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Not able to reach base load, 6FA GT Still at speed control AT 70 MW even Base Load from the HMI is selected.
Kindly help.
Kindly help.
D
DJDB
> What Process Alarms are being annunciated? (All of them, please.)
COMPRSR LIM FSR BACKUP CTRL ACTIVE
Thnx.
[email protected]
COMPRSR LIM FSR BACKUP CTRL ACTIVE
Thnx.
[email protected]
What part of CMPRSR (COMPRESSOR) LIM (LIMIT) ... CTL (CONTROL) ACTIVE isn't clear?
Some compressor operating limit as been exceeded, or the inputs to the compressor operating limit function aren't working properly. It's likely the compressor operating limit function is preventing L70R from picking up which would increase the turbine speed reference to increase the load to Base Load (exhaust temperature control).
Some compressor operating limit as been exceeded, or the inputs to the compressor operating limit function aren't working properly. It's likely the compressor operating limit function is preventing L70R from picking up which would increase the turbine speed reference to increase the load to Base Load (exhaust temperature control).
Sort of on topic (for CSA lol).....
I had to do a 1% speed reference step change on frame 6 for testing. The testing company says GE usually puts in a sum block with logic that adds 1% to the speed ref signal, but the GE TA wasn't familiar with that.
So I found the constant that controls the manual load increase rate (L86 or something?) and increased it until one click on the speed increase button gave me 1% change in speed ref (Idos). Turned out about 246%/min was the value. Took forever to ramp to that in the constants program--it doesn't let one adjust the ramp rate like the WinNT HMI.
Anyway, we'll see if this gave the testing guys what they need after they look at the data.
Pretty good for a mechanical guy that barely passed controls class, eh?
PS: I'll never figure out why GE has to make speed control logic so complex.
I had to do a 1% speed reference step change on frame 6 for testing. The testing company says GE usually puts in a sum block with logic that adds 1% to the speed ref signal, but the GE TA wasn't familiar with that.
So I found the constant that controls the manual load increase rate (L86 or something?) and increased it until one click on the speed increase button gave me 1% change in speed ref (Idos). Turned out about 246%/min was the value. Took forever to ramp to that in the constants program--it doesn't let one adjust the ramp rate like the WinNT HMI.
Anyway, we'll see if this gave the testing guys what they need after they look at the data.
Pretty good for a mechanical guy that barely passed controls class, eh?
PS: I'll never figure out why GE has to make speed control logic so complex.
S
sjdb
Base load is reached at a very high value of 80 MW instead of 70MW for this 6FA unit.
Please guide us for the possible reasons.
Please guide us for the possible reasons.
I neglected to ask the most important question when troubleshooting an problem:
When did the problem begin? After a maintenance outage? After the "gas valves" were recalibrated? After a trip?
If Base Load is being reached at a very high value, then it's likely that the CPD transmitter(s) and/or the other inputs to the CPR calculation are not working properly! This means that the internal firing temperatures are higher than design, meaning that the hot gas path parts are being subjected to higher than design temperatures and are being stressed, possibly to the point of failure.
Please have a qualified individual look at all of the critical inputs to the unit and resolve this condition. By critical, I'm referring to the CPD transmitter(s) (for an F-class unit, there should be redundant transmitters) and the "performance monitoring package" (including the atmosphere (barometric) pressure transmitter(s) (again, there are likely redundant devices for this parameter, also), the inlet pressure drop transmitter, the bellmouth pressure drop transmitter, and the exhaust duct pressure transmitter(s)).
When did the problem begin? After a maintenance outage? After the "gas valves" were recalibrated? After a trip?
If Base Load is being reached at a very high value, then it's likely that the CPD transmitter(s) and/or the other inputs to the CPR calculation are not working properly! This means that the internal firing temperatures are higher than design, meaning that the hot gas path parts are being subjected to higher than design temperatures and are being stressed, possibly to the point of failure.
Please have a qualified individual look at all of the critical inputs to the unit and resolve this condition. By critical, I'm referring to the CPD transmitter(s) (for an F-class unit, there should be redundant transmitters) and the "performance monitoring package" (including the atmosphere (barometric) pressure transmitter(s) (again, there are likely redundant devices for this parameter, also), the inlet pressure drop transmitter, the bellmouth pressure drop transmitter, and the exhaust duct pressure transmitter(s)).
P
Process Value
frame 6 FA base load
This is a interesting topic, i have never seen a frame 6FA get a base load of 80MW, even its ISO rating is only 70MW. the alarm given is coming because the back up temperate curve has come active. The TTRXP is based on the CDP while the TTRSX is based on FSR. The lower of the two values is used for TTRX. which is used to calculate the FSRT , which is then the limiting FSR at base load.
COMPRSR LIM FSR BACKUP CTRL ACTIVE
to resolve this issue you need to look into functions / core control / exhaust control / exhaust reference - in this you will find TTRXV5 block , here if the
signal L60 TRF is high , then what i have told you in the cause of the alarm. The back up curve is now active. check to see if the control constants in this block are correct , or compare it with a existing installation.
As for base load no reaching 80 MW !!!! i think it is quite a stretch to expect 6FA to give 80MW , have you gone for any power augmentation in this unit??
there are so many unknowns here it is not possible for any of us to pinpoint the exact reason , but i will give you a list of probable reasons
1. poor compressor performance , this leads to higher exhaust temp and as exhaust temp is the one limiting the FSR your machine will not reach expected base load.
2. Poor control constant tuning , GE provides a standard control constants for its machines and lists changeable parameters and limits of change , is your plant constants , especially ones relating to core control , CDP control , exhaust control , FSRT control have typical values which are within limits.
3. mechanical problems with the turbine it self
- mismatched combustion liner
- extended space between the rotor and stator blades etc .... ( i am not a big expert in this CSA can help by extending this list)
4. Environment conditions - Ambient temperature and humidity plays an important role in determining the base load , higher the ambient temp lower the base load , you would have chara graps which will tell you how much the machine can load up in the given conditions.
and lastly , can you provide us with a detailed list of plant parameters , taken from a operator log so that we can pinpoint the problem area better. It should include , fuel flow , IGV opening , ambient temp , CDP , CTD ,wheelspace , exhaust , frequency etc ...
This is a interesting topic, i have never seen a frame 6FA get a base load of 80MW, even its ISO rating is only 70MW. the alarm given is coming because the back up temperate curve has come active. The TTRXP is based on the CDP while the TTRSX is based on FSR. The lower of the two values is used for TTRX. which is used to calculate the FSRT , which is then the limiting FSR at base load.
COMPRSR LIM FSR BACKUP CTRL ACTIVE
to resolve this issue you need to look into functions / core control / exhaust control / exhaust reference - in this you will find TTRXV5 block , here if the
signal L60 TRF is high , then what i have told you in the cause of the alarm. The back up curve is now active. check to see if the control constants in this block are correct , or compare it with a existing installation.
As for base load no reaching 80 MW !!!! i think it is quite a stretch to expect 6FA to give 80MW , have you gone for any power augmentation in this unit??
there are so many unknowns here it is not possible for any of us to pinpoint the exact reason , but i will give you a list of probable reasons
1. poor compressor performance , this leads to higher exhaust temp and as exhaust temp is the one limiting the FSR your machine will not reach expected base load.
2. Poor control constant tuning , GE provides a standard control constants for its machines and lists changeable parameters and limits of change , is your plant constants , especially ones relating to core control , CDP control , exhaust control , FSRT control have typical values which are within limits.
3. mechanical problems with the turbine it self
- mismatched combustion liner
- extended space between the rotor and stator blades etc .... ( i am not a big expert in this CSA can help by extending this list)
4. Environment conditions - Ambient temperature and humidity plays an important role in determining the base load , higher the ambient temp lower the base load , you would have chara graps which will tell you how much the machine can load up in the given conditions.
and lastly , can you provide us with a detailed list of plant parameters , taken from a operator log so that we can pinpoint the problem area better. It should include , fuel flow , IGV opening , ambient temp , CDP , CTD ,wheelspace , exhaust , frequency etc ...
Y
yichao
Please check Compressor Bleed Valve solenoid and all limit switch whether fully close. Not just judge by limit switch, it's better to visually check actual valve position. Did you calculate how many mega-watt lose when GT on baseload in the past? with my experience that I personally think it would be possible caused by Compressor Bleed Valve. that's just my point of view.
