LONDON: A fire that shut Heathrow Airport in March, stranding thousands of passengers, was caused by National Grid’s failure to maintain an electricity substation, an official report said on Wednesday (Jul 2), prompting the energy watchdog to open a probe.
The closure of Heathrow, the busiest airport in Europe, cost airlines tens of millions of pounds. It also raised questions about the resilience of Britain’s infrastructure.
Energy minister Ed Miliband said the report was “deeply concerning”.
“Known risks were not addressed by the National Grid Electricity Transmission, and (energy regulator) Ofgem has now opened an official enforcement investigation to consider any possible licence breaches,” he said in a statement.
The report follows a review of the incident on Mar 21 by the National Energy System Operator, which manages the electricity network and was separated from National Grid last year.
As a result of the report, Britain’s energy regulator Ofgem launched an enforcement investigation into National Grid Electricity Transmission, which owns and maintains the high-voltage electricity transmission network in England and Wales.
The report said its review had seen evidence that a “catastrophic failure” on one of the transformer’s high voltage bushings at National Grid Electricity Transmission’s 275kV substation caused the transformer to catch fire.
“This was most likely caused by moisture entering the bushing causing a short circuit. The electricity likely then ‘arced’ (causing sparks) which combined with air and heat to ignite the oil, resulting in a fire,” it added.
An elevated moisture reading in one of the bushings had been detected in oil samples taken in July 2018, indicating “an imminent fault and that the bushing should be replaced”.
However, “controls in place were not effective and failed to identify subsequently that action had not been taken in relation to the elevated moisture reading,” it said.
“This includes an opportunity in 2022 when a decision was taken to defer basic maintenance. The issue therefore went unaddressed,” added the report.
