Heathrow: Fault that caused power outage was ignored for seven years
Heathrow has said it is considering legal action against National Grid after it was revealed that a “catastrophic failure” of equipment led to the substation fire which caused a huge power outage at the airport earlier this year.
A damning report into the incident found the UK’s electricity operator had failed to address excessively high moisture levels for several years despite internal acknowledgement that some electrical parts needed to be replaced.
“This review has seen evidence that a catastrophic failure on one of the transformer’s high voltage bushings at National Grid Electricity Transmission’s 275kV substation caused the transformer to catch fire,” the report, which was conducted by the National Energy System Operator, found.
Heathrow told the BBC National Grid “could and should” have prevented the fire and should “take accountability for those failings”.
“Those failings that resulted in significant damage and loss for Heathrow and our airlines,” a spokesperson added.
There were two opportunities to tackle the issue, with the first stretching as far back as 2018 when high levels of moisture were detected in oil samples.
Scheduled maintenance at North Hyde was then missed in 2021 and cancelled each year subsequently until October 2025.
The fire at North Hyde Substation, which supplies Heathrow with electricity, ultimately led to the closure of Heathrow Airport and chaos for more than 270,000 passengers in March.
Heathrow’s airlines claim the incident will cost them between £80m and £100m.
They have also raised questions over the response by Heathrow’s senior leadership on the night of the blaze, with chief executive Thomas Woldbye found to have been asleep with his phone on silent as the fire erupted.
Heathrow blames National Grid ‘failure’
Energy Secretary Ed Miliband described the report as “deeply concerning” and said “known risks” had not been addressed by the National Grid Electricity Transmission.
A Heathrow spokesperson said: “Heathrow welcomes this report, which sheds further light on the external power supply failure that forced the airport’s closure on 21st March.
“A combination of outdated regulation, inadequate safety mechanisms, and National Grid’s failure to maintain its infrastructure led to this catastrophic power outage.
“We expect National Grid to be carefully considering what steps they can take to ensure this isn’t repeated. Our own Review, led by former Cabinet Minister Ruth Kelly, identified key areas for improvement and work is already underway to implement all 28 recommendations.”
A spokesperson for National Grid said the organisation has a “comprehensive asset inspection and maintenance programme in place, and we have taken further action since the fire.
“This includes an end-to-end review of our oil sampling process and results, further enhancement of fire risk assessments at all operational sites and re-testing the resilience of substations that serve strategic infrastructure.
“We fully support the recommendations in the report and are committed to working with NESO and others to implement them. We will also cooperate closely with Ofgem’s investigation.
“There are important lessons to be learnt about cross-sector resilience and the need for increased coordination, and we look forward to working with government, regulators and industry partners to take these recommendations forward.”