Determine the most economical size of a 3-phase line whichsupplies the following loads at 10 kV : (i) 100 kW at 0·8 p.f.(lag) for 10 hours (ii) 500 kW at 0·9 p.f. (lag) for 8 hours (iii)100 kW at unity p.f. for 6 hours. The above gives the daily loadcycle. The cost per km of the completely erected line is Rs (8000 a+ 1500) where a is the area of cross-section of each conductor. Thecombined interest and depreciation is 10% per annum of capitalcost. Cost of energy losses is 5 paise per kWh. Resistivity ofconductor material = 1·72 × 10−6 Ω cm.
