Generator Burning Up

[mkees]

I am very new to the power generation industry, and have been thrown into a sticky situation. I have a couple of large generators (2000kw 13200vac 3 phase). This situation happened before my arrival with my current employer, these generators burned up with very low operating hours. These generators are not standby they are continous run gensets, I didn't mention that they have diesel engines. They are not parellel with the utility, complete stand-alone packages. I understand that the breakers for the gensets were tripping prior to the generators burning up. There is also a transformer mounted between the generator breaker and the load (step down to 600v). I have heard one of the issues could be a corona effect (not sure what it means, but I didn't think it had anything to do with generators). Another theory is that there should have been surge suppression installed between the generator and the breaker, because of the reactive effects of the conductor that connects the generator to the breaker. And still another idea is that the generator windings were bad to begin with and simply failed. Does anyone have experience with anything like this? If so, please respond with ideas.

 

[EEJaime]

MKEES,

Additional information would be helpful. Are these generators paralleled with each other? What type of grounding system is employed-solidly grounded, resistance grounded? Did they fail simultaneously? Within a short time of each other? Do they feed just one single, consistent load, one load each? And what size and what type of load? Was there a load tracking system installed? Was a proper vibration isolation system installed? Have you already researched the original submittals and/or manufacturer's data to assure that these in fact are continuous duty rated machines? There certainly seems to be something about the installation that is causing this. If this is one of the major manufacturs, Caterpillar, Cummins-Onan, Detroit Diesel, etc..., you need to contact the factory and get there assessment as well. I am sure they don't want the reputation of their equipment just "burning up" and should be eager to find a cause.

It would certainly be interesting to find out what caused this. We have many installation of similar size running as both standby and co-generation. Hope you find a solution and keep us abreast. Good luck.

 

[ScottyUK]

What 'burned up'? The insulation or the core? What was the appearance of the affected area? Was it the rotor or stator affected?

Partial discharge activity on the winding is certainly a possibility at that voltage. It would have to be either very aggressive or the maintenance inspection has missed it to cause a failure before it was noticeable. Corona seems a little unlikely - perhaps the terms are being confused?


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I don't suffer from insanity. I enjoy it...

 

[mkees]

Fellows, thanks for the advise, it seems I have lots of questions to ask, and I will ask. These generators are manufactured by one of the major manufacturers, which is another problem, since they are saying their generators don't fail, I've been around long enough to know everything fails at some point, but these are still under warrenty.

 

[waross]

I think that this may be a pointer to the problem;

I understand that the breakers for the gensets were tripping prior to the generators burning up.

When a generator breaker trips, it is common practice to investigate and rectify the cause of the breaker tripping.
If the breaker is repeatedly reset, a failed generator is not surprising.

There are a lot of possible causes;
We must know if the generators were operating singly or in parallel with each other or in parallel with other gensets.

If a new set is added to a lineup of existing sets and the governor is not configured to match the other governors, the new set may "hog" the load.

Are the sets being paralleled with other sets and the governors are set to Autogenous?

With low hours, I suspect something like a mistake in the protection or control wiring, or a configuration issue with the AVR, or or with governors.

The bottom line is:
We must find out why the breakers were tripping and rectify this problem, or the replacement generator ends will probably fail also.
respectfully

 

[mkees]

Fellows,

Thanks for the help, I still haven't gotten all the questions answered, I do know tghis is a parellel operation know seems to know much else. I am going to the job site this week, to check it out myself. I did here from an independent testing agency and some of their findings are that the windings were poorly insulated. These generator have been working fine since they have been replaced.