LV neutral grounding in IEC standards

[radug]

Hello,

In large plants we usually design the LV neutral grounding as TN-S, but do not distribute the "protection cable" with the phases and neutral cables to some loads. We do join does loads through a cable that we extract from the ground mesh.

I was wondering if in IEC standards, there is any "must have" for the distribution of the "protection cable".

Thanks.

 

[pisimatza]

I do not think there is a Standard that shows as mandatory using 5 wire cables(or 3 wire in case of 1phase loads).
You can use 3p+N cables, and connect PE from grounding system of building, with steel band.

 

[radug]

OK. Functionally I do not find anything wrong with that procedure, in fact, it is what we are doing, but as I said, I was wondering if there is any "mandatory" standard.

Thanks.

 

[7anoter4]

Some indications could be found here:

http://www.cired-s2.org/Sessions/2001/Documents/Proceedings/CIRED01_RT_Earth.doc

Regards

 

[ScottyUK]

Most European countries have their own requirements which override the IEC standards, although most of the national codes are derived to some extent from the IEC standards. In the UK there's no mandatory requirement to include an earthing conductor with every circuit, but it is often necessary to provide the earthing conductor to reduce loop impdance values and meet fault clearance times. Maximum fault clearance times are specified in the wiring regulations.


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If we learn from our mistakes I'm getting a great education!

 

[pugwash]

What Scotty says. Sounds like you have a common ground mesh, or linked meshes (electrodes) across the site. In this respect you're describing a TN system, so no problem so long as the ground mesh is adequately sized to carry fault current. If your electrodes are independent you've got a TT system and you need to have the appropriate protective devices. Obviously if you're in the UK, don't ground the neutral at the load centre - PEN conductors not allowed.