Earthing Resistance (R Function); Performing Measurements - Gossen MetraWatt ProFiTEST C-GB int. Operating Instructions Manual

8 Earthing Resistance (R function)
E
Earthing resistance is the sum of earth electrode dissipation resistance
(R D ) and resistance of the earth conductor.
Earthing resistance is roughly calculated with an "earth electrode loop
resistance measurement". The resistance value R ELoop determined with
this measuring method includes resistance values for functional earth R F
and phase L as well. These two values must be subtracted from the
measured value in order to determine earthing resistance.
Assuming equal conductor cross-sections (phase L and neutral N),
resistance at the phase conductor is half a great as line impedance Z I
(phase + neutral).
According to DIN VDE 0100, functional earth R
0  to 2 .
Earthing resistance is calculated with the following equation:
R = R
E
E
When calculating earthing resistance, it is advisable to ignore the
resistance value for functional earth R
unknown.
The calculated resistance value thus includes the functional earth
resistance value as a safety factor.
Line impedance Z can only be measured with the 3-phase measuring
I
adapter (accessory) in the Z
Loop
Note
Interference voltages at the protective conductor PE or at the
earth electrode have no influence on measuring results.
They can be measured by performing a voltage measurement with
the test plug.
If dangerous contact voltage occurs during measurement
(> 50 V), the measurement is interrupted and safety shutdown
ensues.
GMC-I Messtechnik GmbH
must lie within a range of
F
1

R R
– -- - –
Loop I B
2
, because this value is generally
F
mode.
Connections
R
E
R
F
8.1

Performing Measurements

Automatic Measuring Range Selection
L1
L2
L3
N
PE
START
29