505 Turbine Control "Over speed"

Dear Sir
Our generator are 2 x 7 MW, the governoor controlled by woodward 505, contract capacity are 11 MW, internal power consumtion for about 1 MW. First start turbine using speed mode, then generator connect to the grid using limiter, the problem is, when grid cutout, our woodward 505 trip "Over speed" indication. please help us to solve the problem, for information see attachment file. Thanks alot
 

Attachments

hadi,

When the grid "cutout" occurs what are you wanting or expecting to happen?

1) Are you expecting the steam turbine generator breaker will remain closed and the Woodward 505 will automatically reduce steam flow into the steam turbine to maintain rated frequency to supply the "internal power consumption"?

2) Are you expecting the steam turbine generator breaker will open VERY shortly after the grid "Utility Breaker" opens (see Contact Input 5 Function in the lower right corner of Sheet 1 of the 505 Configuration sheet you attached)--AND that the steam turbine will remain at rated speed waiting to be re-synchronized?

If you're expecting "1" above, I don't see where the Woodward 505 is configured to switch to Isochronous Speed Control from Droop Speed Control when Contact Input 5 ("Utility Breaker") opens. That is what would need to happen to prevent the 505 from overspeeding when the utility breaker opened and the generator breaker remained closed--the governor (the Woodward 505) has to know to switch to Isochronous Speed Control mode to vary steam flow as required to maintain frequency while the steam turbine is separated from the grid.

If you're expecting "2" above, well, I think that's going to be very difficult to achieve. When the load from the grid is lost there is still a LOT of steam flowing (when the load is at 11 MW or so) and if the generator breaker were to open also then that steam flow has to be severely limited and the steam trapped between the control valve(s) and the steam turbine has to dissipate, and that's going to cause the steam turbine speed to rise, very possibly to the overspeed trip setpoint. It takes so little steam to spin the generator at rated speed and the control valve(s) have to close VERY quickly when load is lost if there is any hope of keeping the turbine spinning without overspeeding on loss of load. AND, that steam which has to be stopped by the control valves is probably going to cause the steam drum safeties to lift--because the steam has nowhere to go (unless the system is equipped with some kind of "dump" valves to dump steam to the condenser to prevent lifting boiler safeties). And, most small utility boilers and steam turbines don't usually have such a sophisticated steam pressure control system.

Even if you're not expecting "1" or "2" and you're just simply trying to avoid an overspeed trip when the utility- and generator breaker opens suddenly, again--there's steam trapped between the control valves and the steam turbine and that has nowhere to go except through the steam turbine. The stop and control valves would have to close EXTREMELY QUICKLY when both utility- and generator breakers open to prevent a speed increase above the Overspeed Trip setpoint. Again, it doesn't take very much steam at all to keep a steam turbine and generator spinning at rated speed. And, unless the steam flow is shut off EXTREMELY QUICKLY the steam turbine speed is going to increase--hopefully not enough to trip on overspeed, but if the control valves and the stop valve aren't working properly it's entirely possible the speed increase could cause an overspeed trip.

So, you need to understand what you expectations are, what the limitations of the governor and steam delivery system are, AND if this turbine has just begun to experience overspeed tripping on separation from the utility I would suggest you need to look at the stop- and control valves to be sure they are operating per specification (specifically--are they closing fast enough).

That's about it. If this overspeed tripping problem started recently and hadn't been occurring before on utility separations (grid cutouts), then something has changed--most likely it's something with the stop and/or control valves, causing them to close slower than previously and allowing too much steam to flow into the turbine after the utility breaker has opened. If the valves have recently been refurbished, I would say the refurbishment wasn't up to specification. If it's been a long time since the stop and/or control valves have been serviced or refurbished then it's probably time for that to happen--and for proper testing of the close times after the service/refurbishment.

Hope this helps!

Please write back with any further details or questions.
 
hadi,

When the grid "cutout" occurs what are you wanting or expecting to happen?

1) Are you expecting the steam turbine generator breaker will remain closed and the Woodward 505 will automatically reduce steam flow into the steam turbine to maintain rated frequency to supply the "internal power consumption"?

2) Are you expecting the steam turbine generator breaker will open VERY shortly after the grid "Utility Breaker" opens (see Contact Input 5 Function in the lower right corner of Sheet 1 of the 505 Configuration sheet you attached)--AND that the steam turbine will remain at rated speed waiting to be re-synchronized?

If you're expecting "1" above, I don't see where the Woodward 505 is configured to switch to Isochronous Speed Control from Droop Speed Control when Contact Input 5 ("Utility Breaker") opens. That is what would need to happen to prevent the 505 from overspeeding when the utility breaker opened and the generator breaker remained closed--the governor (the Woodward 505) has to know to switch to Isochronous Speed Control mode to vary steam flow as required to maintain frequency while the steam turbine is separated from the grid.

If you're expecting "2" above, well, I think that's going to be very difficult to achieve. When the load from the grid is lost there is still a LOT of steam flowing (when the load is at 11 MW or so) and if the generator breaker were to open also then that steam flow has to be severely limited and the steam trapped between the control valve(s) and the steam turbine has to dissipate, and that's going to cause the steam turbine speed to rise, very possibly to the overspeed trip setpoint. It takes so little steam to spin the generator at rated speed and the control valve(s) have to close VERY quickly when load is lost if there is any hope of keeping the turbine spinning without overspeeding on loss of load. AND, that steam which has to be stopped by the control valves is probably going to cause the steam drum safeties to lift--because the steam has nowhere to go (unless the system is equipped with some kind of "dump" valves to dump steam to the condenser to prevent lifting boiler safeties). And, most small utility boilers and steam turbines don't usually have such a sophisticated steam pressure control system.

Even if you're not expecting "1" or "2" and you're just simply trying to avoid an overspeed trip when the utility- and generator breaker opens suddenly, again--there's steam trapped between the control valves and the steam turbine and that has nowhere to go except through the steam turbine. The stop and control valves would have to close EXTREMELY QUICKLY when both utility- and generator breakers open to prevent a speed increase above the Overspeed Trip setpoint. Again, it doesn't take very much steam at all to keep a steam turbine and generator spinning at rated speed. And, unless the steam flow is shut off EXTREMELY QUICKLY the steam turbine speed is going to increase--hopefully not enough to trip on overspeed, but if the control valves and the stop valve aren't working properly it's entirely possible the speed increase could cause an overspeed trip.

So, you need to understand what you expectations are, what the limitations of the governor and steam delivery system are, AND if this turbine has just begun to experience overspeed tripping on separation from the utility I would suggest you need to look at the stop- and control valves to be sure they are operating per specification (specifically--are they closing fast enough).

That's about it. If this overspeed tripping problem started recently and hadn't been occurring before on utility separations (grid cutouts), then something has changed--most likely it's something with the stop and/or control valves, causing them to close slower than previously and allowing too much steam to flow into the turbine after the utility breaker has opened. If the valves have recently been refurbished, I would say the refurbishment wasn't up to specification. If it's been a long time since the stop and/or control valves have been serviced or refurbished then it's probably time for that to happen--and for proper testing of the close times after the service/refurbishment.

Hope this helps!

Please write back with any further details or questions.
Dear CSA, thank you for your explanation.

Refer to your explanation, i expected No 1.
"1) Are you expecting the steam turbine generator breaker will remain closed and the Woodward 505 will automatically reduce steam flow into the steam turbine to maintain rated frequency to supply the "internal power consumption"?" Yes I expected, there are 2 breaker to connect our system to the Grid ( lets see may attacment file ).

"If you're expecting "1" above, I don't see where the Woodward 505 is configured to switch to Isochronous Speed Control from Droop Speed Control when Contact Input 5 ("Utility Breaker") opens. That is what would need to happen to prevent the 505 from overspeeding when the utility breaker opened and the generator breaker remained closed--the governor (the Woodward 505) has to know to switch to Isochronous Speed Control mode to vary steam flow as required to maintain frequency while the steam turbine is separated from the grid." So, i should be connect Open/ Close signal from 101 and 201 to woodward 505, and set contact Input 5 ( Utility Breaker ) right? or any other setting?

Valve controller using Voith I/H Converter



Regard
 

Attachments

If you're expecting 1, has this ever worked as you expected before? Or is this new behaviour?

I'm no 505 expert, and I would have to read the manual to determine how it can be switched into Isochronous Speed Control.

BUT, only one steam turbine can be switched into Isochronous! And if the house load (when separated from the grid) is only about 1 MW, it's probably going to be difficult to get two turbines to share the load with one unit in Isochronous mode. That's because the other unit is going to have to shed a LOT of load to be able to share the 1 MW load with the other turbine, and I don't know how that can happen with two 505s. Woodward does offer some "auxiliary" modules that might be useful and help with your situation, but you are going to need to work with a control system integrator who has experience with Woodward control systems in your application.
 
If you're expecting 1, has this ever worked as you expected before? Or is this new behaviour?

I'm no 505 expert, and I would have to read the manual to determine how it can be switched into Isochronous Speed Control.

BUT, only one steam turbine can be switched into Isochronous! And if the house load (when separated from the grid) is only about 1 MW, it's probably going to be difficult to get two turbines to share the load with one unit in Isochronous mode. That's because the other unit is going to have to shed a LOT of load to be able to share the 1 MW load with the other turbine, and I don't know how that can happen with two 505s. Woodward does offer some "auxiliary" modules that might be useful and help with your situation, but you are going to need to work with a control system integrator who has experience with Woodward control systems in your application.
This new behavior since using Limiter mode. Before limiter mode, we use speed mode ( some time able to house load when grid cut out some time also overspeed)

Yes of course One steam turbine only, it's OK. The target is, Our both steam turbine not stop.
 
And, hadi,

I was just sitting down to write that part of the problem is likely that the 505 isn't switching from limiter (I presume Inlet Pressure Limiter or Load Limiter????) control to speed control at the instant the utility tie breaker opens.

I think you are going to need to work with a control system integrator to find a way to use an external load control module that puts out a 4-20 mA signal which can be used to drive the two 505s to say 0.5 MW on utility tie breaker open (grid separation), and then the operators will have to manually decide what to do next. IF the 505 has an Isoch mode, they could cut out the external load control, switch one 505 to Isoch and the other to Droop and and let the 505s do their thing until it's time to resynchronize. (To resynchronize the units, you would need a stable house load, switch both 505s to droop, and use one to synchronize back to the grid (both units could be resynchronized at the same time in this way if they both share the same bus when the grid separation occurs--to be honest, I haven't had chance to study the electrical diagram you sent--yet).

But, I would suggest the limiter needs to be exited for Droop speed control, at a minimum, on both 505s, when a grid separation occurs. I may have more ideas after I have a chance to review the electrical diagram later.
 
This new behavior since using Limiter mode. Before limiter mode, we use speed mode ( some time able to house load when grid cut out some time also overspeed)

Yes of course One steam turbine only, it's OK. The target is, Our both steam turbine not stop.
Dear CSA, thank you for your explanation.

Refer to your explanation, i expected No 1.
"1) Are you expecting the steam turbine generator breaker will remain closed and the Woodward 505 will automatically reduce steam flow into the steam turbine to maintain rated frequency to supply the "internal power consumption"?" Yes I expected, there are 2 breaker to connect our system to the Grid ( lets see may attacment file ).

"If you're expecting "1" above, I don't see where the Woodward 505 is configured to switch to Isochronous Speed Control from Droop Speed Control when Contact Input 5 ("Utility Breaker") opens. That is what would need to happen to prevent the 505 from overspeeding when the utility breaker opened and the generator breaker remained closed--the governor (the Woodward 505) has to know to switch to Isochronous Speed Control mode to vary steam flow as required to maintain frequency while the steam turbine is separated from the grid." So, i should be connect Open/ Close signal from 101 and 201 to woodward 505, and set contact Input 5 ( Utility Breaker ) right? or any other setting?

Valve controller using Voith I/H Converter



Regard
Hi All,

Hadi,

I was reading this thread, after seen the SLD, i have questions on it:

-How both breakers ( 101 & 201) are operated, during grid separation?

-In case of Failure to open/trip of CB101 during grid separation , how it is managed by control/protection system??

Thank you for giving us some clarifications on the controls/protection philosophy of this plant.

You should , and must study this case with concentration, on differents cases that can appear during the "grid separation".

Regards,
James
 
I especially like the fact that two--not one, but two--transformers are named T11 on the SLD (Single Line Diagram)....

Very interesting.

But, the governors (505s) need to be in speed control mode when the grid separation occurs; "limiter" mode is probably not going to work to achieve the designed outcome. hadi said that prior to using limiter control mode they had limited success in maintaining house load when a grid separation occurred, but that since beginning to use limiter control mode they haven't been able to maintain house load. When the governors aren't trying to control speed when separated from the grid then speed--and frequency--aren't going to be at or near rated, UNLESS operators can manually intervene, which doesn't seem very likely when going from near full load to near zero load. Even with speed control becoming active at the instant the utility breaker (i'm presuming 102, but it could be 101) the drop in load--and the required drop in steam flows to get down to that load--are going to be hard to achieve without some "over-shoot" of speed.
 
I especially like the fact that two--not one, but two--transformers are named T11 on the SLD (Single Line Diagram)....

Very interesting.

But, the governors (505s) need to be in speed control mode when the grid separation occurs; "limiter" mode is probably not going to work to achieve the designed outcome. hadi said that prior to using limiter control mode they had limited success in maintaining house load when a grid separation occurred, but that since beginning to use limiter control mode they haven't been able to maintain house load. When the governors aren't trying to control speed when separated from the grid then speed--and frequency--aren't going to be at or near rated, UNLESS operators can manually intervene, which doesn't seem very likely when going from near full load to near zero load. Even with speed control becoming active at the instant the utility breaker (i'm presuming 102, but it could be 101) the drop in load--and the required drop in steam flows to get down to that load--are going to be hard to achieve without some "over-shoot" of speed.
CSA,

Just a small clarification , there is no breaker named 102 But 201 in the provided SLD,

I also noticed transformer T11 named twice, you right,

I asked Hadi for some operating instructions regarding "grid separation" before to go further on the SLD .

Didnt want to tell him that the SLD is little bit "confusing" ...

Regards,
James
 
Hi All,

Hadi,

I was reading this thread, after seen the SLD, i have questions on it:

-How both breakers ( 101 & 201) are operated, during grid separation?

-In case of Failure to open/trip of CB101 during grid separation , how it is managed by control/protection system??

Thank you for giving us some clarifications on the controls/protection philosophy of this plant.

You should , and must study this case with concentration, on differents cases that can appear during the "grid separation".

Regards,
James
-How both breakers ( 101 & 201) are operated, during grid separation? During separation ( Off From Grid ) 101 and 102 Open
-In case of Failure to open/trip of CB101 during grid separation , how it is managed by control/protection system?? if CB101 fail to open, CB110 and CB120 should be Trip/ open
 
CSA,

Just a small clarification , there is no breaker named 102 But 201 in the provided SLD,

I also noticed transformer T11 named twice, you right,

I asked Hadi for some operating instructions regarding "grid separation" before to go further on the SLD .

Didnt want to tell him that the SLD is little bit "confusing" ...

Regards,
James
I'm sorry about the name of transformer, i attach the revision
 

Attachments

I especially like the fact that two--not one, but two--transformers are named T11 on the SLD (Single Line Diagram)....

Very interesting.

But, the governors (505s) need to be in speed control mode when the grid separation occurs; "limiter" mode is probably not going to work to achieve the designed outcome. hadi said that prior to using limiter control mode they had limited success in maintaining house load when a grid separation occurred, but that since beginning to use limiter control mode they haven't been able to maintain house load. When the governors aren't trying to control speed when separated from the grid then speed--and frequency--aren't going to be at or near rated, UNLESS operators can manually intervene, which doesn't seem very likely when going from near full load to near zero load. Even with speed control becoming active at the instant the utility breaker (i'm presuming 102, but it could be 101) the drop in load--and the required drop in steam flows to get down to that load--are going to be hard to achieve without some "over-shoot" of speed.
CSA,

i'm Sorry. The big one off Tranformer is T1
 
hadi,

From the date on the SLD it's presumed the plant is going through commissioning and having some difficulties.

The name of the transformer isn't the problem; but, it could be signs of other (larger) problems.

You hit the nail on the head with the change in operations from speed control to limit control. When the turbine-generators are separated from the grid they can't remain on limit control; they have to switch, and quickly, to speed control--AND they have to reduce load quickly, at the same time. If the units are at higher loads when this happens, well, the sudden decrease in steam flow is likely to cause the inlet pressure to the units to rise quickly--maybe high enough to cause the boiler safeties to lift.

You have already said that when operating in speed control when the grid separation occurs it's sometimes possible to prevent tripping (I imagine on overspeed) and sometimes not. But, you said that with the change to limit control operation the overspeed trips are pretty certain. So, when troubleshooting problems like this one has to look at, "What has changed?" And, it's the change to limit control that has apparently caused the certain tripping.

Please write back to let us know how this gets resolved. If you write back for more help, it would be helpful if you could provide some P&IDs of the steam supply system.
 
hadi,

From the date on the SLD it's presumed the plant is going through commissioning and having some difficulties.

The name of the transformer isn't the problem; but, it could be signs of other (larger) problems.

You hit the nail on the head with the change in operations from speed control to limit control. When the turbine-generators are separated from the grid they can't remain on limit control; they have to switch, and quickly, to speed control--AND they have to reduce load quickly, at the same time. If the units are at higher loads when this happens, well, the sudden decrease in steam flow is likely to cause the inlet pressure to the units to rise quickly--maybe high enough to cause the boiler safeties to lift.

You have already said that when operating in speed control when the grid separation occurs it's sometimes possible to prevent tripping (I imagine on overspeed) and sometimes not. But, you said that with the change to limit control operation the overspeed trips are pretty certain. So, when troubleshooting problems like this one has to look at, "What has changed?" And, it's the change to limit control that has apparently caused the certain tripping.

Please write back to let us know how this gets resolved. If you write back for more help, it would be helpful if you could provide some P&IDs of the steam supply system.
From the date on the SLD it's presumed the plant is going through commissioning and having some difficulties. Actually 10 years running allready. FYI, why we change from speed mode to Limiter Load? because when there's "boom load", alway running down to us, ( for example from 11 MW to 14 MW ). After we chnage to load limiter, the problem become solved. But, there was a new problem "Over speed"

You have already said that when operating in speed control when the grid separation occurs it's sometimes possible to prevent tripping (I imagine on overspeed) and sometimes not. But, you said that with the change to limit control operation the overspeed trips are pretty certain. So, when troubleshooting problems like this one has to look at, "What has changed?" And, it's the change to limit control that has apparently caused the certain tripping. Do you mean parameter setting? there are no Change any thing, just press the LMTR button on woodward 505.

I Just added some file. thanks for your attention and repply
 

Attachments

From the date on the SLD it's presumed the plant is going through commissioning and having some difficulties. Actually 10 years running allready. FYI, why we change from speed mode to Limiter Load? because when there's "boom load", alway running down to us, ( for example from 11 MW to 14 MW ). After we chnage to load limiter, the problem become solved. But, there was a new problem "Over speed"

You have already said that when operating in speed control when the grid separation occurs it's sometimes possible to prevent tripping (I imagine on overspeed) and sometimes not. But, you said that with the change to limit control operation the overspeed trips are pretty certain. So, when troubleshooting problems like this one has to look at, "What has changed?" And, it's the change to limit control that has apparently caused the certain tripping. Do you mean parameter setting? there are no Change any thing, just press the LMTR button on woodward 505.

I Just added some file. thanks for your attention and repply
Hadi,

Did you have take a read, on the Woodward 505 Operating Manual?

It looks like there are plenty of interesting informations, for the case that you described on this thread.

Well, i guess that you will have to pick up some money, for purchasing some parts like "peripheriques/auxiliary" devices and for sure, a control TA for getting your issue to be solved .

I have a read on this manual , and there are setting /parameters described for the Wodward 505 and associated devices as these examples:
- "Example 5–Inlet Pressure Control with Isochronous Loadsharing Control in Island Mode"
- "Example 6–Import/Export Control or Exhaust Pressure Control with Isoch Load
Sharing in Island Mode"
You can read the document and search/find the best solution for your problem!
I guess these examples can be an help for you!

Looking to hear back from you soon,

James.
 
Hadi,

Did you have take a read, on the Woodward 505 Operating Manual?

It looks like there are plenty of interesting informations, for the case that you described on this thread.

Well, i guess that you will have to pick up some money, for purchasing some parts like "peripheriques/auxiliary" devices and for sure, a control TA for getting your issue to be solved .

I have a read on this manual , and there are setting /parameters described for the Wodward 505 and associated devices as these examples:
- "Example 5–Inlet Pressure Control with Isochronous Loadsharing Control in Island Mode"
- "Example 6–Import/Export Control or Exhaust Pressure Control with Isoch Load
Sharing in Island Mode"
You can read the document and search/find the best solution for your problem!
I guess these examples can be an help for you!

Looking to hear back from you soon,

James.
James,

Thanks for your advice, if the solution only some parts like "peripheriques/auxiliary", so I think end of discuss. I hope any other way, looks like change parameter PID gain maybe. (i expect when the grid separation occurs, the governoor close very fast )

But, i have already said that when operating in speed control when the grid separation occurs it's sometimes possible to prevent tripping, But, with the change to limit control operation the overspeed trips are pretty certain.

Hadi.
 
Hadi,

It's clear English is not your first language. Please explain as best as possible what you mean by ”boom load”--as that appears to be the reason for beginning to use Limiter Control when you had been using Speed Control. That's a change in operating procedure--the type of change that quite often results in the kind of problem you are describing.

Just because the unit experienced occasional overspeeds while operating on speed control during a grid separation and now when operating on Limiter Control it always experiences overspeeds does not mean that by changing the gain you can cause it not to experience overspeeds on grid separations. If you increase the gain you will likely cause instability at other operating conditions.

You need to understand that when the grid separations occur if the units don't switch to speed control and instead use another reference (header pressure?) when load is reduced drastically and suddenly the unis are going to at best going to be unstable and at worst trip on overpeed. The load acts as a ”brake” on unit operation. When load is suddenly lost--especially on a steam turbine--if the control is not in speed control the speed is going to increase pretty quickly.

Continued overspeeds are not good for either the turbines or the generators. Look, if the units would just be switched back to speed control on separation that's better than leaving it in Limiter Control. But, I maintain there needs to be something that drives the load or speed reference to the equivalent of approximately 0.5 MW per unit when the grid separation occurs or the likelihood of overspeeds isn't going to change or get much better.

Please try to clearly explain”boom load” and perhaps we can try to offer some suggestions for helping to survive the ”boom loads.” But that's about all we can offer at this point.

You, of course, are free to try increasing the gain. Please write back to let us know if it had the desired effect on grid separations, and on any other operating conditions. We are not there and we don't have a good understanding of the issues--like why do grid separations occur? And, if the turbines are tripping on overspeed I suspect the generator breakers are opening prior to the overspeeds and most likely because of over-frequency. That would be helpful if you would confirm that.

Do you have anyway to gather data during a grid separation? Turbine speeds, loads, generator breaker status, utility breaker status, steam supply pressure?
 
James,

Thanks for your advice, if the solution only some parts like "peripheriques/auxiliary", so I think end of discuss. I hope any other way, looks like change parameter PID gain maybe. (i expect when the grid separation occurs, the governoor close very fast )

But, i have already said that when operating in speed control when the grid separation occurs it's sometimes possible to prevent tripping, But, with the change to limit control operation the overspeed trips are pretty certain.

Hadi.
Hadi ,

Please have a look on these quotes i guess that it may be interesting for this case:
Example 4–Plant Import/ Export Control with DRFD Servo Interface
This is an example of a typical turbine generator application where plant import/ export control is desired when paralleled with the utility, and frequency control when isolated from the utility. With this type of application, when paralleled to the utility, turbine load varies based on the plant power demand. Other applications may or may not use all the functionality shown in Figure 10-4 and described below.
With this application, plant import/export control is performed within the 505 through the Auxiliary PID controller. Optionally the Cascade PID controller could have been used instead. For this application the Auxiliary PID is configured to be enabled and disabled on command, instead of performing a limiting action. This gives a system operator full authority of when to enable or disable plant import/export control.
When programmed for this type of control action, the Speed PID is disabled when the Auxiliary PID is enabled, and can only limit the 505’s valve output signal if unit load reaches 100%. Also, the Auxiliary setpoint automatically tracks the PID’s input value when not in-control.

...............



That statement that "frequency control when , from utility" is possible via 505 and associated devices .
It also saying that :

Because of the 505’s configuration, this unit will automatically switch to Frequency control, upon the opening of the plant-to-utility tie breaker.


Here anothers cases examples:


Example 5–Inlet Pressure Control with Isochronous Loadsharing Control in Island Mode
For this application, it is desired to control Inlet Pressure when paralleled to the utility, and Frequency while loadsharing with three other units, when isolated from the utility. With this type of application, when paralleled to the utility, load varies based on plant process steam demand, and when isolated load varies based on plant power demand.

......................
This application uses an EGCP-3 LS for synchronization and isochronous loadsharing. With this
configuration, the EGCP-3 LS is disabled when the generator is paralleled to the utility, and enabled when
isolated from the utility. When the unit is paralleled to the utility, the EGCP-3 LS is disabled and the 505’s
internal load setpoint or Cascade PID (plant import/export power) is used to control/set unit load. When
the plant becomes isolated from the utility, (utility tie breaker opens), the EGCP-3 LS is enabled, Cascade
control is disabled, and the 505 is switched to a Frequency control/loadsharing mode.
An EGCP-3 LS can only interface to a 505 through an analog input signal. The 505’s Analog Input #6 is
the only analog input directly compatible with the EGCP-3 LS, thus it is required that this input be
programmed to receive the EGCP-3 LS’s Speed Bias signal. When a Sync/LD Share analog input is
programmed, the input is automatically enabled if the generator breaker input is closed and the utility tie
breaker input is open.







Example 6–Import/Export Control or Exhaust Pressure Control with Isoch Load
Sharing in Island Mode
.....................
With this application, during normal operation, one unit is switched to control plant process steam and the other units are switched to the loadsharing mode and are loaded based on the MSLC plant load demand. If the plant should become isolated from the utility, the MSLC will become disabled and all units in the loadsharing mode will share plant load. When desired the MSLC can be enabled to re-synchronize the plant bus to the utility bus and close the plant-to-utility tie breaker. After synchronization the MSLC will either ramp plant power to a 5 MW export power level, or ramp plant load to a base load setting, depending on the mode of operation selected.


I strongly recommend to have a look on 505 operating manual , after that you can have a better idea of what can match with your current situation and find the sources of solution ( as there are many examples described depending on Turbine controls ).

Please write us back , what you think about this ,
Regards,
James.
 
Dear Hadi,
After going through your docs and with my experience and to the best of my knowledge, whatever you are expecting that during a load cutout from 11 MW to 1 MW that the turbine should still be running without over-speed is just not possible. Generally for this type of application a dump valve is utilized which is provided with an open interlock with Inlet steam pressure or maybe with grid breaker contact depending on application. What it does is that, it dumps the excess steam from going to the turbine and thus preventing an overspeed. So a dump valve designed with minimum flow as required for 1MW load is to be considered. But that comes under designing/modification part and as of now it cannot be considered. Anyways, you might want to try utilizing the inlet steam pressure transmitter signal back to the governor and running the governor controller in cascade control with a remote set point so that the governor at any time will be maintaining a set inlet steam pressure to prevent pressure excursions. But that will require a lot of tuning and it has its own drawbacks too like reaching max load. Every aspect needs to be considered when designing a system and as with your current system designed (according to the pdfs) its just not possible without some heavy modifications.
 
Hadi,

Did you have take a read, on the Woodward 505 Operating Manual?

It looks like there are plenty of interesting informations, for the case that you described on this thread.

Well, i guess that you will have to pick up some money, for purchasing some parts like "peripheriques/auxiliary" devices and for sure, a control TA for getting your issue to be solved .

I have a read on this manual , and there are setting /parameters described for the Wodward 505 and associated devices as these examples:
- "Example 5–Inlet Pressure Control with Isochronous Loadsharing Control in Island Mode"
- "Example 6–Import/Export Control or Exhaust Pressure Control with Isoch Load
Sharing in Island Mode"
You can read the document and search/find the best solution for your problem!
I guess these examples can be an help for you!

Looking to hear back from you soon,

James.
Dear Hadi,

It would be fine to tell us how things are going on this thread subject??
As we spent time trying to support/help, you and then we can ask for miminum feedback to close the thread.

Thank you for your understanding,
Controlsguy25
 
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