Power supply to Heathrow?

[Agile]

Now my experience of repairing large transformers is limited to just one repair to a 150 kW oil filled one. It provided the HT supplies to the 100 kW transmitter when I worked in Doha Qatar!

And that was just to help the Pakistani engineer in the SW transmitting station. And on the basis that he had the man power to remove the cover and drain the oil out!

Now that one was overheating to about 80 C as a result of arcing on the tap changer switch. I showed him how to file the contacts clean!

Now the substation transformer might be about 250 kVA. But residents told of a huge explosion from it. Most I have seen have a thermal cooling oil circulation to an elevated cooling tank well above the transformer.

Now clearly the transformer oil was well alight!

So how might it have overheated so much that it presumably boiled and vented to the outside where it caught fire?

Usually an important load like Heathrow would have two seperate 11 kV feeds and often with an automatic changeover!

The BBC Droitwich 400 kW transmitter takes a load of about 900 KVA and has two seperate 11 KV feeds which were manually switched in the rare event that the one being used failed. Since I worked there they may have had an automatic changeover fitted.

In the very rare event that both supplies failed then they had four 100 KVA generators available to be manually started with compressed air and put on load.

But at Bilsdale I think the single gas turbine was an automatic change over. They fitted that because a second source 11 KV supply was not available. It was about 1 MW and based on an RR jet engine similar to an RB211. You could stand close to it and talk to each other!

So where might I be able to read the report on the failures in due course?

 

[oceansoul]

If the transformer was overheating then you'd expect a buildup of gas pressure inside the transformer. This should cause the bucholz relay to trip the incoming and outgoing side CB's.

 

[ericmark]

It seems the back-up did work, but once on back-up, they have no further back-up, so it is used only to complete things already in action.

I suppose I am the same at home, the back-up keeps freezers running and central heating working, but no more. Still need touches etc. If my back-up was a generator which could be refuelled, then it would not matter how much I used, but my back-up limited to 5 kW (size of inverter) and the sun plus 6.4 kWh of battery, and I use around 15 kWh, so much shed some load with a power cut, and living room chandelier has 8 x 6 watt bulbs, but only need 1 to see where I am going, so want to simply use touches, and keep the main battery for essentials.

So the airport has the same options, does back-up allow safe shut down, or can it keep the whole place running? They paid their money, and decided what they wanted.

 

[Agile]

Yes, but why would a transformer suddenly seriously overheat? Particularly on a warm 14 C day when domestic demand is low?

The buchholz relay obviously failed to trip the OCBs.

 

[JohnD]

So the airport has the same options, does back-up allow safe shut down, or can it keep the whole place running? They paid their money, and decided what they wanted.

They have now learned better.

Though they might say that a 24 hour blackout once in 50 years is less costly than resilience.

Long ago, when doing risk assessment and disaster recovery, we used to say "Just in case a 747 crashes into the centre, destroying all the equipment and killing the staff on shift, we need a backup facility somewhere else."

It had to be far enough away that it would be out of range of a nuke sub blowing up nearby.

We used to think neither eventuality would ever really happen.

We only got away with the cost by showing it could be used for test and training as well as backup.

 

[Agile]

The BBC report on the problem seems to say that the Heathrow emergency generators did start up as expected.

But it seems they decided that was insufficient output to power everything needed when handling passengers like luggage handling facilities and lighting so just decided to close completely. Maybe it is only designed to power safety critical aspects like Control Tower communications and landing lights. Perhaps only about 30 KVA.

Most area power outages are resolved by using remote switching facilities to restore supplies within a maximum of an hour or so.

But it could be that the burning transformer oil had damaged the OCBs or wiring at the substation. It was reported as a large explosion followed by a signifcant ongoing fire.

I am interested in reading the official report into the substation failure if I can find a copy.

At a Christmas day lunch I met a black girl who worked as a project engineer at UK Power Networks. Pity I did not take her telephone number. But then her husband was there too and he might not have liked me even asking for it.

I may ask a retired BBC Power engineer as I know how to contact him and he might be able to help with finding me a copy.

 

[crystal ball]

The BBC report on the problem seems to say that the Heathrow emergency generators did start up as expected.

But it seems they decided that was insufficient output to power everything needed when handling passengers like luggage handling facilities and lighting so just decided to close completely. Maybe it is only designed to power safety critical aspects like Control Tower communications and landing lights. Perhaps only about 30 KVA.

Most area power outages are resolved by using remote switching facilities to restore supplies within a maximum of an hour or so.

But it could be that the burning transformer oil had damaged the OCBs or wiring at the substation. It was reported as a large explosion followed by a signifcant ongoing fire.

I am interested in reading the official report into the substation failure if I can find a copy.

At a Christmas day lunch I met a black girl who worked as a project engineer at UK Power Networks. Pity I did not take her telephone number. But then her husband was there too and he might not have liked me even asking for it.

I may ask a retired BBC Power engineer as I know how to contact him and he might be able to help with finding me a copy.

What does her skin colour have to do with anything?

 

[endecotp]

What does her skin colour have to do with anything?

About as much as their gender ?!

 

[SUNRAY]

So the information I have been offered today is: There are 2 standby generators, supposedly adequate to run essential services and they did start correctly...

In order to make the 'net zero' targets the generators are installed away from the airport complex sadly the apparently obvious place to site the standby arrangements was deemed to be at the substation... OOPS.

However how accurate this is or how it fits into the plethora of unfounded rumours I have no idea.

 

[fourtytwo]

So the information I have been offered today is: There are 2 standby generators, supposedly adequate to run essential services and they did start correctly...

In order to make the 'net zero' targets the generators are installed away from the airport complex sadly the apparently obvious place to site the standby arrangements was deemed to be at the substation... OOPS.

However how accurate this is or how it fits into the plethora of unfounded rumours I have no idea.

I think it unlikely that a customers equipment that requires servicing would be allowed within a substation compound!

The whole debacle smells strongly of "sweating the assets" to keep the shareholders happy and minimize investment both by the electricity network and the airport. They can get away with this as they have no morals and thanks to deregulation there are no enforced standards of service. Add to that overpaid incompetent management and that just about sums up commercial activity in this country in this day and age, you only have to look at other public utilities such as water companies for other examples.

I don't suppose there will ever be a report in the technical sense of the word it would be too embarrassing assuming someone of competence was appointed to carry it out which is extremely unlikely in any event, after all the biggest fraud in energy has already got his nose in the matter!

 

[JohnW2]

I think it unlikely that a customers equipment that requires servicing would be allowed within a substation compound!

Indeed - but are we sure that the standby gennies actually are/were "customers equipment" (rather than the network operator's) ?

 

[SUNRAY]

Indeed - but are we sure that the standby gennies actually are/were "customers equipment" (rather than the network operator's) ?

From the description I was given it sounded more like contracted to the DNO/supplier? and hence located in their compound.

 

[JohnW2]

From the description I was given it sounded more like contracted to the DNO/supplier? and hence located in their compound.

That's obviously what I was wondering.

From the POV of the DNO/supplier, providing gennies to afford at least some back-up might well be more financilly attractive that providing two totally separate (and geographically separated) supplies.

Of course, whoever's they are, locating the gennies in the proximity of the substation's transformers (if such is the case) was presumablyu not too clever an idea

 

[Sureitsoff?]

looking at the location of that sub station on google maps, its a long way from heathrow considering the power draw that heathrow must need. why is there not one closer?

and i cant see any evidence of gennies in the sub station compound

 

[SUNRAY]

looking at the location of that sub station on google maps, its a long way from heathrow considering the power draw that heathrow must need. why is there not one closer?

and i cant see any evidence of gennies in the sub station compound

it's only 3Km