.4 Press and release the TEST button to start the test.
.5 On completion of the test, the display will show the loop resistance on the large display segments, and the fault
current on the small display segments.
7.4 Prospective Fault Current and Short Circuit calculation (PFC & PSCC)
The prospective fault current and short circuit current of a circuit is automatically calculated when making a loop impedance test. The
calculation uses a nominal circuit voltage, not the actual circuit voltage, and is displayed above the loop impedance measurement, as
below:
The fault current is calculated using the expression:-
PSCC or PFC = (Nominal supply voltage in Volts / Loop resistance in Ohms
Example PSCC or PFC = 230 V / 0.13 Ω
= 1769 VA (displayed on the MFT as 1.77 kA)
The nominal supply voltage used in the calculation is automatically selected depending on the actual circuit voltage. The instrument uses
the following voltage values:-
Actual measured voltage Nominal voltage
< 75 V 55 V
≥= 75 V and <150 V 110 V
≥= 150 V and <300 V 230 V
≥=300 V 400 V
7.5 Zmax test mode (MFT1720 and MFT1730 only)
Ideal for multiple loop measurements on a ring final circuit where the highest loop value is to be recorded.
Both
test options can be used.
The current loop test value is displayed on the lower (larger) readout, whilst the maximum measured value of the sequence
is displayed on the upper (smaller) readout.
7.6 Making A Zmax loop impedance measurement
.1 Set the LEFT rotary range knob to the
range
.2 Set the RIGHT rotary knob to
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