Getting a better understanding of GT control PART 3

N

Thread Starter

Neo

CSA,very glad to receive your response.

Your explanation on L2FSTG is enlightening,and i think i should not read siganl names literally.

As for this thread is very long and disorganized, i open the part 3 thread.
PART 1 URL: http://www.control.com/thread/1399292917
PART 2 URL: http://www.control.com/thread/1405133283
-----------------------------------------------------------------------------<pre>
L12HF_ALM L12HFD_C_ALM L12HFD_P_ALM L12H_P L12H_ACC L4PSTX3
--------|/|--------|/|--------|/|---------|/|--------|/|---------( )</pre>
L12HF_ALM = CONTROL SPEED SIGNAL LOSS - HP
L12HFD_C_ALM = CONTROL SPEED SIGNAL TROUBLE
L12HFD_P_ALM = PROTECTIVE SPEED SIGNAL TROUBLE
L12H_P = VPRO HP Overspeed Trip
L12H_ACC = VPRO - Loss Of Protective Speed Signal


<b>L12HF_ALM</b><pre>
L12HF L12HF_ALM
--------||------( )</pre>
L12HF = Loss of control speed signal
L12HF_ALM = Control speed signal loss

I think this signal is similar to L12H_FLT,and L12H_FLT is for protective HP speed signal.

<b>L12HFD_C_ALM</b><pre>
L12HFD_C L12HFD_C_ALM
--------||--------()</pre>
L12HFD_C = HP overspeed fault - control input trouble
L12HFD_C_ALM = Control speed signal trouble


<b>L12HFD_P_ALM</b><pre>
L12HFD_P L12HFD_P_ALM
--------||--------()</pre>
L12HFD_P = HP overspeed fault - Protective input trouble
L12HFD_P_ALM = Protective speed signal trouble

I think L12HFD_C_ALM and L12HFD_P_ALM are similar too, both of these two signals are indicating that TNH and TNH_OS are not matching.

<b>L12H_P</b>

L12H_P = VPRO overspeed signal

It is overspeed signal,and it comes from VPRO card. I was curious whether it should be lower case.

<b>L12H_ACC</b>
L12H_ACC = VPRO-Loss of Protective Speed Sigal

It is a signal that comes from VPRO card.

<b>In conclusion, siganls in L4PSTX3 rung are all related to speed siganls.</b>

--------------------------------------------------------------------------------------<pre>
L3SFLT L86GCVT L86FPG2LT L4PSTX4
------|/|-------|/|------|/|--------( )</pre>
L3SFLT = CONTROL SYSTEM FAULT TRIP;
L86GCVT = GCV Not Following Reference Trip;
L86FPG2LT = P2 post-ignition low pressure trip logic;

Best regards!
Neo
 
Neo,

Thanks for breaking up this thread again.

As for not reading signals literally, well, it's so unfortunate that they can't be trusted. It should be clear that if signal names are chosen and written correctly they would be so much easier to read and understand. If only, .... And, if wishes were horses I'd be neck deep in horse manure.

I believe if there are no Toolbox rungs for L12HF_C and the like that there may be some explanation in the Mark VI System Guide, GEH-6421. It's also unfortunate that "firmware" signals and logic can't be seen using Toolbox. But, again, the horse manure gets even deeper.

I think we're getting a little lax with the statements of the rungs....

And, yes; you are correct. All of the signals for L4PSTX3 are speed related. I hope it was by some (slight) design.

Please continue with the next Protective Status Trip rung. I know this is getting long, but I'd like to go through the logic signals for each of the contacts in the rungs. Sometimes, like with the 'Excessive Fuel Flows' the text messages can be misleading and we can learn a lot about GE heavy duty gas turbine control philosophy.

By the way, you didn't comment on the lack of a Master Reset Latch for the 'Excessive Liquid Fuel Flow on Start-up' trip.... It's odd that it's "necessary" for one fuel, but not the other. Just another inconsistency we must learn to deal with, eh?
 
<pre> L3SFLT L86GCVT L86FPG2LT L4PSTX4
------|/|-------|/|------|/|--------( )</pre>
L3SFLT = CONTROL SYSTEM FAULT TRIP;
L86GCVT = GCV Not Following Reference Trip;
L86FPG2LT = P2 post-ignition low pressure trip logic;

<b>L3SFT</b><pre>
XVCMIR0S01_A XVCMIS0S01_A L14HSX L94X L3SFLT
-----|/|----------|/|-----------|/|------|/|--------( )
XVCMIT0S01_A | |
-----|/|------- |
XVCMIR0S01_C XVCMIT0S01_A |
---|/|-----------|/|--------</pre>
L3SFLT = CONTROL SYSTEM FAULT TRIP;
L14HSX = Auxiliary signal to L14HS;
L94X = Startup Check Stop GT Normal Shutdown;
XVCMIR0S01_A = <S> SLOT 1 VCMI DIAGNOSTIC ALARM;

I don't get XVCMIR0S01_A,XVCMIT0S01_A,XVCMIR0S01_C. What i know is that VCMI card is for communication between <R>, <S>, <T>, which is essential for SIFT.

According to the rung above,when 2 out 3 VCIM diagnostic alarms,and the unit is under normal operation, L3SFT will go to
logic 1, and the unit trips.

CSA,can you explain the signal name XVCMIR0S01_A, i have no idea about it.

<b>L86GCVT</b>

L86GCVT = GCV Not Following Reference Trip

This signal is one of out outputs of GCV_FAULT block.

If abs(gcv_pos-gcv_ref) >= 5 and it last for more than 5 sec, L86GCVT will go to logic 1, and L86GCVT need master reset.

I think this signal means GCV is a little out of control. CSA, if this happens, what should i do to find out the problem?
I think we should check MOOG, right?

<b>L86FPG2LT</b><pre>
(KFPG2LT>FPAG2)--------
| L84TG L2TVZ L2WX L86FPG2LT
------| |------||--------||--------|/|------( T )
15sec</pre>
L86FPG2LT = P2 post-ignition low pressure trip logic;
KFPG2LT = 24psig;
FPAG2 = Interstage Auxgas press,P2;
L84TG = On Total Gas Fuel;
L2TVZ = Firing permissive;
L2WX = Warm complete;

If P2 is less than 24 (psig) during the period between firing and warmup complete,than L86FPG2LT will go to logic 1.
I don't get it, what is this trip signal for, and why it only works between the period between firing and warmup complete.

<b>By the way, you didn't comment on the lack of a Master Reset Latch for the 'Excessive Liquid Fuel Flow on Start-up' trip.... It's odd that it's "necessary" for one fuel, but not the other. Just another inconsistency we must learn to deal with, eh?</b>

To be honest,i have no idea about it too. I think Master Reset is to make operator to confirm that they have dealt with this problem. For the difference between gas fuel and liquid fuel, i think this unit burns liquid fuel fuel during startup.

So why L2SFTL is lack of Master Reset?
CSA, i bet you know that!

Best regards!
Neo
 
Neo,

<b>L3SFLT</b><pre>
XVCMIR0S01_A XVCMIS0S01_A L14HSX L94X L3SFLT
-----|/|----------|/|-----------|/|------|/|--------( )
XVCMIT0S01_A | |
-----|/|------- |
XVCMIR0S01_A XVCMIT0S01_A |
---|/|-----------|/|--------</pre>
L3SFLT = CONTROL SYSTEM FAULT TRIP;
L14HSX = Auxiliary signal to L14HS;
L94X = Startup Check Stop GT Normal Shutdown;

XVCMI<b>R</b>0S01_A = <R> RACK 0 SLOT 1 VCMI DIAGNOSTIC ALARM
XVCMI<b>S</b>0S01_A = <S> RACK 0 SLOT 1 VCMI DIAGNOSTIC ALARM
XVCMI<b>T</b>0S01_A = <T> RACK 0 SLOT 1 VCMI DIAGNOSTIC ALARM

I think there was a typo in the rung; all three signals should end in _A, for a two-out-of-three (2oo3) voting.

Yes; VCMI is important for SIFT--but not just for SIFT, but for all hardware voting of signals, as well. It's how each processor knows what the other two processors are "thinking" and seeing (inputs).

> According to the rung above,when 2 out 3 VCIM diagnostic alarms,and the unit is
> under normal operation, L3SFT will go to logic 1, and the unit trips.

Look at the rung closely--there are L14HSX contact and L94X NC contacts in the rung, which says that whenever L14HSX or L94X is a logic "1" that the trip will be blocked. So, this rung will be enabled only when below L14HSX or when L94X is active. <b>Please post the rung for L14HSX (if we haven't done so already.</b>

<b>L86GCVT</b>

L86GCVT = GCV Not Following Reference
Trip

> This signal is <b>one</b> of out outputs of GCV_FAULT block.

You only covered <b>one</b> of the three possible outputs of the GCV_FAULT block. What about the other two?

> I think we should check MOOG, right?

This is classic tribal knowledge mentality thinking--which is another way of saying it's <b>not correct</b> to automatically suspect the Moog servo-valve! Let's examine all the outputs of the GCV_FAULT block, and then we'll determine what to do if any one of the three outputs of the block are active. But, I can pretty much assure you--checking the servo is not correct.

By the way, please explain how one would check the servo-valve. It's always informative for me when people make statements like this because that's what they heard the GE field service person say, or what they've heard other people say. I really need to understand what you mean when you say this, because I'm on a personal mission to try to understand how people would actually check the servo-valve to see if it's working properly--and how to determine if it's not.

One former poster to control.com said his company spent a LOT of money to buy a servo-valve tester. Unfortunately, we've never heard back from that person to see if the tester has helped reduce the cost of purchasing "new" (more likely, rebuilt/refurbished) servos, or if it's helped resolve operational problems with servos. It would be most helpful to a lot of people if we had that feedback....

I'm short of time today, and we'll cover the rest of the L4PSTX4 rung after we cover L14HSX and the other two outputs from GCV_FAULT--and how one checks servo-valves.
 
CSA:

We have dealt with L14HSX before,and it is an aux signal to L14HS. It will keep logic 1 while L14HS is logic 1 until L94X is logic 1 or L4 is logic 0. It meant for low grid freq situation.

<b>L86GCVT</b>

"This signal is one of out outputs of GCV_FAULT block. You only covered one of the three possible outputs of the GCV_FAULT block. What about the other two?"

The other two outputs of GCV_FAULT block is covered in L3ACS. <pre>
L3ACS L4PRETX
-----|/|---------( )
l27qel |
-----||-------
L45HGD_PRET |
-----||-----


L4PRETX L28FDX L4PRET
-----||-------|/|-------( )</pre>
So,this time i would like to interpret this time.
As we can seen from above rung,when L3ACS is logic 0 <b>pre-ignition</b>,then the unit trips.<pre>
L3GFLT L3LFLT L62TT2 L3ACS
----|/|-----|/|------|/|--------( )
| |
L84TL | L84TG |
-----||------||----</pre>
L3GFLT = Gas fuel control fault;
L3LFL = Liquid fuel control fault;
L84TL = On total liquid fuel;
L84TG = On total gas fuel;
L62TT2 = startup check stop multiple start counter;

As we use liquid fuel during startup (L84TL=1), and if L3LFLT is logic 1, then L3ACS will go to logic 0, the unit trips.

<b>L3GFLT</b><pre>
L3GCVFLT L3GFLT
-------||---------------( )
L3GRVFLT |
-------||------
L3GRVPFLT |
-------||------</pre>
L3GFLT = Fuel Gas Control Fault;
L3GCVFLT = GCV SERVO TROUBLE;
L3GRVFLT = GAS RATIO VALVE POSITION SERVO TROUBLE;
L3GRVPFLT = Stop/Speed Ratio Valve Not Tracking Trip.

<b>L3GFLT for GCV, and L3GRVFLT, L3GRVPFLT for SRV.</b>

<b>L3GCVFLT</b><pre>
L3GCVFB L3GCVFLT
-----||----------( )
L3GCVO |
-----||-------
L3GCVSC |
——||-------</pre>
L3GCVFLT = GCV SERVO TROUBLE;
L3GCVFB = GCV1 Position Feedback Fault;
L3GCVO = GCV1 Open Trouble Alarm Logic;
L3GCVSC = GCV1 Servo Current Fault.

L3GCVFB will go to logic 1 when gcv_pos is less than -5;
L3GCVO will go to logic 1 when gcv_pos is larger than 5 when GCV is ought to be closed(L3GCV=0).

I am a little curious about L3GCV.

<b>L3GCVSC</b><pre>
(GCV_CUR<K3GCVSC)---
| L3GCV L3GCVSC
-----| |--------|/|---------(T)
5sec</pre>
GCV_CUR = GCV Servo Current Feedback;
L3GCV = Fuel Stop Valve Enable;
K3GCVSC = 37.5;

According to the above rung,when the GCV is closed, if servo current is less than 37.5PCT, then L3GCVSC will go to logic 1, and the turbine trips.

I don't understand why there exist servo current when the GCV is closed. I think the PI algorithm in VSVO card is different from that in steam turbine. As i once told by my colleague,when LVDT feedback equals cmd value, the servo current ought to be zero.

<b>L3GRVPFLT</b><pre>
(abs(fpragout-fsagr)>5)---
| L3GRV L2WX L3GRVPFLT
----| |------| |-----------------|/|--------(T)
| |
| L3GRVT L86MR1 |
|--| |--------| |---- </pre>
I think this signal is similar to L86FPG2LT,both of them is relevant to SRV.
But there are also differences:

1) One measures P2,while the other measures valve position.

2) L3GRVPFLT cannot be unlatched while L2WX is logic 1.

3) If L28FDX is logic 1, the unit will not trip although L3GRVPFLT is logic 1.

L3LFLT is similar to L3GFLT, if necessary, i will cover it next time.

As for the <b>servo-valve</b>, i would like try to do it next time.

CSA, it's not hurry for you to respond, work well, sleep well:)

Best regards!
 
Neo,

I thought we'd covered the L14HSX before. So I'm kind of surprised about how it was misread.

I'm getting more confused by the thread; this is getting quite disorganized--not at all what I'd envisioned when we started this journey of discovery. Anyone coming along later will surely find some nuggets of information, but it will only be after some serious head-shaking. I'm really sorry this got so disorganized; even I'm confused when I try to go back and look up things we may or may not have talked about.

Oh, well--we can't turn around and go back, and we're not quitters. So, onward we go--once more unto the breach!

Not being able to see the Toolbox signals in a running panel I'm kind of confused about the XVCMIx0S01_A signals. It would seem they would be a logic "1" when there is no "Alarm" (I'm presuming the '_A' means 'Alarm'--but that's just a presumption at this point. Can you confirm what the states of the logic signals are when the VCMIs are all good, Neo, please? Thanks!

The statement for L3SFLT should read something like:

<b>If the VCMI for <R> OR the VCMI for <T> AND the VCMI for <S> OR the VCMI for VCMI for <R> AND the VCMI for <S> <i>DO NOT</i> have a serious "Alarm" (fault) AND L14HSX <i>IS NOT</i> a logic "1" AND L94X <i>IS NOT</i> a logic "1" then L3SFLT will be a logic "0".</b>

Now, good signal naming would mean the XVCMIx0S01_A signals were a logic "1" when they were in alarm, BUT, how can a logic signal be a "1" if there's no communication.?.?.? So, again, it seems it's just another bad choice of a signal name (or our presumption is incorrect!). So, it would seem that the signals must be a logic "1" when there's NO alarm, and they are healthy and communicating, and a logic "0" when there IS an alarm and they are not healthy and not communicating. (Isn't this confusing??!!??)

So, what this rung is saying is: Anytime two-out-of-three VCMIs are not healthy and not communicating and the unit is above 14HS and a STOP is NOT active the unit will trip, because L3SFLT will go to a logic "1", which will drop out L4PSTX3, which will pick-up L4PST, which will pick up L4T which will drop out L4. (Again--isn't this fun???)

Anyway, continuing on, ... actually, that's all the time I have for today.

One question: What do you mean by you'd like to do the servo next time?
 
Neo,

Do you want to answer the question about servos, or do you wish to continue with the Protective Status trips?

Maybe it would be best to open another thread for the servo question(s)?
 
CSA:

I find this website is very helpful,because i can search for what i need.
And i can always find helpful threads answered by you and many others.

I think our thread will help others too in this way, and i think what we do now is very meaningful, though it is not perfect.

If you come up some ideas, and think it should be talked, i can open a new thread. this will keep our main thread in order. Is that OK?

In fact, i have little knowledge about servos, so i need some time. When i think i am ready, i will respond in a new thread.

I respect your idea, and would like to do as you command.

Nowadays, i spent some time reading application code, and i find the journey with you help me a lot in reading application code. This is a miracle!

Best regards!
Neo
 
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