When the lights go out: what the Heathrow substation fire tells us about resilience in a net zero world

The substation fire near Heathrow Airport was a stark reminder of something we often take for granted, that power will always be there.

A large transformer fault triggered a blaze that shut down power to one of the UK’s most critical pieces of infrastructure. With not enough electricity to supply all of its operations, Heathrow had no choice but to cancel over 1,300 flights. Emergency generators kept the safety systems alive, but not enough for business as usual. It was a rare and extreme case but one that left a lot of infrastructure owners asking, could this happen to us?

Hidden vulnerabilities in a connected system

From the outside, critical power systems often look robust - firm supply, duplicate feeders and standby generation, but as the Heathrow incident showed, there can be hidden single points of failure such as common substations, shared transformers and switching systems exposed to common hazards.

From images and reports, it appeared that one of the supergrid transformers (SGTs) at the Hayes substation caught fire, and the adjacent SGT was also visibly affected. While we don’t know the exact electrical configuration, SGTs typically operate in parallel to meet firm demand. At the Hayes substation, the entire site had to be taken out of operation, not necessarily due to the lack of electrical capacity or resiliency, but due to safety precautions. Accessing the site to tackle the fire required isolating the site, then according to news reports, around 70 firefighters were needed to get the fire under control.

Interestingly, the fact that power was restored and Heathrow resumed operations in around a day suggests that resilience measures worked. The utility companies will have reconfigured the network, rerouted supply, and coordinated restoration once the substation could safely be brought back online. That speed of recovery shouldn't be overlooked as it demonstrates there was redundancy, even if the physical substation became a single point of failure.

Can you design for the worst case?

There’s no such thing as zero risk but how do you decide what level of risk is acceptable? Taking the Heathrow example, if you’d run a risk assessment on a total loss of substation supply, the output might have suggested: catastrophic impact, very low likelihood. Faced with that potential outcome, could you justify spending millions on additional feeds, switchgear, or distributed generation? Or is there a point where you accept the risk and focus your investment elsewhere? The reality is resilience isn’t a binary choice, it’s a judgement call and increasingly, a business decision. You’re weighing cost versus consequence, reliability versus risk appetite and increasingly, carbon versus security. That’s not an easy balance to strike.

Rethinking utility resilience

Many clients we speak to assume that if they have a firm supply from a Distribution Network Operator with dual feeders or N-1 compliance, that’s enough. However, that doesn’t always account for how that supply is routed. Are the transformers independent? Are they physically separated? Does the backup rely on the same switching infrastructure? Put simply, do you know where your single points of failure are? This isn’t just about protecting against rare black swan events. It’s about recognising that, as electrification increases, the consequence of failure rises. So, resilience planning becomes more than technical, it becomes strategic.

Net zero and resilience can go hand-in-hand

There’s a tendency in some circles to pit net zero carbon goals against energy security, as if you can only have one or the other. We don’t see it that way. In fact, decarbonisation is often the catalyst for upgrading ageing infrastructure, replacing legacy assets and improving system visibility. Modern grid connections, battery storage, decentralised generation; these aren’t just sustainable technologies, they’re also enablers of resilience. Yes, there’s a carbon cost in building and maintaining backup systems but there’s also a cost in doing nothing and being exposed when it matters most.

How do you assess the real risk?

The Heathrow incident also highlighted the difficulty of assessing residual risk. From a customer perspective, once you’ve secured a firm utility connection with duplicated feeders, it’s easy to assume that risk is fully mitigated. Although critical sites often install secondary or tertiary generation as a hedge against utility-side failures, that approach is changing. As we move towards net zero, many are moving away from traditional standby generation, reducing diesel usage, limiting carbon intensity, and avoiding the embedded emissions of extra infrastructure and rightly so. However, electrification increases dependency, so the question becomes, how do you assess the real risk? What is the likelihood of a common-mode failure, such as both SGTs being taken offline by fire, or a substation locked down for safety? Is the consequence severe enough to justify further investment, or is it a level of risk that’s understood and accepted? These are difficult questions but they’re essential to answer, especially for sites where failure carries a public, operational or reputational cost.

So, what should you be thinking about?

If you’re responsible for a critical site, or even a moderately sensitive one, this is a good moment to ask:

• Do I have true independence between my A and B supplies?
• Could a single fire, flood or fault take down both?
• Is my backup system realistically sized and will it operate when I need it?
  
• Do I understand the residual risks I’ve accepted?
  
• Is now the right time to revisit our resilience strategy, considering growing dependency on electricity?
  

None of us can eliminate all risk but we can make informed choices. We believe those choices need to be grounded in a clear understanding of how infrastructure is evolving and not just in response to net zero, but in how we value resilience in an electrified world.