Sir,

I work in a combine cycle power plant, which has 3 GE 9E gas turbines and one GE C7 steam turbine. The control system is MarkVIe.

Can you please explain to me the difference between TTRXP & TTRXS.
My second question is we normally operate on external load & AGC. When on Droop Speed control is TTRXP > TTRXS

 

Open a Watch Window in ToolboxST and put TTRX, TTRXP & TTRXS in it. Also put TTRX, TTRXB, FSRN, and FSRT. You should find that the Exh. Temp. Reference, TTRX, is equal to the Primary Exh. Temp. Control Reference, TTRXP, and that the Secondary, or back-up Exh. Temp. Control Reference, TTRXS, is just slightly higher than than TTXP. IF the unit is operating at Base Load then FSRT (which is driven by TTTX) will be less than FSRN (Droop Speed Control FSR). Also, the average calculated actual exhaust temperature, TTXM, will be equal to TTRX.

Exh temp references are being calculated all the time, even when the unit is not running.

By the way, TTRXB is a signal that is used when the turbine is a two-shaft machine. For most generator drives, it is equal to the lesser of TTRXP or TTRXS, and also equal to TTTX.

When the unit is <b>NOT</b> on Base Load, then FSRN will be less than FSRT and that's when the unit is on Droop Speed Control.FSR is always the lesser of FSRN or FSRT when the unit is running. The Speedtronic will use External Load Control when it's on Droop Speed Control and up until the the time that TTXM equals TTRX at which time the control will switch from Droop Speed Control to Exh. Temp. Control.

If the unit has conventional combustors, then if CPD feedback is lost the unit will switch to back-up Exh. Temp. Control. At all other times (under normal conditions) TTRX should be equal to TTRXP; and TTRXS should be greater than TTRXP.

You can use Trend Recorder to monitor these signals and capture them for analysis (to save disk space use a low resolution time base of once per second).

Learn to use the "tools" that ToolboxST has. You can observe data and save it for analysis and examination.