Proper Voltage for Steam Turbine

It is application specific.

Higher voltage makes advantage from the generation angle. Better efficiency (less losses)

at 3.5MW phase conductors will be carrying @6000A current @415V whereas it will be only about 230A @11KV.

But then you have to step down at the user level (assumedly to 415V) - the necessary switch gears will be adding the cost. Then the protections etc.

For our factory, the 220KV line is stepped down to 11KV and fed to each shed. Then in each shed the transformers and substations bring it down to the workning level (ie 415VAC)

The standby generators about 10MVA are also for 11KV. But that is our choice since the factory is distributed over a few sq mile area. If you are going to have the generator just by the side of the shed, may be the 415V may,just, make sense.

And all this will make sense provided you are able to get hold of one that has the 415V rating at this power.