Commissioning; Earth Resistance Measurement (Two-Wire Method); Earth Resistance Measurement (Three-Wire Method) - BEHA UNITEST Telaris Erde Instruction Manual

Commissioning

6.0 Commissioning
Measurements in dangerous proximity of elec-
trical installations are only to be executed when
instructed by a responsible electrical special-
ist, and never alone.
To perform this measurement the user re-
quires the Earth Measurement Set (Cat.
No.1048)
The instrument may only be connected to volt-
age-free earth connectors.
Prior to inserting grounds or rods, check the
soil for possible dangerous objects present
(pipes, conductors, etc.).
If a voltage exceeding approx. 5V AC/DC is pre-
sent at the test leads, the warning message
'Unoise' is displayed.
To avoid faulty measurements, installed metal
pipes, cables in the ground, or in open area un-
derground waterways or roots must be taken
into account. Additionally, the specific ground
resistance is subject to seasonal weather-re-
lated variations.
6.1 Earth Resistance Measurement
(two-wire method)
The two-wire method consists of measuring the re-
sistance between the earth under test and a known
earth. For this purpose, the PEN conductor of a TN
system can be used, for example. The resistance of
the known earth connection has to be subtracted
from the measurement result. This measurement is
also feasible in a densely populated or in sealed
areas where rods and auxiliary earth connections
may not be installed.
24
E
earth to be tested
zu messender Erder
R
RE
PEN
Figure 3: two-wire method
Connect earth to be tested wiht socket (E) and
known earth wiht socket (H), also refer to fig. 3
Turn the rotary switch (13) to the "2 pole" posi-
tion.
Set contact voltage (11) by using key "UL".
If required choose maunal frequency selection
by using key "auto/man" (16), and select test
frequency with key "f1/f2" (12).
Press key "Start" (14).
Read the measurement result from the display.
Also refer to display indications in chapter 7.0
After the measurement, selection can be made
between display of earth resistance or mea-
surement current (I M ) by using key "Dis-
play"(8), depending on the measurement re-
sult.
Possibility to measure conventional resistance
by using the grounding resistance measure-
ment range. For this purpose, connect test
leads E and H to the DUT. Test current is fed via
lines E and H, measurement voltage is mea-
sured via E and H.
6.2 Earth Resistance Measurement
(three-wire method)
To perform this measurement the user re-
quires the Earth Measurement Set (Cat.
No.1048)
The three-wire method consists of inserting
two earth rods (one auxiliary earth and one
probe) into the soil, at a minimum distance of
20m. This layout can also be realized by trian-
gular shape. The test current is fed between
PEN
bekannter Erder