Preventable Fault Known Seven Years Causes Heathrow Shutdown, Ofgem Investigates

A fire at the North Hyde electrical substation in West London caused a shutdown of Heathrow Airport in March 2025, disrupting over 270,000 passenger journeys and shutting the airport for nearly 20 hours. The National Energy System Operator (Neso) report identified that the fire was most likely triggered by moisture entering electrical insulators called bushings, causing a short circuit and igniting oil in the transformer. This fault had been detected as an elevated moisture reading in July 2018, but necessary maintenance and replacement of the bushings were not carried out, with a decision in 2022 to defer basic maintenance further delaying action. Additionally, the fire suppression system at the substation was found to be inoperable from 2022 through mid-2024. The internal power network design at Heathrow contributed to the prolonged outage because it relied on manual switching and was not configured for rapid recovery after the loss of one supply point. Following the findings, Ofgem has launched an investigation into National Grid Electricity Transmission for possible breaches of license conditions and is conducting an independent audit of critical assets, emphasizing the need for improved maintenance and infrastructure investment to prevent similar incidents.