The root cause of the fire that sparked a major power outage at Heathrow Airport remains unknown, the UK’s national energy system operator has said.
The blaze in March at the North Hyde Substation, which supplies electricity to Heathrow about 1.5 miles away, caused a power outage, which meant Europe’s biggest airport had “no choice but to close” for 16 hours.
More than 1,000 flights to and from Heathrow were cancelled and hundreds of thousands of passengers were affected.
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The National Energy System Operator (NESO), in its interim findings into the North Hyde Substation outage, said the London Fire Brigade and National Grid Electricity Transmission were continuing to conduct forensic investigations.
The Metropolitan Police previously confirmed on 25 March that officers had “found no evidence to suggest that the incident was suspicious in nature”.
NESO anticipates that the final report, due to be published in June, is expected to make findings and recommendations relating to the resilience of energy infrastructure in the UK, the response and restoration of energy infrastructure, and the resilience of critical national infrastructure to energy disruption.
Fire crews were called to reports of a transformer alight at the west London substation at 11.23pm on Thursday, 20 March.
Power was restored to the terminals around seven hours before flights resumed, investigators said, noting the flow of electricity to all four passenger terminals was restarted by 10.56am on 21 March.
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The airport was shut for most of that day, before flights resumed around 6pm.
Neso said power was restored to the “wider Heathrow Airport Limited network” by 2.23pm.
That was followed by “a period of safety checking” to ensure “safety critical systems were fully operational prior to passengers arriving at the airport”.
Energy Secretary Ed Miliband welcomed the NESO report, admitting the fire and power loss led to “major disruption to thousands of people and many businesses”.
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He said the report into the incident “rules out the possibility of any suspicious activity.
“We now 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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Heathrow is the world’s fifth-busiest airport, handling more than 79 million passengers in 2023, Flightright said on its website.
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