In my power plant we have mark vi system for two frame Ge 6f gas turbines.
I am looking at the mark vi hmi where I've found gride code block, where thete are various control modes given. Among them there are two controls that catch my attention one is droop and other one is Deadband control

Operators told me that deadband is only active when machine is under 40 MW load (base load is 75 MW). There is a frequency given there around 0.15 Hz. So what is the role of this mode. How it is different from " lower band" which restricts the prime mover respond to frequency under lower band range.
Secondly I've seen some turbines that the droop setpoint is 8%. Which means when turbine speed is at 108% machine comes to no load so how does this is possible as at 105 % and 95 % the 52G opens on under and overfreq protections.

Thirdly in mark VI what are droop set point and reference values.

 

In my power plant we have mark vi system for two frame Ge 6f gas turbines.
I am looking at the mark vi hmi where I've found gride code block, where thete are various control modes given. Among them there are two controls that catch my attention one is droop and other one is Deadband control

Operators told me that deadband is only active when machine is under 40 MW load (base load is 75 MW). There is a frequency given there around 0.15 Hz. So what is the role of this mode. How it is different from " lower band" which restricts the prime mover respond to frequency under lower band range.
Secondly I've seen some turbines that the droop setpoint is 8%. Which means when turbine speed is at 108% machine comes to no load so how does this is possible as at 105 % and 95 % the 52G opens on under and overfreq protections.

Thirdly in mark VI what are droop set point and reference values.

Is there any question/issue that you are facing with....

Or this post is "just for information"

 

Is there any question/issue that you are facing with....

Or this post is "just for information"

kindly read again my post.

 

Ok you asking a question but no "? " ....
Kindly highlight your question by adding "?"
It not a big deal i know but people like to read clear post...

 

Each prime mover's governor (control system) will respond to a change of frequency as a function of the amount of droop that the control system is programmed to have. A 1% change in frequency on a machine with 5% droop will result a 20% change in load, nominally, supposing the machine was running at 80% of load or less to begin with. A unit with 4% droop will respond with a 25% change in load, nominally, again presuming the machine was running at 75% or less than rated load to begin with.

Some manufacturers use the above scenario, what happens to the power output of a machine whose primer mover is operating in droop speed control when the grid frequency changes as their definition of "load sharing".

 

In my power plant we have mark vi system for two frame Ge 6f gas turbines.
I am looking at the mark vi hmi where I've found gride code block, where thete are various control modes given. Among them there are two controls that catch my attention one is droop and other one is Deadband control

Operators told me that deadband is only active when machine is under 40 MW load (base load is 75 MW). There is a frequency given there around 0.15 Hz.
So what is the role of this mode? How it is different from " lower band" which restricts the prime mover respond to frequency under particular range?
Secondly I've seen some turbines that the droop setpoint is 8%. Which means when turbine speed is at 108% machine comes to no load so how does this is possible? As at 105 % and 95 % the 52G opens on under and overfreq protections.

Thirdly in mark VI what are droop set point and reference values?

 

Thanks for clarifying your questions


Here some answers/notes :

1.The dead band filter cause the controller to ignore small in the turbine speed...SUCH AS +/-0.5% FROM speed setpoint ( depending on your application code settings of course)

2.I will have a look on Lower band vs Dead band definition

Widening the dead band filters range to +/-1.5% FOR EXAMPLE increase the range of fluctuations of Turbine speed..
A wide range of dead band can cause the droop governor to dealy in reacting to turbine speed ( such as load rejection)

Because of the delay a Turbine that experiences a fast accelaeration may exceed the overspeed /overfrequency setting!

Other approach is to adjust Turbine speed set point setting to match Grid/load frequency fluctuations , but repeadly adjust speed setpoint is dangerously since it change the overspeed control response ...!

Other approach is multi sloped caracthersitic of the turbine frequency , to use with Droop controller to prevent fasyt overspeed response...and add corrections to the load reference setpoint based and the actual and rated load frequency.......These approachs have resulted in potential excessive values of the spped reference and load reference setpoint , also referred as "WIND UP " wich leads to loss of overspeed control, or overfrequency ...



Which is NEARLY similar the case on your system when GT 52G trip on overfrequency...


There are very good documents describing such control mode !have a good search on the web..

3.As we do not have the application code program of your unit , we cannot tell you what is the Droop settings (setpoint & reference values) ...
You should be able to get these values by a search on the App code program, Or other OEM manuals..


Iam sure that these notes can higlight some points !

Jamal