A lossless 400 kV, three-phase 50 Hz line has inductance 1.6 mH/km/phase and capacitance 10 nF/km/phase. Sending voltage is maintained at 400 kV. When delivering 300 MW, the shunt compensation needed to maintain receiving voltage 400 kV is
The surge impedance is $Z_c=\sqrt{L/C}=\sqrt{1.6\times10^{-3}/10^{-8}}=400$ Ω. Surge-impedance loading is $V_{LL}^2/Z_c=(400000)^2/400=400$ MW.
The actual 300 MW is below this natural loading, so line capacitance supplies more reactive power than its series inductance consumes. Shunt reactors absorb the surplus to control receiving voltage. Compensation is **inductive, B**.
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