The selection of conductors for overhead lines is done considering the following points:
H.V. lines upto 33 kV:
1.All aluminium conductor is used only for LT distribution, for pole spans upto 35 metres or so.
Above this it is advisable to use ACSR conductor. At higher voltages either ACSR, cadmium copper or hard drawn/annealed copper conductor can be used.
2.It is not sufficient to select the conductor from current carrying capacity point of view, but voltage drop should also be limited to permissible value. Indian Electricity rules permits a voltage drop of 12.5% on 11.V. line from Licensee’s metering point to consumers substations
LT. lines of 415/430 volts:
1.Since distribution transformers are rated for 433 volts on LT, side, this village can be adopted as sending end voltage. In distribution line, current are tapped at various points.
It is customary that, first some conductor of current rating equal to total current is chosen and then voltage drop in complete line is checked up
2.It is advisable that instead of resorting to several exact nearest equivalent sizes of conductors, only 2 or 3 different sections are used.
