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Steam turbine governor control swing
Power generation equipment control. topic
Posted by pichetp on 4 April, 2011 - 9:23 am
The governor of steam turbine (Kawasaki) is swing even though the sliding pressure control mode is on. And,there is a "KW Limit" alarm from the woodward 505 governor control unit. If the setting parameter of woodward 505 remain unchanged. what is the root cause to governor swing? and, Why the governor control unit generated alarm "Kw limit" while increased the output ramp and the actual kw output of ST generator did not reach the kw limit about 38MW?
When, the Generator kw limit is 41.25kw

pls. advise


1 out of 1 members thought this post was helpful...
Posted by Phil Corso on 4 April, 2011 - 1:53 pm
Pitchep... I suggest you search Control.Com Archives for "Generator or TG Hunting!"

Regards, Phil Corso


Posted by pichet on 4 April, 2011 - 11:46 pm
Hi, Phil Corso

Thank you, I tried to search as you recommended but not found a related topic.

pls. advise.

Regards,
pichet p.


1 out of 1 members thought this post was helpful...
Posted by Phil Corso on 5 April, 2011 - 10:00 am
Pitchet... Thread # 1026226787 may provide you with a course-of-action toward solution!

Regards, Phil Corso


Posted by pichet on 18 April, 2011 - 9:02 am
Phil Corso,

With respect, How i can find "Thread # 1026226787"? Because,each posted in website not specific with ID No. as your mention. please, tell me.

Best regards,
pichet.

moderators note: to find a thread on control.com, attach the thread number to the following url:

http://www.control.com/thread/

Pichet, your url is: http://www.control.com/thread/1026226787


>Pitchet... Thread # 1026226787 may
>provide you with a course-of-action
>toward solution!
>
>Regards, Phil Corso



1 out of 1 members thought this post was helpful...
Posted by Phil Corso on 18 April, 2011 - 10:40 am
Pitchet... try:

http://control.com/thread/1026226787

If you are unable to retrieve it, then contact me of list for additional detail!

Regards, Phil Corso (cepsicon[at]aol[dot]com)


Posted by pichet on 19 April, 2011 - 9:20 pm
Thank you,

Phil I thing it is not exactly. Because, my problem occurred on STG with Woodward 505 governor control not GT. Is there someone expert in Woodward control guide to check the problem.

Regards,
pichet


Posted by M Rangacharya on 20 April, 2011 - 12:53 am
Dear Pitchet,

To further understand your problem you may have to clarify following queries,

1) Whether your STG is in parallel operation with other STG or Grid

2) At what load or pressure the governor is hunting

3) Whether the hunting is continuous or intermittent

4) Purpose of inlet steam pressure control programming

Regards,
Rangacharya


1 out of 1 members thought this post was helpful...
Posted by Phil Corso on 20 April, 2011 - 10:05 am
Pitchet... now try:

http://control.com/thread/1026238188

It discusses setting up an "Operations Matrix Table" OMT) to find 'coincident' Electrical and Mechanical parameters!

Regards, Phil Corso


Posted by CSA on 20 April, 2011 - 11:20 am
pichet,

It would seem that there isn't anyone here on control.com with sufficient Woodward experience to help you with your problem.

I have had limited experience with the 505 and found it to be a very simple control system, complete with a relatively good manual that can be used to understand the configuration and workings of the device.

It has few inputs and outputs, and the configuration possibilities are limited. If you would sit down with the manual, and take a pencil and cross out the non-relevant sections (like mechanical drive applications since yours appears to be a generator drive application) and then start reading and putting together your own understanding of the inputs and outputs you could probably come to a very quick troubleshooting procedure.

There are also some alarm explanations there, as I recall.

If I recall correctly, the 505 can be operated from the keypad or from external commands (contact inputs or an analog input). You haven't said how the unit is being operated when these swings occur. Is it in "local" or "remote" control?

The 505 can also be operated in "droop control" mode or in inlet pressure control mode, if I recall correctly. And you haven't said which mode the 505 is being operated in.

Also, M Rangacharya wrote and asked for some information which you have yet to provide.

I'm not offering to provide any further troubleshooting, just trying to direct you to some information that can be used to understand the 505, its configuration and operation.

Lastly, Woodward has authorized parts and service organization around the world. If this problem is critical and you can't take the time to understand the 505 and its configuration and operation, then you will likely need to have a service person come to your site to help with the problem resolution.


Posted by krush on 20 April, 2011 - 10:03 pm
....and unlike GE, Woodward usually has very good documentation and nearly all of it is available on their website--including governing and power system fundamentals.


Posted by 4-20Camp on 24 April, 2011 - 6:20 pm
Pitchet...
My experience with 505 on STG agrees with CSA.

The STG "thing" that the GTG thread does not identify clearly is the inlet valves in the ST are often the issue when there is a certain load range that is unstable. Usually the issue is some wear inside the steam chest -- somehow making steam flow through the throttling inlet valve unstable. If not fixed then eventually pieces are likely to damage the turbine blades ...

Regards, 4-20 Camp


Posted by pichet on 28 April, 2011 - 4:20 am
Dear all,

Thank you very much for your suggestion and sorry for late response.I just came back from vacation.

Dear Rangacharya,

Here are the answers of your question?

1. Whether your STG is in parallel operation with other STG or Grid?--> Parallel with Grid (we have two GE F6B and one Kawasaki ST)

2. At what load or pressure the governor is hunting?--> All ranges of load (peak and off-peak load)

3. Whether the hunting is continuous or intermittent?--> The governor is hunting all the time.

4. Purpose of inlet steam pressure control programming?--> KW limit by speed control.

Best regards,
pichet


Posted by Rangacharya. on 10 May, 2011 - 3:25 am
Dear Pitchet,

There are two basic reasons for governor hunting,

1) Due to oil contamination in the circuit causing sticky operation of pilot valve which in turn cause hunting

2) Disturbance in the PID values of the governor also cause hunting,

I am reproducing the PID tuning given in the woodward manual which may be help full for tuning,

"If the system is unstable, make sure the governor is the cause. This can be checked by closing the valve limiter until it has control of the actuator output. If the governor is causing the oscillation, time the oscillation cycle time. A rule-of thumb is, if the system's oscillation cycle time is less than 1 second reduce the Proportional gain term. A rule-of-thumb is, if the system's oscillation cycle time is greater the 1 second reduce the Integral gain term (proportional gain may need to be increased also).

On an initial startup with the 505, all PID dynamic gain terms will require adjustment to match the respective PID's response to that of its control loop. There are multiple dynamic tuning methods available that can be used with the 505's PIDs to assist in determining the gain terms that provide optimum control loop response times (Ziegler Nichols, etc.). The following method is a simplified version of other tuning methods, and can be used to achieve PID gain values that are close to optimum:

1. Increase Derivative Ratio (DR) to 100 (This is the default setting).

2. Reduce integral gain to minimum.

3. Increase proportional gain until system just starts to oscillate.

4. Record the system gain (G) and oscillation period (T).

5. Set the dynamics as follows:

- For PID control set the proportional gain=0.60*G; integral gain=20/T; DR=5
- For PI control set the proportional gain=0.45*G; integral gain=12/T; DR=100

This method of tuning will get the gain settings close, they can be fine-tuned from this point. Figure 6-18 shows the typical response to a load change when the dynamics are optimally adjusted."

It is better to tune the PID values in the presence of Woogward representative,

I am interested in knowing the final out come of your problem


Posted by pichet on 12 May, 2011 - 10:44 pm
Dear Rangacharya,

Thank you very much for your recommendation. Actually, for the last week i spent my time with the Woodward manual to do understanding the control functions.

Yes, there is a high possibility that the root as your mention. But, difficult to prove which is the real cause. Because, the unit is running.

For the PID tuning, I have a confuse which is the function should be tuning because there are three functions (Speed control, Casecade control and Auxiliary control) used to control the unit during paralleled with grid network. For my STG the main steam inlet pressure is controlled by Cascade PID controller and the generator power limiting is controlled by Auxiliary PID controller and no control the steam extraction.

When the unit paralleled with grid network the unit will control by Speed PID controller. However, i will let you know for the further information.

Best regards,
pichet


Posted by pichet on 13 June, 2011 - 4:32 am
Hi Rangacharya,

Recently, we have shut down total plant for repairing condenser tube leaked for a few days.

I have used this opportunity to do stock test for governor valve via Woodward control panel and replacement governor valve filter including re-calibreated pressure transmitter. But, not found any error of instrument devices. After the steam turbine is running at full load and governor fully open the governor oscillation problem has been gone and the PID controller of woodward did not tuning. While, I have done the stock test the governor valve is moving quite smoothly.

Best regards,
pichet


Posted by CSA on 13 June, 2011 - 10:20 am
pichet,

Thanks for the feedback!



Posted by Rangacharya. on 15 June, 2011 - 12:24 am
Dear Pichet,

In my earlier reply sticky operation of governor valve was also one of the reason for hunting, i think by operating the valve in shut down you have smoothed its operation and this could have solved your problem. Any way this forum is helping many people to understand various problems and making why why analysis by using various feed back.

Regards,
Rangacharya


Posted by Brendan on 23 March, 2013 - 12:28 pm
Good afternoon,

I am a field engineer for Woodward Nederland B.V. I think that the guidelines laid out in Volume 2 of the manual are very good and usually work. You can first try to apply the limiter on the valve until the system is stable. Then reduce the I gain and increase the SDR to 100. Then Increase the proportional gain until the system starts to oscillate. This can be tested by increasing the limiter slightly to allow the PID to take control of the process. Once you have a steady oscillation you can apply the following formula to set the PID settings. Probably best to keep the limiter on while your increasing the I gain and lowering the SDR so the process is still stable.

For PI control: G=P(I/s + 1)
Set: Proportional gain = 0.45*Kc
Integral gain = 1.2/T
Derivative ratio = 100
For PID control : G=P(I/s + 1 + Ds)
Set: Proportional gain = 0.60*Kc
Integral gain = 2/T
Deriv ratio = 8/(T*Integral Gain) for fdbk dominant
= (T*Integral Gain)/8 for input dominant

Hope this helps! For further guide on PID tuning Woodward has application note 83402. This is available on www.woodward.com

Best Regards,
Brendan

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