The sudden loss of power at North Hyde substation and Heathrow Airport in March 2025 was more than just an outage — it was a stark reminder of how fragile our energy infrastructure can be.
NESO’s Interim Report has revealed critical vulnerabilities in system design, asset management and emergency responses. It should be a sharp wake up call for CTOs tasked with ensuring reliability in an increasingly electrified world.
The incident: A cascading failure
The crisis began when SGT3, one of three supergrid transformers at the North Hyde 275kV substation, tripped and caught fire. Automated switching restored the supply temporarily but within minutes, the adjacent SGT1 also failed, severing the substation’s connection to the grid entirely. The result? 66,919 customers, some private companies and most of Heathrow Airport—were left without power, forcing the airport to shut down for nearly a full day. While emergency crews and network operators worked tirelessly to restore supply, the outage exposed deep-seated risks in the UK’s energy resilience strategy.
Early investigations suggest the fire was not malicious, but rather a symptom of ageing infrastructure and insufficient redundancy. With SGT1 and SGT3 dating back to 1968, questions are being raised about lifecycle management and whether current regulatory standards go far enough in preventing such failures.
For too long, accountants and number crunchers have delayed the regular replacement of assets at the end of their lifecycle, allowing them to fail before replacing them. While it’s a strategy that works to protect the bottom line of the balance sheet, the North Hyde outage demonstrates just how catastrophic it can be when things inevitably do go wrong.
Key lessons from the NESO report
1. The limits of redundancy in critical infrastructure
The North Hyde substation was designed with N-1 redundancy—meaning it could withstand the loss of one transformer. But when two failed simultaneously, the system collapsed. Additionally, an outage at an adjacent site meant that another backup was not available. This highlights a dangerous gap in resilience planning, particularly for sites supporting critical national infrastructure like airports.
2. Private networks need stronger interconnections
Heathrow’s private electrical network, fed by three independent supply points, was theoretically resilient. Despite there being sufficient power available to Heathrow from the grid, reconfiguring supply during the outage took far longer than anticipated, delaying restoration. The incident underscores the need for seamless failover mechanisms between private and public grids to minimise downtime, and the need for risk assessment and disaster planning which should include sufficient manpower and automation schemes.
3. Ageing assets are a ticking time bomb
With much of the UK’s transmission infrastructure built in the mid to late-20th century, the North Hyde failure is unlikely to be an isolated case. Proactive monitoring and replacement programs are essential to prevent similar disasters.
4. Faster, more coordinated response protocols
While collaboration between fire services, National Grid and SSEN Distribution was effective, the hours-long delay in fully restoring Heathrow’s internal network suggests room for improvement in cross-sector crisis management.
How could the North Hyde power outage have been prevented?
One of the biggest challenges during the outage was the lack of dynamic load management to reroute power in the Heathrow private network efficiently. Utilligence has a modular, AI-driven grid flexibility solution which could have mitigated the impact by:
- Automatically redistributing load to alternative circuits in real-time, reducing dependency on failed transformers.
- Enabling faster reconfiguration of Heathrow’s private network by optimising available supply paths.
- Providing predictive analytics to flag transformer health risks before catastrophic failure occurs.
Using modern adaptive grid technologies, operators could move beyond static redundancy models and build truly resilient networks capable of self-healing during crises.
What needs to change?
- Upgrade redundancy standards: Moving from N-1 to N-2 resilience for critical substations would prevent cascading failures.
- Accelerate asset replacement: Prioritising the modernisation of ageing transformers and switchgear is non-negotiable.
- Mandate smart grid solutions: AI-driven flexibility platforms should be deployed to enhance real-time response capabilities.
- Improve public-private coordination: While we know that in this instance, everyone worked together, developing standardised emergency protocols between DNOs, private operators and emergency services will streamline recovery efforts.
Will it happen again?
Unfortunately, yes—unless decisive action is taken.
The UKs energy demands are growing, with data centres, EV charging and industrial electrification placing unprecedented strain on the grid. The high reliance on renewable energy is reshaping the way the grid operates. While we are seeing a major grid upgrade being deployed, legacy equipment, inadequate monitoring and maladaptive load management technologies and strategies mean that failures like the North Hyde power outage and the Spain power outage will become more frequent—and potentially even more damaging.
Conclusion:
The North Hyde outage is a pivotal moment for the energy sector. The final NESO report, due in June 2025, will likely call for stricter resilience standards, accelerated infrastructure investment and smarter grid management. NESO and OFGEM do not have any remit over private networks. The CAA must set its own standards, and the most valuable report will likely be from the CAA – but this may not be published.
For CTOs, the message is clear: The cost of inaction far outweighs the cost of prevention.
By embracing flexible grid solutions, predictive maintenance, and turnkey projects, we can build a system that doesn’t just quickly recover from failure—but reduces the number of outages.
If you’d like to learn more about how we can support your grid resilience and disaster recovery strategies, contact us today.
(Sources: NESO North Hyde Review Interim Report, May 2025)