Question

An 800 kV transmission line has a maximum power transfer capacity of P. If it is operated at 400 kV with the series reactance unchanged, then new maximum power transfer capacity is approximately

• A. P
• B. 2P
• C. P/2
• D. P/4

Answer 1

The correct option is D P/4

Power transfer capacity $\propto V^2$
$\frac{P_1}{P_2}=\frac{V_1^2}{V_2^2}$
$\Rightarrow P_2=P_1\times {\left(\frac{V_2}{V_1}\right)}^2$
$=P\times {\left(\frac{400}{800}\right)}^2=\frac{P}{4}$