400MW Generator pulling too many MVARS (lagging power factor)

[GamecockEngr]

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!

 

[waross]

Good point Pete. If the grid voltage drops and the AVR does not make a correction, expect a lot of VARs.

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

 

[GTstartup]

Please read the OP again.

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.