2013 Grenfell Power Surge

[lumenmachine]

Just been doing a bit of reading about the Grenfell tragedy. There are a few articles that mention an series of "Power Surges" in 2013 and briefly put it down to "Faulty Electrics in the building". What type of fault would cause this type of thing to happen? I always thought surges were very rare in the UK and were usually attributed to lighting strikes. Any thoughts?

 

[davesparks]

Are they technical articles or newspaper articles?

Do you have any links to the articles in question?

 

[lumenmachine]

Just standard newspaper articles, link to one here:

Subscribe to read - https://www.ft.com/content/33a32fec-52b3-11e7-bfb8-997009366969

And another:

Grenfell Tower fire warnings 'fell on deaf ears', residents' group says - http://metro.co.uk/2017/06/14/tower-block-fire-safety-warnings-fell-on-deaf-ears-residents-group-claims-6707156/


Finally a page by the "Grenfell Action Group";

GRENFELL TOWER – FROM BAD TO WORSE - https://grenfellactiongroup.wordpress.com/2013/05/29/grenfell-tower-from-bad-to-worse/

 

[davesparks]

None of those are technical reports, unlikely to have been written by technically minded people and are almost certainly not unbiased.

My best guess, and it is a guess, based on the reports would be that there was a loose neutral on the incoming supply.

 

[lumenmachine]

Yes, it's a bit of a strange one. Definitely not an area in which I have any practical experience, but I was going down the route of a faulty HV transformer in the building.... Again, not something I am anything close to being an expert in! Just trying to think of a rational explination. What made you think of a loose neutral causing the problem?

 

[davesparks]

Yes, it's a bit of a strange one. Definitely not an area in which I have any practical experience, but I was going down the route of a faulty HV transformer in the building.... Again, not something I am anything close to being an expert in! Just trying to think of a rational explination. What made you think of a loose neutral causing the problem?

What specific transformer fault are you thinking could cause a voltage spike?

A disconnected neutral on an imbalanced three phase supply is the only thing I know of which can cause excessive voltage to appear on one of the lives whilst the voltage dips on others. This would seem to correlate with the report of some people's appliances emitting smoke whilst other people's lights were dimming.

 

[lumenmachine]

It was mere speculation, as mentioned I am nothing even close to an expert on HV. I suppose I was starting to think of insulation breakdown, or something else leading to a winding failure.

I do see how your suggestion could have caused the fault, however I am maybe paying too much attention to this statement

"An emergency temporary electrical by-pass supply has been provided"

 

[davesparks]

It was mere speculation, as mentioned I am nothing even close to an expert on HV. I suppose I was starting to think of insulation breakdown, or something else leading to a winding failure.

I do see how your suggestion could have caused the fault, however I am maybe paying too much attention to this statement

"An emergency temporary electrical by-pass supply has been provided"

Speculation is a dangerous thing.
Think a little further on what an insulation breakdown in a transformer would cause. You don't need to be an expert on HV, transformers are the same basic thing at any voltage.
The insulation breaking down could cause a short to the metal case or a short between windings, logically neither of these would increase the output voltage. To get more volts out you would need to increase the number of turns on the output winding.
And if you were thinking of a fault connecting the HV side directly to the LV side, that would be one hell of a surge doing a lot more damage than was reported with almost certainly the loss of lives!

That phrase looks a lot like a bit of media nonsense which probably resulted from the action of Chinese whispers.
If it was a poor connection on a neutral I would guess that a temporary arrangement was put in place to bypass the poor connection until it could be fixed, this would have been far too boring for the newspapers so they would have added words like 'emergency' to make it look better.

 

[snowhead]

Agreed a loss of neutral would have been the problem.
If they had to use a bypass then the most likely fault on the Neutral would have been an underground cable or joint fault.

They will have just run a cable overground, either neutral only or all phases as well, from the Transformer to the the L.V panel.

 

[Andy-1960]

What specific transformer fault are you thinking could cause a voltage spike?

A disconnected neutral on an imbalanced three phase supply is the only thing I know of which can cause excessive voltage to appear on one of the lives whilst the voltage dips on others. This would seem to correlate with the report of some people's appliances emitting smoke whilst other people's lights were dimming.

Do you mean an ungrounded neutral because if it was a disconnected neutral, this would have caused serious problems with a much higher voltage being present across single phase equipment

 

[lumenmachine]

Is a lost neutral quite a common occurrence in situations like this then? Something I've never come across to be honest. Great feedback though, and good to get the mind in gear

 

[lumenmachine]

Also, I have to agree with the media jazzing up the plain boring!

 

[lumenmachine]

Do you mean an ungrounded neutral because if it was a disconnected neutral, this would have caused serious problems with a much higher voltage being present across single phase equipment[/QUOTE

Forgive my ignorance, but what would the difference between disconnected and ungrounded be?

 

[davesparks]

Do you mean an ungrounded neutral because if it was a disconnected neutral, this would have caused serious problems with a much higher voltage being present across single phase equipment

No I mean disconnected.
If the load is perfectly balanced then disconnecting the neutral has no effect as it is carrying no current (ignoring harmonics for now)
If the load is not perfectly balanced then the disconnection causes the star point to shift resulting in different voltages from each phase to the star point. Some loads will se a greater voltage and others will see less.

 

[davesparks]

An ungrounded neutral is one where the N-E link at the transformer is disconnected.

 

[westward10]

My thoughts are that is far too much non qualified speculation in the press and by other means by unenducated people trying to earn a fast buck.

 

[davesparks]

My thoughts are that is far too much non qualified speculation in the press and by other means by unenducated people trying to earn a fast buck.

I agree whole heartedly, but that is the whole point of the press and the media, to convince the general populus that their opinion is fact

 

[PEG]

Three things to know,regarding the press...never let the facts get in the way,of a good story...three sides to every story- yours,his,and the truth...and,today's news-tomorrows chip-papers

...and that's from a chap,with both parents,life-long journalists...

But,it has given this thread some legs

 

[lumenmachine]

So; lessons learned are that a disconnected neutral can cause a voltage surge, and that the press can make a mountain out of a molehill?

 

[marconi]

If there was a voltage surge then this would cause a surge in current being drawn by energised loads. If the surge in voltage was out of the ordinary ie: the tolerance of the mains supply and allowed volt drop in wiring one might expect instances of mcbs/rcbos tripping, (fuses rupturing less likely unless the surge is high and prolonged), and even perhaps RCDs operating. Were there such instances reported?