By Jonathan Prynn
The fire that caused the chaotic shutdown of Heathrow airport in March was likely caused by a 鈥渃atastrophic鈥 failure of a crucial component at an electricity substation that should have been prevented, Britain’s National Energy System Operator (NESO) said in a report on the incident on Wednesday.
鈥淭his review has seen evidence that a catastrophic failure on one of the transformer鈥檚 high voltage bushings at National Grid Electricity Transmission鈥檚 275kV substation in Hayes caused the transformer to catch fire,鈥 the report by the National Energy System Operator said.
鈥淭his was most likely caused by moisture entering the bushing, causing an electrical fault.鈥
The electricity likely then “arced” which combined with air and heat to ignite the oil, resulting in a fire.”
The fire led to a loss of electricity to Britain鈥檚 biggest airport, resulting in its total closure for most of Friday March 21, as well as to more than 70,000 other customers. Around 270,000 passenger journeys were cancelled or redirected.
The airport鈥檚 拢3.2 million a year chief executive Thomas Woldbye was criticised for going to bed and turning his phone to silent on the night of the shutdown, leaving the chief operating officer, Javier Echave, to take key decisions,
The report said 鈥渇orensic analysis鈥 carried out by National Grid Electricity Transmission and London Fire Brigade uncovered he cause of the blaze.
However it said an 鈥渆levated鈥 level of moisture had been detected in oil samples taken as long ago as July 2018 鈥 but mitigating actions appropriate to its severity were not implemented.鈥
A decision to defer vital maintenance in 2022 also meant that 鈥渢he issue went unaddressed鈥
National Grid鈥檚 own internal technical guidance dictated that if elevated moisture samples are detected at a substation, it should be put out of service until the bushing can be replaced, or mitigating actions put in place.
But the report said: 鈥淲hile the reading was recorded, the mitigations appropriate to its severity, as set out in National Grid Electricity Transmission鈥檚 relevant policy, were not actioned at the time.鈥
Once the fire had broken out it 鈥渨as not possible to keep either the North Hyde 275kV or 66kV substation sites operational because of the effects of heat and smoke from the fire, and the need to fight the fire safely.鈥
A Heathrow spokesperson said: “Heathrow welcomes this report, which sheds further light on the external power supply failure that forced the airport鈥檚 closure on 21st March. A combination of outdated regulation, inadequate safety mechanisms, and National Grid鈥檚 failure to maintain its infrastructure led to this catastrophic power outage.
鈥淲e expect National Grid to be carefully considering what steps they can take to ensure this isn鈥檛 repeated. Our own Review, led by former Cabinet Minister Ruth Kelly, identified key areas for improvement and work is already underway to implement all 28 recommendations.”
Akshay Kaul, Director General for Infrastructure at Ofgem, said:鈥 鈥淭he North Hyde substation fire resulted in global disruption, impacted thousands of local customers, and highlighted the importance of investment in our energy infrastructure.
“As a result of the report鈥檚 findings, we have opened an investigation into National Grid Electricity Transmission (NGET). We have also commissioned an independent audit of their most critical assets.
鈥淥fgem will also further examine the incident and its causes and take further action as appropriate.
鈥淲e expect energy companies to properly maintain their equipment and networks to prevent events like this happening. Where there is evidence that they have not, we will take action and hold companies fully to account.
鈥淏ritain has one of most reliable energy systems in the world and thankfully incidents like this are rare. We must continue to invest in the system to maintain that resilience.鈥
Fintan Slye, Chief Executive Officer, NESO said: 鈥淣ESO鈥檚 final report into the North Hyde Substation outage sets out the root cause and a clear set of recommendations to further improve the resilience of Great Britain鈥檚 energy system, and the resilience of its critical national infrastructure
.鈥淲hilst the power outage and closure of Heathrow airport were hugely disruptive, all parties responded quickly and professionally. This report seeks to improve the way parties plan for and respond to these incidents, building on the underlying resilience of our energy system and the wealth of expertise and commitment across the sector.