Dear all,

Our gas turbine is MS5001PA-DLN generator, rated 21MW. When it works in Iso. mode, the power of Generator at 17MW which supplies for our plant only. I synchronize my Generator to the grid. The power is very high vibration, The peak is 25MW.
Are there any problems for my generator?
And why is the overshoot power so high?
How can I reduce the overshoot?
Are there any problem with our synchronization system?

Best regards,

Hung

 

You seem to be saying that when the unit is operated in Isochronous mode everything is fine. Then you say that when you synch the unit to the grid there is some problem. You mention high vibration, but say the "peak is 25 MW".

Are you synchronizing with the grid at an Isoch load of 17MW? Or, does this just happen when you synchronize to the grid from Full Speed-No Load?

What does high vibration have to do with 25MW? Isn't the unit nominally rated at approximately 25MW?

Are you saying that after synchronizing the unit the load is spiking to 25MW? Is this from FSNL or from 17MW? How long does it take for the spike to occur? How long does the spike last? What fuel is the unit running on?

The thing that concerns me about this posting is not so much the possibility of damage to the generator, but damage to the turbine. DLN combustor-equipped units can experience catastrophic failures much easier than conventional combustor-equipped units. What is the combustion mode you are operating in when running in Isoch mode: Lean-Lean and Extended Lean-Lean? If you are synchronizing to the grid while running at 17 MW, what combustion mode is the unit in just prior to synchronization and after synchronization? Is the unit automatically transitioning to Premix combustion mode after synchronization or do you have to manually unload/load the unit to affect the transition to Premix combustion mode?

Where does the high vibration occur? During synchronization? During the combustion mode transfer? When running at 25MW?

Please be more specific about what speed/load you are running at when synchronizing, what combustion modes the unit is operating in before and after the synch'ing, when the high vibration occurs, etc. It's just not clear exactly what the problem is.

 

Excuse me for trying to interpret, but I feel it might help the poster. It appears to me that the poster is trying to say 'fluctuations' when he says 'The Power has high Vibration' and the peak fluctuation is 25MW.

Regards,

 

Just guessing! Sounds like fall has arrived and cooler outside temperatures have allowed the turbine to PERFORM and exceed it's rated capacity. Isoch limits your output to plant needs. Sync to the grid will try to obtain all the MW you can produce depending on droop settings.

Limit the generator output to 20MW until you have resovlved you balance/load problems in the generator. Possible issues are in the DLN. Did not specify which bearing was vibrating excessively.

 

Hello,

Our MIKV has two modes for governor
"Droop" or "ISO". Sounds like you typically run your unit in "ISO" mode and are not connected to the grid. Question: do you change the governor mode to "Droop" before closing the breaker which ties you to the grid?

If you are running with droop and tied to the grid,the grid has control of system frequency, your unit is magnetically interlocked and produces at the same frequency as the grid.... since fuel input is constant, you will see MW load changes on your unit if there are frequency changes in the grid.

Is the grid frequency stable?

Best wishes
RTK

 

RTK brings up a good possibility. Most *but not all* control systems are programmed to automatically switch from Isoch to Droop when the unit is re-synchronized to the grid. If yours is not you must select Droop just before re-synchronizing to the grid or when the breaker closes the unit will likely suddenly increase output and may even experience sudden load swings when the breaker closes--which may be the "vibration" you are reporting. If you must manually select Droop when re-synchronizing to the grid you must do so immediately before re-synchronizing to the grid, not after re-synchronizing.

Again, it's not so injurious for the generator but more so for the turbine and load gear and load coupling.

 

The answer could be simple to this 'issue'. The unit is is running in low frequency (the turbine is forced at a lower speed) to gain on the load output after synchronising with the grid!