Substation Ground Well

[DistCoop]

Does anyone have any thoughts on how a substation ground well might be modeled? I'm using ETAP, which does not have a formal procedure or element to model one. I know the overall grid resistance, and I know the resistance of each well.

Ultimately I'm trying to determine GPR, touch and step voltage. I'm certain the ground wells will solve my voltage violations, but I wish I could verify it.

 

[mbk2k3]

isn't the ground well simply a point where you can test resistance values? how would wells solve voltage violations? unless the wells have ground rods within them to improve your resistances?

 

[DistCoop]

The ground well (unless I'm using the term incorrectly) is a metal tube filled with bentonite, through which a large conductor tied to the ground grid runs. This goes down to the water table. The lower resistivity should then lower the overall voltage rise.

That's another question though... how much would a ground well actually lower touch/step voltage? I've been playing with an idea I had of how to model the well which I believe to be correct, but it has minimal effect on touch voltage. Perhaps I misunderstand what a ground well is really for.

 

[cuky2000]

A substation ground well could be modeled in a similar way as a ground rod using the diameter of the encased pipe and the equivalent deep soil resistivity.
The voltage profile could be improved since significant amount of current will be forced to the ground well because the expected low resistance path in this point.

 

[7anoter4]

See:
file:///D:/D_My%20Documents/Engineering/Grounding/10-Decreasing%20Grounding%20Resistanc%20Deep-Ground-Well%20Method.pdf
ch.VI. ESTIMATION OF EQUIVALENT LOW-RESISTIVITY REGION FORMED BY DEEP GROUND WELL