MVAR Spikes

[Anonymous]

Hello,
We’ve noticed a large spike in MVAR output when our Units approach minimum load. See link below to .jpg of graph. It seems to be caused by large difference between the voltage setpoint and machine voltage when the remote setpoint becomes active (like a step response).

Are there any other members experiencing these large MVAR spikes? How was it resolved?

The operator is not changing the voltage setpoint during startup. Is there a reason the control logic would automatically change the voltage setpoint?

Also, Should we be concerned about damage to the generator? The MVAR spikes are occurring during daily startups. I understand that generators are designed to withstand short periods of overload but I’m unsure of the unit’s capability to withstand these spikes on a daily basis.

AvK Generator Rating: 10.549 MVA, 80% pf

AVR: ABB Unitrol 1000-15

Link to .jpg of Graph

Thank you

• This topic was modified 5 years, 4 months ago by .

[Anonymous]

We don’t use the remote setpoint option.

We are not seeing the spike.  However, shouldn’t the remote setpoint match the plant setpoint prior to swapping over.  Back in the old days when we had to manually swap from auto voltage control to manual voltage control it was a big “no no” to swap without matching.  Not only do you have to consider what it’s doing to the machine but all of the auxiliary equipment seeing the spike – assuming you’re supplying house power.

[Author]

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