How to Determine Voltage Drop in an Electrical Conductor

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Owing to the effect of voltage drop on electrical equipment, determination of the voltage drop of an electrical conductor is very important in helping to predict voltage drop level and ensure that it is in line with the relevant standard.
For an electrical conductor with impedance Z, the voltage drop is calculated by the following formula:

Where:
K   =     a coefficient equal to 2 for single phase and two phase systems.
             SQRT(3) for three phase systems
IB   =     load current in Amps. if no information are available, the cable carrying   
             Capacity of the conductor shall be considered.
L    =     Length of conductor in Km
n     =     is the number of conductors in parallel per phase
R    =     is the resistance of the single cable per kilometre in (Ω/km)
X    =     is the reactance of the single cable per kilometre in (Ω/km)
CosФ = power factor of the load


Resistance and reactance values
per unit of length of Copper and Aluminium conductors at 50Hz are available in tables for easily calculating voltage drop. In the case of 60 Hz, the reactance value can be determined by multiplying that at 50Hz by 1.2

Percentage of Voltage Drop in Electrical Installation
The percentage voltage drop can be calculated in relation with the rated voltage of the installation Vr as :