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When electrics go wrong!!!

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Darkwood

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Just setting up a new sticky thread that unlike the dodgy trade pics thread is focused on showing the result of failures in electrical installations IE - damage caused which may be due to various reasons. Please do not post pics of poor workmanship if there is nothing else to show like the consequences, use the dodgy pics thread for that.

I will start off below with an example. I am hoping the fresh faced members and inexperienced can get a visual incite of what to expect when you come across such things and how to understand what has occured.
 
Here is a call out today, 2 houses lost power, it is clear here the culprit is the incoming cable to the first property, on this occasion I am in no confusion not to even touch or get close to that as it could potentially (no pun intended) be still live and ready to blow at the slightest disturbance.

Actions taken was to switch off all loads IE the fuse-boards, and ring the DNO doctor out, this is where I leave it with the landlord and will not see this resolved but I expect this is a dig up outside the property as that cable is only 1ft long before it exits through the wall.

EDIT - Update, DNO came out and took a look, expressed to landlord that he doesn't realise how dangerous that is, of course he already did because I explained it all, anyhow it was as predicted, they dug the road up to cut power and put in a new cable. The scary part here is I have a friend in the trade who is rewiring this house and its lucky he wasn't changing the board above or anywhere near it, it looks like any knock on that cable could have blown the cutout and we all know it won't take out the substation as the DNO like to use its cables as the fuse wire.
 

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If you ever see this on an install where the earth wire has totally burnt out of the flex then proceed with extreme caution, this has been caused by a massive current melting the earth wire and is usually an external source of what the flex is supplying or controlling.
Recommended to shut off all power if you find this and do a full test on all circuits local to the issue, possible causes for this is lightning and welding rigs.

Either way this could just be touching the surface of what else has been damaged in the fixed installation, on this occasion it was a welder with a poor return path, it found an alternative route by sending 300amps down that flex and other earth wires in local circuits to return back to the welder, a loose wire on a welder cost the customer about £1000 in repairs, if you can imagine other earthing systems gets destroyed and exposed burnt live wires are possible you can understand it has caused many deaths in the industry in the past.
1617188277542.png
 
If you ever see this on an install where the earth wire has totally burnt out of the flex then proceed with extreme caution, this has been caused by a massive current melting the earth wire and is usually an external source of what the flex is supplying or controlling.
Recommended to shut off all power if you find this and do a full test on all circuits local to the issue, possible causes for this is lightning and welding rigs.

Either way this could just be touching the surface of what else has been damaged in the fixed installation, on this occasion it was a welder with a poor return path, it found an alternative route by sending 300amps down that flex and other earth wires in local circuits to return back to the welder, a loose wire on a welder cost the customer about £1000 in repairs, if you can imagine other earthing systems gets destroyed and exposed burnt live wires are possible you can understand it has caused many deaths in the industry in the past.
View attachment 84023
Had a similar one about a year ago, welding something hanging off a chain hoist .
earth clamp was not attached correctly.
it destroyed most of the fixed wiring as it was all singles in trunking, earth wire had melted itself into most of the other conductors.
they were not happy when I told them they were looking at a 2 day rewire when they thought it was just a faulty supply to the chain hoist.
 
Short in commercial unit, foreign object entered bus bar chamber took out the whole building supply. 65 units/businesses no electricity. I had to find out what happened pronto and get the whole installation back on. Took about an hour to get to the point where I had located and removed the bus chamber in an old Merling Gerin board. A freak incident chances of happening 1000-1. Whatever it was, it was vapourised across two phases inside.
 

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There was a design flaw in the old Merlins in that although the busbar links between the main switch and the body were insulated with a cover from above, they were exposed at the back, due to the habit of running cables up the back in the nice gap provided behind the main busbar chassis it wasn't uncommon for the supply to the DB to shorted out if you moved cables and an exposed earth touched down or bridged the phases.
 
Here is a call out today, 2 houses lost power, it is clear here the culprit is the incoming cable to the first property, on this occasion I am in no confusion not to even touch or get close to that as it could potentially (no pun intended) be still live and ready to blow at the slightest disturbance.

Actions taken was to switch off all loads IE the fuse-boards, and ring the DNO doctor out, this is where I leave it with the landlord and will not see this resolved but I expect this is a dig up outside the property as that cable is only 1ft long before it exits through the wall.
A thing to note here; When getting the DNO involved it is encouraged that we make use of the MOCOPA guidance for reporting such issues as it puts the fault into a term that the agent on the other end of the phone will understand. This would certainly attract an 'A' code with immediate rectification required - When you pass over to the DNO; Get a case number or reference number that can help prove you handed over to the responsibile party. If at all possible get an email notification of the fault.

While we have no legal authority to switch off a supply, I believe it would be a hard case to argue that locking off wasn't in the clients interest, even of you took the lock off once the DNO arrvied.
 
A thing to note here; When getting the DNO involved it is encouraged that we make use of the MOCOPA guidance for reporting such issues as it puts the fault into a term that the agent on the other end of the phone will understand. This would certainly attract an 'A' code with immediate rectification required - When you pass over to the DNO; Get a case number or reference number that can help prove you handed over to the responsibile party. If at all possible get an email notification of the fault.

While we have no legal authority to switch off a supply, I believe it would be a hard case to argue that locking off wasn't in the clients interest, even of you took the lock off once the DNO arrvied.
Or simply say the DNO cutout is cracking and banging and pouring out smoke, it gets the same fast response ;)
 
Had a similar one about a year ago, welding something hanging off a chain hoist .
earth clamp was not attached correctly.
I have never had to play with an electric welder (other than a hour or two training as a student) so I would assume the high current secondary is not earthed to avoid a direct burn-out of the welder's earth. Or is it?

So was it two metal objects linked via conduit/CPC, and the welder's clamp was on one and the electrode arcing to the other?
 
Don’t know, it is a customers mine.
it might be that the earth clamp was touching a piece of bonded metal.
i wasn’t there when it happened, just saw the damage afterwards.
 
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