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General Information
4.0 General Information
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) until the other current source
pole. The measurement determines the loop impe-
dance between external conductor and the PE con-
ductor. The Loop impedance value is measured by
short-term mains loading.
Additionally, the instrument TELARIS Loop allows
the user to test the mains internal resistance mea-
surement (L-N). This measurement is not required
by DIN VDE [German Standard], however it is con-
sidered as important and valuable support in prac-
tical applications e.g. for evaluating an installation
as well as for trouble shooting.
Simultaneously to measurement, the instrument
TELARIS LOOP determines (by calculation) the
short-circuit current. The short-circuit current must
be known to guarantee that an excess current re-
lease having been switched in series can trigger at
an appropriate current level and thus at sufficient
speed in the event of short-circuit.
Z
L
V
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Terms:
Loop Impedance (ZL):
Sum of impedance values within a current loop (bet-
ween the L and PE conductor).
Internal Resistance (RI):
Sum of resistance values within a current loop (bet-
ween the L and N conductor).
RL:
Phase resistance
RPE:
Protective conductor resistance
RN:
Neutral conductor
RE:
Earth-Resistance
Short-Circuit Current (IPSC):
Occurring current flow in the event of short circuit.
Specified Threshold Value of Contact Voltage (UL):
Peak value of contact voltage (Limit), which may be
maintained without time limit under specific envi-
ronmental influence and corresponding to an rms
value of 25V / 50V AC
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