Net Zero Secretary Ed Miliband described the National Energy System Operator’s report as ‘deeply concerning’

A fire at an electrical substation near Heathrow Airport which resulted in 24-hours of travel chaos was most likely caused due to moisture found in a transformer since 2018, a review has revealed.

The National Energy System Operator said that moisture had been detected in oil samples at the North Hyde site seven years ago.

 

However, it also claimed that no action was taken to replace electrical insulators, known as bushings.

The fire, which broke out March 21, resulted in Europe’s biggest airport closing for around 16 hours.

Around 1,300 flights were cancelled, leaving at least 270,000 passengers facing travel disruption.

No flights operated at the London airport until around 6pm in the evening.

Neso’s final report said there was a “catastrophic failure” in one of the transformers, “most likely caused by moisture entering the bushing causing a short circuit”, which ignited the oil.

It added: “An elevated moisture reading in one of SGT3’s (the transformer’s) bushings had been detected in oil samples taken in July 2018.

Ruddy Farmer

a reading of moisture from 7 years ago is blamed? This is only a theory and it doesnt sound credible unless there was a large quantity of water there which of course cannot be proven. if it was important, maintenance would have been scheduled to repair it. Oil floats on water, so any water would have fallen into the sump.

“According to National Grid Electricity Transmission’s relevant guidance, such readings indicate ‘an imminent fault and that the bushing should be replaced’.

“While the reading was recorded in National Grid Electricity Transmission’s online system, the mitigations appropriate to its severity were not actioned.

“The controls in place were not effective and failed to identify subsequently that action had not been taken in relation to the elevated moisture reading.

“This includes an opportunity in 2022 when a decision was taken to defer basic maintenance on SGT3. The issue therefore went unaddressed.

Following Neso’s report, energy regulator Ofgem confirmed it is now opening an investigation into the Heathrow fire.

An Ofgem spokesman said: “Based on today’s report and findings, Ofgem will examine the incident, its causes and take further action as necessary.”

The Metropolitan Police had initially launched its own investigation into the substation fire.

However, Scotland Yard quickly confirmed that officers “found no evidence to suggest that the incident was suspicious in nature”