Operation Manual

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L1
L2
L3
PE
R
E
Zi
L1
PE
L2
L
/
L
1
N
/L
2
P
E
/L
3
RCD
R E2
RCD
EIN/AUS
ON/OFF
SPEICHERN
MEM
HILFE HELP
KAL CAL
IT 120 B
IT 120 B
Figure 11.3: FI/RCD test in an IT system
11.3.4 First fault leakage current (ISFL)
TheISFLmeasurementiscarriedoutinordertomeasurethemaximumcurrentwhichcouldow
fromthetestedlineintotheprotectiveconductor.Thiscurrentowsthroughtheinsulatingresis-
tance and the insulation reactive impedance (capacitive) between the protective conductor and the
other conductors.
Howtomeasurethefaultcurrentincaseofarstfault:
Step 1 First select the ISOLATION/ INSULATION function by means of the function selector
switch.Then,selectthe„ISFL(rstfaultcurrent)“bymeansofthe▲/▼keys.Thefol-
lowing menu is displayed:
Figure 11.4: Measuring menu for fault current in case of a rst fault
Connect the test cable to the BENNING IT 120 B.
Step 2 Set the following limiting value:
  - uppercurrentlimitfortherstfault
Step 3 Connect the test cable to the component to be tested. For carrying out the fault current
measurementfortherstfault,followtheconnectionplanshowningure11.5.Please
use the help function, if necessary.