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The fire that led to the closure of Heathrow airport for 24 hours in March was caused by a “catastrophic failure” of equipment at an electrical substation, according to an official review of the incident.
The blaze at the North Hyde substation in Hayes, west London, started when moisture got into the “bushing” — material through which current flows in and out of the transformer — causing an electrical fault, the government-owned National Energy System Operator (NESO) said on Wednesday.
The blaze destroyed the substation, triggering power outages for about 70,000 customers in the region including Heathrow airport, Europe’s busiest airport.
The closure led to the cancellation of more than 1,300 flights and raised widespread questions about the resilience of critical national infrastructure.
The NESO report found that a high moisture reading in the bushing was detected in oil samples in 2018, but “mitigating actions appropriate to its severity were not implemented”.
The finding raises questions for National Grid, the FTSE 100 company which owns and operates the substation along with the rest of the electricity transmission network in England and Wales.
Britain’s energy regulator said this morning that it had opened an enforcement investigation into National Grid Electricity Transmission, and that the cause of the fire was “preventable”.
“In the NESO final report, it has been established that the root cause of the fire was a preventable, technical fault,” Ofgem said in a statement.
National Grid’s transmission division has started an “end-to-end review of its oil sampling process, with a view to ensuring that it is robust,” NESO added.
“In addition, they are undertaking a review and assurance exercise of all recorded oil samples to ensure all appropriate actions have been taken where required.”
