Neglected Substation Fault Behind Heathrow Airport Blackout
A catastrophic power failure that shut down Heathrow Airport in March has been traced to a long-ignored transformer fault first detected seven years ago, according to an official investigation by the National Energy System Operator (NESO).
Key Findings from the NESO Report
✔ Faulty transformer bushing – Moisture ingress caused a fire at the North Hyde 275kV substation
✔ Warning signs since 2018 – Elevated moisture levels were detected but never acted upon
✔ Maintenance deferred in 2022 – Basic checks on the transformer were postponed
✔ Cascading failure – One transformer’s collapse triggered a full shutdown
✔ Ofgem investigation launched – National Grid under scrutiny for maintenance lapses
What Went Wrong?
🔹 July 2018 – Oil samples detected high moisture levels in a transformer bushing (a known fire risk)
🔹 No action taken – National Grid failed to replace the faulty part despite internal warnings
🔹 March 2025 – The weakened bushing catastrophically failed, causing a fire and blackout
Impact of the Blackout
✈ 1,300+ flights cancelled
🏥 Hillingdon Hospital affected
🏠 70,000+ homes & businesses lost power
💷 Millions in economic losses
Who’s to Blame?
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National Grid – Responsible for maintenance but missed critical repairs
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Heathrow’s backup plan failed – Only 2 of 3 power feeds were operational
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Systemic gaps – Energy firms don’t always know which sites are Critical National Infrastructure
Recommendations to Prevent Future Failures
✅ Proactive maintenance – Mandate timely repairs for high-risk equipment
✅ Improved grid resilience – Ensure backup power for critical sites
✅ Stricter Ofgem oversight – Enforce compliance with safety regulations
What Happens Next?
🔎 Ofgem investigation into National Grid’s maintenance practices
🛠️ Heathrow upgrading its power redundancy
⚡ UK-wide review of substation resilience
Key Quotes
“This was a story of missed opportunities. Had the fault been fixed in 2018, the blackout could have been avoided.”
– Fintan Slye, NESO Chief Executive
“We’ve taken further action, including re-testing substations serving critical infrastructure.”
– National Grid statement
