Manual

72 Gossen Metrawatt GmbH
A number of typical soil resistivity values for various types of
ground are summarized in the following table.
Calculating Dissipation Resistance
Formulas for calculating dissipation resistance for common types
of earth electrodes are included in this table.
These rules of thumb are entirely adequate for actual practice.
R
A
= dissipation resistance ()

E
= soil resistivity (m)
I = length of the earth electrode (m)
D = diameter of a ring earth electrode, diameter of the equivalent surface
area of a mesh earth electrode or diameter of a hemispherical earth
electrode (m)
F = surface area (sq. meters) of the enclosed surface or a ring or mesh
earth electrode
a = Edge length (m) of a square ground plate; a is replaced with the fol-
lowing for rectangular plates: 
bxc, where b and c are the two
sides of the rectangle.
J = volume (cubic meters) of an individual foundation footing
Type of Soil Soil Resistivity

E
[m]
Marshy ground 8 60
Arable soil, loamy and clayey soil, moist gravel 20  300
Moist sandy soil 200  600
Dry sandy soil, dry gravel 200  2000
Rocky ground 300  8000
Rock 10
4
 10
10
Number Earth Electrode Rule of Thumb Subsidiary Variable
1
Earth strip
(star type earth electrode)
—
2
Earth rod
(buried earth electrode)
—
3 Ring earth electrode
4 Mesh earth electrode
5 Ground plate —
6
Hemispherical earth
electrode
R
A
2 
E

I
------------
=
R
A

E
I
-----
=
R
A
2 
E

3D
------------
=
D 1,13 F
2
=
R
A
2 
E

2D
------------
=
D 1,13 F
2
=
R
A
2 
E

4,5 a
------------
=
R
A

E
 D

----------
=
D 1,57 J
3
=