A power outage that shut Heathrow Airport earlier this year, causing travel chaos for more than 270,000 passengers, was caused by a “catastrophic failure” of equipment in a nearby substation, according to a new report.
Experts say the fire at the North Hyde Substation, which supplies electricity to Heathrow, started following the failure of a high-voltage bushing – “most likely” caused by moisture entering the equipment – before spreading.
The report says elevated moisture readings in one of the bushings had been detected in oil samples taken in July 2018, and, according to the National Grid Electricity Transmission’s relevant guidance, such readings indicated “an imminent fault and that the bushing should be replaced”.
However, the report says mitigations appropriate to the severity of the issue were “not actioned”, including in 2022 when a decision was taken to defer basic maintenance.
“The issue therefore went unaddressed,” the report adds.
Europe’s biggest airport closed for around 16 hours on 21 March following the fire.
Around 1,300 flights were cancelled and more than 270,000 air passenger journeys were disrupted.
Tens of millions of pounds were lost, thousands of passengers were stranded, and questions were raised about the resilience of the UK’s infrastructure.
In May, the National Energy System Operator (NESO), in its interim findings into the incident, said forensic investigations were ongoing.
The Metropolitan Police previously confirmed on 25 March that officers had “found no evidence to suggest that the incident was suspicious in nature”.
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