Heathrow Shutdown Caused by Problem Left Unfixed for Years, Report Says

The fire at an electrical substation was caused by a short circuit in a part that hadn’t been properly maintained by National Grid, an official report found.

The fire at an electrical substation that forced Heathrow Airport in London to close for more than 16 hours was caused by a short circuit in a transformer part that was identified seven years ago, an official report said on Wednesday.

More than 1,000 flights were disrupted at Heathrow, one of the world’s busiest travel hubs, during the March 21 shutdown after the fire cut electricity to much of the airport, disabling critical safety systems and forcing officials to ground flights for most of the day.

The 77-page final report, by a regulator, the National Energy System Operator, found that moisture in a bushing — an insulated conductor in a transformer — had been detected in 2018 by National Grid, the electricity operator responsible for power in the area. But the issue went untreated for years, including in 2022 when basic maintenance on the transformer was deferred.

“Evidence provided to the review revealed that multiple attempts were made to schedule basic maintenance,” the report said, “none of which went ahead.”

Alice Delahunty, president of electricity transmission at National Grid, said in a statement on Wednesday that the company was performing an “end-to-end review” of procedures for discovering moisture in a transformer.

She said that National Grid was also “retesting the resilience of substations that serve strategic infrastructure.”

Ofgem, which regulates Britain’s electricity industry, said it had opened a review into National Grid’s maintenance and other issues relating to the power outage. The regulator said that it would also commission an audit of National Grid to see whether the maintenance issues were systemic.

“We expect energy companies to properly maintain their equipment and networks to prevent events like this happening,” said Akshay Kaul, Ofgem’s director general for infrastructure.

The loss of power at Heathrow prompted an outcry from travelers, airline officials and some of Britain’s political leaders about the vulnerability of the country’s electrical grid.

Ed Miliband, the energy secretary, said that the report Wednesday was “deeply concerning” because “known risks were not addressed” by National Grid.

The report also concluded that Heathrow’s internal power systems, which were disrupted by the fire, were not able to quickly switch to power from two other nearby substations. The report said that airport officials had not expected to have to deal with a catastrophic power outage.

“The loss of supplies from a supply point was not assessed to be a likely scenario” by the airport company, the report said, because of “its expectation of the resilience of the wider network.”

The report added that the airport’s internal electrical system had not been configured to recover quickly from such an event by having “multiple supply points” and had relied on manual switching.

After the fire, Heathrow officials said that they had been forced to close the entire airport because the loss of power affected so many crucial areas, including security systems, ticket counters, baggage claim, moving walkways, escalators and bathrooms, as well as terminal shops and restaurants.

But the report on Wednesday said that the lengthy delays in reopening, which caused disruptions that rippled through international travel, were the result of the airport’s decision not to invest in electrical systems that could switch power sources more quickly.

“The ability to either connect or automatically switch load between Heathrow Airport’s supply points may have aided in re-securing its network for the loss of supplies without interrupting critical functions and would have, as a minimum, reduced the restoration time,” the report said.

It added that the risk of power disruption was known to and accepted by the airport as “a high-impact, low-probability event.”

In a statement, Heathrow officials said that they were already implementing 28 changes intended to “enhance infrastructure and processes” at the airport. But they criticized National Grid for the failure to properly maintain the transformer.

“A combination of outdated regulation, inadequate safety mechanisms and National Grid’s failure to maintain its infrastructure led to this catastrophic power outage,” said Weston Macklem, the airport’s head of media.

“We expect National Grid to be carefully considering what steps they can take to ensure this isn’t repeated,” he added.

The report on Wednesday also found a lack of proper communication between energy companies and important customers.

Energy companies, the report said, are not informed that they may have users who are part of what is known as “critical national infrastructure.” The report acknowledged that such information was “extremely sensitive” but urged officials to review regulations to ensure that energy providers knew when a loss of power would affect such customers.