Substation fire / Heathrow rail closed (21/03/25) - Rail Discussion Only

[Russel]

Heathrow Express - half hourly service, for Airport staff ONLY towards Heathrow

How is/was this being enforced?

 

[Horizon22]

How is/was this being enforced?

Probably at the gateline - there's a dedicated Heathrow Express barrier for P6/7

 

[stuving]

Isn't there some electrical switchgear at the end of Keith Road in Hayes, just by Dawley Road bridge?

That's railway - must be Hayes ATS. There is a distribution substation (bulk supply point) by the bend in Blyth Road, but all the stuff is kept indoors. It's one of four BSPs fed from the grid at North Hyde; two are collocated with North Hyde GSP and one is further away at Vicarage Farm Road.

 

[Taunton]

It doesn't. Multiple systems at multiple places must have failed to totally shut the airport down like this.

There's only been one fire. If that causes knock-on issues that shut the whole airport down then, regardless of what other arrangements might be in place, that is a single point of failure.

Electricity is the easiest service to design alternative supply routes for. Gas and water are far more challenging.

 

[stuving]

This, according to SSEN (the distribution operator), is the "illustrative" supply area of the North Hyde grid supply point. It does not include that much of the airport: only T3 of the terminals, though there may be important central services in there. But I'm not sure it should be taken that literally, in the absence of any knowledge of the boundary between SSEN and HAL in terms of providing power circuits within the airport. That "illustrative" must cover up something.

 

[m0ffy]

This, according to SSEN (the distribution operator), is the "illustrative" supply area of the North Hyde grid supply point. It does not include that much of the airport: only T3 of the terminals, though there may be important central services in there. But I'm not sure it should be taken that literally, in the absence of any knowledge of the boundary between SSEN and HAL in terms of providing power circuits within the airport. That "illustrative" must cover up something.
View attachment 176913

It’s probably worth mentioning that the airport is supplied and managed by UK Power Networks who act as an independent Distribution Network Operator (iDNO) for the entire site. Depending on where the point of connection is, it’s entirely possible that this supply is UKPN from the 66kV compound at North Hyde.

 

[RichardAsh1981]

Power is now back on.
My understanding is that North Hyde GSP is a fairly standard arrangement with two of everything critical (two main transformers and so on). This covers for any piece of plant being out of service without affecting supplies.

However the pictures show an outdoor, exposed busbar site, and a large scale fire fighting operation. So not at all surprising that for safety both halves of the site had to be shut down. This should be short term until the fire is out, unlike the Super Grid transformer itself which will take a long time to replace!

Heathrow will undoubtedly have multiple main feeds, but both via the shortest available route, which was presumably (indirectly) from the two sides of North Hyde BSP. Better supply diversity is always available, but at the customers expense - it will be up to Heathrow whether they wish to pay for installation of a backup circuit from the next GSP, which is likely quite a long way away!

 

[WAO]

That's railway - must be Hayes ATS. There is a distribution substation (bulk supply point) by the bend in Blyth Road, but all the stuff is kept indoors. It's one of four BSPs fed from the grid at North Hyde; two are collocated with North Hyde GSP and one is further away at Vicarage Farm Road.

It was a FS initially, supplied by a buried cable, now re-purposed.

WAO

 

[hwl]

This, according to SSEN (the distribution operator), is the "illustrative" supply area of the North Hyde grid supply point. It does not include that much of the airport: only T3 of the terminals, though there may be important central services in there. But I'm not sure it should be taken that literally, in the absence of any knowledge of the boundary between SSEN and HAL in terms of providing power circuits within the airport. That "illustrative" must cover up something.
View attachment 176913

I think there are at least 10 main DNO feeds into the airport from 4 bulk supply points. The newer feeds from the other supply points are 33kV, but two (including the one that when pop) are older 22kV ones.
The West Hyde transformers are not all the same voltage size/capability some are 66-->22kV (like the one that went pop also the highest current rating) and others 66-11kv and 66--> 6.6kV.

The control tower is linked to T3 for most purposes as are other central systems.

There is an emergency rerouteing talked about on the news probably involves feeding the South Eastern "blue" corner around Hounslow (not the airport) being fed from UKPN (London) to the east - there is emergency capability built in to do this as one of the elements. This would then allow some shuffling around of other loads if demand was reduced.

The newer feeds from Longford and Staines have very high resilience in terms of multiple cables and routings upstream and Bedfont is not quite as good but still better that West Hyde.

Very very bad luck in that particular transformer going...

 

[stuving]

In terms of supply from the grid at other places, Staines and Bedfont are fed from Laleham GSP and Longford from Iver GSP. So alternative feeds are present on the site.

The recovery process today has presumably involved making new connections from these alternatives to the loads now with no supply, manually and so slowly. And I can only conclude, from what HAL have said, that the answer to everyone's question - why did this take about ten hours rather than ten minutes - is "this behaviour is by design". HAL's commercial decision was that the loss of a grid power feed had such a low probability that the cost of rapid (not necessarily automatic) changeover switching was not justified.

 

[Peter Mugridge]

There's only been one fire. If that causes knock-on issues that shut the whole airport down then, regardless of what other arrangements might be in place, that is a single point of failure.

Electricity is the easiest service to design alternative supply routes for. Gas and water are far more challenging.

I never said there was more than one fire...

 

[Mikey C]

Eurostar will now run two additional trains each way between London and Paris.

Fermeture de l'aéroport d'Heathrow: Eurostar ajoute des TGV entre Paris et Londres

L'opérateur a décidé "d'ajouter de la capacité afin d'aider les voyageurs affectés par ces perturbations".

www.bfmtv.com

No extra services from Brussels, but I was on the last train of the day from Amsterdam/Brussels to London, and it definitely had diverted air passengers on it. I think it would otherwise have been fairly empty, so was able to take up a bit of the slack.

 

[Nicholas Lewis]

In terms of supply from the grid at other places, Staines and Bedfont are fed from Laleham GSP and Longford from Iver GSP. So alternative feeds are present on the site.

The recovery process today has presumably involved making new connections from these alternatives to the loads now with no supply, manually and so slowly. And I can only conclude, from what HAL have said, that the answer to everyone's question - why did this take about ten hours rather than ten minutes - is "this behaviour is by design". HAL's commercial decision was that the loss of a grid power feed had such a low probability that the cost of rapid (not necessarily automatic) changeover switching was not justified.

Loss of grid supply is low probability but impact is massive which is why railway signalling systems have at least two independent source supplies and signalling centres/ROCs will supplement that with standby generators and 2-4hr UPS battery backed supplies to all safety critical systems. Heathrow isn't some regional airport its national critical infrastructure and should be able to deal with this scenario.

 

[dosxuk]

There is no suggestion that Heathrow lost power on any safety critical infrastructure.

There have been plenty of occasions of railway stations or lines closing due to power cuts.

 

[Class 170101]

Not exactly a lot of additional capacity but you know what fair play to them for scrouging something together at very very short notice. It can't have been that easy to cobble together an additional crew and unit without also risking leaving their normal service uncovered.

Most likely making the 'spares' work the additional trains but the resilence would have been lost if someone phoned in 'sick' at the last minute.

 

[matt_world2004]

DId this incident plunge the heathrow stations onto complete darkness until the emergency power kicked.in.

 

[noddingdonkey]

In terms of supply from the grid at other places, Staines and Bedfont are fed from Laleham GSP and Longford from Iver GSP. So alternative feeds are present on the site.

The recovery process today has presumably involved making new connections from these alternatives to the loads now with no supply, manually and so slowly. And I can only conclude, from what HAL have said, that the answer to everyone's question - why did this take about ten hours rather than ten minutes - is "this behaviour is by design". HAL's commercial decision was that the loss of a grid power feed had such a low probability that the cost of rapid (not necessarily automatic) changeover switching was not justified.

Or that introducing such switching added an extra point of failure that had a bigger probability of causing disruption than losing the grid feed.

 

[Ediswan]

Or that introducing such switching added an extra point of failure that had a bigger probability of causing disruption than losing the grid feed.

I once squished a proposal to add an additional layer of reslience to the company intranet service. All I did was ask for the with and without expected reliability for the whole service. The proposer was free to make their case, never heard any more.

 

[sharpener]

Or that introducing such switching added an extra point of failure that had a bigger probability of causing disruption than losing the grid feed.

Well it sounds as though the extra switching paths were already present, so any additional risk already baked in.

What is less clear is why this process took many hours to accomplish. Even if not automated (which I agree has its own risks) wasn't there a fallback procedure along the lines of "If X supply fails do this, this and this to feed the whole site from the alternative connections that already exist"?

 

[WAO]

I'm sorry to read that UK national infrastructure managers are happy with H&S box ticking but unmoved by public/customer inconvenience, based on the soft privatisation regulation.

Most systems should be automatically reset even after a power interruption, even more complex systems governed by a BMS (building management system) should restart once alternative power is available, which a manned control room should be able to provide in minutes.

Happily m'learned friends acting for the airlines, inconvenienced customers etc might teach a severe lesson, running into many £100's of millions.

WAO

 

[badzena]

On the Friday morning, Hayes & Harlington station had lost some/all power, but it was open, and trains were calling there. Eastbound trains could not open the doors in the rear 4/5 carriages. Does anyone know why this would have been?

 

[TFN]

On the Friday morning, Hayes & Harlington station had lost some/all power, but it was open, and trains were calling there. Eastbound trains could not open the doors in the rear 4/5 carriages. Does anyone know why this would have been?

If there’s no power then the DOO cameras would have been offline. The drivers would lock out the rear 4/5 carriages and self dispatch the front.

 

[jonb]

If there’s no power then the DOO cameras would have been offline. The drivers would lock out the rear 4/5 carriages and self dispatch the front.

That’s correct, this also affected platforms 1/2 (Down & Up Mains) and platform 3 (Down Relief). A diesel generator was brought to site later in the day, which once setup allowed normal working to resume without doors being inhibited.

 

[125Spotter]

The drivers would lock out the rear 4/5 carriages

How do they go about doing that on the Lizzie? Are there some secret hidden internal barriers/doors that can be deployed to prevent internal access to carriages or would this be handled solely by announcements that SDO is in operation and certain doors won't open?

 

[Horizon22]

How do they go about doing that on the Lizzie? Are there some secret hidden internal barriers/doors that can be deployed to prevent internal access to carriages or would this be handled solely by announcements that SDO is in operation and certain doors won't open?

It's done from the driver's cab prior to arrival at the station - it's effectively an SDO setting to inhibit the rear half of the train. There's no internal access prevented, just external doors won't open.

 

[Mojo]

It's done from the driver's cab prior to arrival at the station - it's effectively an SDO setting to inhibit the rear half of the train. There's no internal access prevented, just external doors won't open.

Although FWIW, not that it’s relavent here but for the benefit of the person asking the question, there are smoke doors half way down the train, not sure if these are capable of being physically locked closed.

 

[Horizon22]

Although FWIW, not that it’s relavent here but for the benefit of the person asking the question, there are smoke doors half way down the train, not sure if these are capable of being physically locked closed.

They are, but normally that happening unintended (I.e unable to be opened even with the push button), means the train is not fit for passenger service.

 

[fandroid]

It's done from the driver's cab prior to arrival at the station - it's effectively an SDO setting to inhibit the rear half of the train. There's no internal access prevented, just external doors won't open.

That would have been fun for any pax wishing to alight from those carriages!

 

[Purple Train]

That would have been fun for any pax wishing to alight from those carriages!

It's not uncommon - I've encountered it a couple of times when the cameras haven't been operational at a certain station.

On both occasions, the driver made multiple announcements: one was on a lightly-loaded train and the driver kept the doors open for longer than usual to let people at the rear who weren't listening off the train, and the other was a busy peak service at Iver and the driver said, "If you can't make your way forward, go to Langley and double back."

The system on the 345 is pretty good insofar as it can just lock out individual doors without any physical barrier (and hence delay/faff) required: the only downside is that the indication that the door isn't in use is quite inconspicuous if you aren't listening to announcements, or there aren't any.

It happens in certain platforms at Paddington mainline station where the curve of the platform is so sharp that the middle doors of some carriages are locked out of use, and of course at stations with short platforms, but there are auto-announcements to that effect to go along with the small symbol on the door.