Question

The p.u. reactance of a 25 MVA, 13.2 kV alternator 0.5 pu. On a base of 50 MVA and 13.8 kV, the p.u. value shall be

1. 0.4575 p.u.
2. 0.9149 p.u
3. 1.0000 p.u.
4. 1.8299 p.u.

Answer 1

Correct Answer - Option 2 : 0.9149 p.u

\(\begin{array}{l} {X_{new}} = {X_{old}} \times \left( {\frac{{MV{A_{new}}}}{{MV{A_{old}}}}} \right) \times {\left( {\frac{{k{V_{old}}}}{{k{V_{new}}}}} \right)^2}\\ {X_{new}} = 0.5 \times \left( {\frac{{50}}{{25}}} \right) \times {\left( {\frac{{13.2}}{{13.8}}} \right)^2} = 0.9149\;p.u. \end{array}\)