Earthing Design Calculation for Substation.

Hiren,

The average specific resistivity for Copper can be considered as 0.02 ohm*mm2/m, at 25 C.

Thus the resistance of a rectangular bar ( 50 x 6 mm, whose cross-section area is 9 mm2 would be 0.02/9 = 0.00222 ohm/m

For the other bar ( 75 x 10) the resistance would be 0.000727 ohm/m

The values are for approx pure Copper. Depending on the percentage of impurities, the 0.02 may go up.

Dear Tomed,

Thanks for reply but we are using either 75 x 10 mm GI (Galvanized Iron) Flat or 50 x 6 mm GI (Galvanized Iron) Flat.

So, I want the resistivity of GI (Galvanized Iron) Flat instead of Copper Flat. i.e 50 x 6 mm GI Flat & 75 x 10 mm GI Flat.

Hope for prompt reply soon.

With regards,

Hiren

Even without the excel sheet you could calculate it. Search on the internet for its formula. OR you could use softwares for this. In my company we are one software for substation grid design. plus, in you data above, you didn't provide the weight of the person, ground fault current and many other parameters.