Question

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, when the line is delivering \(300\;MW\) load, the shunt compensation required is
1. capacitive
2. inductive
3. resistive
4. zero

Answer 1

Correct Answer - Option 2 : inductive

Surge impedance \(= \sqrt {\frac{L}{C}}\)

\(= \sqrt {\frac{{1.6 \times {{10}^{ - 3}}}}{{10 \times {{10}^{ - 9}}}}} = 400{\rm{\Omega }}\)

Surge impedance loading \(= \frac{{{V^2}}}{{{Z_c}}} = {\left( {\frac{{400 \times {{10}^3}}}{{400}}} \right)^2}\)

\(= 400\;MW\)

Given Load \(= 300\;MW\)

Load is lesser than surge impedance loading.

So in order to maintain rated voltage at receiving end shunt inductance is required.