recommendations for consultant on medium-voltage rotating machinery insulation condition 1

[electricpete]

On a 13.2kv motor we have partial discharge and loss of the semicon (visible in slot vent ducts and at core exit) on three coils near the line end, appearing 10 years after rewind. (there are lots more details I might post later, but not necessary for this request).

We need to decide among options to address the condition: rewind or reverse the leads and rewind 10 years later. I made a recommendation to my management, but they asked for an independent review.

I've struck out on my top three consultant options. One was busy. Two have have potential conflict of interest that would negate their input in the eyes of my management.

Does anyone have any recommendations for a reputable consultant on this matter?

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(2B)+(2B)' ?

 

[Gr8blu]

electricpete Not knowing who you've already tried, here's who I believe you should seek.
There is the possibility of fixing the condition (more or less permanently) in-situ as well - without switching leads. Contact Integrated Power Services (Houston shop) for details. Ask for either the southeast region engineer or the VP of engineering (they are two different people, but both have the knowledge you seek). Although they might try to push you toward the "fix in place" alternative, they can both act as objective consultants for your other two options.

Converting energy to motion for more than half a century

 

[electricpete]

Thanks.

I know the vp of engineering (initials T. R.). Great choice. Very knowledgeable AND very generous with his time. But there is a potential conflict of interest ;-( Btw I'll mention we have two different repair companies involved....the one that originally rewound it and a different company (competitor) that is currently refurbishing the motor 10 years later, so don't draw any conclusions about any company from that potential conflict of interest.

> There is the possibility of fixing the condition (more or less permanently) in-situ as well - without switching leads

Please explain that.

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(2B)+(2B)' ?

 

[Strong]

How about Motor Doc?

 

[electricpete]

Lol. On that option I'll say "pass".

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(2B)+(2B)' ?

 

[Gr8blu]

electricpete That VP (yes, TR!) has a method to refurbish medium (6.6-7.2 kV) and high (10+ kV) coils without dismantling the whole machine - or usually cutting out coils / swapping leads. Didn't want to say more about it on the forum here - but it DOES work. A fairly large petrochemical company had him apply the "fix" on at least one and possibly two of their 13.8 kV compressor motors about 6-8 months ago. No recurrence of PD/corona (yet) that I know of.

Converting energy to motion for more than half a century

 

[electricpete]

Thanks. Just to follow up I did talk to TR awhile back and he had some very useful info about how to address degrading semicon. He sent a copy of his paper on the subject which will be published in IEEE PCIC in July. He asks that details not be shared publicly before he publishes it.

It's safe to say (without divulging any secrets) the goal (along with repairing any damaged semicon) would be to re-establish electrical contact between the semicon and the core. It is also important to reestablish electrical contact between the semi-con and the grading, but that's not nearly as critical because the partial degradation of the groundwall which can occur in the slot section can be much more aggressive (faster).

We will use that type of approach in conjunction with lead reversal (rather than in lieu of lead reversal). There has been some attack on the groundwall for example we can see look at the side of a line-end coil through a vent duct, the black paint is completely gone and you can see the fiber of the tape (which means some of the tape binder resin is also gone). Although dc step voltage test still passes with flying colors so we don't think that already-degraded line-end groundwall insulation will pose any significant risk as long as we move it to the neutral end).

If I get a chance I will post more details of what we saw on this motor (photos and test results etc).


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(2B)+(2B)' ?

 

[edison123]

I have seen such cures (injecting semicon putty / paint in the slot walls) not work for a long time. More than the PD levels, which are subject to variable interpretations, I trust AC HV test to operation proof the machine.

Muthu

http://www.edison.co.in