disturbances to spread quickly if a major synchronisation failure occurs. In this case, the disruption appears to have propagated rapidly through the Iberian Peninsula.
Are the grids connected in such a way that they are dependent on one another?
“Yes, national grids across Europe are linked to allow electricity trading and to improve overall reliability. This embedded economy of scale principle also helps reduce electricity costs for customers. However, this interconnectedness also means that serious faults, like a large loss of synchronisation, can spread across multiple regions or even countries if not rapidly contained.
How will the situation be resolved and how long will it take?
“Grid operators usually need to resynchronise disconnected parts of the network step by step. Depending on the complexity of the system separation and the safeguards in place, full restoration usually takes several hours to a day. Some areas may be restored sooner than others. In extreme cases, full restoration can take several days. However, the increasing electrification of critical services such as transport, communications, heating, and cooling, which are key elements of the low-carbon transition, means that society’s dependency on electricity is growing. Even after electricity supply is restored, other infrastructure services could take days or weeks to fully recover. We must therefore re-examine how we design and operate not just our energy infrastructure but also other critical infrastructures, with greater focus on managing interdependencies. Alternative low-carbon fuels, such as hydrogen or ammonia, will also play an important role in improving the resilience of our future energy system.
What is induced atmospheric vibration?
“I am not familiar with this term. It is not widely used or frequently encountered in power system engineering. ‘Induced atmospheric vibration’ could mean unusual physical movements of power lines caused by rapid and extreme changes in atmospheric conditions, such as temperature shifts or localised weather phenomena. These vibrations can alter the electrical properties of transmission lines or trigger protective mechanisms designed to prevent damage, leading to unexpected disconnections. Alternatively, it could refer to unusual changes in electricity demand and generation caused by rapid atmospheric shifts, potentially leading to small signal stability problems (sorry, a professional term). However, further information is not yet available from the network operators, and the true mechanism still requires verification.
Professor David Brayshaw, Professor of Climate Science and Energy Meteorology, University of Reading, said:
“Power systems are networks, connecting local disruptions to wider areas. They must balance supply and demand almost instantaneously, and generators need to stay precisely in sync (AC ~50 Hz). If something on the network — a generator, a power line, or even a large electricity user — suddenly disappears, it creates a supply-demand imbalance, and the system frequency starts to shift. If that shift becomes too large, other components can trip offline, creating a snowball effect that worsens the imbalance and can trigger a major blackout — sometimes within seconds.
“The European system, including the UK, has become increasingly interconnected in recent years. This is generally positive, helping balance variations in supply and demand, particularly as we decarbonize. But it also means greater interdependence with other countries, and heavier reliance on electricity across sectors like transport, heating, cooling, and datacentres, which leads to new routes in which the power system is exposed to weather risk. Meanwhile, technical changes mean the system now has less ‘inertia’, so imbalances must be corrected more quickly. Outage events, when they occur, are likely to become more significant and widespread.
“What stands out is that the power system is changing fast — driven by renewables, electrification, and massive investment (over US$2 trillion globally into clean energy in 2024). Yet there’s limited research into how climate change will affect future power systems, or how to design grids that are truly robust. If this event was indeed driven by atmospheric conditions, it underlines the urgent need for much deeper investigation into climate risks for power.”
Prof Janusz Bialek, Principal Research Fellow Department of Electrical and Electronic Engineering, Imperial College London, said:
“This piece has been written as a high-level overview of usual causes of wide-area blackouts. The author does not want to speculate about the reasons for the blackout in Spain/Portugal until more reliable information is released.
“Electrical grids tend to be interconnected as that brings great advantages in terms of lowering the costs (as the cheapest energy can be utilised wherever it is produced and reserves can be shared) and reliability (as when there are power shortages in one part of the interconnected grid, power can be imported from other parts). However interconnections makes it possible for disturbances in one network to automatically affect other networks, potentially leading to a wide-area blackout. The usual mechanism is of a fault causing tripping of a line, which causes overloading of another line leading to a trip, and hence leading to a domino effect propagating trips across a network. To prevent that happening, power utilities apply so-called (N-1) security criterion meaning that a trip of a single element (transmission line or a power station) should not cause problems. They consider only 1 element failing as probability of two or more failures happening at the same time is very low and protecting against them would be prohibitively expensive. Hence, when blackouts happened, it is usually because of more than one failures.
Europe
“The European continental network is divided into a number of parts [1]. The main part (in dark blue) is connected with Scandinavia (green) and GB (brown) using High Voltage Direct Current (HVDC) lines. HVDC lines make it possible to transfer energy from one network to another but are separating them in the sense that disturbance in one network cannot automatically affect the other network. This is the reason why the disturbance in Spain did affect Portugal, Spain and partly France, as they are in the same AC interconnection, but did not affect GB which is connected to France using HVDC lines.
Previous European blackouts
“European network is well-developed and controlled which means that blackouts are rare. Apart from some local disturbances, wide area blackouts affecting millions of people last happened in 2003 (separate blackouts in Italy and Scandinavia) and 2006. The 2006 blackout is probably the most relevant as it affected 15 million of people in different parts of Europe. The blackout was initiated by a routine disconnection of a power line in northern Germany to allow a ship to pass under a line crossing a river. However the (N-1) security situation has not been assessed properly in Germany and Netherlands leading to overloading of transmission lines. The German utility EON took some remedial actions which, with the hindsight, had the detrimental effect. This caused a cascading tripping of transmission lines causing the main European network to separate into 3 areas and disconnecting customers in many countries including Spain and Portugal [2] .
“Extensive post-mortem investigation revealed that the main underlying reason for the blackout was insufficient coordination of actions between the German and Dutch system operators. Hence, the operational coordination and exchange of information between the European system operators has been strengthen and prevented further blackouts until 2025.
GB
“British network comprising England, Wales and Scotland is well-connected and maintained so we have never had a wide-area blackout in GB. The closest was in August 2019, when an almost simultaneous trip of two power stations following lightning strikes caused about 1 million of customers to lose power for up to 45 minutes.
Impact on connected infrastructures
“Functioning of modern societies depends critically on the continuous supply of electricity and blackouts often reveal some critical vulnerabilities. For example, the biggest effect of the GB disturbance of August 2019 was not that 1 million people lost electricity for 45 minutes but rather that many electrical trains shut down when frequency dropped. Many trains have to be restarted manually by specialised units which took time. As the disturbance happened on Friday afternoon, the effect was a chaos on rail networks around London at peak time with large numbers of passenger affected.
“It is highly worrying that the current blackout caused the mobile networks in Spain to fail (my son lives in Barcelona and confirmed that). Critical infrastructures like mobile networks, rail networks, hospitals etc have their own back-up supplies (usually Diesel engines) in case the main supply fails. For some yet unknown reasons the back-up supplies failed this time. It is highly worrying as we depend critically on our mobiles for many aspects of our lives.
Possible causes for the 2025 blackout
“It is very dangerous to speculate about the causes without having reliable information which at the time of writing is missing. It is only possible to give some high-level analysis. It is quite likely that the blackout was caused by coincidence of more than one unfortunate events. As stated above, (N-1) security criterion prevents a single event to cause a blackout so the blackout must have been caused by more than one event. List of possibilities is quite long. Apart from faults tripping lines or power stations, it could be a malfunction of a computer system, communication network, alarm system, a human mistake, or unforeseen interaction between different controllers in the system. Early reports talk about a “rare atmospheric phenomenon” but there is no information about what it was and what it caused. It should be appreciated that system operators tend to be well prepared and equipped to keep the lights on so it is usually a “unknown unknown” that causes a blackout.
Prof Victor Becerra, Professor of Power Systems Engineering, University of Portsmouth, said:
“Today’s major power outage affecting Spain and Portugal highlights the high level of interconnection between European electricity grids. Although investigations are ongoing, some early media reports are mentioning a phenomenon known as “induced atmospheric vibration” linked to unusual atmospheric conditions, including rapid temperature variations and resulting wind patterns in the interior of Spain. If these conditions have been in place they may have triggered abnormal oscillations in very high-voltage power lines (a phenomenon known as galloping or wind-induced oscillation), leading to potential mechanical failure (such as snapped conductors), short circuits, or damage to key infrastructure like transmission towers. Protection systems are designed to automatically disconnect affected power lines in response to such faults. The resulting electrical disturbances may cause instability in some generators and, in extreme cases, trigger their automatic disconnection. The loss of large generators can create a sudden and significant imbalance between power supply and demand in the power grid, potentially escalating into widespread outages. Europe’s interconnected power grids are designed to share resources and improve resilience, but this interconnectivity also means that disruptions can spread quickly across national borders.
“Whatever the cause, a major failure in one area can place sudden pressure on neighbouring systems, causing protective shutdowns to prevent further damage. These actions help protect infrastructure but can also temporarily leave large areas without power. Incidents like this underline the complexity of managing modern energy systems, particularly as they integrate increasing levels of renewable energy (such as wind and solar, which are intermittent) alongside traditional sources (such as gas and nuclear power plants), face growing energy demand, and contend with some ageing infrastructure. It’s important to note though that currently, there is no evidence to suggest that the integration of renewable energy in these systems has caused this outage.
“Restoring supply to a large interconnected power grid involves a carefully coordinated process to isolate the problem, stabilise the system, and progressively bring generation and transmission assets, such as power stations, transformers, and high-voltage lines, back online, allowing operators to restore the electricity service to the affected areas gradually. Depending on the nature of the fault, complete restoration could take several hours or, in more complex cases, longer.
“Events like this are rare, but they demonstrate the importance of robust grid management, investment in infrastructure, and regional cooperation to ensure resilience against technical failures and external threats.”
Prof Chenghong Gu, Department of Electronic & Electrical Engineering, University of Bath, said
What do we know about the situation and how it happened?
“According to some media reports quoting Portuguese energy company REN, due to extreme temperature variations in the interior of Spain, there were anomalous oscillations in the very high voltage lines (400 KV), a phenomenon known as ‘induced atmospheric vibration’. These oscillations reportedly caused synchronisation failures between the electrical systems, leading to successive disturbances across the interconnected European network.
What could have caused the outages?
“We don’t know, but there has been some suggestion that it could be due to the induced atmospheric vibration. High temperature, high humidity, rough conductor surfaces, can cause corona effects on transmission conductors. The current in these conductors produce electric fields, and they can interact with the electric charges in the ambient atmosphere. Under certain conditions, this can cause the vibrations of conductors. Then, the vibrations can cause the changes of the physical characteristics of conductors, reflecting in their key parameters, such as their impedance, reactance. The stability of power systems is very sensitive to these parameters, and if they keep changing, currents in transmission lines, voltages in different locations, and system frequency would change. In the worst case, system frequency could drop too low, and customers must be cut off to re-balance the supply and demand.
Why has this affected such a large area?
“The power grids in EU countries are interconnected. It means all grids are synchronised. If there are any failures somewhere in one part of the system, the consequence can immediately propagate to other regions. If the oscillation causes system frequency to drop below a certain threshold, load shedding should be activated in different grids. It is called low-frequency load shedding, a kind of automatic protection mechanising to maintain the system frequency. This is why we see many customers in different parts of the EU grid are cut off to make sure the whole system can be rebalanced.
Are the grids connected in such a way that means they are dependent on one another and/or interconnected?
“That is right. Interconnected grids can enjoy higher reliability, because resources in the whole system can be shared by all grids in these countries. If there are any issues in one grid, other grids can provide backup supply very quickly. Interconnection is a double-sided sword. It is much harder to operate an interconnected system, because of the much bigger size, the larger number of devices, and more unexpected events in different locations. Thus, failures in one grid can propagate to other grids in the whole system, making the consequence of failures much worse and wider.
How will the situation be resolved and how long will it take?
“It depends on the causes of the failure. If it is transient failure, it could be quicker to restore the power supply. The faulty sections are first isolated from the system, then all generation is re-dispatched, the networks are reconfigured. Once the system has enough supply, customers can be re-connected to system gradually. However, if it is a permanent failure of a key component, it could take much more time to repair, such as transmission lines and transformers. In this case, the restoration of power supply could take much longer.
What is induced atmospheric vibration? What is it caused by?
“As discussed before, high temperature, high humidity, rough conductor surfaces, could cause corona effects on transmission conductors. The current in these conductors produce electric fields, and they can interact with the electric charges in the ambient atmosphere. Under certain conditions, this can cause the vibration of conductors. This vibration can cause fatigue of conductors, the change in their parameters, and in very extreme cases, failures of conductors.
How it can/may have interacted with the power system to cause the outage we are seeing across Spain and Portugal?
“The vibrations on conductors can cause the changes of their physical characteristics, reflecting in their key parameters such as their impedance, reactance, and in the worst case, fail to work. The stability of power systems is very sensitive to these parameters, and if they keep changing, frequency will change. In the worst case, this can cause systems frequency to drop out of the statutory range. In this case, customers must be cut off from the grid to make sure the supply and demand is re-rebalanced, i.e., system frequency close to 50 Hz. This is a kind of automatic frequency restore mechanism to protect the system.”
Dr Adrià Junyent-Ferre, Reader in Power Electronics, Department of Electrical and Electronic Engineering, Imperial College London, said:
“Portugal’s power grid is heavily interconnected to Spain’s; however, the link between the Iberian peninsula and the rest of Europe is relatively weak. The connection to France is a bit less than 3 gigawatts (GW). This means that if France was importing the maximum amount of power from the Iberian peninsula and there was an outage, the loss that France would see would be of 3 GW. The interconnected European system can handle a sudden loss of 3 GW; therefore, it should be able to handle such loss without major consequences. Moreover, France tends to export power to Spain rather than importing it, although this does fluctuate. Today’s event caused local outages in different parts of Southern France, such as Perpignan.”
Dr Grazia Todeschini, Reader in Engineering at King’s College London:
What do we know about the situation and how it happened?
“Red Eléctrica reported that a sudden large fluctuation in power flows of unknown origin caused Spain to disconnect from Europe’s grid and the Iberian grid was abruptly islanded, creating a huge power imbalance that resulted in system failure.
What could have caused the outages?
“Frequency recordings in various parts of continental Europe shows fluctuations before the disconnection took place, but at this stage attributing a source is still premature. It is worth noting that electricity system operators carry out studies to ensure system stability under contingency conditions. Therefore, these types of events are typically the results of exceptional circumstances.
Why has this affected such a large area?
“Electrical grids are large interconnected systems, and their stability is related to a very close balance between electricity generation and demand. If one area is disconnected, it can cause knock-on effects in nearby areas that may rely on supply (or demand) from the affected area. Some measures exist to limit the impact of outages to small areas, but when the power unbalance is too large, these outages may spread very quickly and very far.
Are the grids connected in such a way that means they are dependent on one another and/or interconnected?
“The Continental Europe Synchronous Area is one of the largest synchronous electrical grids in the world, supplying over 400 million customers in 32 countries, including most of the European Union. This allows power exchange between countries, but under very special and extreme situations it may mean that outages may propagate across different countries.
How will the situation be resolved and how long will it take?
“Power system restoration (PSR) is the process of re-establishing power supply after a power outage or blackout, with the goal of rapidly restoring electricity to customers. This is a complex process, and may take hours. For reference, a similar outage that affected Italy on 28/09/2003 took up to 16 hours to be solved.”
Dr Onyema Nduka, Senior Lecturer in Power Sustainability, Royal Holloway, University of London, said:
“The reports about power outages in large parts of Spain and Portugal is still an evolving event and therefore a detailed investigation is required to determine what caused the power cuts.
“Electricity outage is highly undesirable as it can impact several aspects of lives in modern societies; it can be caused by different factors such as equipment failures or mal-operation, overloading of electricity assets (transformers, cables/wires, etc.), disasters (both natural events and those triggered by human activities) and so on.
“While electricity outages are rare in European countries, they are possible as the events in Portugal and Spain have shown.
“Power networks usually span a large geographical area – this is because large generation plants are usually located farther away from the cities and through the transmission and distribution networks, the electricity is supplied to the customers.
“As a result, such networks are usually interconnected including across regions and countries. Hence, the occurrence of a power cut in one part of the power grid could lead to a cascading effect in other areas.
“Ideally, redundancies are built into the system such as having multiple supply points, backup generators sited at different locations, interconnected wires/cables, etc.
“The grids are interconnected, which is common, as it helps to manage the export and import of electricity, hence, improving the reliability of supply.
“The solution on resolving the situation is, as one would expect, for the electricity utility companies to make efforts to restore electricity to the affected customers ASAP.
“However, the procedure for restoration of electricity supply will be influenced by the cause of the power cuts, which at this stage has not been revealed.”
Professor Solomon Brown, Professor of Process and Energy Systems at the University of Sheffield, said:
“My understanding is that the power systems are connected through ‘interconnectors’ in the same way that Scotland and the rest of the GB network are connected, and also GB with other parts of Europe. This means that there is interdependency between the networks but also that they will have to be re-started separately.
“As the two networks have gone down they will have to be re-powered, which means that the grid operator will slowly bring on key generators matched with users (so that production and consumption of electricity match) in regions of the network that slowly expand until the whole system is back on and can then be reconnected to external networks. This process can take a number of hours and may have to be attempted more than once if things don’t go smoothly.”
Declared interests
Prof Keith Bell “My Chair at the University of Strathclyde is sponsored by Scottish Power. I receive no personal remuneration in respect of the sponsorship. I am involved in ongoing work with the National Energy System Operator (NESO) to provide training. I receive no personal remuneration for this. (The University receives a fee). I am involved in a publicly funded research project (“HVDC-WISE”) with many collaborators from Europe and the UK including SSEN Transmission. I receive no personal remuneration for this. (The University receives a fee).I am a member of the Climate Change Committee. I am a member of the Scottish Energy Advisory Board convened by the Scottish Government. I receive no personal remuneration for this. I am a member of Ofgem’s climate resilience expert panel for which I am due to receive remuneration of £800 per year. In the past, I have led or undertaken research projects funded by Scottish Power, National Grid or SSE (for which I received no personal remuneration). I retained full editorial control over reports. Also in the past, I have carried out consultancy work for what is now NESO for which I received a fee. I was a Member of the Advisory Committee of the Electricity Networks Commissioner, 2022-23. I received no remuneration for this. I was Scientific Director of Electrical Infrastructure Research Hub with the Offshore Renewable Energy Catapult and University of Manchester, June 2018 to 2024. I received no personal remuneration for this. (The University received a fee).I was Special Advisor to the House of Lords Science and Technology Committee inquiry into Long Duration Energy Storage, October 2023- March 2024. I received a fee for this. I was an employee of National Grid between September 1998 and August 2005. From that time, I have 77 ordinary shares in National Grid with a value of £762 and my wife has 650 ordinary shares in National Grid with a value of £6435.”
Professor David Brayshaw “None”
Professor Jianzhong Wu “no conflicts of interest to declare in relation to this comment”
Prof Chenghong Gu “I don’t have any to declare”
Prof Victor Becerra “I have no conflicts to declare”
Dr Adrià Junyent-Ferre “No conflict of interest”
Dr Grazia Todeschini “No conflicts to declare”
Dr Onyema Nduka “No conflicts”
Professor Solomon Brown “No interests to Declare”
For all other experts, no reply to our request for DOIs was received.