White powder in generator stator 1

[npower0073]

Dear all. On iste we have a 324 hydrogen cooled generator of GE. During last outage we opened the end shields, GE made the MAGIC inspection and also inspection on the stator. It was found signs of white powder on the end windings. It was all over the end windings where some type of tightening material is used to keep the windings attached.
I have seen some comments on the old thread thread605-148662.
Can you give me some idea for a possible casue? I suspect that the specific tightening material is not the fit for purpose one.

 

[rmw]

You don't give the age of the generator or the hours of service, but the fact that you are opening it would indicate that it must have some age on it. Without further information I'd give the same answer here that I did in the thread that you referenced. White powder inside a generator (especially one that is not air cooled) is always potentially an indication of corona activity.

There is a lot of information in the trade publications and technical literature about corona. I'd suggest that you do some googling or research on the topic. I think you will be disheartened by what you will find.

rmw

 

[npower0073]

Hi rmw. The generator has run from January 2006. It has less than 2 years of operation and this was the first inspection. It is a brand new generator. We also installed partial discharge capacitors for insulation monitoring but it is still pending some hardware. This poweder was found mainly on the end winding area.

 

[MJCronin]

I think your generator may have a substance abuse problem...

 

[electricpete]

Both partial discharge and abrasion of endwinding bracing may be possibilities.

To distinguish you need to look closely at the pattern. PD will have patterns that can trace to voltage stress. For example stronger phase-to-ground pd at line-end coil and possibly stronger phase-to-phase pd between pole phase groups (that's a little trickier). Abrasion would be more uniform.

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[electricpete]

Also you could do chemistry analysis of the powder.

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[rmw]

Enough freedom of movement to cause abrasion should be evident in loose blocking and bracing.

I picked up a brochure from

http://www.agtservices.com

at a recent trade show dealing with dusting due to abrasion and showing examples of corona dusting vs abrasion dusting, but I don't see it on their website. You may be able to contact them and get one sent to you.

rmw