Earth Well

HI ALL
I am bored!
I am searching about Earth well resistance calculation for 2 weeks and I can't find anything!
when I speak about Earth Well , my mean is one Well about 4 to 6 meters that we put a copper plate in it.one stranded copper wire connects to plate and the other End of wire come out from well entrance.then we fill the well with conductive concrete and soil.
NOW, I need a mathematical formula to calculate the resistance of well,that depends on the depth of well,the size of plate, the resistivity of soil and conductive concrete , ....
can anyone help me? plzzz

The point becomes "What are you referencing to?" If you measure with a meter lead to the ground conductor the other test lead goes to what? There really is no hard standard, I have seen .01 and .005 as "standards". Lets say you had two ground wells and connected your ohm meter to both, in all likelyhood you would come up with something less than .01 ohm, but what if you came up with 10 ohms, where would you start to find the high resistance? The soil type, moisture content, surface area of the conductors all come into play. Most of the info that I have seen, on what is acceptable, has been in building codes not in electrical references. That is because building codes are local and the soil types in the area are well known. Since that is the case they can simply refer to a minimum conductor surface area and minimum conductor size. Per NEC 2011 the minimum standard size is #6 AWG bare solid copper so then you just need to see how deep and surface area of the conductor. I am sure you can find some formulas somewhere but they will probably include a disclaimer saying that they are not applicable in all cases. If nothing else consult your local building inspector and they can probably point you in the right direction.

One aspect is discussed here: http://en.wikipedia.org/wiki/Soil_resistivity. I would also point out that the quantity of power to be dissipated will have a direct bearing on the size of the earth ground required. If I remember correctly I heard about a powerplant being built and that it's "earth well" was a 1 kilometer in diameter conductor. If I can come up with the article I'll post it.

Wow ! There are not many factories making conductors 1 km in diameter ! :-)

Could that be a kilometer in length, running in a circle ?

Actually a conductor in a 1 kilometer circular path which would be 3.1416 in length

Found this reference for you. Since you're bored and looking for grounding data you can probably fill a day with the data presented here. It goes into the testing of quality of the grounds and some on construction methods. You can save the data for future reference as well
http://www.weschler.com/_upload/sitepdfs/techref/gettingdowntoearth.pdf

ok ,thanks dear
I read it,but it does not seem , I can find anything abou*t earth well*

That's probably not a common term. I did notice your drawing indicates a conductive powder not a conductive concrete. Maybe if you gave an idea of what this would be used for, you might get a specific recommendation. If you notice they talk about grids laid in the ground and what size they need to be for certain situations. The function is the same as this earth well you are looking at. I guess I just don't understand the specific desire to use that configuration. One thing that you might look up as well are Single Wire Earth Return (SWER) distribution systems. Since they rely on earth to be a conductor in the system they should get pretty specific on ratings for allowable grounds.

hi I am looking for document about earth well same you. Did you find out how to calculate it ? Can you send for me ? thanks a lot

Amazing share..