Europe | July 3, 2025

Heathrow substation fire blamed on bushing

According to available information, delayed maintenance of a defective HV bushing and poor network management contributed to the fire and flight disruption at Heathrow.

 

burnt transformer_Shutterstock_1410832883

Image for illustrative purposes

UK, England, London: Based on information shared by industry professional Simon Gallagher on LinkedIn, the final report by the National Energy System Operator (NESO) into the fire at North Hyde substation points to several critical failures by both National Grid Electricity Transmission (NGET) and Heathrow Airport.

The root cause of the substation fire is reported to be moisture in a high-voltage bushing, first identified in a 2018 oil sample and categorised as a ‘Category 1’ issue under NGET’s own standards, indicating it required immediate action. Despite this, the bushing was not replaced, and maintenance was deferred as recently as 2022.

The fire, which occurred at a key substation serving Heathrow Airport, led to the cancellation of approximately 1,300 flights. While the substation lacked modern fire barriers due to its age, Gallagher states that no firefighting began until the site was fully isolated and made safe, which he notes was the correct protocol.

In his analysis, Gallagher highlights a major issue in Heathrow Airport’s own power network operations. Although the airport was designed with three independent grid supplies, each capable of supporting the full load, Gallagher claims that Heathrow’s network was not configured to take advantage of this built-in resilience.

He also questions the airport’s understanding of its own infrastructure, citing its expectation of an “uninterruptible” power supply from the grid as unrealistic.

The NESO report, as interpreted by Gallagher, indicates a combination of asset management failures by NGET and operational shortcomings at Heathrow as contributing factors to the severity of the incident.

Source: Simon Gallagher via LinkedIn