14.12 Setting i-vdrop for volts drop measurements
14.12.1 Volt drop
How to measure the volt-drop of a circuit
Volt drop is the voltage the supply will fall to under maximum load current for a circuit. This is NOT the maximum
fault current, but the circuit current. This is usually the rating of the MCB protecting that circuit.
Volt drop is the Phase to Neutral (L-N) voltage of a circuit, or the Phase to Phase (L-L) voltage. It is NOT the Phase to
Earth voltage. Consequently, you should only need to use the L-N or L-L options of Hot key 5.
The instrument calculates the volt-drop based on the Loop Impedance for the circuit and the maximum rated current
for the circuit. This means it is the volt drop in the conductors between the point where you measured and stored
Zref, usually the point the supply enters the building and the end of the circuit.
ATTENTION : The instrument can only calculate the volt drop if you have stored a value for Zref, and also
set the maximum current for the circuit called i-vdrop.
14.12.2 Setting Zref
Set the Zref (Refer to 14.10 Zref – making and using the reference impedance for R1+R2 and Vdrop
calculations on page 71.). Remember this is usually the point the supply enters the building, or as close as is
safely practicable.
NOTE : To measure the volt drop between the point the supply enters the building and the end of a final
circuit, measure Zref at the point the phase and neutral enter the building.
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Earth Loop Impedance testing – TrueLoop™
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