How do we determine the size of cable required for a particular current of a distance?
A current which flows in a conductor will cause a voltage drop over the length of conductor due too its resistance.
The cable size can be determined to find Vc as shown below:
When Vc is found, it is then necessary to look up the appropriate table of volt drop factors in AS/NZS 3008.1.1 to find a cable size which has a lower voltage drop factor than that just calculated.
After obtaining the cable size, the continuous current rating must again be checked.
If the cable size meets or exceeds the required current, I, then this is the answer. If not, the cable size must be increased until the current, I, is obtained.