A fire at a nearby electrical substation that caused a power outage at Heathrow Airport was “most likely” caused by moisture entering an electrical component, a review has found.
The National Energy System Operator (NESO) was ordered by the energy secretary to look in to the cause of the fire, which started late on 20 March at the North Hyde substation in west London, which supplies power to the airport.
The fire led to Heathrow deciding to close the following day, leading to thousands of cancelled flights and stranded passengers.
Neso said previously that the the power outage affected 66,919 domestic and commercial customers, including Heathrow Airport. Around 270,000 journeys were affected.
The report said the fire “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.”
Bushing is a mechanical device used to temper energy between two electrical parts.