What will be the voltage regulation of alternator, when it supplies leading pf load?

Correct option is D

The voltage regulation of a synchronous generator is the rise in voltage at the terminals when the load is reduced from full-load rated value to zero, speed and field current remaining constant.
It can be written as

​$$\text{Per unit voltage regulation} = \frac{\Delta E_a \, |V|}{|V|} \\\\\text{Percent voltage regulation} = \frac{\Delta E_a \, |V|}{|V|} \times 100$$​​
where|En|= magnitude of generated voltage per phase
|V|= magnitude of rated terminal voltage per phase
· The voltage regulation depends upon the power factor of the load.
· For unity and lagging power factors, there is always a voltage drop with the increase of load, but for a certain leading power, the full-load voltage regulation is zero.
· In this case, the terminal voltage is the same for both full-load and no-load conditions.
· At lower leading power factors, the voltage rises with the increase of load, and the regulation is negative.