400MW Generator pulling too many MVARS (lagging power factor)
400MW Generator pulling too many MVARS (lagging power factor)
(OP)
We have checked the voltage meters used to sync and they are good as are the PT's used to read the voltage. We just installed a new excitation system. The generator terminal voltage is controlling to the proper set point and the dc is balanced perfectly. Here is the problem...when we tie on the MVARS are running ~60-80 MVARS at almost no load (5-10 MW). Usually we run 0-10 MVARS at 0-10 MW. The power factor is .1-.3
What could be causing this in the excitation system?
I am a dumb flange head (mechanical engineer). I need help with this stuff!
What could be causing this in the excitation system?
I am a dumb flange head (mechanical engineer). I need help with this stuff!





RE: 400MW Generator pulling too many MVARS (lagging power factor)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
I am hesitant to give too much specifics because in the off chance someone reads this I dont want to get in any hot water if we have a warranty claim on the OEM.
RE: 400MW Generator pulling too many MVARS (lagging power factor)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
Plus check you are not actually in Field Current control.
RE: 400MW Generator pulling too many MVARS (lagging power factor)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
You could also try putting the AVR in manual and try adjusting the field voltage to see if you have any control at all.
I suspect the AVR is not getting the correct sensing voltage - could be a line-neutral voltage when it is expecting a line-to-line. A 400 MW generator should be able to move the system voltage a bit.
I'd walk back through the PT connections, PT ratios, and AVR configuration.
RE: 400MW Generator pulling too many MVARS (lagging power factor)
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If we learn from our mistakes I'm getting a great education!
RE: 400MW Generator pulling too many MVARS (lagging power factor)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: 400MW Generator pulling too many MVARS (lagging power factor)
"when we tie on the MVARS are running ~60-80 MVARS at almost no load (5-10 MW). "
Is this immediately on synchronizing? If yes, then it's not an AVR issue but a synchronizer issue.
RE: 400MW Generator pulling too many MVARS (lagging power factor)
May you grow up to be righteous, may you grow up to be true...
RE: 400MW Generator pulling too many MVARS (lagging power factor)
We know.
"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)
RE: 400MW Generator pulling too many MVARS (lagging power factor)
Bill
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"Why not the best?"
Jimmy Carter
RE: 400MW Generator pulling too many MVARS (lagging power factor)
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Eng-tips forums: The best place on the web for engineering discussions.
RE: 400MW Generator pulling too many MVARS (lagging power factor)
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: 400MW Generator pulling too many MVARS (lagging power factor)
As other have indicated, drop your voltage and the VARs will follow. If your unit has picked up VARs after a long period post syncing, your bus conditions have changed and the unit is boosting VARs to attain the voltage set-point. This is normal.
RE: 400MW Generator pulling too many MVARS (lagging power factor)
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 400MW Generator pulling too many MVARS (lagging power factor)
Quote
"when we tie on the MVARS are running ~60-80 MVARS at almost no load (5-10 MW). Usually we run 0-10 MVARS at 0-10 MW. The power factor is .1-.3"
The voltage setpoint at synchronizing is set by the synchronizer. It is unlikely that the voltages match just at synchronizing and then just after synchronizing the system voltage changes, or even if the AVR setpoint changes.
It is more likely that the Unit is synchronizing with too high a voltage.
A 400 MVA generator with a 4-5% voltage difference at synchronizing, depending on generator Xd and system reactances, could easily result in a reactive power of 60 mvar.
In my opinion, the synchronizer is synchronizing at the upper limit of the voltage window.