19
®
®
20
2-wires simple method for measurement of earth ground
resistance, its reading on tester is the total value of earth ground
resistance value of measured earthing object and that of
commercial earthing object, that is :
R = RX + re
In which :
R
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 = R – re
8. Soil Resistivity Measurement :
Soil resistivity
ñ
is a determining factor of earthing resistance of
earthing body. Different nature of the soil, there is a different soil
resistivity. Even the same kind of soil, due to different temperature
and water content and so on, the soil resistivity will correspondingly
have a significant change. Therefore, in order to have a correct
basis in the design of the earthing device, ensure the designed
earthing device be more in accord with the need of practical work,
soil resistivity measurement is very essential.
Soil resistivity is measured by 4-pole method (Wenner method)
According to formula
ñ
=2
ð
aR(
Ù
m)
calculating soil resistivity
ñ
,
its unit is
Ù
m
, in which :
a
––electrode distance
R
––soil resistivity between electrode
P
(S)
-ES
4-pole method (Wenner method) :
Connect testing wires as
shown below, pay attention to the distance between auxiliary
earthing rods, and the embedding depth. Respectively insert
C
(H)
,
P
(S)
,
ES
,
E
auxiliary earthing rods deep into the earth in a straight
line, and then connect testing wires (red, yellow, green, black)
corresponding to
C
(H)
,
P
(S)
,
ES
,
E
of interfaces and measured
auxiliary earthing rods.
E
ES
P
(S)
Green
Yellow
Red
C
(H)
Black
a
>20h
h
H.i65
000
EARTH-
TESTER
0
10
20
30
40
C
MEM
AL
CLR
SET
START
FUNCTION
OFF
EARTH
R
EARTH
EARTH
VOLTAGE
OFF
C
(H)
E
P
ES
(S)
AC 600V Max
Rs232
.
m
a
>20h
a
>20h
a/20 max
Setting distance between auxiliary earthing rods :
After finishing
wires connection, firstly rotate rotary switch to ‘“
ñ
EARTH
”,
long press “ ” button (about 3 seconds) to enter setting, short
press “ ” button to move the cursor, press “ ” or “ ” button
to change current data value (a range:1m-100m), then long press
“ ” button to save the set a value, and return soil resistivity
testing mode.
FUNCTION
SET
SET
SET
After setting a value, in soil resistivity testing mode, press the
“ ” button to start testing, and countdown display testing
process, stable soil resistivity value is shown when finish testing.
START
SET
As shown below, the measured soil resistivity is 53.38
Ù
m, already
stored 157 sets of data. Press “ ” button, the earth resistance
rC
of
auxiliary current electrode
C
(H)
and earth resistance
rP
of auxiliary
voltage electrode
P
(S)
will be displayed, and then automatically return
display of measured soil resistivity
ñ
.
H i57
5338
10
20
30
40
0
.
.
m
036
.
c
:
k
027
.
p
:
k
