TESTBOY TV 450
Fault loop impedance
44
Fault loop impedance measurement procedure
* model TESTBOY TV 450 (TYPE B)
Select the
Zloop
or
Zs rcd
subfunction using the function selector switch and
¿
/
À
keys
Select test
parameters
(optional).
Connect
test cable the TESTBOY TV 450.
Connect
test leads to the the item to be tested (see
figure 5.24 and 5.17
).
Press the
TEST
key to perform the measurement.
Store
the result by pressing the MEM key (optional)*.
Figure 5.25: Examples of loop impedance measurement result
Displayed results:
Z..............Fault loop impedance,
I
SC
............Prospective fault current,
Lim ..........Low limit prospective short-circuit current value or high limit fault loop
impedance value for the UK version.
Prospective fault current I
SC
is calculated from measured impedance as follows:
Z
k
Un
I
SC
SC
×
=
where:
Un ........Nominal U
L-PE
voltage (see table below),
ksc .......Correction factor for Isc (see chapter
4.2.6
).
U
n
Input voltage (L-PE)
115 V (100 V
≤
U
L-PE
<
160 V)
230 V (160 V
≤
U
L-PE
≤
264 V)
Notes:
High fluctuations of mains voltage can influence the measurement results (the
noise sign
is displayed in the message field). In this case it is recommended
to repeat few measurements to check if the readings are stable.
This measurement will trip-out the RCD in RCD-protected electrical installation if
test Zloop is selected.
Select Zs
rcd
to prevent trip-out of RCD in RCD protected installation.