Benning IT 130 - Page 47

BENNING IT 130 Measurements
- 47 -
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.
 Save the measuring result by pressing the "MEM" key (optional).
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
kUn
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).