Why Is Isolated Neutral Preferred In Some Generators?

[SteamTurbine]

Dear engineers,

I need your help in analyzing this query:

Our plant consists of 11x 635 KW, 415V Waukesha gensets, 2 x 3.5MW,11KV wartsila gensets, 11 KV main bus for synchronization & 10 MW,11KV, 50 Hz gas turbine. The neutral of gas turbine is earthed against the manufacturers recommendations.

Now, a 2.7MV, 11KV, 50 Hz steam Turbine is being added to the system whose neutral is recommended to be earthed. but before taking this action the Neutral of existing Gas Turbine is to be un-earthed.

So, Under which conditions the Neutral of a generator should be earthed & what are the conditions when "isolated neutral" is recommended?

I am not asking from manufacturer's point of view but I am simply asking from synchronization point of view. Any questions will be welcomed!

THANKING IN ADVANCE :)

 

[anorlunda]

Huh? I can't think of any connection to synchronization.

Grounding practices have to do with unbalanced loads, and especially short circuit conditions.