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jpflying (Electrical) (OP)
3 Jul 08 18:45
I am using Ground Mat to check the designs of a number of external substations in an existing factory. Adajacent to the substations are building foundations which have been bonded to the existing earth grids.

How do I simulate these foundations in Ground Mat?

Thanks
7anoter4 (Electrical)
6 Jul 08 1:38
I think you have to ask SKM:
http://www.skm.com/contact_us.shtml
 
jpflying (Electrical) (OP)
6 Jul 08 16:51
Yep - sounds like a plan!!!
Simmi123 (Electrical)
6 Jul 08 18:12
I am not sure, if modelling and connecting building foundatons will help in learning more about the Grid in question.  
jpflying (Electrical) (OP)
6 Jul 08 18:29
Simmi123

Building foundations can be used as ground electrodes. In this case there are large building foundations adajacent the substations. These foundations are 6m in depth. There are also foundations in the substation compound. The transformes are situated on concrete pads with foudations approximately 1m in depth.

For more inforation regarding building foundations being used as ground electrodes google UFER.
7anoter4 (Electrical)
7 Jul 08 3:20
Hi jpflying
The Foundation Grounding is very useful if it is designed and dedicated for grounding purpose.
The rebar dedicated for grounding has to be 10mm dia at least, and electrical continuity has to be assured by good welding. A grounding ring at the lowest level will collect all the groundings from all foundations and from here all the electrical equipment will be bonded.
If it is so designed, you may introduce it in the calculation as a grounding rod. Of course,it is still conservative, as the adjacent vertical rebars will decrease the total resistance.
We don't use the SKM Ground Mat software so I can't tell more.
Regards
 
jpflying (Electrical) (OP)
7 Jul 08 3:32
7anoter4

Thanks for the reply.

I am based in Australia and the code here only requires the rebar to be tied with tie wire. The job I am looking at has other grounding electrodes in the system - copper sheathed steel vertical rods and copper horizontal grids, but these vary in size in the different areas of the installation. The footings I am interested in all have rebar larger than the 10mm - some of it is up to 32mm in diamaeter. In a couple of areas I am having problems with the touch potential and due to concrete floors everwhere adding more electrodes into the ground is not very practicable, hence the interest in the existing footings.

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