Investigators have been unable to determine the underlying cause of the substation fire that led to the closure of Heathrow airport in March, six weeks after the government initiated an “urgent” inquiry.
The National Energy System Operator (Neso) released a preliminary report dismissing any indication of foul play in the incident that resulted in a power outage affecting over 1,350 flights and nearly 300,000 travelers.
However, the state-operated organization acknowledged that the “root cause of the fire” remains “unknown,” which also resulted in around 67,000 homes losing power.
The system operator has committed to further examining the maintenance records and design aspects of the 57-year-old power substation in west London that ignited in late March to ascertain compliance with legal standards.
Additionally, it will investigate the configurations of the airport’s private electricity grid, which required hours to restore power following the outage, while two nearby substations continued functioning as usual.
According to the report, it took Heathrow an additional seven hours to reopen after power was restored, resulting in nearly 24 hours of flight disruptions following the fire on March 20.
Neso indicated that a specialized team reviewed over 600 pieces of evidence from the involved companies to inform its interim findings, with a final report expected by the end of June.
In late March, the energy secretary, Ed Miliband, requested that the system operator conduct an “urgent” inquiry into the incident and submit its initial findings within six weeks of the fire.
On Thursday, he stated: “We now await the comprehensive report to better understand the events and derive insights to enhance the UK’s energy resilience and safeguard our critical national infrastructure.”
Heathrow airport noted that the report has raised concerns regarding National Grid—the owner of the substation that caught fire—and Scottish and Southern Electricity Networks (SSEN), which oversees power distribution in that region.
A representative for the airport commented: “Gaining further insight into the cause of the fire and the subsequent impact on two transformers can aid in bolstering the resilience of the UK’s energy grid in the future.”
The energy companies implicated in the outage are also set to face scrutiny from the industry regulator, Ofgem, which is tasked with overseeing the investments and revenues of electricity network operators.
Heathrow plans to initiate its own internal investigation into its resilience, led by Ruth Kelly, a former transport secretary and current independent board member of the airport.
Within days of the outage, executives from both the energy and airline sectors were called to appear before parliament’s cross-party transport select committee.
Heathrow’s CEO, Thomas Woldbye, expressed regret over the disruptions, explaining to MPs that such a large-scale power outage was considered a “very low probability event,” and the airport had invested in a “supposedly resilient” power supply.
Both National Grid and SSE released statements affirming their commitment to collaborate closely with Neso throughout the investigation and looked forward to the comprehensive report.
