Grouding System Problem

Is this another one of your theoretical / homework questions?

I have looked at your previous posts

With such high available fault current and poor (high) soil resistivity, it's not surprising to have problems achieving safe step and touch potentials. There are only a few things you can do to improve your ground grid resistance to remote earth:

1. Make your grid as large as possible (use the whole 100 x 200m).

2. Make your perimeter ground rods as long as possible. Note that rods within the grid mesh have insignificant effect on the resistance, since they are within the sphere of influence of the grid and perimeter rods, so don't waste your time on them.

3. Make your meshes smaller - put more conductors in the ground closer to each other, especially at the outer edges and corners of the grid. This will reduce step and touch potentials in the worst areas.

4. Make your conductors physically larger (heavier gauge cable). You can even add "Ground Enhancement Material" (GEM) or salts to the soil to improve its resistivity, which increases the effective size of your conductors significantly. See the following link:

http://www.erico.com/products/GEM.asp

5. Add one or more deep grounding wells around the perimeter, especially in troublesome areas. Drill a borehole 20m or more deep, drop a ground rod bonded to ground cable that connects to your grid down the hole, and fill it with GEM.

There's not a lot more you can do.

Peter,

Thanks for comments. I am also looking for Ground Enhancement Material due to worst value of soil. Mean while I share my idea for design the ground mesh. We prepare 3x 3 m mesh with available Area of 170x 140. Rods 9 meter deep Qty : 200 and mount around the grid periphery and some of them closure to Trafo areas, Make 4x well at four corners with deep up to water level + 5 meter more due to seasonal variation in level & put 4 x rod of same length to touch the water level with Ground Enhancement Material

Just need to know your point # 3

3. Make your meshes smaller - put more conductors in the ground closer to each other, especially at the outer edges and corners of the grid. This will reduce step and touch potentials in the worst areas.

As per above point either I need to go further smaller mesh 2x 2 m and some additional conductors run around the periphery of girds or what is your concern !!!

Because As I reduce the mesh size it difficult to make CADWELD in small patches.

AS

I am afraid I cannot contribute much to this discussion, although information on SWER lines may be helpful, http://en.wikipedia.org/wiki/Single-wire_earth_return My interest is in similiar situations where I am installing grid/connect stand/alone dual systems, where Solar and Wind charge up a battery bank and when it is full export to the grid, (in these cases a SWER line) where earthing issues may be complex, so I would appreciate being kept in this discussion. Regards, Geoff Thomas.