I have a question i was curious about adjusting frequency on a finite grid before synching in with an infinite grid.

If i say am operating a small island with 3 3mw generators or 9mw capacity, providing power to a small grid of at the time say 4.5mw and i am trying to raise the frequency in order to match the infinite grid frequency before i synch what other variables are being changed when i raise the frequency. I hope this is clear i'm just trying to get a proper understanding as i have had trouble explaining this to others as to what is happening when you are raising frequency when under some load but disconnected from the grid mainly what variables are changing.

Thanks

 

Presuming one of the units is operating on Isochronous control, the only thing you are changing is the turbine speed control reference, to "match" the infinite grid frequency (which is directly proportional to speed per the formula:

F = (P * N)/120

or

N = (120 * F)/P

where, F = Frequency (in Hertz)
P = Number of poles of the generator
and N = Speed (in RPM)

More speed equals higher frequency; less speed equals lower frequency.

Whether you're synch'ing one generator or three, the frequency of the "incoming" generator(s) has to "match" (usually be just slightly greater than) the frequency of the "running" system being synch'ed to. Frequency is directly proportional to speed, per the formula above.

It's as simple as that.

And, even if you are running all the generators in Droop mode, you still are changing the turbine speed reference of at least one when you are attempting to "match" frequency.

Hope this helps!

 

Ok great thanks. so it's that simple. I kinda already knew that. but was really wondering If I'm generating a load on a finite grid and about to synch to an infinite grid when I raise or lower the frequency of my island to match the Grid am I affecting proportionately any other factors other than speed. Such as amps kvars voltage etc.. In my mind I thought there was some change under load as you raised or lowered the frequency but maybe I'm making it more complicated than it is.

Thanks alot CSA I've read alot of your post and gained alot of understanding about power generation theory.

 

Thanks alot, just one more thought i wasn't sure that if you raise or lower the frequency it didn't change any other variables such as voltage amps vars etc.. for some reason i thought there was something it affected.

Thanks again CSA I have read many of your post and have learned alot and brought understanding to many concepts i wasn't quite clear about.