Do the same exercise as above with the replacement of the earlier transformer by a 40,000-220 V step-down transformer (Neglect, as before, leakage losses though this may not be a good assumption any longer because of the very high voltage transmission involved). Hence, explain why high voltage transmission is preferred?

Explanation

Current `=(800xx1000W)/(40,000V)=20A`
(a) Line power loss `=(20A)^(2)xx(15Omega)=6kW`.
(b) Power supply by the plant `=800kW+6kW=806kW.`
(c) Voltage drop on the line `=20A xx 15Omega=300V`.
The step-up transformer is `440V-40,300V`. It is clear that percentage power loss is greatly reduced by high voltage transmission. In Exercise this power loss is `(600//1400) xx 100 = 43%`. In this exercise, it is only `(6//806)xx100=0.74%`.