I noticed in the BBL FSRNV3 “Speed Control FSR“ that there are two control loops:

Loop 1: The upper control loop with TNKRNR signal as reference and TNH as feedback.

Loop 2: The lower control loop with TNR signal as reference and TNL as feedback (or TNH if the OVERSPEED test is selected).
And the outputs of these control loops are the input of a Minimum Selection block.

I have 2 questions:

1) Under which conditions we can have loop 1 active, and under which conditions we can have loop 2 active.

2) In this block, FSRNV3 there is a logic signal L83SCDB, is represented as and input to this block. I searched in the CSP for the source of this signal but I couldn’t find it. it is used only in this block. I want to know the source of this signal and also the operation of the loop when it is enabled.

For your information, I found the state of L83SCDB signal in rung display to 0. And the machine is MS5002C (TWO SHAFT MACHINE) which drives centrifugal compressor with Mark5 control system.

 

saha,

GE frequently leaves some unused signals in the CSP--especially in Mark V. Sometimes, as much as 60% of the Control Constants listed in the Control Constants Display are not used for a particular turbine. Unused logic signals are set to logic "0" by default--but if forced to logic "1" they will remain "1" even if the force is removed--because there is nothing writing to them to make them return to logic "0". This really confuses a lot of people. (Don't force L83SCDB--especially if the turbine is running!!!)

I don't have access to a CSP at this time, but if I recall correctly L83SCDB has to do with Isochronous Speed Control--something that's not used with compressor drive applications, but is used with generator drive applications.

Since yours is a two-shaft machine, there are two shafts which need controlling, though once the LP shaft is near rated speed the HP shaft speed control is basically secondary to the LP shaft speed control. GE's philosophy with respect to two-shaft heavy duty gas turbine control is that fuel is used to control LP shaft speed and the second stage nozzles are used to control HP shaft speed when the unit is at rated "speed" (after start-up and acceleration). Yes; changing fuel does also change HP speed, but the second-stage nozzle control works its magic to make sure the change in fuel does more to drive the LP than the HP--since the LP is producing the torque to drive the compressor.

Again, I don't have access to a CSP so I can't comment specifically on FSRNV3. I'm not sure you're exactly interpreting the block correctly, but the MIN SEL function is where the "heart" of the switch between "Loop 1" and "Loop 2" takes place. Once the LP speed gets to the region where it is to be controlling, it becomes the driving force for FSRN--FSR Speed Control.

Wish I could be more help. Perhaps if you could paste the BBL to a response in control.com (the FSRNV3.pic file is an ASCII text file) or you could copy the block from CSP.PRN and paste it in a post to control.com (you can drag the lower right corner of the 'Text' box in control.com to make it larger, and you can use the pre and /pre HTML tags to change the font to fixed pitch).

I'm on a well-deserved holiday for the next week-and-a-half in the middle of the South Pacific Ocean and will not be accessing the Internet. (Or at least that's my plan for now, anyway!) But, I'll check this thread on my return.