Earth Pit Resistance

The electrical code applicable to your country gives the procedure, Guv.

It depends on soil resistivity data of the location. By the way, it is mostly used to ensure that the earth resistance value must be less than 5 homs in a electrical grids.

Read these files

EARTHING SYSTEM

A practical guide to earth resistance testing

You will need : Earth Tester, earthing rods, cables approximately 30 meters & 15 meters length.

On earth tester P1 & E1 are to be shorted & Connected with particular Pit. P2 is to be connected to rod (Fixed in to ground) with approximately 15 +/- 10% meters of cable from Earth Pit. same as, E2 is to be connected to rod in line with first rod but at a distance of 30 +/- 10% meters. Then take the readings of earth pit.

If you have disconnected the earth pit from grid , it will show Earth resistance of particular pit otherwise grid resistance. i think individual E.res should be less than 1Ω & Grid resistace should be less than 10Ω.

hope this is sufficient for you.

Its sufficient, Thank you very much for your reply.

If individual pit's earth resistance is 1ohm,when you connect many of them to the grid the combined resistance should be less than 1ohm because they are in parallel due to 1/R=1/R1+1/R2+1/R3 etc

your equation is very much true, but when you see practically test the whole grid which is a mesh of vertical electrode & horizontal strip electrode will have resistance of welding joints, bends & cuts. all this factor will account for some resistance in a path. however grid of designed to discharge the many KA fault current independent of what material used & what is the soil resistivity. mentioned 10Ω is the limit to discharge fault amps. if you exceeds this limits, soil treatment or standard earth pit treatment will be needed.

Pls Explain me about Earth pit treatment.

Pls Explain me about Earth pit treatment.

> Can you post all your homework in one go then we can get it done in time.

Soil resistivity could be reduced by treating the soil (say watering, adding coke, wood charcoal, bentonite clay). common salt is popular additive. after treatment there is gradual decrease in soil resistivity, however there is a gradual increase in soil resistivity with time as salt is washed away by continual water seepage.

The second method is to increase the length of buried conductor to the length max. possible. this is one time procedure but cost has to be borne at the begining.