Heathrow

[IanB]

Situation: "Transformers are filled with cooling oil, and unfortunately this caught fire"

Question from member of public: "Why not fill the transformers with water instead, since water doesn't burn?"

[factory]

 

What temperature does it take to cause the oil to burn? Water apart from having obvious electrical problems, would boil away* leaving the rest to melt/burn and then there is the corrosion issues.

*we had a sub-station building at work turn into a sub-sauna, because of damaged cables that were under water.

David

[mikeselectricstuff]

With a building full of high voltage and oil, you'd think that some sort of automatic fire suppression system would be an idea...

[floobydust]

It looks like many failures, just in the substation alone.
I worked in the utility industry SCADA and transformers have many sensors. Sudden pressure sensor (SPR), Buchholz relay, pressure relief valve switch contact etc.
There are other sensors, typically: oil temperature 26T, winding temperature 49T, low oil level main tank 71T and conservator 71A, cooling fan fail etc.
There can also be a differential protection relay 87T which monitors current (power) in and out. If an internal arc occurs there is a big difference which means trouble, they trip in 30msec.
The protection relays are supposed to trip breakers and disconnect power fast to prevent such a big fire in the first place.
You can see in Hayes pics there is also the fire suppression system that missed the boat. Red piping and sprayers surrounding each transformer.
These systems can get old and rarely tested.
The oil is typically mineral oil but less flammable silicon-based synthetics are used.

Nevermind the airport's new Net Zero emergency generators using woodchips and requiring mains? I wonder if this is true, seems ridiculous.

[themadhippy]

"Why not fill the transformers with water instead, since water doesn't burn?"

With the added bonus of hot water for a nice cup of tea whilst fighting the fire

[Xena E]

Polychlorinated biphenyl oil wouldn't have caused all this disruption.

X

[tom66]

What's crazy is that critical British infrastructure depended upon a single substation, a disaster waiting to happen - wait, no, that's par for the course really for this country.

I am sure a certain V. Putin is looking at how vulnerable our infrastructure actually is and hybrid warfare remains on the table here.  It really wouldn't take much to cripple the UK for days at a time.

[SiliconWizard]

Yeah, fire water burn!

[NE666]

What's crazy is that critical British infrastructure depended upon a single substation

The truth will come out in the wash, however, I have seen it reported that there is alleged to have been a pre-existing fault with a transformer in their alternate supply, rendering it inoperable as a backup. Still a sh1tshow, but at least if true that would at least mean that redundancy had been designed in.

This incident couldn't have come at a better time, a time when the current government is again considering the option of allowing a third runway. I can't think of a clearer example why we should not continue to place all our eggs in one basket, rather than distribute capacity across the country.

[floobydust]

There are two transformers, so that one can be taken out of service for maintenance, redundancy etc. - standard practice for the bus architecture there.
But... it's right next to the one that blew up and it shows some dents and dings. Certainly the heat would damage control panels nearby.
Also, smoke has a much lower breakdown voltage than air, dense smoke will easily arc.
You would not switchover/energize the second transformer without more trouble.

What's with the 133 brush fires in Wales? Space lasers are real! lol.

[radar_macgyver]

Situation: "Transformers are filled with cooling oil, and unfortunately this caught fire"

Question from member of public: "Why not fill the transformers with water instead, since water doesn't burn?"

The Z-machine does use deionized water, but that picture should scare off any concerned members of the public.

[Nominal Animal]

The Z-machine does use deionized water, but that picture should scare off any concerned members of the public.

As I understand it, the water needs to be continuously deionized and filtered.  Not exactly a suitable option for transformers, especially since the failure of deionizing and filtering the coolant water would be basically just as catastrophic.  Better KISS.

[UnijunctionTransistor]

What's crazy is that critical British infrastructure depended upon a single substation, a disaster waiting to happen - wait, no, that's par for the course really for this country.

I am sure a certain V. Putin is looking at how vulnerable our infrastructure actually is and hybrid warfare remains on the table here.  It really wouldn't take much to cripple the UK for days at a time.

This exact theory has been put forward;

https://youtu.be/ZuN8Fi1Kv0A?si=zU6RJaAUNObnU1lz

[themadhippy]

What's crazy is that critical British infrastructure depended upon a single substation,

Nope,seems theres at least 3,bit more info here.  https://www.telegraph.co.uk/news/2025/03/21/heathrow-electricity-substation-fire-north-hyde-hayes/   Having worked in place with 3 HV grid supplies it sounds a fairly accurate description,it took us around 12 hours to get fully back to 100% mains power when one of the HV feeds was lost and that was on a site much smaller than heathrow

[5U4GB]

"Why not fill the transformers with water instead, since water doesn't burn?"

With the added bonus of hot water for a nice cup of tea whilst fighting the fire

Feck off, cup!

[tggzzz]

What's crazy is that critical British infrastructure depended upon a single substation,

Nope,seems theres at least 3,bit more info here.  https://www.telegraph.co.uk/news/2025/03/21/heathrow-electricity-substation-fire-north-hyde-hayes/   Having worked in place with 3 HV grid supplies it sounds a fairly accurate description,it took us around 12 hours to get fully back to 100% mains power when one of the HV feeds was lost and that was on a site much smaller than heathrow

To my surprise, that article does contain useful information.

One point that deserves expansion is that the power grid across west London is creaking. A couple of years ago National Grid state they would not be connecting any new housing blocks to the grid. That was politically unacceptable, so some compromising (in both senses) wording was issued.

Not a good starting point when considering the future extra load as electric vehicles become more common.

[tggzzz]

What's crazy is that critical British infrastructure depended upon a single substation,

Nope,seems theres at least 3,bit more info here.  https://www.telegraph.co.uk/news/2025/03/21/heathrow-electricity-substation-fire-north-hyde-hayes/   Having worked in place with 3 HV grid supplies it sounds a fairly accurate description,it took us around 12 hours to get fully back to 100% mains power when one of the HV feeds was lost and that was on a site much smaller than heathrow

To my surprise, that article does contain useful information.

One point that deserves expansion is that the power grid across west London (i.e. Hillingdon, Ealing, and Hounslow including Heathrow) is creaking. A couple of years ago National Grid state they would not be connecting any new housing blocks to the grid.
https://www.bbc.co.uk/news/uk-england-london-62346322
https://www.datacenterdynamics.com/en/news/report-home-building-to-halt-in-west-london-due-to-data-center-power-demands/
That was politically unacceptable, so some compromising (in both senses) wording was issued.

Not a good starting point when considering the future extra load as electric vehicles become more common.

[tom66]

Grid connectivity (not just in London) has been an issue for some time for EV infrastructure, it took Tesla 6 years and 1 day to get power to their Fleet Supercharger because of connectivity delays.  It is the reason the government has missed their target of 6 rapid chargers at every motorway service area.  This is also why the supermarkets are getting into installing chargers, with Asda and Morrisons just starting and Sainsburys with 50 x 6 station stalls already installed - they often have existing connectivity to the grid at their supermarkets, so putting in chargers is not as difficult as MSAs where they often only had 50kVA service and gas heating.

I don't think it's as much of a problem for home charging since we're talking 3.6kW or 7kW intermittently switched on and off and for the average UK mileage it's equivalent to a few long electric showers running now and then which the grid manages fine already.  But it's definitely a big problem for rapid charging. 

Might be more of an issue for heat pumps though as that's roughly 2-3kW winter load continuously for every house on the street on top of anything else, with current capacity sized for around 1kW per home (averaged over 24 hours).

[tggzzz]

Grid connectivity (not just in London) has been an issue for some time for EV infrastructure, it took Tesla 6 years and 1 day to get power to their Fleet Supercharger because of connectivity delays.  It is the reason the government has missed their target of 6 rapid chargers at every motorway service area.  This is also why the supermarkets are getting into installing chargers, with Asda and Morrisons just starting and Sainsburys with 50 x 6 station stalls already installed - they often have existing connectivity to the grid at their supermarkets, so putting in chargers is not as difficult as MSAs where they often only had 50kVA service and gas heating.

I don't think it's as much of a problem for home charging since we're talking 3.6kW or 7kW intermittently switched on and off and for the average UK mileage it's equivalent to a few long electric showers running now and then which the grid manages fine already.  But it's definitely a big problem for rapid charging. 

Might be more of an issue for heat pumps though as that's roughly 2-3kW winter load continuously for every house on the street on top of anything else, with current capacity sized for around 1kW per home (averaged over 24 hours).

Agreed.

There was a minor scandal about a large hub, possibly near Birmingham. It was built but not connected to the grid due to grid capacity limitations. IIRC, it has finally been connected.

[floobydust]

Critical infrastructure, utilities being sold off to private companies, is a basic disaster recipe.
Of course you'd run the assets into the ground, to provide maximum return to shareholders.
No penalties for running antique transformers, rated 76MVA and running max was 80.6MVA so 6% over design. No penalties for not keeping up with upgrades.

The Hayes substation, it's got empty land, two plots next to the exploded transformer for expansion. North Hyde Electricity- they got room for more or bigger/newer transformers. Better get on it lol.

National Grid publicly traded, just disgusting because that profit comes out of ordinary folk's pockets and they can charge for any shortcomings that occur.

[TimFox]

A problem with unregulated privately-owned infrastructure:
If the only penalty to the infrastructure owner from failure-induced interruptions of service is lost revenue from the consumers, then the external costs to those consumers from an interruption can be much larger than the lost revenue, while the required investment to achieve higher reliability may not be covered by the elimination of that lost revenue.

[Zero999]

A problem with unregulated privately-owned infrastructure:
If the only penalty to the infrastructure owner from failure-induced interruptions of service is lost revenue from the consumers, then the external costs to those consumers from an interruption can be much larger than the lost revenue, while the required investment to achieve higher reliability may not be covered by the elimination of that lost revenue.

I believe in the UK the regulator Ofgem forces them to pay compensation to their customers for lack of service. I wouldn't be surprised if in other countries they can be sued.

[UnijunctionTransistor]

A problem with unregulated privately-owned infrastructure:
If the only penalty to the infrastructure owner from failure-induced interruptions of service is lost revenue from the consumers, then the external costs to those consumers from an interruption can be much larger than the lost revenue, while the required investment to achieve higher reliability may not be covered by the elimination of that lost revenue.

That is exactly what has happened to the Texas grid, and one of the reasons ERCOT hasn’t interconnected to either the Eastern or Western grids.
After the disastrous 2021 near-total blackout, what was the Texas government’s response? Instead of passing legislation to require that the utilities have plans for those contingencies, it gave a tax-holiday to encourage the consumer to purchase emergency generators.

In other words, place the burden of investment on reliability on the consumer, not the utilities. Typical Texas solution.

[Stray Electron]

A problem with unregulated privately-owned infrastructure:
If the only penalty to the infrastructure owner from failure-induced interruptions of service is lost revenue from the consumers, then the external costs to those consumers from an interruption can be much larger than the lost revenue, while the required investment to achieve higher reliability may not be covered by the elimination of that lost revenue.

That is exactly what has happened to the Texas grid, and one of the reasons ERCOT hasn’t interconnected to either the Eastern or Western grids.
After the disastrous 2021 near-total blackout, what was the Texas government’s response? Instead of passing legislation to require that the utilities have plans for those contingencies, it gave a tax-holiday to encourage the consumer to purchase emergency generators.

In other words, place the burden of investment on reliability on the consumer and the taxpayers, not the utilities. Typical Texas United States solution.

 

   Corrections added but yeah, otherwise I agree completely.

[TimFox]

UJT: precisely.
It is still true that there are three main power grids in the US: eastern, western, and Texas.
Without connections across State borders, Texas avoids Federal regulations.
(There are corners of Texas, for example El Paso, that for geographical reasons are part of interstate grids, and therefore avoided the big problems of 2021.)
Stray Electron:  In many ways, including ones that it is proud of, Texas is not typical of the US.