Grumbles, Glory, Corona and All Your Off Topic Discussions

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Richard Haselgrove
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Message 108432 - Posted: 12 Jun 2022, 18:13:46 UTC - in response to Message 108431.  

... I backspaced and corrected something in Word without looking at the screen.
My fingers know when I've typed something wrong, but I have to look at the screen to see what it was.
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Profile Jord
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Message 108435 - Posted: 12 Jun 2022, 22:56:11 UTC

For those wondering about the transformer situation: I'm de-facto living in a construction site for the next 3 years - at minimum. 2 large bank buildings will be demolished, after which 2 new apartment block building towers come back, while part of the mall lying behind is converted into the new City Hall. All this requires a different and stronger power transformer than the one we already have, and I can understand why when you're moving 6 to 10KV lines between transformers while it may be raining, you just want to make sure NOTHING is connected.
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Profile Jord
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Message 108446 - Posted: 13 Jun 2022, 18:54:09 UTC - in response to Message 108438.  
Last modified: 13 Jun 2022, 18:55:37 UTC

They managed 11kV lines here without turning them off
Right... everyone around must've been thrilled about that with the possibility of someone being fried alive, let alone all the hardware catching power surges and blowing up. Our network provider will find it a thrilling exciting prospect to try out and have to replace everyone's electronics in a thousand households. Yep.

See https://www.youtube.com/watch?v=U1LEhgwF3Zg for how to do it. I can tell you, that suit isn't just to be fancy. This isn't the high voltage power lines you see on the big metal towers outside the city, this is moving the actual underground cables from one transformer housing to another.

But I'm absolutely sure you will find something denigrating to say about that. As you do with everything people say around here.
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robsmith
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Message 108447 - Posted: 13 Jun 2022, 19:38:44 UTC - in response to Message 108446.  

Too true - Swapping between one HV transformer for another can be done while live, but unless the station has been designed for it the consequences can be "somewhat exciting". Even when the station is designed for hot swapping things can go wrong, and do.
Just down the road from my parents was a fairly large sub-station with several transformers, over the years two of them were changed while "live". The first went very well, but the second was something of a disaster to put it mildly - the whole area was black, and due to the damage to both the input and output cables it took several days to get the first outputs working from the incoming grid supply, and it was weeks before a new transformer arrived (in the interim the whole area was fed by a number of large diesel generators that were "rushed" to site). Needless to say the replacement new transformer was installed with everything turned off for a good few hours.
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robsmith
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Message 108451 - Posted: 14 Jun 2022, 8:37:33 UTC - in response to Message 108450.  

I'm guessing the 11kV could easily jump onto the 240V, then eveyrerone's house catches fire.


That's actually the least likely outcome of 11kv jumping onto the street 3-phase supply. The most likely thing to happen is one or more of the out-going over-voltage trips trigger and the circuit would go dead resulting in a load of very annoyed house holders. Next is that the over-voltage trips don't trigger, but the insulation in the street level feeder would breakdown and smoke, eventually leading to a short (phase to phase, or phase to neutral, or phase to earth) and the short-circuit or earth leakage trips would fire. No house fires, but lots of upset householders, men have to come along and replace the damaged cable section. Then its a house feeder that fails, same effect, but its someone's front garden that gets dug up.
Weak links are deliberately built into the system, very close to the street distribution transformers, and (normally) a far as possible from the incoming 11kv (or greater) supply. These are there to reduce the possibility of the incoming HV from reaching the street-level (or site level) supply.
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Sirius B
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Message 108453 - Posted: 14 Jun 2022, 16:11:33 UTC - in response to Message 108272.  

Glory.
Claim online now live. Applied. Don't know when it'll hit my bank. :-(

Grumble.
WTH is happening to this country?
Had too create an account for PCC to provide details to make claim.
No problem. Funny site though.
grantapproval.co.uk.
Can't this country do anything without having it to involve other countries?
That donaim name is registered in France. Whether or not the website is run by our lot on French servers is the question.
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robsmith
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Message 108461 - Posted: 15 Jun 2022, 5:41:52 UTC - in response to Message 108458.  
Last modified: 15 Jun 2022, 6:01:50 UTC

You are describing what the LEB term "A domestic EARTH or NEUTRAL fault", not an 11kv fault. Earth or Neutral faults are sadly aren't that uncommon. The transformer will complain with such faults. Old broken suspension brackets do cause problems, add a bit of wind and rain (plus maybe a bit of bird/rodent activity) and over times the insulation wears out and things start arcing away.

(It's worth noting that the transformer side protection when the actual domestic supply is on posts is set to trip at a higher level than when buried.)
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Profile Gary Charpentier
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Message 108464 - Posted: 15 Jun 2022, 13:03:01 UTC - in response to Message 108462.  

Another that thinks they know how electricity distribution works, sad.
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Sirius B
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Message 108466 - Posted: 15 Jun 2022, 17:17:40 UTC - in response to Message 108461.  

Questions also arise from that one.
Registered 20/03/20..
Expires 20/03/29.
Last updated 19/01/22.
Think Lock-down & furlough scheme.
Some time ago, the council switched over to the Cloud.
Just wondering who has their hands on our data.
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Profile Dave
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Message 108469 - Posted: 15 Jun 2022, 18:45:11 UTC - in response to Message 108464.  

Another that thinks they know how electricity distribution works, sad.
What is really sad is when people who think they know but don't do the work on these things!
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robsmith
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Message 108470 - Posted: 15 Jun 2022, 18:50:25 UTC - in response to Message 108464.  

Earthing (at the "street" level) & phase segregation is a bit of a mess in the UK.
It depends on when the installation was designed, commissioned, and modified (if it has), what the local ground conditions are.
Crudely there are two main schemes., each with a number of variations.....
Derive the neutral at the transformer, and earth the transformer (an "earth grid" in normally buried near or around the transformer). This means that each consumer has two "big" cables, plus a local earth (which may, or may not, be tied back to the transformer earth).
Tie neutral and earth at the transformer and distribute the earth and a single "phase" cable. Frequently the earth is distributed using an armour sheath on the phase cable (as in Peter's example)

(In both cases there are normally some enormous resistors in the earth circuit to limit the earth current - well sort of.)
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Message 108472 - Posted: 15 Jun 2022, 18:59:32 UTC - in response to Message 108462.  
Last modified: 15 Jun 2022, 19:13:02 UTC

Rob's reply is better than mine. So I've deleted mine.

Edit] If you really want to be confused by earths then get into the comms business.
There you could have the earth supplied from the substation*, the comms building power earth, comms equipment earth, telegraph (in the old days of teleprinters) earth and in a few cases telephone exchange earth.

*I've been on a site where we had two substations, one for the transmitter building and one for everything else.
The co-ax cables between the multiplex equipment and the transmitters was deliberately open circuit, to stop earth loops and 50hz noise getting into the system.
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Message boards : The Lounge : Grumbles, Glory, Corona and All Your Off Topic Discussions

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