15
total value of earth ground resistance value of measured earthing object and
that of commercial earthing object, namely:
RE=RX
＋
re
In which:
RE
is the Tester reading value;
RX
is the earth ground resistance value of measured earthing
object;
re
is the earth ground resistance value of common earthing
object like commercial use power system.
Then, the earth ground resistance value of measured earthing object is:
RX=RE
－
re
8
．
Soil Resistivity Test
The soil resistivity
ρ
is an important factor that determines the
grounding resistance of the grounding body. Different types of soil, of
course, have different soil resistivities, that is, even the same kind of soil,
because of different temperature and moisture content, the soil resistivity
will also change significantly. Therefore, in order to have a correct basis
in the design of the grounding device, so that the designed grounding
device can more meet the actual needs of the work, the soil resistivity
must be measured.
The soil resistivity was measured by the four-pole method (Winner
method).
The soil resistivity
ρ
is calculated according to the formula
ρ
=2
π
aR
(
Ω
m), and the unit is
Ω
m, and:
a - electrode spacing
R
——
Soil resistance between S-FR electrodes
Four-pole method (Winner method): Connect the test wire as shown
below. Pay attention to the space between the auxiliary grounding rods
and the depth of burial. H, S, FR, and E auxiliary ground rods are buried
in the ground and buried deep into the earth. The ground test lines (red,
yellow, green, and black) are connected from the H, S, FR, and E ports of
the meter to the H, S, FR, and E auxiliary ground bars under test.
