Making A Loop Impedance Measurement - Megger MFT1700 series User Manual

The test mode is displayed as below:
Default mode
Note: RCDs can still trip when performing a "non-trip" loop test if there is an existing high level of fault current flowing in the Earth
conductor, or the RCD is not operating within specification.
7.1.2 L-N or L-L circuits:
L-N (or L-L) selected
7.1.3 Z, Zmax, Zref and R1+R2 (MFT1720 and MFT1730 only)
The right range knob has addition options.
Z -
Zmax -
Zref -
R1+R2 -
For general loop impedance testing the Z seeing should be selected.
Refer to section 7.5 to 7.7 for additional functionality.
7.2

Making a loop impedance measurement

7.2.1 Ze measurements at the origin (Phase to Earth)
.1 Set the LEFT rotary range knob to the
.2 On the MFT1720 and 1730, set the RIGHT rotary knob to
MFT1710
The MFT automatically uses the Phase and Earth terminals.
.3 Connect test leads as below, with the Red test lead connected to the L1 (Red terminal on the MFT and the Green
test lead connected to the Green (L2) terminal.
1st Press
Standard loop impedance measurements
For multiple loop measurements where the worst case value is required
the Ze or Zdb value used when calculating the R1+R2 value
The loop impedance less the Zref value.
2nd Press
Test performed
range.
.
MFT1720 and MFT1730
15