5.5 Loop Impedance Measurement /
Prospective Short-Circuit Current
Measurement
The loop impedance (L-PE / loop impedance) is un-
derstood as the sum of all resistance values within
a current loop, consisting of the resistors of the cur-
rent source, the external conductor of the current
source up to the measurement point and the return
line (PE conductor) and the other current source
pole. The measurement determines the loop im-
pedance between the external conductor and the PE
conductor. The loop impedance value is measured
by short-term mains loading. With the instrument
the TELARIS 0100 plus, short-circuit current is de-
termined by calculation.
The short-circuit current must be known such that
an excess current release having been switched in
series can trigger at an appropriate current level and
thus at sufficient speed in the event of a short-cir-
cuit.
This measurement is used to perform the loop
measurement within current circuits which are
not equipped with an RCD. If this measurement
is started in correct circuits equipped with
RCDs, the RCD will trip!
To obtain precise measurement results, switch
off all loads or disconnect them from the mains.
To obtain fairly precise measurement results,
switch off all loads or disconnect them from the
mains. Ensure that the UUT is faultfree.
Only the calibrated test lead which are in scope
of supply must be used!
Connect the 'Schuko-Plug - Measurement Plug'
mains adapter to the Telaris 0100 plus, by in-
serting the measurement plugs labelled with L,
N, PE into the respective sockets L (33), N (34),
and PE (35).
Connect the mains to the socket plug by re-
specting the correct polarity.
Select measurement range („ZL, IPSC") by
means of the measurement range selection
switch (32).
Select the contact voltage limit by pressing the
'VL' key (24).
18
Loop Impedance Measurement / Prospektive Short-Circuit Current Measurement
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