Watchdog report says substation fire that shut Heathrow 'preventable'

REPORT BY NATIONAL ENERGY SYSTEM OPERATOR SAYS FAULT FOUND BUT DECISION TAKEN TO 'DEFER BASIC MAINTENANCE'

- By ROSIE SHEAD

ENERGY watchdog Ofgem has launched an investigation after a report found a fire that caused the shutdown of Heathrow Airport was due to a preventable technical fault.

The report by the National Energy System Operator (Neso) said an “elevated moisture reading” had been found in oil samples at the North Hyde substation in west London in July 2018, but action was not taken to replace electrical insulators known as bushings.

In 2022, a decision was made to “defer basic maintenance” at the substation, meaning the issue went “unaddressed”, the final report said.

On Wednesday, Ofgem said it had opened an official enforcement investigation into National Grid Electricity Transmission (NGET) based on the Neso review’s findings.

The fire, on March 20 this year, was caused by a “catastrophic failure” in one of the transformers, “most likely caused by moisture entering the bushing causing a short circuit”, which ignited the oil, the Neso report said.

A review by the National Grid in 2022 found the fire suppression system at the North Hyde site was “inoperable”, while another assessment in July 2024 indicated the system was still “out of service”, the report said.

No flights operated at the west London airport until about 6pm on March 21 because of the blaze which started late the previous night. More than 270,000 air passenger journeys were disrupted by the closure.

The electricity outage led to 71,655 domestic and commercial customers losing power and the “complete loss of supplies” to part of Heathrow Airport's internal electrical distribution network, the report said.

Akshay Kaul, director general for infrastructure at Ofgem, said: “The North Hyde substation fire resulted in global disruption, impacted thousands of local customers, and highlighted the importance of investment in our energy infrastructure.