The cause of a fire at an electricity substation, which led to the shutdown of Heathrow Airport for almost an entire day in March, remains unknown, according to an interim report.
Initial findings into the North Hyde substation outage by the National Energy System Operator (NESO) have been published ahead of a final report due next month.
London Fire Brigade and National Grid Electricity Transmission are continuing to conduct forensic investigations.
On 25 March, the Metropolitan Police Service confirmed that it had ‘found no evidence to suggest that the incident was suspicious in nature’.
The final report, which is due in June, will make findings and recommendations relating to the resilience of energy infrastructure; the response and restoration of energy infrastructure; and the resilience of critical national infrastructure to energy disruption, said NESO.
NESO Chief Executive Officer Fintan Slye said: “It is important that the right lessons are learnt from this incident to prevent future instances where possible and to manage them effectively when they do occur.”
Energy Secretary Ed Miliband welcomed the report, adding the fire and power loss led to ‘major disruption to thousands of people and many businesses’.
The power outage and subsequent closure of Heathrow Airport meant that around 1,300 flights were grounded, disrupting up to 270,000 passengers
Ed added: “We now await the full report to understand what happened and learn lessons to strengthen UK energy resilience and protect our critical national infrastructure.”
A Heathrow spokesperson said: “Heathrow welcomes the NESO review’s initial report, which raises important questions for National Grid and Scottish and Southern Electricity Networks (SSEN) that we hope the final report will provide answers to, including the cause of the fire.
“Further clarity on how the fire started and why two transformers were subsequently impacted can help ensure greater resilience for the UK’s energy grid moving forward.”
