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diagram of an earth fault loop impedance path for TN-S and..


 
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Carloss

from United Kingdom

Joined: 31 Mar 2004
Posts: 168
Location: United Kingdom

PostPosted: Sat Mar 06, 2010 2:18 pm Reply with quote

Im in need of a circuit diagram of the earth fault loop impedance path from e.g. a faulty kettle for a TN-S earthing system and TN-C-S. i have done a TT system but not sure how to show on paper how the earths connect together using correct symbols. for example on a tn-s system how do i show how the earthing conductor connects onto the lead sheath?

any thoughts or pictures would be a great help

carlos
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Taylortwocities

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PostPosted: Sat Mar 06, 2010 2:56 pm Reply with quote

I guess this is for a college/learning question.

If we give you the answer, you still won't get it.
So, I am going to suggest this to help you learn:

Go onto Google, etc and search for
fault loop impedance diagram

I have looked, there are tens of diagrams showing this.

Have a look at the ones for TN-S and TNC-S and then draw your understanding of the fault path.

Scan your drawings in and post them back on here and I/somebody will give you constructive help if you have missed anything. OK?

That is like your own, personal on-line tutor!
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Carloss

from United Kingdom

Joined: 31 Mar 2004
Posts: 168
Location: United Kingdom

PostPosted: Sat Mar 06, 2010 5:00 pm Reply with quote

Thanks for the help.

Perhaps i am not searching google properly but i understand all earthing systems. Im just trying to find a diagram similar to this one of a TT earth fault path but for TN-S and TN-C-S. However TN-C-S is pretty straight forward its just the TN-S system on how i show the earth path from the MET. unfortunately im unable to scan.

http://www.tlc-direct.co.uk/Book/5.3.1.htm

here is a TT diagram i just need something similar.

carlos
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Carloss

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Posts: 168
Location: United Kingdom

PostPosted: Sat Mar 06, 2010 5:03 pm Reply with quote

perhaps i can just draw a line from the fault straight back to the N of the supply transformer?

TN-S system that is.
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Taylortwocities

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PostPosted: Sat Mar 06, 2010 5:56 pm Reply with quote

OK but it is to the source earth, not necessarily the source neutral.

In the TT system the fault loop includes the general mass of earth (9 in the diagram).

This is not the case in TN systems.

In a TN-S system the protective earth connection back to the supply transformer is provided by the............. what?

In a TNC-S system the protective earth connection back to the supply transformer is provided by the............. what?

Hint: Look at Earthing Systems in the TLC link you provided. Its all there or look at figs 2.3, 2.4 and 2.5 in BS7671.
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RF Lighting

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PostPosted: Sat Mar 06, 2010 6:34 pm Reply with quote

DIYnot wiki icon_wink.gif
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Carloss

from United Kingdom

Joined: 31 Mar 2004
Posts: 168
Location: United Kingdom

PostPosted: Sat Mar 06, 2010 6:57 pm Reply with quote

AWWWWWWWWWWWWWW

you know i could kick myself. I just looked up in the regs book with your ref. Didn't even know it had those diagrams!!! damn it.

Anyway. the answear to your questions is as follows,

In a TN-S system the protective earth connection back to the supply transformer is provided by the...

metallic covering of the cable supplying the installations or a separateconductor.

In a TNC-S system the protective earth connection back to the supply transformer is provided by the

PEN conductor is earthed at two or more points and an earth electrode may be necessary at or near a consumers installation.

Thanks very much!!

Got my 2391 exam thursday so working hard for it and want to understand everything.

any tips from yourself?

carlos
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Taylortwocities

from United Kingdom

Joined: 27 Jul 2006
Posts: 12475
Location: Oxfordshire,
United Kingdom
Thanked: 1026 times

PostPosted: Sat Mar 06, 2010 9:05 pm Reply with quote

Yes
Read that regs book and GN3
Do as many past 2391 exan papers that you can lay your hands on

Do search on 2391 on this forum, someone else was asking about tips last week - theres some juicy hints in there.

Do let us know how you get on. Good luck.
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