Question

In a system, there are two generators operating in parallel. One generator, of rating 250 MVA, has an inertia constant of 6 MJ/MVA while the other generator of 150 MVA has an inertia constant of 4 MJ/MVA. The inertia constant for the combined system on 100 MVA common base is MJ/MVA.

• A. 21

Answer 1

The correct option is A 21
For 250 MVA generator
$H^{\prime }=\frac{250}{100}\times 6=15MJ/MVA$
For 150 MVA generator
$H^{\prime }=4\times \frac{150}{100}=6MJ/MVA$
$H=15+6=21MJ/MVA$