Operation Manual

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Displayed results:
Z Loop impedance
I
SC
Prospective short-circuit current
Lim Low limit of prospective short-circuit current value
Save displayed results for documentation purposes. Refer to chapter 6.1 for further information on
setting functions and saving of measurement results (BENNING IT 120 B only).
Note:
- Measurement of the loop impedance (Zsrcd) does not normally trip an RCD. However, the trip
limitmaybeexceededasaresultofleakagecurrentowingtothePEprotectiveconductoror
via a capacitive connection between L and PE conductors.
- Thespeciedaccuracyoftestedparametersisvalidonlyifthemainsvoltageisstableduring
the measurement.
5.5 Line impedance and prospective short-circuit current (Zl/ Ik)
Line impedance is a complex AC impedance within the current loop when a short-circuit to the
neutral conductor occurs (conductive connection between phase conductor and neutral conductor
in single-phase system or between two phase conductors in three-phase system). A 2.5 A test cur-
rent is used to perform line impedance measurement.
Prospective short-circuit current is calculated as follows:
L
n
PFC
R
scaling factorU
I
-
x
=
N(L)
where
U
n
Voltage range
115 V 100 V ≤ U
L-PE
< 160 V
230 V 160 V ≤ U
L-PE
≤ 264 V
400 V 264 V < U
L-PE
≤ 440 V
Becauseofdifferentdenitionsoftheprospectiveshort-circuitcurrentIPSCindifferentcountries
the user can set the scaling factor in the Setup menu (See chapter 4.4.2).
How to perform line impedance measurement:
Step 1 Select Zl/Ik (L-N/ L) (line impedance) with the function selector switch. The following
menu is displayed:
Fig. 5.33: Line impedance measurement menu
Connect the test cable to the BENNING IT 110/ BENNING IT 120 B.
Step 2 Set the following measuring parameters:
- Fuse type
- Fuse current rating
- Fuse trip-out time