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TN-C-S Pitfalls
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well, I was feeling lonely here all on my own, :|
well, I was feeling lonely here all on my own, :|
taking a TNCS out of the EZ and to the general mass of earth can actually produce a potential difference between the artificial (DNO supplied) earth and true earth, which you will now be standing on.
[quote name='Andy
you could possibly have 400v wandering across phases trying to get back to star point,
in theory, Im not sure how this would actually pan out in the real world.
in theory, Im not sure how this would actually pan out in the real world.
yes. depends on many factors. 400 would be worst case, but in reality it would probably be less.
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Do they use concentric for 3 phase? (i.e 3 inner phase cores and one outer neutral core)
If so I've not seen it.
With conventional cable, I don't think a ruptured neutral is particularly common, from my understanding it's a design fault with concentric used to feed a single phase install.
Not saying a neutral fault further downstream can't happen, just not so common.
If so I've not seen it.
With conventional cable, I don't think a ruptured neutral is particularly common, from my understanding it's a design fault with concentric used to feed a single phase install.
Not saying a neutral fault further downstream can't happen, just not so common.
yes
they do indeed Dave, dunno how common it was, but Ive seen it a few times, and seems to be getting very common nowadays with the new ali cable they are using
you can also get armoured split con
found a bit on something i had lying around during xmas clearout
found a bit on something i had lying around during xmas clearout
no,
even on single phase the DNO earth on TNCS may be at a signifigantly different potential to the true mass of earth,
remember the horse that got electrocuted at the race course a while back?
similar issue but a bit more complicated due to it being a quadraped with a bigger stride than a normal human and the stride taking the current across its heart,
you can prove it to yourself, but im not going to explain it to you as it could end up getting stupidly dangerous,
let ANDY do the stoopid experiments!!!
tell me what experiment you want done and if i can, i willno,even on single phase the DNO earth on TNCS may be at a signifigantly different potential to the true mass of earth,
remember the horse that got electrocuted at the race course a while back?
similar issue but a bit more complicated due to it being a quadraped with a bigger stride than a normal human and the stride taking the current across its heart,
you can prove it to yourself, but im not going to explain it to you as it could end up getting stupidly dangerous,
let ANDY do the stoopid experiments!!!
yes, you can
see drawing
supose the cable from the left is the transformer and it only feeds 3 properties. 2 of them loose a neutral
house 1 is OK, since it still has both L&N
but house 2 and 3 are not. there is now 400v between the incoming phases, with neutral common to only those 2
ignore external resistance (keeps maths easier)
house 2 has a resistance of 99 ohm. house 3 has a resistance of 1 ohms. so each ohm is 4v
house 2 will now be at 396 volt L-N, house 3 will be 4v
---------- Post Auto-Merged at 22:49 ---------- Previous post was made at 22:46 ----------
whilst there is often reported power failures (especially larger ones), i dont think any of the DNO publish what the actual fault was, wether broken L or N
and there are plenty news stories about peoples stuff being fried by upto 400 after some scumbag as stolen a neutral link from a substation
err, well lets ask the DNO if they permit it then shall we.
the standard answer is what?
or maybe you never ask for permission to alter the supply parameters of your installations.?
it is a requirement to ask the DNO for permission to take their supplied earth to a building other than the one they have supplied it to,
statutory law BTW, so its a criminal offence if you export the supplied earth outside the original building without their permission,
now, would you care to mention or link the actual amount of cowboy installs that ignore this fact?
to your question, I cant be bothered to drag up the amount of times people have been electrocuted in their gardens due to hedgecutters/lawnmowers etc cutting cables/extension leads etc.
try a google search, Im sure you will fill your evening with joy at peoples mis-information and dodgy workmanship by 'sparks' that have absolutely no understanding of the consequences of their actions simply because they didnt understand how earthing worked in the UK
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