Loop Impedance (Hi Current Trip Mode) In It Systems; Line Impedance - Beha-Amprobe Telaris Série Guide D'utilisation

To measure loop impedance—Hi current trip mode:
If no RCDs are present in the system under test, you can use the high current Line Earth (L-
PE) loop impedance test.
1. Turn the rotary switch to the
2. Connect all three leads to the L, PE, and N (red, green, and blue) terminals of the tester.
Only the calibrated test lead which are in scope of supply must be used! The resistance
of the calibrated test leads is subtracted from the result automatically.
3. Press F1 to select L-PE. The
selected.
4. Repeat Steps 4 through 8 from the preceding test.
WWarning
The symbol on the LCD indicates the high current loop mode - any RCDs in the system
will trip - ensure there are no RCDs present.

Loop impedance (Hi current trip mode) in IT systems

The impedance being measured by a phase to earth test depends on the condition of the IT-
system. It should be a very high impedance on a healthy system. Low impedance values may
be caused by a shorted disneuter, loads connected to the system, or an existing first fault
condition. This is not a common test as the state of the system must be known before you
can determine the significance of the measured value.
Use the mains test lead but do not connect the N-wire to the instrument, so just the PE and
L inputs are used. See figure 18a.
Note: An RCD will trip during this test, in case the impedance is low.

Line Impedance

Line impedance is source impedance measured between Line conductors or Line and
Neutral. This function allows the following tests:
• Line to Neutral loop impedance.
• Line to Line impedance in 3-phase systems.
• L-PE loop measurement. This is a way of making a high current, 2-wire loop
measurement. It cannot be used on circuits protected by RCDs because it will cause
them to trip.
• Prospective Short Circuit Current (PSC). PSC is the current that can potentially flow if
the phase conductor is shorted to the neutral conductor or another phase conductor.
The tester calculates the PSC current by dividing the measured mains voltage by the
line impedance.
position.
appears to indicate that hi current trip mode is
Figure 14. Line Impedance Display
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