QUESTION
We have a large 10 MW 6600 volt synchronous generator that was rewound in 2016. Lube oil was leaking inside the generator from DE bearing which caused a dirty winding. We performed a megger test (5 KVdc - 1 min ) and all readings were good and more than 2G ohm.
- What is the effect of operating the generator in this case?
- How can we clean without dismantling the generator? (We do not have the ability to pull up the rotor shaft from the stator.)
- Which solvent we can use ?
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REPLIES
iceworm
2016 NFPA 70B Recommended Practice for Electrical Equipment Maintenance (2019 is published, I have not seen it yet - I suspect little difference in this area)
Chapter 25, Rotating Equipment recommends using a cleaning solvent.
Alstrom generator maintenance manual recommends using “white spirit” (Yep, turpentine - paint thinner). And don’t let the solvent soak into the windings.
Most of the techs I work with like CRC Electro-Clean. After a wipe down (as recommended by Edison and Bill, they will get a case of the CRC, spray, wipe, meg after dried.
Considering the capital investment was $10M - $20M, I highly recommend getting out the mfg maintenance manual and following their recommended procedure - really, that first.
All the maintenance specs say oil contamination degrades the insulation. It needs to be cleaned up.
Personal opinion:
As said, wipe up all you can.
Spray solvent and wipe the rest.
Thoroughly dry and meg before putting into service
SOURCE
https://www.eng-tips.com/viewthread.cfm?qid=451515
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