Heathrow Airport, the busiest airport in Europe, was shut down following a fire at a single electricity sub-station on the night of March 20. The fire at the North Hyde substation in Hayes, about 1.5 miles from Heathrow in west London, seriously disrupted the area’s power supply, including that of the airport.
The closure has caused chaos, leaving thousands of passengers stranded. More than 1,300 flights have been affected, according to the plane tracking website Flightradar24. About 120 of these were already in the air.
Below, a panel of experts offer their insights – and consider the implications of such a major incident. (Elements of this panel were sourced by the Science Media Centre, which published a version here.)
Power in west London is highly constrained
Barry Hayes, associate professor in electrical power systems, University College Cork
It appears that a transformer fire in the North Hyde 275kV substation caused the power outage (videos from the scene clearly show one of the large power transformers ablaze). This is a large electrical substation which supplies the area to the northeast of Heathrow airport as well as the Heathrow airport site. Scottish and Southern Electricity Networks, the local electricity distributor, said 67,000 homes and businesses in the area were cut off overnight as a result of this issue.
While the North Hyde substation is a very important part of the west London electricity grid, it is generally not expected that this would cause such a big impact at Heathrow airport. There are also dedicated supplies to other parts of the airport site.
Typically, a critical electricity load such as Heathrow would be served from multiple supply points in the electricity grid, and therefore there would be an option to feed the loads at Heathrow from an alternative supply point. There are some reports that parts of the airport (for example, Terminal 5) have power.
The exact reasons for such a big impact are unclear at this point, but we do know the North Hyde substation is in a highly constrained area of the UK electricity grid – an area where there has been “a steep increase in the number of new electricity connection requests across west London, driven by new housing developments, commercial investment and datacentres”.
The UK power grid (as in many developed countries) is generally old or outdated, with many of its components at the end of their anticipated service lifetime and in urgent need of modernisation. These issues may be a factor in the power outage affecting Heathrow. However, it will take some time before the exact causes of this incident are established.
Weather, ageing equipment or malicious attacks could be to blame
Chenghong Gu, professor in smart energy systems, University of Bath
This is a very rare event. Substations are built and operated according to very strict standards, and they are monitored 24/7. There are also many automatic devices in substations like this one to deal with faults.
A substation has many components including transformers, circuit breakers, an isolator, busbars and measuring equipment. Transformers are the most vulnerable to fire. There is insulation oil in them and in high-temperature, high-pressure situations, they can explode – meaning the insulation oil leaks and can catch fire.
However, it is very unusual for big substations like this to catch fire. One cause can be extreme weather such as lightning strikes, which could cause extreme high voltage on the equipment. Extreme hot weather together with high demand can also cause transformers to become overheated, thus leading to faults.
Another factor is the ageing of transformers. The insulation gas can degrade, which could cause an explosion inside a transformer. Or there could be a malfunction of other auxiliary devices such as the insulator, switch gears or circuit breakers inside the substation.
Other possible causes include a malicious attack on the substation – someone setting fire to it deliberately, for example. Cyber-attacks on IT systems can also cause a malfunction of devices in the substation, leading to fire.
Serious questions about Heathrow’s back-ups
Kirk Chang, professor of management and technology, University of East London
The airport lost power because of the fire – we understand that. But the back-up system didn’t work. It’s difficult to understand how that could happen.
There are two things we need to look at. Number one is the technical part. Why did the back-up machines not work? Maybe the machines did not have sufficient fuel, or for some reason the system was not linked to the grid. The backup should kick in immediately.
The second point is more the human side. Who is responsible for the power management, and what intervention strategies were attempted? I would assume they would need a second back-up system if the first fails. It’s very unusual to see both Plan A (the back-up) and Plan B (the back-up to the back-up) not working.
Usually, a main back-up (Plan A) will supply about 90% of the power the facility usually receives. Whereas Plan B will usually only supply a fraction of the power – maybe 50% or 30%. The reason is that Plan B is usually expensive to maintain all the time. It may be outsourced to a third party – either the power company or a software company which manages their power distribution network.
Critical infrastructure arguably needs more security
Paul Cuffe, assistant professor, School of Electrical & Electronic Engineering, University College Dublin
An airport like Heathrow requires a lot of electricity to operate, equivalent to a large town. As such, it would be typical for it to be given a dedicated connection from the substation at Hayes.
There is likely a dedicated power line and transformer there that connects the airport to the wider grid. When a major fire severs that link, it will no longer be possible to bring bulk electricity to the airport.
I would anticipate that a major airport like Heathrow would have some on-site emergency capability to ride through a grid disturbance. I would hope the traffic control tower and runway lights weren’t totally plunged into darkness!
However, processing planeloads of passengers requires Heathrow in its totality to consume a town’s worth of electricity, and the inability to meet this requirement is probably why the flights had to be cancelled.
The failure is not overtly abnormal. We can anticipate that, from time to time, substation equipment will fail and downstream power outages will result. But one could argue that a critical piece of national infrastructure like Heathrow deserves special grid connection arrangements to secure its supply of electricity further. For instance, sometimes critical loads like this are fed from two separate substations to provide redundancy when outages happen.
It is ultimately a political and economic question to determine the right level of capital investment into grid infrastructure to avoid the problems that outages like this cause. Redundant power supplies for an airport the size of Heathrow do not come free.
Climate change means the grid will face more threats like this
Hayley J. Fowler, professor of climate change impacts;
Colin Manning, postdoctoral research associate in climate science; and
Sean Wilkinson, professor of structural engineering, Newcastle University
The closure of one of the world’s largest airports due to a failure of just one electricity substation underlines how important it is that critical national energy infrastructure – pylons, substations and so on – keeps functioning. This is only becoming more important as demand for electricity increases, thanks to transport and domestic heating switching to lower-carbon electrified alternatives – notably electric cars and heat pumps.
Yet the UK’s energy system is facing growing threats from unprecedented risks. We still don’t know what caused the Heathrow fire, but it appears to be unusual in this regard, as threats to energy systems come mainly from extreme weather. In the UK, that tends to mean windstorms, flooding, heatwaves and associated wildfires, and cold spells.
2024 was the warmest calendar year on record, and the “fingerprints” of climate change are increasingly evident in more intense and frequent extreme weather events. It is crucial to ensure the energy network can handle this weather.
Gas and electricity operators in the UK have established protocols for managing networks in adverse weather, investing large amounts to protect critical assets. But recent events have exposed vulnerabilities. The storms Arwen and Éowyn left thousands without power for days, underscoring the previous UK government’s admission that the country is underprepared for extreme weather events.
Barry Hayes has an active research collaboration with ESB Networks, and is an academic member of ESB Networks’ Innovation Stakeholder Panel.
Colin Manning receives funding from UKRI.
Hayley J. Fowler receives funding from UKRI, NERC, EPSRC, and the EU Horizon 2020 Programme. She is a member of the UK Climate Change Committee and was a member of the Department of Energy Security and Net Zero Science Expert Group (E-SEG) from 2021 to 2025. This article represents her own work and views, not the position of either of these organisations.
Paul Cuffe has no direct links with the electricity industry in the UK. As an Irish academic, he has had occasional collaborations with Eirgrid, the transmission system operator, and ESB Networks, the distribution network operator. He has received funding as part the ESIPP and NexSys projects; these were co-funded by stakeholders in the Irish energy sector.
Sean Wilkinson receives funding from EPSRC and DESNZ.
Chenghong Gu and Kirk Chang do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
