BENNING IT 115
Safety and operating instructions
- 9 -
Loop impedance
The lower limiting value of the prospective short-circuit current depends on the fuse type,
on the fuse current rating and tripping time as well as on the I
SC
scaling factor.
The stated accuracy of the parameters tested shall only apply, if the mains voltage is
stable during measurement.
Loop impedance measurements (Zs) involve tripping of residual current protection
devices (RCDs).
Loop impedance measurements (Zs
rcd
) normally do not involve tripping of the residual
current protection device (RCD). However, the tripping threshold might be exceeded due
to leakage currents flowing to the protective conductor (PE) or via the capacitive
connection between the conductors L and PE.
Line impedance / voltage drop
During phase-to-phase measurements of the line impedance Z
I
(L-L) with the test cables
PE and N being connected, a warning of dangerous PE voltages is displayed. However,
the measurement will be carried out.
The stated accuracy of the parameters tested shall only apply, if the mains voltage is
stable during measurement.
Depending on the connection voltage detected, the test terminals L and N are inverted
automatically.
Testing the protective conductor connection (PE)
The PE connection can be tested only in switch positions "FI/RCD", "Z
S
(L-PE)" and
"Z
I
(L-N/L)"!
For correct measurement of the PE connection, the "TEST" key must be touched for
several seconds.
Make sure not to stand on an insulated floor, because otherwise the test result might be
incorrect!
