generator power problem

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mark480

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I am a electrian with a waste water plant and we had a problem with our new generator.We got a stand by 700kw generator to provide emergency power.The connections were tied in to a juntion terminal were the existing generator was connected.My partner and I connected the 480v with a ground from the standby generator. I checked phase rotation on both existing & stanby gens.Started the 700kw stand by with the existing generator disconnected. When our plant transfer switch connected to emergency power the lights(fluorescent) flickered and we lost 12 electronic ballasts only on 1 circuit.The system we have is 480/277 4wire.We checked voltage & 60 cycles at the lugs in the stand by gen it was ok.We both considered voltage regulation but the gen was ok.When we fixed the plant new gen everything ran fine. My partner and I both licenced electricians have different theories.My concern is were we connected the gen.From the tranfer switch is boy, neutral & gr and the gen standby had boy with the ground connected to the metal large juntion box.I can go on and on what is your take on this. thanks one hard working stiff.... :confused:
 
Re: generator power problem

To give more info the tranfer switch is 2500amp and the neutral appears to be unswitched at transfer.Normally we connect at the tranfer switch emergency power lugs but in this case the gen wires did not reach. My partner told me they never use a neutral when hooking up a standby gen.They hook up 3 phases and put the ground to a lug to the equipement ground.My problem in disagreeing is the standby gen is not seeing a neutral and is using the conduits for a path back to the transfer switch.I also observed that the terminals for the neutral and grounds were on insulated parallel lugs.So the ground and neutral were isolated from each other.My theory is the ground was acting like a neutral.I hope this helps with my question .. thanks alot :)
 
Re: generator power problem

Sounds like you didn't run a neutral or at least hooked up the neutral from teh standby generator?
With out a neutral you would have floated the 277 loads between the 480 volt lines.
This is just like looseing a neutral in a single phase service or multiwire circuit, If one side of the circuit draws more current it's voltage will go down but the side that draws less current will go up, kind of like a see-saw effect.
In any service that uses a neutral you must provide one.
This has nothing to do with how the grounding is done other then yes the grounding could have been acting as the neutral, which would tell me that it is bonded at both the generator and the service (parallel) if the neutral would have been connected.
 
Re: generator power problem

Wayne thanks for the reply and I totally agree, I think these guys at work must of had the neutral connected some where along the line. I wonder if the standby gen had the neutral and ground connected in the past.The terminals are isolated from each other and some guys jump the wire from the neutral to the ground and run 1 wire to the building to save on pulling a neutral.I not saying that is correct but i can`t see how they never had a problem.the ballasts that blew out were only on one circuit and the numerous lighing circuits were not damaged.
 
Re: generator power problem

Hey guys sorry for the poor spelling,working 14 hour shifts.should of used spell check
 
Re: generator power problem

it will work using the ground and neutral on one conductor, if the generator neutral ends up connected to the panel neutral bar but it won't be safe or meet code.

it won't work without the generator neutral connection making it all the way through the transfer switch and connecting with the panel.

generator neutral may be bonded with generator ground on old generator and isolated on newer generator.

you have to have a neutral if there are line-neutral loads in the panel
 
Re: generator power problem

I got it I wish my partner did.... His theory of not hooking up the neutral up with the standby gen was that the neutral from the transfer switch (normal project power)is connected to the transformer and this always worked.ALL OF THIS BECAUSE HE DID NOT WANT TO RUN A PARALLEL 4/0 NEUTRAL WIRE.He is getting old lol :)
 
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