MZC-304
– USER MANUAL
7
2.7 Measurement of fault loop parameters
If there are residual current devices in the tested network, they should be bypassed by
bridging for the period of impedance measurement. However, it should be remembered
that the tested circuit is modified in this way and the obtained results may slightly differ
from the actual results.
Each time after completion of measurements, modifications introduced to the installation
for the period of measurements should be removed and operation of the residual current
device should be checked.
The above remark does not apply to measurements of fault loop impedance with the use of
the Z
L-PE
RCD function
Measurements of fault loop impedance performed downstream of inverters are ineffective
and their results are unreliable. This is due to the instability of internal impedance in in-
verter circuits during its operation. The measurements of fault loop impedance should not
be performed directly downstream of inverters.
2.7.1 Cable length selection
Turn the rotary switch to one of the loop imped-
ance measurement ranges.
Set the parameters according to the following algorithm, and according to
the rules described in general parameters setting.
NOTE
: The WS-07, WS-05 and WS-01 cables are detected by the meter
and it is then impossible to select the cable length (the
symbol is dis-
played for WS-05 and WS-01 and symbol
for WS-07). Using cables ter-
minated with banana plugs, before starting to measure, select the appropri-
ate length of the phase conductor, compatible with the length of cable used
for measurement.
Note:
Using cables from known manufacturers and selecting the correct length guarantees the
declared measurement accuracy.
