earth bed in a desert location
earth bed in a desert location
(OP)
i have to install an earth bed in a desert site,earth spikes only go down roughly a metre in depth.the client wants soil resistance to electrode reading of 4 ohms or less.tips for getting readings down to this without bentonite or anything similar?






RE: earth bed in a desert location
Depending on the installation, you could use:
1) Longer ground rods
2) Multiple ground rods
3) Buried ground grid/counterpoise
RE: earth bed in a desert location
RE: earth bed in a desert location
Also, soil resistivity measured at one location will not be same if measured at a point 5-10 mtrs away. So, if you have to achieve 4 ohms, it will be a very much debatable issue where are you measuring the resistance.
Refer IEEE 80 for specific methods to achieve proper grounding as per standards. Also, nowadays the requirements are not to specify ground resistance, but to concentrate on touch & step potentials.
RE: earth bed in a desert location
One method is to run the earth grid to a place where the ground is damp all year like a river bed or swampy area and install at enough depth to ensure all year moisture around the grid.
Another is use concrete which is a fantastic way to earth. Connect to the reinforcing steel in building foundations and piles. Piles are really good if they are deep. Dryness might be a problem with surface foundations. Also the building slab, if concrete, and installed on grade (on the ground surface) and it is not insulated by waterproof membrane, can also work well as moisture retention under a large slab can be quite good, although if really dry, even this could fail.
Another answer might be deep rods. For instance, on the site I am at in Qatar, the earth rods pilot holes will be drilled to depths of something like 30 m to find the summer water table, and multiple rods installed to reach 1 ohm resistance. Here the ground is lime rock after about 500mm and the surface super dry. Only the deepest end of the rods really do anything useful.
Your rods need to reach something consistently wet in the undersurface and again only the deep ends really do the work. Can't help with how to install deep rods in sandy soils.
The one that I think might work the best is deep rods. This doesn't require considerations like whose land in the swamp on and is it corrosive in there, or will the structural engineers like their concrete/steel being used for earthing.
RE: earth bed in a desert location
RE: earth bed in a desert location
In substations the earth grid placed in Bentonite (equivalent).