Plantwide equipotential grounding.

Hi all.

I have never given grounding much thought, apart from that there must be a "good" grounding covering the entire plant.
I though that a 16mm² wire all around was most common.
Actually I am confused about the requirements for the earth wire size. An earth wire in a cable that leads a current is sized together with the cable. But what about an equipotential earth ?

Now, we have a subsupplier that specifies a 30mm x 3.5mm galvanized bar to protrude 1 meter from the floor in various strategic places.
The subsuppliers system is hefty inverter system for a melting furnace. So maybe the requirements for grounding is specially severe in this case.

Questions:
Does anyone else use grounding in this dimension ?
Any good source for standards for grounding and equipotential bonding ?
Any suppliers of the stuff ? I would like to find one that actually supplies 30mm x 3.5mm galvanized bars for this purpose.

Hi Jesper,

are they looking for something like this? This is a grounding system build into the building structure.

http://de.wikipedia.org/w/index.php...eichsschiene.jpg&filetimestamp=20070119104242

Looks normal for me. We work alot in Ex zones.
Then customers provides this bars arround to factory so we can earth our equimpent to it.
I don't know if it is 30*3 but we mostly have 35mm² earthning providied to it, at the picture the steal bar that comes out of the ground.
And you connect with 16mm²

Thanks guys, yes that looks like it fits the bill !

You wouldnt know where to look for this stuff ?
I guess that if you work with electrical installations in buildings it is trivial, but for me is not normal.

Never bought them myself (customer provides them) but i think you can find them here

http://www.cablejoints.co.uk/sub-product-details.php?itemid=3159

I asked this question in the States recently when I realised there was no earthing between conveyors, I was looked at daft and told don't be silly, they are metal and connected together and in any case the conduits (yes they use this abundance) give an earthing route.

This is standard and to my knowledge a must in german buildings. You may also find it as protection against lightning as lightning conductor.

Jesper
There is a British company called Furse who specialise in earthing and lightning protection. They might be worth a look.

Thanks Andy.
Take a gander at Thim's link.

You should see the earthing requirements aroud a power or sub station. Earth rods everywhere at 2 metre intervals - a grid if you like, all joined together with copper wire. Half the time you also have to use Bentonite and water down the holes to get the required resistance.