Megger LCB2000/2 Guide De L'utilisateur page 17

Operation - Loop Testing
Phase-Neutral or Phase-Phase loop resistance
measurement
To measure the loop resistance of a circuit
Phase-Neutral, or between two phases of a multi-phase
system, connect using the 3-wire lead set.
1. Connect the red lead to phase and the black lead to
neutral or the other phase. There is no need to
connect the green lead.
2. Select Loop L-N/L-L.
3. The supply voltage is displayed. The polarity
indications are invalid and should be ignored.
4. Press the TEST button.
5. Measured loop resistance is displayed.
The prospective fault current may be displayed by
pressing the Enter key.
Prospective Short Circuit Current measurement
(PSCC)
The PSCC of a circuit is the largest Prospective Fault
Current (PFC). In a single phase system, this would be
the larger of the earth loop PFC and the neutral loop
PFC. In a multi-phase system phase-phase loops also
need to be considered and these can be measured
using the Loop L-L switch position.
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When the instrument measures the loop resistance, it
also calculates the PFC. After any loop test, this may
be displayed by pressing the ENTER key.
The PFC is calculated by using the sum:-
Nominal supply voltage
Loop resistance
The supply voltage used in the calculation depends on
the measured voltage and the configuration of the
instrument. As supplied, the instruments are configured
as follows:-
Actual Measured Voltage
150V
>150V and <300V
>300V
Assumed Nominal Voltage
110V
230V
400V