The fire at an electrical substation that crippled Heathrow Airport also took out at least one of the main backup systems designed to keep the power running, Britain’s energy secretary said, contributing to the lengthy disruption at Europe’s busiest air travel hub.
“There was a backup generator, but that was also affected by the fire, which gives a sense of how unusual, unprecedented it was,” Ed Miliband, Britain’s energy secretary, said in an interview early on Friday with Sky TV.
Mr. Miliband said the National Grid, which operates the transformer that failed near the airport, was trying to route power through a second backup system, but even that was proving difficult given the scale of the fire at the substation.
Transformers convert current from high voltage to a lower voltage. In the case of the transformer that caught fire, experts said it would have been turning 275,000 volts into 66,000 volts when it apparently failed. Jonathan Smith, the deputy commissioner for the London Fire Brigade, said the blaze involved “a transformer comprising 25,000 liters of cooling oil that was fully alight” at the substation.
By early afternoon on Friday, officials at National Grid said the network of the North Hyde substation, where the fire happened, had been reconfigured to restore power.
“This is an interim solution while we carry out further work at North Hyde to return the substation and our network to normal operation,” the power company said.
The failure of at least one backup system to quickly restore power after such a major outage is likely to be at the center of questions about the reliability of Britain’s infrastructure in the aftermath of the fire and airport closure. Those questions started within hours of the shutdown. In a post on social media, Willie Walsh, the director general of the International Air Transport Association, a global trade association of airlines, wrote: “How is it that critical infrastructure — of national and global importance — is totally dependent on a single power source without an alternative.”
“If that is the case — as it seems,” he added, “then it is a clear planning failure by the airport.”
Mr. Miliband said the government would focus on understanding the cause of the outage, telling Sky TV: “Obviously, with any incident like this, you will want to understand why it happened and what if any lessons it has for our infrastructure.”
Officials with National Grid did not immediately respond to an email requesting information about the backup systems.
In a statement, Heathrow Airport said the facility had “multiple sources of energy” but that there was no backup that would supply enough power to operate the entire airport, which it said “uses as much energy as a small city.” The statement said that backup diesel generators and uninterruptible power supplies did kick in that would have allowed planes to land and passengers to disembark. But they would not have been enough to allow the airport to operate fully.
Simon Gallagher, a former senior executive at Britain’s largest power provider, said that he believed the substation near Heathrow was designed so that if the first transformer has a problem, a second one could kick in quickly. But he said the fire appeared to have raged through the prevention systems and damaged both of the transformers.
That is highly unusual, he said, indicating a series of failures to the fire suppression systems that are designed to rapidly cut power to a faulty transformer to avoid that kind of damaging blaze.
“Basically, we designed things so that something can fail,” said Mr. Gallagher, who is now the managing director at U.K. Networks Services, which advises clients on the resilience of their electricity networks. But, he added, a number of things must have gone wrong “to allow that to fail, and then it’s damaged the one next to it as well.”
The police have said that counterterrorism investigators would examine the possibility of sabotage. But Mr. Gallagher said that judging by the video footage from the scene, the incident appeared to him to be a “classic transformer fault,” which happens often with little impact to customers because power is quickly routed to a nearby transformer.
The incident has raised questions about whether the airport had — or should have had — backup generators run by batteries or gas that might have allowed the entire airport to continue operating normally after the fire.
Mr. Gallagher said that was not possible given Heathrow’s current systems, which are not capable of providing enough energy to keep all of the lights on if the airport’s regular connection to the electrical grid is disrupted.
The emergency generator systems mentioned in the Heathrow statement were designed to keep runway lights and control tower systems working, he said, even during an incident like the one that took place on Friday.
But he said that it would have been impossible to continue to land planes because there would have been no electricity to move luggage, light the terminals, operate doors and more. To do that would require at least 20 massive diesel generators the size of a 40-foot shipping container, each one capable of generating a megawatt of power.
Heathrow did not have such a system, which would have been capable of keeping the power to the entire airport flowing for about six hours before needing to be refueled, he said. But he added that other major power customers, such as data centers, had installed big backup generators to ensure power in the event of an emergency.
“I think things will change,” Mr. Gallagher said. “I think Heathrow and other airports will install backup generation.”
A decision to do that could run up against questions about the impact on the environment. Officials at Heathrow have been working for years toward a “net zero” goal by increasing the efficiency of the planes that land at the airport and reducing the emissions of the infrastructure and cars on the ground.
Mr. Gallagher said that, contrary to some claims circulating on social media, none of those efforts would have caused Friday’s disruption, or prevented a quicker return of the power.
