Isoc/Droop Control

[tenntech]

I was just trying to get a full understanding of the purpose of Isoc / Droop Control and at what time would be best to be in each mode. All help would be appreciated!

 

[EEJaime]

Are you referring to Isochronous syncronization of a generator system?

 

[davidbeach]

Search this forum for those terms, lots of discussion.

 

[tenntech]

Yes,
Combustion Turbines
Droop control
Isoc operation

 

[byrdj]

first, need to know that generation must equal load exactly or the frequency will change. load greater, frequency down.
with that understanding, the turbine's governor is used to control system frequency by varing the generator's output.

In droop, the frequency will only be 60.000 Hz at SET output. with a 5% droop setting, and the SET output at 50%, if the frequency increased to 61.5% due to load shedding, the turbine will back the generator output to 0%. Droop is normally used when synched to a large grid.

In Isoc, the governor will try to maintain 60.000 Hz at all times. thus if operating at 50% output and the frequency droops to 59.99, the turbine will go to 100% output. in isoc, the stablity is determined by a time constaint, ie how fast will the unit change load as per the deviation. Isoc is normally used when in island mode, ie small system and only one T/G

Since large grids are constaintly varing speed as every light is switched on or off, a unit in isoc would be swinging wildly. And since the droop governor will not correct back to 60.000, dispatch watches a grid clock and changes the T/G SET output to correct to bring the daily average to 60.00 hz. thus the dispatcher becomes the isoc governor