User Manual

GMC-I Messtechnik GmbH 5
3.3 Measurement of Fault Loop Impedance and Line Imped-
ance
3.3.1 Measurement in Circuits without RCD – ~ Function
The “~” function is suitable for measuring fault loop impedance in
electrical circuits without RCCBs, as well as line impedance.
➭ After switching the instrument on, connect it between L and
PE in order to measure fault loop impedance, and between L
and N to measure line impedance.
➭ After the voltage value has settled in, briefly press the START
key in order to trigger measurement. Assure good contact be-
tween the test probes and the device under test while mea-
surement is being performed!
Results after completion of the measurement:
Key:
Z Measured impedance ()
Z x 1.5 Multiplier for measured impedance Z ()
I
K Short-circuit current calculated as: I
SC
= 230 / (Z x 1.5) (A)
➭ Remove the instrument.
3.3.2 Displaying Further Measured/Calculated Values
Stated briefly: The following are displayed, one after the other, by
pressing the DISP
▲ and DISP ▼ keys:
– Short-circuit current
– 1.5 times measured impedance
– Impedance corrected by a value equal to measuring error
– Measured impedance
In detail: Impedance corrected by a value equal to measuring error
is displayed by pressing the DISP
▲ key, and only the measured
value without correction is displayed by pressing the DISP
▼ key.
3.3.3 Measurement in Electrical Circuits with RCD
Testing Without Tripping the RCCB
Select the “RCD” function if loop impedance needs to be mea-
sured via an RCCB, without causing it to trip.
➭ After switching the instrument on, connect it between L and N
in order to measure line impedance.
➭ After the voltage value has settled in, briefly press the ~/RCD
key, which starts measurement of line impedance without trip-
ping the RCD. This is important if loop impedance needs to be
measured via an RCCB.
➭ Assure good contact between the test probes and the device
under test while measurement is being performed!
The results appear at the display, and the “~” symbol is replaced
with the “RCD” symbol at the same time.
Figure 3.12: Connection Example: Loop Impedance Measurement, L2–PE
Figure 3.13: Sample Results for Imped-
ance Measurement (brief
representation)
Figure 3.14: Sample Results for Imped-
ance Measurement
(detailed representation)
Figure 3.15: Short-Circuit Current Figure 3.16: 1.5 Times Impedance
Figure 3.17: Impedance + Measuring
Error
Figure 3.18: Measured Impedance
Figure 3.19: Measured Impedance +
Measuring Error
Figure 3.20: Measured Impedance