Gas Turbine Corrected Output Less

S

Thread Starter

suryapower

Dear all,

Our gas turbine is frame 9fa with dln 2.6+

When gas turbine was operated few months back the unit corrected output is around 210 mw (gross mw is 228 mw), and recently we did the baseload test. this time the corrected output is around 206 mw (gross mw is 233 mw), to compare and know what could be the reason for drop in corrected output. i was confused as recent time gross generation is more and seems all parameters are okay. however its due to ambient conditions. but once its corrected to the site conditions, the unit output should be closer to the previous base load test results. what could be the reasons for drop in gas turbine 4 mw load.


gas turbine base load operation is when gt is in combined cycle operation only, as there is 4 mw drop in gas turbine output steam turbine output also reduced.

please suggest me the parameters which i need to look into so that i can spot the reasons for drop in mw. i mean how to start the root cause analysis. i can provide whatever the data you want.

Shipson
 
Can you post the data from the previous base load test and the recent one? How are you converting the data back to Site or ISO conditions? Is the machine being regularly on/offline cleaned? To be honest 4 Mw is just about within calculation error at 228 Mw.
 
S
Hi...firstly thanks for your reply.

we are converting the gross output to site conditions using the correction curves provided by GE for our site conditions. i don't think this was a calculation error. we double checked all the signals and calculations etc. what data you required for your analysis? let me know.
 
For performance monitoring, the most important bit is the accuracy of the instrumentation used. Simply, Ambient Temp. CPD and Mw. are probably the primary factors, also inlet and exhaust losses, humidity, barometric pressure, compressor Inlet & Discharge Temp. are useful.
In your case, the accuracy of the CPD measurement is critical, when was this instrumentation (and all other instrumentation) last calibrated?

Can you document exactly how you performed the test?
 
suryapower,

What about the water washing question?

How many starts since the last maintenance outage?

What is the inlet filter differential?

What is the exhaust duct back pressure?

Are you using the DWATT transducer or counting watt hour meter revolutions/increments?

How many starts and trips since the last maintenance outage?

How certain of the IGV LVDT calibration are you?

How clean are the bellmouth and IGVs?

Was the "test" data taken when the grid frequency was stable?

A true performance test would be measuring fuel flow to a higher degree of accuracy than typical instrumentation would provide and then calculating heat rate to determine performance. Anything else is just an estimate, with uncertainties.
 
S
>What about the water washing question?
Yes, Offline wash done 20 days or (20*24=580hrs) before base load operation

>How many starts since the last maintenance outage?
No major maintenance outage

>What is the inlet filter differential?
ipdp 113.0 mm of h2o

>What is the exhaust duct back pressure?
417 mm of h2o

>Are you using the DWATT transducer or counting watt hour
>meter revolutions/increments?
>
>How many starts and trips since the last maintenance
>outage?

>How certain of the IGV LVDT calibration are you?
yes. before the capacity test ..igv lvdt and all performance instrumentation calibration done by I&C.

>How clean are the bellmouth and IGVs?
they are really clean, hand wash too also done by our MMD team

>Was the "test" data taken when the grid frequency was stable?
yes grid frequency is stable.
 
S
> OK, so all looks OK from how you are doing it. Can we see
> the before and after data?

Please provide your personal mail address.
 
On reading through the posts again, is this a fairly new machine? How many hours has it operated? Do remember that if you are comparing new to now, and the machine has not had any overhauls, there is what is notionally known as an aging factor, it can be as much as 2%, your loss is 1.9%.
 
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