Benning 044104, Руководство по эксплуатации, Страница: 42 / 67

BENNING IT 115 Device description
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How to perform loop impedance measurements

Select the Z
S
(L-PE) [English: Z
LOOP
(L-PE)] function by means of the function selector
switch.

Set the sub-function to Zloop or Zsrcd (for systems with RCDs).

Set the testing parameters.

Connect the test cables to the test object (see figure 5.24).

Press the " TEST " key to start the measurement.
Figure 5 .25 : Example of a loop impedance measurement
Results displayed:
Z ............... loop impedance
Isc ............ prospective short-circuit current
Lim ........... lower limit of the prospective short-circuit current
The prospective short-circuit current I
SC
is calculated as follows:
Z
k Un
I SC
SC


with:
Un ......... nominal voltage L-PE (see table below),
ksc ........ correction factor for short-circuit current Isc (see chapter 4.4.6 Isc factor (scaling
factor) )
U
n
Voltage range (L-PE)
110 V (93 V
 U
L-PE
 134 V)
230 V (185 V
 U
L-PE
 266 V)
Notes:

High fluctuations of the nominal voltage might influence the measuring results ( icon
on the LC display). In this case, it is recommended to repeat the measurements and to
check whether the measuring results are stable.

The loop impedance measurement Zloop trips the residual current protection devices
(RCDs).

Select the Zsrcd measurement in order to prevent the tripping of a residual current
protection device (RCD).