What is the maximum continuous current expected? Is the system liable to have any overload for a considerable time? If necessary, the complete load cycle may be plotted. While choosing the conductor size for this particular current, proper care is to be taken for all rating factors depending upon actual conditions of installation. Moreover, the type of protection should also be checked.

The voltage drop that will occur when the cable is carrying full load current. This should be especially checked for LT distribution cables having longer runs.

Expected short circuit level of the system. On the basis of short circuit current expected and the time of clearance, the appropriate conductor size of cables may be selected.

While factors given above decide the minimum conductor cross section, economies govern the optimum sizes which will give the minimum running costs. For this purpose, the minimum size along with two or three higher sizes are considered, and annual running costs are worked out by calculating I2R loss (in money) and interest/depreciation of the cable cost. The total of these two give running costs. The size which gives the minimum running cost should be chosen.

Back To Top