A fire at a Heathrow airport substation, owned by the National Grid, was caused by a problem first detected seven years ago but never fixed, according to a final report by the National Energy System Operator (NESO).
On 20 March, a fire at the North Hyde 275kV substation, which feeds most of Heathrow, resulted in the airport’s closure.
Aviation chaos ensued, with more than 1,300 flights cancelled and hundreds of thousands of passengers affected. More than 70,000 other businesses, homes and services were also affected, including Hillingdon Hospital.
Energy watchdog Ofgem commissioned NESO to conduct an investigation, assessing the reasons the fire started in the first place as well as a broader assessment about the UK’s energy resilience and actions that could be taken to prevent similar incidents in future.
The report found that at 11.21pm on 20 March one of three supergrid transformers (SGT3) at the North Hyde substation and its associated circuit tripped. Shortly after, the other transformers...