Bus Duct Noise and Vibration

What type of noise? Electrical or mechanical? Have you taken electrical readings? What did you get? Is the Generator loaded when the noise occurs, or unloaded? How old is the generator? Has any maintenance been done recently? Have you looked for hot spots with IR? Has the generator been megged? ...any signs of flashing?

It is not old it made at 2011 alstom type . The sound come in loadind and no loading but when switch of the DC excition voltage the sound gone . I mean the sound come when generator build the voltage . The sound electrically with vibration

...then the equipment needs to be isolated and repaired.

Sounds like you are arcing to ground....could be insulator failure, or you might have a small rodent or snake that has been caught in the wrong place, at the wrong time....

Is it time to arrange a call-out with a Service Engineer from <...alstom...>?

I would look at the bus duct conductor supports for loose mounting hardware. When you switch on the excitation, you now have magnetic forces acting on the conductors, where with excitation off, you have only the mechanical excitation of rotor balance, bearing eccentricity, and other forces relating to the purely mechanical components.

If you are able to switch on the excitation at a low speed, then raise the speed to normal, i.e. 40Hz to 50Hz, then the pitch of the sound should change, supporting the concept of magnetic forces being the excitation for the vibration. Good test to spin it up with no excitation, BTW.

So that you mean that the problem with the support of busbar ?

Possible, or the attachment of conductors within the stator laminations, perhaps less likely. When you say near the neutral, you mean physically, not electrically, I assume

...plus there should be a fault-finding section in the Operation and Maintenance Manual that was supplied with it, plus there should be telephone numbers therein with which one might readily contact <...alstom...> for advice.

If possible give separate excitation from an external source and see whether the same noise comes.If so problem with bus bar support othersise need to check exciter