A recently released report investigated a fire at an electricity substation that caused Heathrow Airport to shut down for almost a full day, resulting in chaos for over 200,000 travelers. The National Energy System Operator (NESO) determined the likely cause of the fire and revealed that National Grid, the operator of the substation, had been warned about a potential issue seven years prior.
Here are five key findings from the report:
The NESO report provided an answer to one of the main questions – what caused the fire? The device that caught fire was a “supergrid transformer” responsible for reducing high voltage electricity from the transmission grid to a lower voltage for use at Heathrow Airport and surrounding homes. Inspectors concluded that moisture had entered the high-voltage insulation surrounding the connections, causing a short-circuit and electric sparks that led to a “catastrophic failure.” This resulted in the oil used to cool the transformer catching fire and taking two transformers offline, cutting power to Heathrow.
The report also noted that signs of moisture were detected at the substation in July 2018, and while National Grid’s guidance stated that these were indicators of an impending fault that should be addressed, the issue was not fixed at the time. Additionally, basic maintenance on the transformer was postponed in 2022, and multiple attempts to schedule maintenance were unsuccessful.
Heathrow Airport relies on as much electricity as a small city and has three connections to the national grid. However, it was not considered a likely scenario for one of these connections to fail, so the decision was made not to invest the necessary funds to fix the issue, which was estimated to cost a billion pounds. The report suggests that having three connections to the grid presents opportunities to improve Heathrow’s resilience of supply.
National Grid and energy supplier SSEN were aware that electricity from the substation served Heathrow Airport, but they did not know that a disruption in this supply would result in the airport having to shut down. The report suggests that better communication between critical national infrastructure (CNI) operators, such as those in the transport, defense, government, and communications sectors, and their energy suppliers is necessary to prevent interruptions in supply.
Heathrow Airport faced significant criticism after the fire, including the revelation that the CEO was asleep when the decision was made to close the airport. While the report does not aim to assign blame, Heathrow is considering taking legal action against National Grid, stating that the report highlights “clear and repeated failings” that could have prevented the fire. Heathrow expects National Grid to take responsibility for these failings. National Grid maintains that it has a comprehensive maintenance program and will cooperate with the Ofgem investigation.