A 150 km long, 3-phase, 400 kV overhead line is used to transmit 1800 MW to a distribution area at 0.9 power factor lagging. The line parameters per phase and per unit length in standard notation are as follows: r = 0.017 Ω/km, x = 0.27 Ω/km and y = j10.58 μS/km. Using the medium-line representation method and pi-equivalent circuit, calculate:
a) The required sending-end voltage.
b) The power loss in the line.
c) The efficiency of the transmission.