MI 3108 EurotestPV
Measurements
– a.c. LV installations
62
5.8.1 Line impedance and prospective short circuit current
Circuits for measurement of line impedance
Figure 5.33: Phase-neutral or phase-phase line impedance measurement
– connection
of plug cable and 3-wire test lead
Line impedance measurement procedure
Select the
Zline
sub-function.
Select test
parameters
(optional).
Connect
test cable to the instrument.
Connect
test leads to the item to be tested (see
figure 5.33
).
Press the
TEST
key to perform the measurement.
Store
the result by pressing the MEM key (optional).
Figure 5.34: Examples of line impedance measurement result
Displayed results:
Z .............. Line impedance,
I
SC
............ Prospective short-circuit current,
Lim .......... High limit line impedance value.
Prospective fault current I
PFC
is calculated from measured impedance as follows:
factor
scaling
Z
U
I
L
N
L
N
PFC
_
)
(
where:
Un ........ Nominal U
L-N(L)
voltage (see table below),
Scaling factor.......Impedance correction factor (see chapter
4.4.5
).
U
n
Input voltage range (L-N or L1-L2)
