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The inductance and capacitance of a 400 kV, three-phase, 50 Hz lossless transmission line are 1.6 mH/km/phase and 10 nF/km/phase, respectively. The sending-end voltage is maintained at 400 kV. To maintain a voltage of 400 kV at the receiving end while the line delivers a 300 MW load, the shunt compensation required is
- capacitive
- inductive
- resistive
- zero
Correct answer: inductive
Solution
For a lossless line, the surge impedance loading can be estimated from the line parameters. Since the 300 MW load is below the natural loading for a 400 kV line, the line produces excess reactive power and the receiving-end voltage tends to rise. Therefore, inductive shunt compensation is required to absorb reactive power and hold the receiving-end voltage at 400 kV.
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