A report released on Wednesday suggests that a fire at an electrical substation in March, which led to a significant shutdown at London’s Heathrow Airport, was most likely caused by moisture infiltrating electrical components.
This issue was first identified as early as 2018.
According to the National Energy System Operator (NESO) report, water entering a transformer and creating a short circuit “most likely” ignited the blaze.
The report highlighted that “elevated moisture readings” were detected in July 2018, but “mitigating actions appropriate to its severity were not implemented.”
The fire erupted at the North Hyde substation in West London, approximately two miles north of Heathrow, at 11:21 PM on March 20. This incident resulted in a complete loss of power to a section of the airport’s private internal electrical distribution network.
Consequently, Heathrow Airport remained closed for most of March 21, impacting thousands of passengers globally and raising serious concerns about the reliability of this crucial UK infrastructure.
Forensic analysis by the National Grid Electricity Transmission and the London Fire Brigade concluded that a “catastrophic failure” in high-voltage “bushing” components caused the transformer to catch fire.
The report detailed, “This was most likely caused by moisture entering the bushing, causing a short circuit. The electricity likely then ‘arced’ (causing sparks), which combined with air and heat to ignite the oil, resulting in a fire.”
The elevated moisture reading in one of the bushings in July 2018 should have indicated “an imminent fault and that the bushing should be replaced.”
However, the report found that “controls in place were not effective and failed to identify subsequently that action had not been taken about the elevated moisture reading.”
Energy Minister Ed Miliband described the report as “deeply concerning.”
In a statement, he noted, “Known risks were not addressed by the National Grid Electricity Transmission, and (energy regulator) Ofgem has now opened an official enforcement investigation to consider any possible licence breaches.”
