Manual

Gossen Metrawatt GmbH 61
15.3 Earthing Resistance, Mains Powered – 2-Pole Measurement with 2-Pole Adapter or Country-Specific Plug (Schuko) without Probe
Key
R
B
Operational earth electrode
R
E
Earthing resistance
R
i
Internal resistance
R
X
Earthing resistance through equipotential bonding systems
R
S
Probe resistance
PAS Equipotential bonding busbar
RE Overall earthing resistance (R
E1
//R
E2
//water pipe)
In the event that it’s impossible to set a probe, earthing resistance
can be estimated by means of an “earth loop resistance measure-
ment” without probe.
The measurement is performed exactly as described in section
15.4, “Earthing Resistance Measurement. Mains Powered – 3-Pole
Measurement: 2-Pole Adapter with Probe”, on page 62. However,
no probe is connected to the probe connector socket (17).
The resistance value R
ELoop
obtained with this measuring
method also includes operational earth electrode resistance R
B
and resistance at phase conductor L. These values must be sub-
tracted from the measured value in order to determine earthing
resistance.
If conductors of equal cross section are assumed (phase conduc-
tor L and neutral conductor N), phase conductor resistance is half
as great as supply impedance Z
L-N
(phase conductor + neutral
conductor). Supply impedance can be measured as described in
section 14 from page 57. In accordance with IEC 60364, the
operational earth electrode R
B
must lie within a range of “0  to
2 ”.
1) Measurement: Z
LN
amounts to R
i
= 2 × R
L
2) Measurement: Z
L-PE
amounts to R
ELoop
3) Calculation: R
E1
amounts to Z
L-PE
– ½ × Z
L-N
, where R
B
= 0
The value for operational earth conductor resistance R
B
should be
ignored in the calculation of earthing resistance, because it’s gen-
erally unknown.
The calculated earthing resistance thus includes operational earth
conductor resistance as a safety factor.
If the parameter is selected, steps 1 through 3 are
executed automatically by the test instrument.
Select Measuring Function
Select Operating Mode
Set Parameters
❏ Measuring range: AUTO, 10 k (4 mA), 1 k (40 mA), 100 
(0.4 A), 10  (3.7 … 7 A). In systems with RCCBs, resistance
or test current must be selected such that it is less than trip-
ping current (½ I
N
).
❏ Connection: 2-Pole adapter
❏ Touch voltage: UL < 25 V, < 50 V, < 65 V
❏ Test current waveshape: Sinusoidal (full-wave), 15 mA sinusoidal
(full-wave), DC offset and positive half-wave
❏ System type: TN/TT, IT
❏ Transformer ratio: irrelevant in this case
Start Measurement
T
E
S
T
I
N
S
T
R
U
M
E
N
T
Ri
W
a
t
e
r
P
i
p
e
E
2
E
1
B
R
E
Limit Value:
R
E
> Limit Value
U
L
 R
L