It has been my impression all along that this problem--the one with the unit being unable to accept a 1.0 or 1.2 MW motor starting--only became a problem after the MI (Major Inspection). Please confirm or correct this impression. Was this happening before the MI, too? Or only after the MI? When was the Mark V "upgraded" to a Mark VIe-compatible turbine control system? Before the MI, or during the MI?
I am unfamiliar with the TTRXV5 block you have provided; it's very unusual--to me, anyway. It's not the "normal" way I've seen exhaust temperature control done, but then I haven't seen every version that has ever been used and this is just new to me.
The IGV data indicates the unit is operating on the TTKI_[n] value--which you have provided once above as 968 deg F (520 deg C). (This business of providing some information in SAE unit and some in metric units is frustrating.... Not impossible, but frustrating).
One of the things I'm unclear about is this: TTRXB is approximately 536 deg C, and TTRX is 520 deg C, and TTXM is 520 deg C. I don't understand why they are biasing TTRX with some IGV-related value. What re the values of LSPDB2 and LIGVB and CSRGVTB? (CSRGVTB does not appear to be a Control Constant; is it a calculated value from another block/algorithm?)
That little snippet of TTRXB and the handwritten bit is probably NOT exactly how the TTRXV5 block works. It looks like something which was taken from some manual (maybe pre-Mark V-to-Mark VIe Life Extension upgrade???). So, if that's the case (you are trying to use something from a manual which was provided with the Mark V)--then it's likely it's not too applicable to the Mark VIe.... GE documentation can be pretty bad and confusing and misleading at times. The ONLY "documentation" that really means anything is what's running in the control processor(s) in the turbine control panel. Period. Full stop. Everything else requires logical thinking and analysis to see if it matches the application code (in this case: the TTRXV5 block). And, you would be a VERY LUCKY person if there was Item Help or Block Help in ToolboxST for this block (GE seems to be eliminating the descriptions of many, if not most, of these blocks--which is not good for Customers, technicians--or even their field service personnel). Sorry to be the bearer of this little bit of bad news, but somebody had to do it, apparently.
From the Mark VIe TTRXV5 block snippet you supplied, one can see TTRXP, TTRXS and TTRXB--but those are all outputs from the block. What happens to them AFTER they are output from the block??? I see a 'ttr_min' bit that interacts with a ramp limiter and a comparator and some fault and speed bias logic, but I expect that somewhere in the application code the lesser of TTRXP, TTRXS and TTRXB becomes, ultimately, FSRT.
In my experience in the past what was done was the IGV exhaust temperature control reference temperature was derived from TTRX. I have seen some cases where a small value was subtracted from the TTRX so that the IGVs were always open to TTRX--so that if there was an "event" (like, say, the starting of a large motor when the exhaust temperature (TTXM) was exactly equal to the exhaust temperature control reference (TTRX) because the IGVs were closed and keeping TTXM exactly equal to TTRX there wouldn't be this issue like you are experiencing.
It's pretty clear from the data you provided, that the IGVs opened after the motor started, because TTRXP and TTRXS both decreased, but both were still above TTRX (which is equal to TTKI_[n], 520 deg C, or 968 deg F). Again, the definition of Base Load is when the IGVs are a maximum operating angle (CSKGVMAX, on most units). So, the unit is definitely at Part Load; I can't say why the L30D_B logic went momentarily to "1"--because the IGVs don't appear to have ever gone to maximum operating angle.
Also, I don't ever recall ever monitoring TNR when a GT was operating on Isochronous Speed Control.... So, I'm kind of a little surprised about you "obsession" with TNR in this thread. In my previous experience, there was a TNR (Droop Speed Control) and a TNRI (Isochronous Speed Control) value. To be honest, all I recall was if the operator tried to change load by clicking on RAISE- or LOWER SPEED/LOAD the frequency changed. When the unit is running on Isoch Speed Control, the operator has NO direct control of load--the turbine control will do everything it can to try to maintain speed (frequency) when load changes (motors start or stop or are unloaded or unloaded, electric tea kettles start and stop, Air Conditioners start and stop, etc.). When one tries to change the load of a machine running in Isoch Speed Control, one only succeeds in changing the speed reference--which changes the frequency (reference). If more fuel is put into the turbine than is required for maintaining speed (frequency), it CAN'T get turned into load by the generator. It just becomes speed (frequency)--more fuel equals more speed (equals more frequency); less fuel equals less speed (equals less frequency).
I hate to ask again fir more data (one of GE's FAVORITE requests when they haven't got a friggin' clue what is happening!), but I need to have data with CPD.... I apologize for not asking earlier.
Anyway, I have another question. You have mentioned Iceland. Are daily temperatures as high as 38- or 39 deg C this time of year? (I've only flown through Reykjavik once, and that was literally in the middle of an unexpected snow storm and because the snow plows couldn't keep up with the unusually deep snow that was accumulating in a very short period of time we were delayed leaving for several hours, which didn't upset me too much as the restaurant and salespeople were all very nice and polite). I know this probably doesn't make any difference to the problem at hand, but, I kind of get distracted by these kinds of little things.
Thanks for your patience!
Good Morning Sir
a). yes This problem comes after MI. We upgraded our control system to mark VIe from mark IV in 2011.
b). I try to explain about TTRXB.
If IGV opening is <76 deg, Then TTRXB=TTRX+CSRGVTB(30 deg F)
If IGV opening is >76 deg Then
for Example if IGV opening is 80 degree and TTRX is 968 deg F then
CSRGVTB=(86-80)*3=18 deg F
TTRXB= 968+18= 986 degree F.
After watching CSP, I will share the CSRGVTB algorithm/block.
c). L30D_B logic becomes to "1" when FSR shifted to FSRT in place of FSRN.
d). For CPD trend please find the attachment.
e). Iceland- this was due to auto spelling correct. I was asking for island unit(captive power plant). at this time of year, ambient temp reaches upto 45 deg C.
f). It is regular activity to change over the 1.0 or 1.2 MW motor at our unit. Today again we started 1 MW motor in droop mode. GT again shifted to base load. this time also TNR did not changes when load increased. (Unfortunate I have no trend for this event).
please mention what parameter you required to resolve this problem. I will share the trend file for next event.
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