Heathrow airport took more than seven hours to restart flights after power was restored to its terminals following a fire six weeks ago, according to an interim report that admitted the cause of the blaze was still unknown.
Europe’s busiest airport shut down shortly after 1am on Friday March 21 after a fire at a nearby electricity substation feeding the airport led to widespread power cuts.
Power was restored to all of Heathrow’s terminals by 10.56am that Friday, while airport-wide electronics such as fire management and security systems were online by 2.23pm, according to the interim report published on Thursday by the UK government’s National Energy System Operator.
One flight with crew members landed at about 6pm, after the airport had completed safety checks. The airport did not reopen fully until Saturday.
“There was a period of safety checking to . . . ensure safety critical systems were fully operational prior to passengers arriving at the airport,” the report said.
The report’s findings illustrate why some airlines were frustrated by the time it took to reopen the airport, given that their terminals had power back by mid-morning.
Airlines have said they believe that at least Terminal 5, the home of British Airways, could have reopened sooner. One airline executive said Thursday’s report raised further questions about how long it took to restart operations.
But Heathrow has previously said that it needed power restored across its site, including the critical systems outside its terminals, before it could safely reopen to passengers.
Thomas Woldbye, Heathrow’s chief executive, told MPs last month that an internal review would consider whether the airport could have reopened some terminals more quickly.
Power supplies were cut to almost 67,000 homes and businesses as well as the airport. About 42,000 homes and businesses were reconnected before 1am on Friday, and all domestic customers shortly after midday, the report said.
The interim report laid out details about the fire at the substation, but said the root cause was not yet known. The final report, which is due by the end of June, may lay out further details about the cause of the blaze. The Metropolitan Police has previously said it found no evidence to suggest it was suspicious.
The electrical site in North Hyde, west London, owned by National Grid, had three transformers, including one designed for backup and positioned more than 30 metres away from the other two, the report said.
The fire took hold in the cooling oil inside one of the transformers, causing it to disconnect automatically. The backup transformer initially kicked in as designed, leaving two transformers working and no interruption of supply.
But, according to the report, the second transformer automatically disconnected 28 minutes later due to “protection systems”. This cut off the backup transformer as well, because it was connected to the same circuit.
The disruption caused by the substation fire has triggered widespread questions about the resilience of the UK’s critical national infrastructure.
The National Energy System Operator said it expects to make recommendations in its final report covering the resilience of energy infrastructure, site design and “assessments of asset health” as well as “cross-sector incident management”.
Heathrow said the report raised “important questions” for National Grid and the distribution system operator, SSEN.
It added: “Further clarity on how the fire started and why two transformers were subsequently impacted can help ensure greater resilience for the UK’s energy grid moving forward.”
Ed Miliband, the energy secretary, said his department would “await the full report to understand what happened and learn lessons to strengthen UK energy resilience and protect our critical national infrastructure”.
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