I am facing speed hunting in Gas turbine frame V. We are running turbine in Isochronous mode and it's speed hunting from 5090 RPM to 5115 RPM while it should be fixed at 5104 RPM. Turbine is running at 16-17 MW load. It's FSR variation between 44 to 50% which is fluctuating more. So we change GCV servo, cylinder, filter, intervalve pressure transmiiter on doubt basis but no improvement in FSR & speed hunting. Now i changed on constant FSKRN4 frm 18.48% to 17%. So there is any further scope of checking. Please suggest.

 

When did this problem begin?

How long has it been happening?

How fast is the speed changing?

Are the speed changes periodic, or are they random?

How fast are the oscillations?

Which version of Speedtronic turbine control panel is being used to control the turbine?

The reference for Isochronous Speed Control (TNRI) should be a constant value, unless something is driving the Speed/Load RAISE and -LOWER logic which shouldn't be. Is there some kind of power management or load control system which could be trying to control frequency by initiating speed reference changes?

What is TNRI doing when speed is varying?

What is logic L70IR and L70IL doing when the speed is varying?

The feedback is turbine shaft speed. Is the turbine shaft speed feedback stable? Have you checked all the speed feedback signals independently with the unit running using a good multimeter with a frequency counter, or multiple voltmeters with frequency counters connected to multiple speed pick-up inputs?

Is the P2 pressure stable?

Is the gas fuel supply pressure stable?

Have you tried "gagging" the GCV to see if that helps the problem (using MANUAL FSR, just decreasing it slowly until MANUAL FSR is equal to or just slightly less than FSRNI)? If so, what were the results?

Do you have large loads starting with large inrush currents? Do you have large loads stopping suddenly?

Can you explain what you hoped to accomplish by changing FSKRN4?

What are the values of TNKRIMN and TNKRIMX and TNKRIPR?

You say you have a Frame 5 gas turbine and it's running at 16-17 MW. What is the Base Load rating of the unit?

What is the value of FSRT when FSRNI is at it's highest?

What are all the values of FSRx doing while the speed is changing? (FSRSU, FSRSD, FSRACC, FSRN, FSRNI, FSRT, FSRMAN)

What is CPD transducer feedback doing?

If the unit has modulated IGVs, what are they doing?

What is TTXM doing when load is changing?

What is TTRX doing when load is changing?

What is the generator frequency doing when the speed is changing (usually signal name SFL, or SFL1 or SFL2)?

 

Check you GCV LVDT tuning.

 

In percentage terms - TNH variation is from 99.73 to 100.21. Check your TNKRIMN (Isochronous set point low limit) & TNKRIMX values Isochronous set point high limit). These would ultimately reflect in L33TNRIMN & L33TNRIMX. As it is for your information, TNH value of 100 % is not practically achievable (it is ideal value). For understanding, try L70TRACKV2 & TNRLV3

Is the connected load to the turbine also varying resulting in turbine load variation and hence the speed variation ? I am asking this since you have already tried most of the things particularly related to servo & filter.

Has this problem started after a shutdown ?

 

KK Verma... see Control List topic:
http://www.control.com/thread/1026226787.

Regards, Phil Corso ([email protected])