Burned Generator - Repair or Replace

[cslater]

One of my clients had a 200kW generator get back-fed from the utility, which caused the alternator to catch on fire.

They're talking about having us replace the entire generator with the same unit (it was relatively new). I'm wondering - couldn't we just put a new alternator on it?

Is it possible that other parts of the system were damaged? Maybe the controls could be replaced too, I suppose - it just doesn't seem like the engine itself would be damaged.

Thoughts?

 

[waross]

You probably could put a new generator end on the set. Then, if it didn't work, examine the controls to see what else needs to be replaced. The engine, may be perfectly good or may be toast. You haven't told us the nature of the backfeed or the duration. If the unit was running when the event occurred the engine may have sustained a severe torsional shock. May or may not have done damage. It is possible but not likely that the engine was motored for some time that in itself would probably not cause direct damage to the engine but may have filled the muffler and exhaust system with crankcase oil. That leads to the possibility of fire when the oil is burned out of the exhaust system. Think heat damage to objects close to a red hot exhaust pipe and possible ejection of burning oil. As I said, not likely but possible. If the engine was not running when the event occurred, the engine is probably good to go.
You probably need a new voltage regulator.
Given the redundant multiple safety systems and interlocks that should be in place with an approved transfer switch, we may be happier not knowing how the backfeed came to pass. I am sure there are a number of serious code violations and serious OHSA violations. They were most likely in violation of the service agreement with the utility also. Scary!
By the way, I almost forgot to mention; Given the cost of spares and technical labor, it may be cheaper to replace rather than to repair the set.

Bill
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"Why not the best?"
Jimmy Carter

 

[cslater]

Thanks Bill - great info.

I just spoke with the Generator manufacturer and they said very similar things.

For what it's worth, the generator was turned off and there's no outward indication of major failure. There were flames coming out of the alternator during the event.

This is a rather old installation and the ATS controls failed because only one phase dropped. The established procedure for re-energizing didn't have the right safety checks in place either.

There is already a job in the works to completely replace the switchgear and ATS. Rest assured there will be interlocks!

 

[waross]

Thanks for the reassurance.
I can see how a failed ATS could cause this despite the safeties.

Bill
--------------------
"Why not the best?"
Jimmy Carter