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hello

We have 2 turbines generators MS 6001B control System MKv TMR <I> connected to the grid running in Droop mode.

My question is what are the risks of keeping the turbine in Preselected load (e.g 37 Mw)in case of surges or huge hunting loads. Since as far as I know the preselected load mode is disabled only(?) when i operate the governor manually.

Thanks very much in Advance.

What causes the distrubances? Frequency excursions? Fuel supply disruptions? Dirty oil?

Preselected Load Control causes the Speedtronic to adjust the fuel to try to maintain the Preselected Load Setpoint. If the instability is caused by frequency excursions, then the Speedtronic will NOT be properly responding to frequency excursions as a unit running in Part Load ("manual") control would. Preselected Load Control will over-ride the speed error caused by the frequency excursion to try to maintain the Preselected Load setpoint, which is not what one really wants to happen during frequency excursions.

But there is no risk involved in operating a unit at Preselected Load Control--except for the issue of frequency response as described above.

If the surges or swings are caused by other factors, then operating on Preselected Load Control might help, but it might also make the load swings more exaggerated. It all depends on the frequency and the cause.

So, without understanding the causes of the surges and swings, which are NOT normal and should not be considered normal, its very difficult to respond concisely.

If you have specific concerns based on experiences, please provide the details.

Thanks for responding this post.

The question is about the behavior of the generator against big disturbances of frequency in the National grid [Argentina] where we are connected to, being in Preselected Load Control.

So as you explain is not convenient to operate the turbine on that mode since the Speedtronic Control system is not going to react as should be. Is that right?

PS: We were told to keep the generator on this mode just to provide a fix rate of load to the grid, which i was not very sure if was for better doing it in that mode.

Thanks very much again

Preselected Load Control is really just a lazy man's way of not having to manually make small adjustments to the load.

If an operator manually loads a unit to a desired value, or even if it's loaded to a set point using Preselected Load Control and then Preselected Load Control is canceled effectively leaving the unit in straight Droop Speed Control (just as during manual loading/unloading) there will be very little drift from the value. The amount of load will be affected by ambient conditions (changes in ambient temperature), but that's about all. The variance from the load it was "parked" at will be usually be quite small and
and negligible.

No; operating a GE-design heavy duty gas turbine with a Speedtronic turbine control system at Part Load with Preselected Load Control enabled is not a wise way to operate units which are expected to respond in a normal manner to grid frequency disturbances.

GE will be glad to sell you a fix for their little 'oversight' in this matter; it's called (inappropriately) 'Primary Frequency Response.' (Pretty cool, huh; getting owners to pay for fixing errors in code.)