About Governor speed droop settings

[b.shahvir]

Hi all,

Can someone pls. elaborate on the following;

1) Advantage/disadvantage of very low governor speed droop setting and why...

2) Advantage/disadvantage of very high governor speed droop setting and why...

The ideal droop setting is normally recommended to be around 4%... Pls. comment.

Thanks & Kind regards,
Shahvir

 

[b.shahvir]

Someone pls. reply!

 

[Jobrag]

If you have a very low droop setting the load on the machine will be very sensitive to small frequency changes on the bus.
If you have a very high droop setting the speed set point can be such that if your breaker trips you drive into overspeed.

 

[b.shahvir]

If you have a very low droop setting the load on the machine will be very sensitive to small frequency changes on the bus.

Thanks, but could you pls. elaborate a bit more on the above; i.e. load being sensitive to small frequency changes on the bus?

Regards,
Shahvir

 

[Jobrag]

When running in droop the load on the machine is proportional to the difference between the speed set point (set on the fuel controller) and the actual speed that the machine is running (bus frequency).
Lets put some numbers in
50 Hz system
100 MW machine
4% droop
4% droop equates to 2 Hz so for every 1Hz difference between set point and bus frequency the load will be 50 MW

Suppose you put the set point at 51 Hz the machine will load to 50 MW, but if the bus frequency now drops to 49.9 Hz the machine load will increase to 55 MW if it increases to 50.1 the load will decrease to 45 MW.

If you reduce the droop to 2% the effect of changes in the bus frequency will be doubled etc etc.

 

[b.shahvir]

Dear Jobrag,

Thanks very much for reply. Can the Generator system become unstable as a result of low droop settings? how serious can it get?

Best Regards,
Shahvir