Generator out of phase-shutting down

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Tank11

Member
Location
CO
I am working on a project where a generator is feeding a panel with loads that are inconsistently on/off. Therefore the phase balancing is never predictable and when fed upstream by a generator (during loss of grid power), the generator is shutting down.

What are possible solutions? Is a load bank available that can monitor phase loading and supplement as needed?

Any help is appreciated.
 
Tank11 said:
hen fed upstream by a generator (during loss of grid power), the generator is shutting down.
Click to expand...
What does that mean? Is the generator mentioned in the first sentence being then fed by a second generator? That itself could be a problem.

Almost all modern generators larger than maybe 10kva have electronic controls and will tell you why they shut down. As for load balance, that makes almost no difference to most generators, nor does changing loads.

That aside, I assume that the generator isn't overloaded or being hit by a terrible power factor.
 
Is the generator diesel, natural gas or propane? If natural gas or propane, one possibility is the gas line is too small. With the limited information given, it is one thing to check if increasing the load shuts down the generator.
 
Like they said, we’ll need a lot more info.

It’s very possible the generator was not sized properly for all the inrush current.
 
Thanks for all the comments, here are some clarifications:

-There is one generator only, feeding a panel through an ATS. When grid power is lost, the transfer switch turns the one generator on and it is shutting down.
-Maintenance is stating the loads are unbalanced and that is the reason for shutdown
-The generator is diesel fed
 
Tank11 said:
Thanks for all the comments, here are some clarifications:

-There is one generator only, feeding a panel through an ATS. When grid power is lost, the transfer switch turns the one generator on and it is shutting down.
-Maintenance is stating the loads are unbalanced and that is the reason for shutdown
-The generator is diesel fed
Click to expand...
It sounds to me like it isn't the unbalance per se that is the problem but it's that the load on one line is pulling more amps than the generator can deliver on that line.
 
3 phase I’m assuming?

Someone needs to put a data logger, or even a recording ammeter on it, to get an accurate idea of what’s going on, along with a load Calc.

Right now it’s just speculation.
 
Just throwing this out there. We had a situation where we had to put large motor equipment on delays during transfers. When the loads transferred with all equipment there would be generator shut downs at times, after we delayed some equipment problem was solved.
 
Tank11 said:
Thanks for all the comments, here are some clarifications:

-There is one generator only, feeding a panel through an ATS. When grid power is lost, the transfer switch turns the one generator on and it is shutting down.
-Maintenance is stating the loads are unbalanced and that is the reason for shutdown
-The generator is diesel fed
Click to expand...
For ANSI 46 to be part of the generator protection elements, the generator must be expected to be loaded with unbalanced loads. What is the expected unbalance loading possible? You must know this fact for you to properly set the negative phase sequence current protection setting and prevent nuisance trips.
 
Tank11 said:
Thanks for all the comments, here are some clarifications:

-There is one generator only, feeding a panel through an ATS. When grid power is lost, the transfer switch turns the one generator on and it is shutting down.
-Maintenance is stating the loads are unbalanced and that is the reason for shutdown
-The generator is diesel fed
Click to expand...
I had a diesel generator that was doing that at a Lowes. The local techs couldn’t figure it out, so the manufacturer sent someone out, while we were standing there while it was running at night, the manufacturer’s tech noticed all but one of the ports of exhaust was glowing red. Turns out, it was running on five cylinders instead of six, so the heavy load was shutting it down.
 
ptonsparky said:
Sounds like an imbalance.
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Would an imbalance be a problem as long as no line was being loaded more than the generator's ability to service it? Household generators are virtually always presented with unbalanced loads. It seems to me that a 20kW split phase generator should be able to supply 10kW (83.3A) at 120V per phase, and if either phase is loaded more than that, the generator will shut down even if the total load is drawing less than 20kW.

DISCLAIMER: I do not deal with generators very much and I could be totally wrong.

ASIDE: Some battery backup systems run their output through an autotransformer so that both phases are loaded the same no matter how much the load is unbalanced.
 
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