I’m retired now from NG transmission and this never was my patch, I think the closest I got was some protection equipment work at Iver maybe 25 ish years ago so the only insight I have is what’s been in the press and access to the published transmission system maps which for some reason omit North Hyde completely. In fact I’m really struggling to find any other omissions elsewhere.
I can’t believe the bollocks sprouted by the media and ‘experts’ about this incident although it’s only to be expected!
The total lack of fire separation barriers surprised me, after the massive supergrid transformer fire at either Rochdale or Padiham in Lancashire in the late 1980’s lots of barriers were installed together with increased height bund walls, & fire suppression systems. As far as the North Hyde site is concerned, In the footage and on Google earth, for the one that caught fire you can see rigid busbars from the transformer bushings crossing over the internal access road and around the relay rooms into the lower voltage compound. The western and immediately closest circuit to the one that caught fire looks to cross the road into the compound on a catenary strung from an overhead gantry, and the eastern, most right hand one with large separation from the other two is possibly terminated in a cable sealing end, destination unknown, it could be another DNO substation, or the far side of the North Hyde 66kV/22kV site.
The 275kV busbar sections would in normal circumstances be run split so you’d have two 275kV/66kV transformers effectively on one 275kV feeder, and the remaining 275kV transformer on the other feeder. The 66kV sub with at least two sections and possibly more would then, in normal circumstances, require a double circuit failure of the HV side to cause a total loss of supply (a double circuit feeder fault) At the far end of the 275kV feeders at Iver they’d be on separate busbar sections and so the likelihood of loss of both supplies is quite low but not impossible.
The windings of the transformer are enclosed in oil, circulated and cooled by external coolers (radiators) If there was a transformer fault it might be preceded by the detection of gas being produced within the oil as it decomposes. If this is gradual then in the first instance generate an alarm, normally resulting in a site visit and an oil sample being taken for lab analysis. A rapid production of gas by a failure resulting in an internal arc would result in lots of gas being produced, in those circumstances the transformer would be automatically disconnected from the HV (275kV) supply using a circuit breaker (a device that can break load and fault current) and then automatically disconnected from the LV (66kV) load using a disconnector (a device that isn’t intended to break load and fault current) Hopefully this occurs rapidly without disruption of the transformer tank and cooler bank. But a large overpressure would be relieved by burst discs and oil would end up hopefully within the oil containment bund.
So following the transformer failure, and assuming there is no collateral damage it would still leave the entire 66kV/22kV sub still serviceable, possibly with some loss of supply from bars fed by the failed transformer. At this point reconfiguration to maintain essential supply to Heathrow could be relatively easy.
But if a catastrophic failure of the transformer or cooler bank happened with oil spraying or misting onto live conductors it could ignite.
That’s a holding situation but as the fire progresses the closely sited transformer would at some point either trip on fault maybe with bushing contamination from the combustion products or with winding temperature, or when the extent of the incident became visible it would be manually switched out of service.
One thing to note is all circuits at 66kV and below leave via cable regardless
There are still 66kV networks around elsewhere, off the top of my head, in the North East (Hawthorn Pit, Hartmoor, Lackenby, West Bolton & Norton) and in South Yorkshire (Thurcroft, West Melton & Thorpe Marsh, plus a handful more). All were associated historically with coal mining
Plus the North East has quite a bit of 20kV (yes 20 not 22) lines such as in and around the Hexham area (there was even a new 275kV/20kV sub built on the cross Pennine west of Newcastle route from Stella West to Harker about 25 years ago, named Fourstones)
As an aside, on the previous Friday, the 14th March at 0851 three units near simultaneously tripped at Drax, one on its own and then five secs later two more 1887MW loss of generation. Virtually nothing said anywhere. No lightning activity. No press releases from NESO or Drax plc. Now it could be someone messing up preparing for testing and there is an internal enquiry ongoing but losing generation spread over at least two and possibly three busbar sections is very strange. The frequency dropped to 49.667Hz. Data is visible on elexon. I do have screen caps.
While I too am a bit shocked at the apparent failings of NG, I am a bit wary of focusing too much on them because it diverts attention entirely from what I am pretty sure will eventually be seen as the main issue - the complete lack of competent fail over arrangements within Heathrow itself.
I have zero knowledge of electrical transmission but my experience of backup and failure situations makes me agree with you. Heathrow should not be reliant on anyone but itself for electricity generation in a failure situation. Yes, they should have several points of supply from what I would probably wrongly refer to as "the grid" but their backup onsite generators shoudl easily be able to deal with cut out and several days worth of fuel supply be on hand, something a major airport like Heathrow with a connected fuel farm should be able to arrange very easily.
Martin there was an overview of the Drax incident in this weeks operational transparency forum although cause not discussed but the system response was. Fortunately bad old gas was dominant so inertia was c240GVAs so nothing apparent to majority of consumers as it should be. Had it been running at the 120GVAs minimum when renewable penetration is high could have been more interesting.
National Grid plc are no longer responsible its down to NESO. Until I watched the OTF I had no idea the event had happened and was surprised about the detail that NESO showed to explain how they responded to it so have to give them credit for that. Isn't the 49.5Hz some mandatory requirement that NESO have to keep within?
Thanks for your detailed response. I’m in the US but grid discussions are universal. I got involved with grid operations for the last five years of my career in nuclear power and I found it absolutely fascinating.
IMO, this sounds like a standard transformer failure that cascaded to multiple failures due to protection coordination issues.
Yes, all large power transformers should have robust fire protection systems and certainly that will be a contributing cause.
The op points about backup plans and switching orders are also quite important to this discussion about how this occurred.
I was going to point out that fig 1 in the SSEN document clearly shows the area of supply for the sub going just to the T1/2/3 area, not the entire site.
Sorry the reply earlier was a bit disjointed, I’d been up since 4am so was just going for a much needed nap.
I don't think there's any secret about other nearby substations at 132kV. East Bedfont is near Terminal 4 and Langford is the other side of the M25 just North of J14 for T5. All easily traced via Openinfrastructuremap, as is the location of the 1.8MWe/9MW thermal CHP station by the cargo tunnel entrance near T4. It's all fed by the 400kV London ring via substations at Iver and Weybridge
I suspect that SSEN may be responsible for the supply to the tunnel for lighting, fans and mobile signals (all fighting to capture roaming phones) if it is deemed part of the highway network. Otherwise their responsibility will end at the airport boundary and its substations.
I know very little about electricity supplies so this has been illuminating & fascinating to read. Thanks. The unfortunate facts about old kit not lasting for ever are well known.
The ever increasing demand on all the UK infrastructure & a plan to address this - water, land, roads, power, housing - is rarely acknowledged publicly. At least not in a mature rational discussion. I have so little confidence in those in power to enable this without media meltdown I end up & shrug my shoulders & hope someone skilled & competent who genuinely know what they are doing will sort it out. I wasn’t going in or out of Heathrow at the time - so I’m OK Jack.
I guess we have more of these sorts of catastrophic failures to come.
I work in the water sector but I can see what i think might be parallels. The water regulator (Ofwat) has been obsessed with keeping bills to a minimum (despite all the investment in the last 35yrs bills are, in real terms the same as they were in 1995) and only sanctioning investment for complying with new environmental statutory requirements. This means existing assets suffer from mythical econometric modelling to assess how much maintenance they need. (As an aside when I used to take modellers to construction sites they were blown away with what actually happens as they had little to no experience of the actual practicalities of what was required). Econometric modelling and an obsession with keeping bills to a minimum leads to creeping degradation of existing assets. 'Make do and mend' becomes the norm. Asset failures are only ever a short hop away. And when it's big, like Heathrow, everyone says.... how can this have happened?
I watched the Thames water 2 part TV documentary. Aware of the expected reporting bias, I was horrified to see the state of some of the sites (& to be honest the dreariness of the working environments for the staff). Ancient manually operated equipment & a curious lack of urgency or anger - almost as if entirely spent. A request to OFWAT for bills to increase by 53% was never going to happen - they are appealing the decision. Fines for pollution spills which in many cases are driven by weather events & the ever-present poor human behaviour (anything goes into the sewers). Clean potable water is one of the key elements in increases in human longevity & survival. And it appears the population doesn’t expect to pay what it really costs to produce.
INHO I’ve always thought that every single human as a sign of growing up & taking responsibility of being human should be exposed to the realities of water & waste /food production & waste, farming & primary production including slaughter & the general nuts & bolts of being able to live a free & civilised life.
Thanks for your expert commentary. The woeful MSM and social media coverage of this incident is so illustrative of the dire mess the country is in.
You are right to say that all those in authority need to come to their senses. They surely can't hold out for much longer on their Net Zero nonsense now that the popular vote winning US government openly refers to the "climate change hoax".
If only. I suppose we can hope net zero collapses but they will declare Orange Man bad and don’t forget that he said to inject yourself with bleach during Covid. So climate change.
Its is despairing with all the knowledgably people about that media don't have anyone on tap who can give an objective view of what's happened. Anyhow as I see it the DfT and DENZ should have both combined forces and either instigated or called for an independent investigation of how one of the worlds biggest airport was bought to a stand by a totally credible failure scenario. No sign of that although Milibrain wouldn't have any interest but Heidi Alexander should but all she does is praise Heathrow Airport for its response oh and the usual platitudes for the Emergency Services (it is what they are paid to do!!) but it all pushes the narrative away from the truth. To be fair to Andrea Leadsom she was straight onto it after the 9th August 2019 grid fiasco.
NESO have released interim report gives a bit more detail about system configuration but cause not known yet. They install a nice new SGT in 2010 but sits in hot standby and they run the two 1968 SGTs which sit side by side so they take each other out. Not sure that was the most resilient setup.
Not a lot said on Heathrow who are doing their own investigation but they confirm that HAL were able to reconfigure their own HV system to support the airport wide load on the other two grid intakes but seems they have a multitude of systems that can’t cope with a supply interruption.
Transport Select Committee today investigating Heathrow event. HAL CEO says as a result of the loss of Heathrow Nth S/Stn T2 was off line and the approach tunnel and their operations centre was affected. Says T5 was unaffected but because of the switching they needed to do sounds like they through caution to the wind.
NG say at N.Hyde s/stns two transformers were on line one tripped off after the fire started and they reconfigured the site to a standby transformer but shortly after the remaining two transformers tripped off (the adjacent one i can get but the third was in a different part of the site will have to wait investigation). They had one EHV supply restored at 1000hrs and a second supply available at 1600hrs.
SSEN were able to reconfigure there local network to restore domestic and business customers from 0400 onwards and importantly they were able to reconfigure their 66kV system at 0930 and give Heathrow a supply to their North substation at 1000.
Under questioning HAL are pointing the finger at NG/SSEN as its up to them to provide HAL with resilience. Basically HAL run the airport as three discrete load centres and interconnecting isn’t designed for the scenario that happened. A rep from Heathrow airline operators group claims that HAL waited till 0600 before they decided to reconfigure, SSEN confirmed to HAL they could have provided additional load from their two other s/stns. Also UK power Networks run the internal HAL HV network and sounds like they needed to call people in.
Sounds to me HAL have too many systems that can’t cope with a loss of supply and be satisfied they will self restore so they are taking lowest risk approach and basically booting up every system from scratch and confirm they are working satisfactorily.
HAL hiding behind the Kelly report so they better publicly disclose that report.
PS: Need to listen to another hour of questioning so maybe more clarity given
Both NG and HAL/UKPN have serious questions to answer. NG because they shouldn't have lost all 3 transformers, & HAL/UKPN because they've obviously let their own resilience go to rats in the last couple of decades.
Ultimately though, it's down to HAL to manage their own risks - and react far more quickly/responsibly to an emergency situation - so atm I'd apportion blame 70/30 to HAL/NG.
John Pettigrew told the Financial Times the fire, which knocked out a substation in Hayes, was a “unique event,” but stressed that two other substations remained operational and capable of keeping Heathrow running.
Heathrow’s CEO admitted the issue wasn’t a total power failure but the time it took to switch supply from the damaged substation to the others.
While the airport has diesel generators and battery backups to keep crucial safety systems running—such as runway lights and landing equipment—it still relies heavily on National Grid for its main operations.
A biomass generator also supplies some power to Terminal Two, but it wasn’t enough to keep the airport running.
Pettigrew, said he couldn’t recall a transformer failure like this before.
“Losing a substation is a unique event but there were two others available. That is a level of resilience,” he told the FT.
“There was no lack of capacity from the substations. Each substation individually can provide enough power to Heathrow.”
Several papers seem to have latched onto the 2014 report by Jacobs during the third runway enquiry: reading the full discussion I'm not sure that they really appreciated the realities.
I suspect that internal management attention has been diverted by their push for net zero ground operations. THis from their plan for that:
The biggest source of carbon that we directly control is the gas we burn to heat Heathrow’s buildings. Our proposed solution is based on electrification of space and hot water heating with recovery of surplus heat in summer and storage for use in winter months. This will be a major investment and a complex project which will take us ten to 15 years to complete: we are targeting net zero carbon buildings by the mid 2030s. To hit our goal, we will also need alternatives to the refrigerants used in our air-conditioning and Government regulation will be important here.
By delivering efficiencies, switching off gas and seeking
alternative solutions we can make the greatest carbon savings.
Underpinning most of the solutions is a switch to renewable
electricity – on which there are growing demands. As we
switch to renewable electricity, our airport distribution network
will need to evolve to meet the demand and distribute power
to where it is needed to charge vehicles and deliver heat and
support the needs of the airport.
Therefore, a key aspect of our plan is to upgrade the electrical
distribution network which underpins the solutions we need.
Targets: Detailed scheme design complete for decarbonising
heating supply and upgrading our electrical distribution network
by 2026.
Investment: We have proposed to the CAA £23m to design
network upgrades and a heat solution and begin to implement
these. Further investment is planned subsequently to complete
these upgrades and implement the chosen heat solution.
That’s just for system design. Never mind fixing what's there.
The report into the 2003 South/South-West London outage (Wimbledon) makes very interesting reading. The speed with which grid control worked out what had happened and restored supplies to the DNO was very, very impressive.
Also, in the context of this event, that a proximate cause was the misreading of a Bucholz alarm, reading it to be from a different transformer from the one alarming.
Root cause - mis-set shunt. It triggered an audit of every single protection device setting.
It's a quality report and I see no reason we shouldn't get the same for this incident. And also interestingly, the 2013 superbowl stadium outage was also caused by mis-set protection. In both cases, it seems, remarkably easy to get wrong.
NESO’s investigation will support efforts to build a clear picture of the circumstances surrounding this incident and the UK’s energy resilience more broadly so that it’s prevented from ever happening again.
Headed by former Eirgrid employee and and former head of National Grid Fintan Slye who appointed fellow Irish person Alice Delahunty as Head of Networks at National Grid, where she is now President of Transmission.
Interesting, the claim is that the other two supplies to Heathrow needed some form of "reengineering" (whatever that means) to allow them to be used :
"However, the Jacobs report, titled Operational Risk: Ground Infrastructure Heathrow Airport, stated: “Beyond the management of supply and grid services, which lie outside the airport’s control, the responsibility for managing electricity supply risk lies with the airport and businesses operating from the airport.
“While some services can be temporarily supported with generator or battery back-ups, the key weakness is the main transmission line connections to the airport.”
It warned: “Outages could cause disruption to passengers, baggage and aircraft handling functions and could require closure of areas of affected terminals and potentially the entire airport.
“Even a brief interruption to electricity supplies could have a long-lasting impact as systems can take time to recover.”
The fire destroyed a vital transformer at the North Hyde substation and also a back-up transformer, rendering the substation inoperable.
The airport is also served by two other substations powering different areas. However, in order for these to run the entire airport, the power supply to all the terminals needs to be re-engineered."
I’m retired now from NG transmission and this never was my patch, I think the closest I got was some protection equipment work at Iver maybe 25 ish years ago so the only insight I have is what’s been in the press and access to the published transmission system maps which for some reason omit North Hyde completely. In fact I’m really struggling to find any other omissions elsewhere.
I can’t believe the bollocks sprouted by the media and ‘experts’ about this incident although it’s only to be expected!
The total lack of fire separation barriers surprised me, after the massive supergrid transformer fire at either Rochdale or Padiham in Lancashire in the late 1980’s lots of barriers were installed together with increased height bund walls, & fire suppression systems. As far as the North Hyde site is concerned, In the footage and on Google earth, for the one that caught fire you can see rigid busbars from the transformer bushings crossing over the internal access road and around the relay rooms into the lower voltage compound. The western and immediately closest circuit to the one that caught fire looks to cross the road into the compound on a catenary strung from an overhead gantry, and the eastern, most right hand one with large separation from the other two is possibly terminated in a cable sealing end, destination unknown, it could be another DNO substation, or the far side of the North Hyde 66kV/22kV site.
The 275kV busbar sections would in normal circumstances be run split so you’d have two 275kV/66kV transformers effectively on one 275kV feeder, and the remaining 275kV transformer on the other feeder. The 66kV sub with at least two sections and possibly more would then, in normal circumstances, require a double circuit failure of the HV side to cause a total loss of supply (a double circuit feeder fault) At the far end of the 275kV feeders at Iver they’d be on separate busbar sections and so the likelihood of loss of both supplies is quite low but not impossible.
The windings of the transformer are enclosed in oil, circulated and cooled by external coolers (radiators) If there was a transformer fault it might be preceded by the detection of gas being produced within the oil as it decomposes. If this is gradual then in the first instance generate an alarm, normally resulting in a site visit and an oil sample being taken for lab analysis. A rapid production of gas by a failure resulting in an internal arc would result in lots of gas being produced, in those circumstances the transformer would be automatically disconnected from the HV (275kV) supply using a circuit breaker (a device that can break load and fault current) and then automatically disconnected from the LV (66kV) load using a disconnector (a device that isn’t intended to break load and fault current) Hopefully this occurs rapidly without disruption of the transformer tank and cooler bank. But a large overpressure would be relieved by burst discs and oil would end up hopefully within the oil containment bund.
So following the transformer failure, and assuming there is no collateral damage it would still leave the entire 66kV/22kV sub still serviceable, possibly with some loss of supply from bars fed by the failed transformer. At this point reconfiguration to maintain essential supply to Heathrow could be relatively easy.
But if a catastrophic failure of the transformer or cooler bank happened with oil spraying or misting onto live conductors it could ignite.
That’s a holding situation but as the fire progresses the closely sited transformer would at some point either trip on fault maybe with bushing contamination from the combustion products or with winding temperature, or when the extent of the incident became visible it would be manually switched out of service.
One thing to note is all circuits at 66kV and below leave via cable regardless
There are still 66kV networks around elsewhere, off the top of my head, in the North East (Hawthorn Pit, Hartmoor, Lackenby, West Bolton & Norton) and in South Yorkshire (Thurcroft, West Melton & Thorpe Marsh, plus a handful more). All were associated historically with coal mining
Plus the North East has quite a bit of 20kV (yes 20 not 22) lines such as in and around the Hexham area (there was even a new 275kV/20kV sub built on the cross Pennine west of Newcastle route from Stella West to Harker about 25 years ago, named Fourstones)
As an aside, on the previous Friday, the 14th March at 0851 three units near simultaneously tripped at Drax, one on its own and then five secs later two more 1887MW loss of generation. Virtually nothing said anywhere. No lightning activity. No press releases from NESO or Drax plc. Now it could be someone messing up preparing for testing and there is an internal enquiry ongoing but losing generation spread over at least two and possibly three busbar sections is very strange. The frequency dropped to 49.667Hz. Data is visible on elexon. I do have screen caps.
Thanks for your thoughts and the info!
While I too am a bit shocked at the apparent failings of NG, I am a bit wary of focusing too much on them because it diverts attention entirely from what I am pretty sure will eventually be seen as the main issue - the complete lack of competent fail over arrangements within Heathrow itself.
I have zero knowledge of electrical transmission but my experience of backup and failure situations makes me agree with you. Heathrow should not be reliant on anyone but itself for electricity generation in a failure situation. Yes, they should have several points of supply from what I would probably wrongly refer to as "the grid" but their backup onsite generators shoudl easily be able to deal with cut out and several days worth of fuel supply be on hand, something a major airport like Heathrow with a connected fuel farm should be able to arrange very easily.
Martin there was an overview of the Drax incident in this weeks operational transparency forum although cause not discussed but the system response was. Fortunately bad old gas was dominant so inertia was c240GVAs so nothing apparent to majority of consumers as it should be. Had it been running at the 120GVAs minimum when renewable penetration is high could have been more interesting.
National Grid don't care unless frequency goes below 49.5Hz for more than 60 seconds. Then they have to answer for it.
National Grid plc are no longer responsible its down to NESO. Until I watched the OTF I had no idea the event had happened and was surprised about the detail that NESO showed to explain how they responded to it so have to give them credit for that. Isn't the 49.5Hz some mandatory requirement that NESO have to keep within?
Thanks, just reading it now
Thanks for your detailed response. I’m in the US but grid discussions are universal. I got involved with grid operations for the last five years of my career in nuclear power and I found it absolutely fascinating.
IMO, this sounds like a standard transformer failure that cascaded to multiple failures due to protection coordination issues.
Yes, all large power transformers should have robust fire protection systems and certainly that will be a contributing cause.
The op points about backup plans and switching orders are also quite important to this discussion about how this occurred.
Heathrow officials have some ‘splaining to do!
I was going to point out that fig 1 in the SSEN document clearly shows the area of supply for the sub going just to the T1/2/3 area, not the entire site.
Sorry the reply earlier was a bit disjointed, I’d been up since 4am so was just going for a much needed nap.
Yes, the document is about North Hyde, so it doesn't cover the other supplies - at least one from Laleham I believe.
I don't think there's any secret about other nearby substations at 132kV. East Bedfont is near Terminal 4 and Langford is the other side of the M25 just North of J14 for T5. All easily traced via Openinfrastructuremap, as is the location of the 1.8MWe/9MW thermal CHP station by the cargo tunnel entrance near T4. It's all fed by the 400kV London ring via substations at Iver and Weybridge
The bing maps aerial shots both from above and the bird’s eye view are both way better resolution than google earth
I suspect that SSEN may be responsible for the supply to the tunnel for lighting, fans and mobile signals (all fighting to capture roaming phones) if it is deemed part of the highway network. Otherwise their responsibility will end at the airport boundary and its substations.
I know very little about electricity supplies so this has been illuminating & fascinating to read. Thanks. The unfortunate facts about old kit not lasting for ever are well known.
The ever increasing demand on all the UK infrastructure & a plan to address this - water, land, roads, power, housing - is rarely acknowledged publicly. At least not in a mature rational discussion. I have so little confidence in those in power to enable this without media meltdown I end up & shrug my shoulders & hope someone skilled & competent who genuinely know what they are doing will sort it out. I wasn’t going in or out of Heathrow at the time - so I’m OK Jack.
I guess we have more of these sorts of catastrophic failures to come.
I work in the water sector but I can see what i think might be parallels. The water regulator (Ofwat) has been obsessed with keeping bills to a minimum (despite all the investment in the last 35yrs bills are, in real terms the same as they were in 1995) and only sanctioning investment for complying with new environmental statutory requirements. This means existing assets suffer from mythical econometric modelling to assess how much maintenance they need. (As an aside when I used to take modellers to construction sites they were blown away with what actually happens as they had little to no experience of the actual practicalities of what was required). Econometric modelling and an obsession with keeping bills to a minimum leads to creeping degradation of existing assets. 'Make do and mend' becomes the norm. Asset failures are only ever a short hop away. And when it's big, like Heathrow, everyone says.... how can this have happened?
I watched the Thames water 2 part TV documentary. Aware of the expected reporting bias, I was horrified to see the state of some of the sites (& to be honest the dreariness of the working environments for the staff). Ancient manually operated equipment & a curious lack of urgency or anger - almost as if entirely spent. A request to OFWAT for bills to increase by 53% was never going to happen - they are appealing the decision. Fines for pollution spills which in many cases are driven by weather events & the ever-present poor human behaviour (anything goes into the sewers). Clean potable water is one of the key elements in increases in human longevity & survival. And it appears the population doesn’t expect to pay what it really costs to produce.
INHO I’ve always thought that every single human as a sign of growing up & taking responsibility of being human should be exposed to the realities of water & waste /food production & waste, farming & primary production including slaughter & the general nuts & bolts of being able to live a free & civilised life.
Oh wait - is that what democracy is meant to be?
"Let this ridiculous, entirely avoidable, incident finally be the wake up call that Britain needs." -- don't hold your breathe.
Thanks for your expert commentary. The woeful MSM and social media coverage of this incident is so illustrative of the dire mess the country is in.
You are right to say that all those in authority need to come to their senses. They surely can't hold out for much longer on their Net Zero nonsense now that the popular vote winning US government openly refers to the "climate change hoax".
If only. I suppose we can hope net zero collapses but they will declare Orange Man bad and don’t forget that he said to inject yourself with bleach during Covid. So climate change.
Its is despairing with all the knowledgably people about that media don't have anyone on tap who can give an objective view of what's happened. Anyhow as I see it the DfT and DENZ should have both combined forces and either instigated or called for an independent investigation of how one of the worlds biggest airport was bought to a stand by a totally credible failure scenario. No sign of that although Milibrain wouldn't have any interest but Heidi Alexander should but all she does is praise Heathrow Airport for its response oh and the usual platitudes for the Emergency Services (it is what they are paid to do!!) but it all pushes the narrative away from the truth. To be fair to Andrea Leadsom she was straight onto it after the 9th August 2019 grid fiasco.
Thanks very much for this level headed commentary.
NESO have released interim report gives a bit more detail about system configuration but cause not known yet. They install a nice new SGT in 2010 but sits in hot standby and they run the two 1968 SGTs which sit side by side so they take each other out. Not sure that was the most resilient setup.
Not a lot said on Heathrow who are doing their own investigation but they confirm that HAL were able to reconfigure their own HV system to support the airport wide load on the other two grid intakes but seems they have a multitude of systems that can’t cope with a supply interruption.
https://www.neso.energy/publications/north-hyde-review
It was all known, and (should have been) in the public domain, within a couple of days.
https://x.com/EyesOnThePriz12/status/1903715776634269836
I posted only limited details because my information was from a contact at National Grid who I didn't want to “out” for obvious reasons.
Transport Select Committee today investigating Heathrow event. HAL CEO says as a result of the loss of Heathrow Nth S/Stn T2 was off line and the approach tunnel and their operations centre was affected. Says T5 was unaffected but because of the switching they needed to do sounds like they through caution to the wind.
NG say at N.Hyde s/stns two transformers were on line one tripped off after the fire started and they reconfigured the site to a standby transformer but shortly after the remaining two transformers tripped off (the adjacent one i can get but the third was in a different part of the site will have to wait investigation). They had one EHV supply restored at 1000hrs and a second supply available at 1600hrs.
SSEN were able to reconfigure there local network to restore domestic and business customers from 0400 onwards and importantly they were able to reconfigure their 66kV system at 0930 and give Heathrow a supply to their North substation at 1000.
Under questioning HAL are pointing the finger at NG/SSEN as its up to them to provide HAL with resilience. Basically HAL run the airport as three discrete load centres and interconnecting isn’t designed for the scenario that happened. A rep from Heathrow airline operators group claims that HAL waited till 0600 before they decided to reconfigure, SSEN confirmed to HAL they could have provided additional load from their two other s/stns. Also UK power Networks run the internal HAL HV network and sounds like they needed to call people in.
Sounds to me HAL have too many systems that can’t cope with a loss of supply and be satisfied they will self restore so they are taking lowest risk approach and basically booting up every system from scratch and confirm they are working satisfactorily.
HAL hiding behind the Kelly report so they better publicly disclose that report.
PS: Need to listen to another hour of questioning so maybe more clarity given
Great summary, thanks!
Both NG and HAL/UKPN have serious questions to answer. NG because they shouldn't have lost all 3 transformers, & HAL/UKPN because they've obviously let their own resilience go to rats in the last couple of decades.
Ultimately though, it's down to HAL to manage their own risks - and react far more quickly/responsibly to an emergency situation - so atm I'd apportion blame 70/30 to HAL/NG.
The fur begins to fly
https://www.energylivenews.com/2025/03/24/grid-boss-says-heathrow-did-have-power/
John Pettigrew told the Financial Times the fire, which knocked out a substation in Hayes, was a “unique event,” but stressed that two other substations remained operational and capable of keeping Heathrow running.
Heathrow’s CEO admitted the issue wasn’t a total power failure but the time it took to switch supply from the damaged substation to the others.
While the airport has diesel generators and battery backups to keep crucial safety systems running—such as runway lights and landing equipment—it still relies heavily on National Grid for its main operations.
A biomass generator also supplies some power to Terminal Two, but it wasn’t enough to keep the airport running.
Pettigrew, said he couldn’t recall a transformer failure like this before.
“Losing a substation is a unique event but there were two others available. That is a level of resilience,” he told the FT.
“There was no lack of capacity from the substations. Each substation individually can provide enough power to Heathrow.”
As expected!
Great stuff, very interesting. May your knowledge transformer remain operational for a good while yet.
Several papers seem to have latched onto the 2014 report by Jacobs during the third runway enquiry: reading the full discussion I'm not sure that they really appreciated the realities.
I suspect that internal management attention has been diverted by their push for net zero ground operations. THis from their plan for that:
The biggest source of carbon that we directly control is the gas we burn to heat Heathrow’s buildings. Our proposed solution is based on electrification of space and hot water heating with recovery of surplus heat in summer and storage for use in winter months. This will be a major investment and a complex project which will take us ten to 15 years to complete: we are targeting net zero carbon buildings by the mid 2030s. To hit our goal, we will also need alternatives to the refrigerants used in our air-conditioning and Government regulation will be important here.
By delivering efficiencies, switching off gas and seeking
alternative solutions we can make the greatest carbon savings.
Underpinning most of the solutions is a switch to renewable
electricity – on which there are growing demands. As we
switch to renewable electricity, our airport distribution network
will need to evolve to meet the demand and distribute power
to where it is needed to charge vehicles and deliver heat and
support the needs of the airport.
Therefore, a key aspect of our plan is to upgrade the electrical
distribution network which underpins the solutions we need.
Targets: Detailed scheme design complete for decarbonising
heating supply and upgrading our electrical distribution network
by 2026.
Investment: We have proposed to the CAA £23m to design
network upgrades and a heat solution and begin to implement
these. Further investment is planned subsequently to complete
these upgrades and implement the chosen heat solution.
That’s just for system design. Never mind fixing what's there.
https://www.heathrow.com/company/about-heathrow/heathrow-2-0-sustainability-strategy/our-carbon-strategy
It will be interesting to read the protection system performance report fir this incident. Settings, testing and maintenance regime.
It will indeed!
The report into the 2003 South/South-West London outage (Wimbledon) makes very interesting reading. The speed with which grid control worked out what had happened and restored supplies to the DNO was very, very impressive.
Also, in the context of this event, that a proximate cause was the misreading of a Bucholz alarm, reading it to be from a different transformer from the one alarming.
Root cause - mis-set shunt. It triggered an audit of every single protection device setting.
It's a quality report and I see no reason we shouldn't get the same for this incident. And also interestingly, the 2013 superbowl stadium outage was also caused by mis-set protection. In both cases, it seems, remarkably easy to get wrong.
Milibrain has tasked NESO to investigate what happened
https://www.gov.uk/government/news/neso-to-investigate-heathrow-power-loss
NESO’s investigation will support efforts to build a clear picture of the circumstances surrounding this incident and the UK’s energy resilience more broadly so that it’s prevented from ever happening again.
Terms of reference to follow.
Headed by former Eirgrid employee and and former head of National Grid Fintan Slye who appointed fellow Irish person Alice Delahunty as Head of Networks at National Grid, where she is now President of Transmission.
https://www.nationalgrid.com/about-us/our-leadership-team/the-executive-committee/alice-delahunty
It's like appointing a fox to lead a chicken inquest.
I now understand a little more detail of the incident at North Hyde and the specifics the failed transformer.
https://x.com/EyesOnThePriz12/status/1903715776634269836
Can you link to a thread unroll for those of us not signed up to X? We only get to see the top post.
How's this?
https://threadreaderapp.com/thread/1903715776634269836.html
Brilliant!
Interesting, the claim is that the other two supplies to Heathrow needed some form of "reengineering" (whatever that means) to allow them to be used :
"However, the Jacobs report, titled Operational Risk: Ground Infrastructure Heathrow Airport, stated: “Beyond the management of supply and grid services, which lie outside the airport’s control, the responsibility for managing electricity supply risk lies with the airport and businesses operating from the airport.
“While some services can be temporarily supported with generator or battery back-ups, the key weakness is the main transmission line connections to the airport.”
It warned: “Outages could cause disruption to passengers, baggage and aircraft handling functions and could require closure of areas of affected terminals and potentially the entire airport.
“Even a brief interruption to electricity supplies could have a long-lasting impact as systems can take time to recover.”
The fire destroyed a vital transformer at the North Hyde substation and also a back-up transformer, rendering the substation inoperable.
The airport is also served by two other substations powering different areas. However, in order for these to run the entire airport, the power supply to all the terminals needs to be re-engineered."
Source: The Telegraph via web archive https://web.archive.org/web/20250322201103/https://www.telegraph.co.uk/news/2025/03/22/heathrow-airport-warned-weakness-single-grid-link-decade/
While this is happening, Heathrow relies on its back-up supply, which is not sufficient to run the entire airport."