A small town with a demand of 800 KW of electric power at 220V is situated 15km away from an electric plant generating power at 440 V. The resistance of the two wire line carrying power is `0.5Omega` per km. The town gets power from the line through a 4000-220 V step down transformer at a substation in the town. The line power loss in the form of heat is

Explanation

Line resistance `=30xx0.5=15Omega`.
rms current in the line `=(800xx1000W)/(4000V)=200A`
(a) Line power loss `=(200A)^(2)xx 15Omega=600kW.`
(b) Power supply by the plant `= 800 kW + 600 kW = 1400 kW.`
(c ) Voltage drop on the line `=200A xx 15Omega=3000V`.
The step-up transformer at the plant is `440V-7000V`.