Question

The p.u. reactance of a 30 MVA, 13.2 kV alternator is 0.4 p.u. The p.u. value for a base voltage of 13.8 kV and 50 MVA will be
1. 0.667 p.u.
2. 0.638 p.u.
3. 0.383 p.u.
4. 0.610 p.u.

Answer 1

Correct Answer - Option 4 : 0.610 p.u.

\({Z_{pu\;new}} = {Z_{pu\;old}}\left( {\frac{{MV{A_{base\;new}}}}{{MV{A_{base\;old}}}}} \right){\left( {\frac{{K{V_{base\;old}}}}{{K{V_{base\;new}}}}} \right)^2}\)

\( = 0.4\left( {\frac{{50}}{{30}}} \right){\left( {\frac{{13.2}}{{13.8}}} \right)^2} = 0.609\;pu\)