North Hyde substation fire and the Heathrow closure (2025)
A transformer fire on the night of March 20 to 21, 2025 that cut power to Heathrow and closed the airport for a day, caused by a fault known since 2018 and never remedied.
A large critical site is often fed by several substations, and people conclude that it cannot lose power. But redundancy is only worth something if switching from one source to another is fast: if it takes hours of reconfiguration, losing a single substation is enough to stop operations. North Hyde also showed that a grid's risk lies in the maintenance of each piece of equipment: a defect spotted in an oil sample and classified as urgent can go unaddressed for years. For an insurer, the event illustrates business interruption from the failure of an energy supplier, which strikes hundreds of companies without any physical damage on their premises. It finally shows that the dependence of an airport, a data center or a hospital on a single grid node cannot be read from its own plans.
The fire at the North Hyde 275 kV substation on March 21, 2025 closed Heathrow, canceled more than 1,350 flights, affected nearly 300,000 passengers and cut power to 67,000 homes; airlines estimated the disruption at 80 to 100 million pounds. The final report by the system operator, NESO, attributed the fire to moisture in a high voltage bushing, detected in an oil sample in July 2018 without the required actions being taken.
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