Why Is Isolated Neutral Preferred In Some Turbines/Generators?

[GT]

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 :)

[admin]

You can only have one neutral solidly earthed at each foltage level, w/o causing spurious tripping problems for sensitive earth fault relais systems.

[Author]

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