BEHA UNITEST Telaris 0100 Mode D'emploi page 33

5.3 Loop Impedance Measurement /
Prospektive 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, short-circuit current is deter-
mined by calculation. The short-circuit current must
be known such that an excess current release hav-
ing been switched in series can trigger at an appro-
priate current level and thus at sufficient speed in
the event of a short-circuit.
To obtain precise measurement results, switch
off all loads or disconnect them from the mains.
Prior to any loop impedance measurement, en-
sure that any available RCDs are bridged.
Only the calibrated test lead which are in scope
of supply must be used!
Loop Impedance Measurement
" 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 (24).
" Select contact voltage threshold by means of
the key „VC/UL" (21).
If symbol „turn plug by 180°" (7) appears,
turn the mains plug by 180° and connect to
the socket.
If the symbol „socket error" (6) appears, the
socket is either incorrectly wired or the mains
voltage is missing (internal fuse defect !).
The socket is checked for correct wiring by
touching the contact electrode (23). A dan-
gerously high voltage >50V at the PE is indi-
cated by UB<UL. If the symbol „socket error"
(6) appears when touching the contact elec-
trode (23), a PE error is present.
" If there are no errors with the socket, press the
"start" key (25)
" Read the measurement result on the display.
The loop impedance is indicated in the large
result field (12), short-circuit current Ik is indi-
cated in the small result field (14).
If loop impedance exceeds or falls below
1999Ω, the large result field (12) indicates
„>1999Ω". As no measurement value is avail-
able for ZL, calculation of short-circuit cur-
rent IPSC is impossible and cannot be dis-
played. The symbol „---„ appears in the small
display field (14).
If several measurements are carried out, in-
terrupted only by „short" breaks, the internal
overtemperature protection of TELARIS
0100 is triggered and the symbol for
overtemperature (18) appears on the dis-
play. The next loop impedance measurement
can only be started, once the instrument has
cooled down and after the symbol (18) has
gone out. Instrument damage is therefore
avoided.
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