Frequency setpoint on island mode
Frequency setpoint on island mode
(OP)
On site we have a GE generator with Mark VI control system. The logic has the island mode scheme, when there is a load rejection somewhere upstream to the grid the turbine increases speed with a specific acceleration and when this happens the turbne goes to island mode supplying the auxiliaries of the plant. During the island mode operation the gas turbine keeps constant speed and the generator runs at 49.94 Hz, slightly lower than the 50Hz of the grid. The auto synch function of th eline breaker (52L) did not work becasue the synch scope rotated counter-clockwise and there is no facility to increase the frequnecy by increasing the gas through SRV. Can you advise on this issue? GE was made aware but with no actual work on that item. When you synchronize to the 52G breaker the turbine runs at 100.3% of nominal speed so the generator is alwways higher than the grid in order to have bumpless synch.





RE: Frequency setpoint on island mode
RE: Frequency setpoint on island mode
RE: Frequency setpoint on island mode
RE: Frequency setpoint on island mode
Trans-Canada Turbines
TC Power
I've no connection either of them but they both do a lot work on GE aeroderivatives. Maybe worth an email or phone call.
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Sometimes I only open my mouth to swap feet...
RE: Frequency setpoint on island mode
http://www.pondlucier.com
RE: Frequency setpoint on island mode
But a thought-
If the rated speed referance is a non adjustable referance. then couldn't the calibration of the speed pickups be trimmed to provide the desired frequency (50.00?) when in isoc. This is the technique I use on one of the early Mark ST controls
RE: Frequency setpoint on island mode
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Sometimes I only open my mouth to swap feet...
RE: Frequency setpoint on island mode
In "droop", increase (or decreased) LOAD referance will result in a speed change to allow you to synch
Off subject I was in one country where the speed pulse to auto synch was removed since the grid swings were so bad and Yes, it was luck.
RE: Frequency setpoint on island mode
You need to transfer out of isochronous mode to droop before synchronizing 52L
If the unit is under warranty, just send a warranty claim. If the unit is not under warranty, call your service manager.
saludos.
a.
RE: Frequency setpoint on island mode
RE: Frequency setpoint on island mode
When the breaker closed we received the alarm
Q 1273 ALM FSR LIMITED DUE TO DWATT XDUCER FAILURE.
The output of GT remained lower than 2 MW 5sec after synch.
Also after the synch GT stayed to almost 0 output but with steady FSR (19%) and exhaust mass flow. That probably means that the generator synchronized with wrong angle because in order to have power transfer between two networks the voltage angle difference should be higher than 0, with the generator vector to lead the grid vector. Tell me if this is a correct explanation.
RE: Frequency setpoint on island mode
Again, not GT familair, But if the unit is slow freq in island, that might be the speed pick up translator is mis calibrated with too high output. Now when you synch in droop, the miscalibrated higher speed referance is negating the minimun load referace and you stayed at zero load. Just my wild a$$ guess.
RE: Frequency setpoint on island mode
The problem you are facing is one of oversight during the engineering.
One temporary solution would be to force out the signal that picks up isochronous mode as well as the latch that keeps isoch selected... the unit will default to droop
In the meantime, where are you located? May be it is just a matter of who you know and not what you know...
This seems like a very straightforward problem.
saludos.
a.
RE: Frequency setpoint on island mode
I'm not sure what 'FSR' is an abbreviation for, but a technique we use on bigger Westinghouse turbines is to apply a small step of a couple percent in throttle position immediately on breaker closure. This ensures that the unit immediately takes up load and avoids the problem where the MW transducer reading goes bad. Incidentally, it is worthwhile ranging your MW transducers to ensure the data remains of a 'good' quality even if they go slightly negative. It stops annoying problems when the machine has a slightly rough sync and oscillates a little as it finds its load angle.
I am aware of problems with turbine pressure transmitters upsetting the control scheme on our LM6000 by preventing the throttle demand increasing. Not my area of expertise, but I will ask around for a little more info if I remember.
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Sometimes I only open my mouth to swap feet...