Getting a better understanding of GT control PART 2

N

Thread Starter

Neo

First i would like to thank CSA for him selfless dedication to this thread ,and i think guys who have been following this thread learned a lot from this journey.

It would be good that more and more guys get involved in this journey, and i will continue to play the role of Watson.

<b>In order to make this journey in order and alleviate CSA's load, i would to propose several rules, and i wish everyone engaged will obey if you think they are reasonable.</b>

1) From PART II, i will start a new thread when there are about 15 to 20 replies, making it easier for guys to read. When a new thread is opened, guys who are following this thread can ask your questions about the previous one. I think this would make this journey in order.

2)Think a while before you ask, making it easier for CSA to answer.

<b>So guys you can ask your questions about the previous one. And CSA and i will do our best to continue this journey in PART 2. I will try to make PART 2 within 15 replies, making it easier for you to follow.</b>

Is that OK, CSA?

Here is the PART 1 URL: http://www.control.com/thread/1399292917
-------------------------------------------------------------------------------------------------------
Before interpreting signal L63QTX,i would like to make classification to the L94SD thing CSA mentioned several times.<pre>
(TNH>K60RB)----
| L28FDY L60RB
------------| |-----|/|--------( )




L60RB L94SD L83RB
---------|/|--------||----------( )


L28FD L83RB L94T
-----|/|-----||-------( )



(TNH>K60RB)----
| L60RB
------------| |------( )</pre>

L60RB L94SD L83RB
---------|/|--------||----------( )

L83RB L94T
---------|/|------------------( )</pre>

I didn't remove L94T from the L60RB rung, while i removed L28FDY from the L60RB rung and L28FD from L94T rung. I am confused about the existence of L28FDY in the L60RB rung and L28FD in the L94T rung, for i think as long as the speed ramps down to K60RB during normal shutdown,the L94T will go to logic 1.

I am curious about the difference between L28CAN and L28FD.
I find when any one of the can equipped with flame detectors flames out, L28CAN will go to logic 1. while two out of four flame detectors detects no flame, L28FD will go to logic 1. Can L28FD and L28CAN
replace the other?

If my time is available,i would like to check FSRSD block to see the variation of FSRSD during normal shutdown.
--------------------------------------------------------------------------------------------------------<pre>
L63QTX L45FTX L5ESTOP1_FZA L86GT L63ETH L63CSHH L4PSTX1
------|/|------|/|------|/|-------|/|-------|/|-------|/|-----( )</pre>

L63QTX = Lube Oil Gen Prssure Low Low Trip
L45FTX = Fire Indication Trip
L5ESTOP1_FZA=VPRO E-STOP PB Circuit Open
L86GT = Generator Protective Trip
L63ETH = Exhaust Duct Pressure High Trip
L63CSHH = Flow Inlet Duct Diff Pressure GT Trip

<b>L63QTX</b>
L63QTX is related to L63QT(Low L.O. Pressure TRIP). So when the L.O. pressure is too low to protect the bearings,L63QT will be logic 1.<pre>
L63QT L4 L63QTX
-------||--------||---------( )
L63QTX L4Y |
-------||--------|/|-------</pre>
L63QT = Lube oil Gen low pressure voted
L63QTX = Lube Oil Gen Prssure Low Low Trip

So why there is an existence of L63QTX? And can we change the above rung to the below;<pre>
L63QT L4 L63QTX
-------||--------||---------( )
L63QTX |
-------||-------</pre>
Or just below:<pre>
L63QT L4 L63QTX
-------||--------||---------( )</pre>
Best regards
Neo
 
Neo,

First, you (and anyone else reading this) is quite welcome for any help or insight I may have provided.

Second, I have been offered a last-minute holiday in the South Pacific Ocean and I'm going! I don't plan to check "the Internet" for about a week, maybe a week-and-a-half. I will check in when I return. Hope all goes well with this new thread! I'm leaving in a few hours, and have LOTS to do before I leave (this all came about in just a few hours--I'm a lucky man!). So, unfortunately I don't have much time--none, really. SORRY!

ALOHA!

I'll check in when I return.
 
CSA

I am very happy for you to have a real journey!

Our journey is not in hurry,so have a good time!

And i can also focus on my job for a week.

Just let me know when you are back.

Have a good time!

Best regards
Neo
 
Neo,

Whenever a field engineer says he or she is going on a "trip of a lifetime" it means he or she has been given a really bad assignment...

I have returned a couple of days early from mine, having narrowly averted what could have been a really bad situation. The problem<b>s</b> are all solved (and there were multiple problems, including a serious battery ground and a problem with incorrect servo wiring/polarity and an insane null bias current value).

It seems that when you can't understand or comprehend why a signal is used in a rung you just want to delete it. You are not considering how this would result in nuisance alarms and other problems when situations you aren't considering occur. Good software takes into account all considerations and situations, including when flame has already been lost (prior to L94T picking up) or when the unit is not running (L4 is a logic "0").

We are not re-writing established code here, though we will point out where it might have been written better. The 'chamber flamed out on shutdown' logic is another example of sequencing that was added "after the fact" and the author duplicated some signals that may not have been necessary and which may add to some confusion. But, as I grow older and read more code I find this is very common, and while it leads to software bloat and can cause serious problems for some applications when programmers arent' aware of the existence of such "ancillary" code, it happens very often.

About the only way to avoid such problems is to have one or two individuals who review every single line of code (rung) for symmetry and applicability. Unfortunately, that doesn't happen and can also lead to a feeling of belittlement and being downtrodden on the part of people who are subject to such reviews--if the persons doing the reviews do not take the time to explain why they are not accepting or are modifying the code submitted. It takes a lot of time to explain some things to some people--and when time is at a premium (as it is these days) these things just don't happen. The other situation is that the reviewer can just be a tyrant and make unnecessary changes or just reject submissions without taking the time to understand or comprehend the intent. And, this is also bad for morale and the business as a whole.

So, usually when you read code/software you have to realize that many people may have "had their hand in the pie" and that can lead to a messy pie---even if it's a good one! It may not look so good, but if it is satisfying and doesn't upset the eyes or the stomach too much, it serves it purpose.

I would like to stop with the "re-writes" of code and stick to what's there. If you can't work through the necessity of the signals/permissives, then we will try to take the time to do so. Again, one must consider other possibilities--not just the normal running (or starting or shutdown) situations.

Take, for example, L63QTX. When the turbine is shut down (at zero speed, with Cooldown OFF), L63QT would be a logic "1" and it would be impossible to start if the turbine were tripped because of low-low L.O. pressure. So, the presence of L4 prevents a trip when starting from zero speed with Cooldown OFF.

Why do you suppose L4Y is present in the lower parallel section of L63QT? When is L4Y a logic "1"? When would L63QTX and L4Y bith be a logic "1"?<pre>
> L63QT L4 L63QTX
>-------||--------||---------( )
> L63QTX L4Y |
>-------||--------|/|-------</pre>
As for your rules, I'm not quite sure I understand them....

Anyway, let's not re-write long-standing code but rather try to understand why it's written the way it is--considering as many other possible operating (or tripping) conditions as possible.
 
CSA:

It seems that it is hard for a field engineer to enjoy a "trip",and i feel that you're not in good mood.

So wish you have a good in the first place. :)
----------------------------------------------------------------------------------------------------------
Thank you for your guidance,i will focus on trying to understand why it is written in the way it is.<pre>
L63QT L4 L63QTX
-------||--------||---------( )
L63QTX L4Y |
-------||--------|/|-------</pre>
"Why do you suppose L4Y is present in the lower parallel section of L63QT? When is L4Y a logic "1"?
When would L63QTX and L4Y bith be a logic "1"?"<pre>
L63QT; ----------(1)
|
(0) ----------

L4: (1) ----------
|
-------------(0)

----------(1)
|
L4Y (0) --------------
----(1)
| |
L63QTX(0)----------- -----------(0)</pre>
So in conclusion,the presence of L4Y in the lower parallel section of L63QT is to make the L63QTX a pulse wita width of 1 sec. Is it right, and i am not sure why it is written in this way.But this remind me that there is always a L86MRS signal to reset alarm signal.

"Take, for example, L63QTX. When the turbine is shut down (at zero speed, with Cooldown OFF), L63QT would be a logic "1" and it would be impossible to start if the turbine were tripped because of low-low L.O. pressure. So, the presence of L4 prevents a trip when starting from zero speed with Cooldown OFF."

This is enlightening.But a question occurs to me,during cooldown,L4 is logic 0,how to protect the unit if lube oil pressure is low(L63QT is logic 1).

Best regards!
Neo
 
Neo,

Seems my reply to this post never got posted.... I've been having problems with this recently; don't know if it's my end or what, but, here goes again.

There are good assignments, and there are bad assignments, and there are no-win assignments. A no-win assignment is one where no matter what problem(s) is(are) solved, no matter what explanation is given or instruction applied one is just never going to satisfy that Customer who has wildly inaccurate perceptions of what should or shouldn't be happening and how the Speedtronic and the turbine should work. Since the Speedtronic is such a sophisticated piece of equipment it should fix itself, it should provide guidance and instruction to operators and technicians, it should prevent every possible operator error (and ill-conceived management decision) from causing damage to the turbine, and it should NEVER alarm unless it's willing to provide exact troubleshooting and resolution procedures for the operator and technician. Some people just want to believe everything the salesperson says, and they want every bell and whistle even if they didn't pay for it or it doesn't exist--and they're not going to be satisfied unless and until they get it. That was the kind of assignment I was sent on.

To your comment about my disposition regarding your re-write of long-standing rungs, it's just that I've encountered this before. Someone gets a little bit of knowledge, and suddenly they are expert at writing logic and code and feel that they have a "better idea." I was hoping that wasn't going to happen in this case....

Anyway, your logic diagram for L63QTX was good and correct. The reason there is a 1 second overlap on low-low L.O. pressure is that it ensures the turbine remains tripped on low-low L.O. pressure. There is no latching Master Reset contact in this particular logic.

As for your query about cooldown and low-low L.O. pressure protection, please post (and analyze) L63QT and L4HR.

But, we are straying from the L4T discussion--a little straying is fine, but we need to finish this journey, don't you think?
 
CSA

> To your comment about my disposition regarding your re-write of long-standing rungs, it's just that I've encountered
> this before. Someone gets a little bit of knowledge, and suddenly they are expert at writing logic and code and
> feel that they have a "better idea." I was hoping that wasn't going to happen in this case....

I think you misunderstood me. I do not re-rewrite rungs, and i do that just to propose my questions about why there should be L4Y, and if we delete it from rung ,what will happen.

It is just a way to ask my question.

It feels not good when you are misunderstood by someone you
respect. But that's ok, and i am always grateful about your guidance. Now, i am very interested in gas turbine control.
Thanks again.

Yes,we have to finish L4T. It seems i am not sure to what extent a signal should be read.

I will do my assignment on L4 several hours later.

Best regards!
Neo
 
CSA,

I think it's impossible to satisfy every customer especially those have little knowledge about speedtronic and no interests on GT control.

Wish you have a good day.

Last several weeks i am occupied with work. You know, i am little clumsy ,so it takes me time to do the job.
Glad to say that it is almost done, and i can spend more time on L4T journey. :)

Let's get started!
------------------------------------------------------------------------------------------------------------<pre>
L63QTX L45FTX L5ESTOP1_FZA L86GT L63ETH L63CSHH L4PSTX1
------|/|------|/|------|/|-------|/|-------|/|-------|/|-----( )</pre>
L63QTX = Lube Oil Gen Pressure Low Low Trip
L45FTX = Fire Indication Trip
L5ESTOP1_FZA = VPRO E-STOP PB Circuit Open
L86GT = Generator Protective Trip
L63ETH = Exhaust Duct Pressure High Trip
L63CSHH = Flow Inlet Duct Diff Pressure GT Trip

<b>L45FTX</b><pre>
l45ftx1 L45FTX
-----||------------( )
|
l45ftx2 |
-----||------|
|
l94f1b false|
----||---||-- </pre>
l45ftx1 = fire protection aux/turb/load compt fire detection
l45ftx2 = fire protection exciter compt fire detection
l94f1b = fire protection exciter compt CO2 release
L45FTX = Fire Indication Trip

45:Flame detector; F:Flame; T:Trip;X:?
aux/turb/load compt:Aux/Turbine/Load Compartment. I am confused what aux compartment refers to?

So either of l45ftx1 or l45ftx2 is logic 1,L45FTX will go to logic 1. If fire was detected in aux/turb/load/\exciter compartment,then GT trips.

If i wanna to check where is the flame detector installed, i should to refer to P&IDs?

I am confused about how can l45ftx1 one signal indicates whether there is fire in aux, turb and load these three compartments.

<b>L63ETH</b><pre>
l63et1h l63eah false L63ETH
------||-----||------||-----( )
l63et2h | |
------||--- |
l63et1h l63et2h |
------||----||----</pre>
l63et1h = Exhaust duct press high trip switch 1
l63et2h = Exhaust duct press high trip switch 2
l63eah = Exhaust duct press high trip alarm switch
L63ETH = Exhaust duct pressure high trip

63:pressure switch; E:exhaust T:trip H:high

If any two of the l63et1h, l63et2h and l63eah three signal is logic 1, then L63ETH will go to logic 1. If the pressure drop in the exhaust duct is high, then the GT trips.

CSA, too much pressure drop in the exhaust duct will lead to a GT trip? I think pressure drop in the exhaust duct will decrease the overall efficiency, but never will i think it is considered a severe problem that will lead to a trip.

Why it is so important?

I think i should check the device summary to see the difference between l63et1h and l63eah.

<b>L63CSHH</b><pre>
l63cs2ahh l63cs1h false L63CSHH
------||-----||------||-----( )
l63cs2bhh | |
------||---- |
l63cs2ahh l63cs2bhh |
------||----||----</pre>
l63cs2ahh = Flow inlet duct pressure diff switch 2A very high
l63cs2bhh = Flow inlet duct pressure diff switch 2B very high
l63cs1h = Turbine compressor inlet pressure
L63CSHH = Flow inlet duct diff pressure GT trip (not correct?)

63:pressure switch; C:? S:? HH:very high?

It seems that L63CSHH is similar to L63ETH.
If any two of the l63cs2ahh, l63cs2bhh and l63cs1h three signal is logic 1, then L63CSHH will go to logic 1. If the pressure drop in the inlet duct is high, then the GT trips.
-------------------------------------------------------------------------------------------------------------
CSA,is that ok?
I would like to proceed next time.

Best regards
Neo
 
_________________________________________________________________________

DISCLAIMER: This post is not intended to show that the author have a “better idea” of anything but just to show the author’s interest in the thread and to share his ideas.
________________________________________________________________________

Neo,

I’m sure that CSA will answer all your questions when he get some time.
Here are my ideas on your post.

>> L45FTX: X here indicates that this coil is “auXiliary” to L45FT coil, it does not indicate auxiliary compartment (or any other compartment).

>> CSA, too much pressure drop in the exhaust duct will lead to a GT trip?

There is not a pressure drop.

Consider this condition, when GT is exhausting in HRSG (with bypass stack arrangement). It is actually the “back pressure” exerted by HRSG on GT, and that back pressure will reduce the efficiency of GT. But this is not all; it’s more than that, it’s about GT & HRSG protection. If, by chance the inlet damper and by-pass damper both get closed at the same time (due to any fault) and GT is still exhausting in HRSG. What will happen? Probably there may be an explosion, (but to avoid it, explosion door is provided in the arrangement, that will open to prevent explosion). Now, the GT should be shutdown (tripped) to investigate and rectify the problem.

>> I think I should check the device summary to see the difference between l63et1h and l63eah.

The alarm setting value will be less than the trip setting of the switch.

>> L63CSHH = Flow inlet duct diff pressure GT trip (not correct?)

Air inlet filter house is having filters and that will get dirty. If the filters are too dirty and sufficient air flow is not available to the compressor, vacuum will be created in the filter house, compressor will starve and compressor pulsation will occur. (There are implosion doors in inlet filter house to avoid collapsing of inlet filter house due to vacuum.)

>> 63: Pressure switch; C:? S:? HH:very high?

C: Compressor
S: Suction

>> It seems that L63CSHH is similar to L63ETH

No, this two things are very different, (that may be evident to you now).
 
SB,

Thanks for helping explain. I've been experiencing some problems with posts recently, and I was waiting for Neo to respond, but, I see now my most recent submission didn't get to the Kind, Friendly Moderator. My bad for not checking; sorry.

Neo,

Let's have a very close look at L63ETH and L63CSHH:
<pre>
l63et1h l63eah <b>false</b> L63ETH
------||-----||------||-----( )
l63et2h | |
------||---- |
l63et1h l63et2h |
------||----||------

l63cs2ahh l63cs1h <b>false</b> L63CSHH
------||-----||--------||-----( )
l63cs2bhh | |
------||----- |
l63cs2ahh l63cs2bhh |
------||----||-------</pre>
What the normally open <b>false</b> contact in both those rungs says to me is: Both of these functions are disabled. <b>false</b> is always a logic "0", and so the normally open <b>false</b> contacts in these two rungs will never be closed. And that means that regardless of the states of any of the contacts upstream (ahead of; before) the normally open <b>false</b> contacts that the logic coils of either of the two rungs will never be logic "1".

So, any time one finds a normally open <b>false</b> in a string, it basically means that nothing downstream of it is ever going to be a logic "1"--which effectively means it is disabled.

I would be surprised if any of the devices (the ones with lower-case signal names) are actually listed on the Device Summary for Neo's unit--or if they are, then someone decided that a high-high compressor suction or a high-high exhaust duct back-pressure (as SB has correctly noted) is NOT to be a trip condition for the turbine at his site.

This is another of GE's methods of using as much of the same logic (application code) for as many machines as possible--and disabling the bits that aren't necessary or applicable. And, creating a lot of confusion in the process. It makes GE's job easier, but it makes everyone elses more difficult when it's not clear.

This is, again, what I mean by not paying attention to every contact in the string. They are all important.

Think about how you "work" with a surgical mask on your face. If you are exerting a lot of effort, it can be very difficult to breathe--especially to get enough air when inhaling. And exhaling--if you want to keep the surgical mask firmly in contact with your face--can also be difficult. In turn, you reduce your efforts.

The same is true for any combustion engine. A dirty inlet air filter which causes a high suction will reduce the amount of air which can be ingested--which reduces the work which can be done. Similarly, if the exhaust is "blocked" or restricted then air can't get through the unit to be burned.

Inlet duct pressure drops and exhaust duct pressure drops are important to the performance of the machine--critical even. Some design engineers, in some applications (cement plants; dusty, dirty environments) deem excessive inlet pressure drops to be critical enough to trip the machine. Some inlet duct work can't withstand high compressor suction pressure (high inlet duct pressure drops) and will implode (collapse inward) if the turbine is not shut down or tripped.

Similarly, if there are obstructions in the exhaust that can mean elevated exhaust temperatures which can result in exhaust overtemperature trips and lower output/performance. Some causes can be plugged boiler tubes (usually when insulation gets blown out from behind plates in the exhaust and gets caught on superheater tubes--causing flow restrictions). Some emissions reduction systems can get plugged, and some, which use ammonia, can put too much ammonia in the exhaust raising the pressure (back-pressure in the gas turbine exhaust) and that can be dangerous for many reasons (personnel safety foremost; unit performance secondarily).

So, I would like to know, Neo, if the Trip Display on the HMIs at your site list the two trips which are effectively blocked: L63ETH and L63CSHH? Because if the turbine is not equipped with the devices, or if it is, then either the display is wrong or the application code may be wrong (the normally open <b>false</b> contacts should be removed).

Sorry, again, for being late with my response. I thought I had responded and Neo was busy with work. Thanks, again, SB for your input--and for getting me back on track on this thread.
 
CSA,

Thanks for the appreciation :)

But this is nothing as compared to what you're doing for the community. Posts on control.com by experienced persons like you have helped me a lot in whatever I've learned about control system of GE-design heavy duty gas turbines.

Thanks for contributing!
 
CSA:

Glad to receive your reply,and i have been waiting for your reply.I thought you are busy and you will reply when your time is available.
I need time to reply and interpret remaining signals in l4T rung.
And thanks for SB's reply too,it helps.

Best regards!
Neo
 
CSA:

L63CSHH and L63ETH trips are not listed in trip Display on the HMIs at my site, so they are manually blocked.

Clearly, i misunderstood L63CSHH and L63ETH ,and you and SB's explanation helps a lot. and i find you are good at making comparisons: the surgical mask comparison is interesting.
---------------------------------------------------------------------------------------------------------------
<pre>
L63QTX L45FTX L5ESTOP1_FZA L86GT L63ETH L63CSHH L4PSTX1
------|/|------|/|------|/|-------|/|-------|/|-------|/|-----( )
</pre>
L5ESTOP1_FZA = VPRO E-STOP PB Circuit Open
L86GT = Generator Protective Trip

<pre>
<b>L86GT</b>
l86tgt1 L86TGT1Z L86GT
----|/|--------( )------( )</pre>
l86tgt1 = Generator Differential Trip Chan 1
L86TGT1Z = inverted signal for l86tgt1

86: Lockout Relay G: generator T: trip
So when l86tgt1 is logic 1, then L86GT will go to logic 1, and the GT trips. I have a little knowledge about generator, and i can't comment more.

<b>L5ESTOP1_FZA</b>
<pre> L5ESTOP1_FBZ L5ESTOP1_FZA
----|/|--------------( )------</pre>

5: STOPPING DEVICE E: emergency
So when L5ESTOP1_FBZ is logic i, then L5ESTOP1_FZA is logic 1. I think if L5ESTOP1_FZA is logic 1, it means the emergency pb is pushed down.
------------------------------------------------------------------------------------------------------------
<pre>
L39VT L2SFT L12H_FLT l4ct L45HA_T L45HT_T L4PSTX2
--------|/|------|/|--------|/|--------|/|--------|/|------|/|--------( )</pre>
L39VT = Vibration trip
L2SFT = Startup Fuel Flow Excessive Trip
L12H_FLT = Loss of Protective HP Speed Inputs

<b>L39VT</b>
39 (MECHANICAL CONDITION MONITOR) V: Vibration T:Trip
L39VT = (L39VDIFF_GT+L39VDIFF_GEN+L39VDIFF_LG)

<b>L2SFT</b>
2: SEQUENCE TIMER(?) S: Startup F: Fuel T: Trip
<pre>
L60FFLH L14HA L2WX L2SFTL
--------||-------|/|--------|/|--------( )
2s</pre>
L60FFLH = Liquid Fuel Flow High
L14HA = HP accelerating speed signal
L2WX = Turbine Warmup Complete, Increase Fuel

According to the above rung, if L60FFLH is logic 1, L2SFTL will go to logic 1 when the unit is during startup before warmup is complete (I think before L1HA is logic 1, L2WX is already logic 1).

CSA, what will happen if L2SFT is logic 1 and the unit doesn't trip, and what causes may lead to liquid fuel flow high?

Best regards!
Neo
 
Neo,

We're just learning here, so it's understandable if you miss the <b>false</b> contacts in the rungs. There was also a <b>false</b> in one of the parallel strings of the fire protection rung (L45FTX).

I don't know why we're missing so many things here, but we are.

<b>L86GT</b><pre>
l86tgt1 L86TGT1Z L86GT
----|/|--------( )------( )</pre>
l86tgt1 = Generator Differential Trip Chan 1
L86TGT1Z = inverted signal for l86tgt

You wrote:

> 86: Lockout Relay G: generator T: trip
> So when l86tgt1 is logic 1, then
>L86GT will go to logic 1, and the GT trips. ...

What about L86TG1Z? I see the longname description for l86TG1Z you got from ToolboxST, but is there a rung for L86TG1Z? I think you'll find the longname description is incorrect (SURPRISE!!!), and it's really a timer--but that's just a SWAG (Scientific Wild-Arsed Guess). Please post the rung for L86TG1Z and then re-write your statement for L86GT. If it is actually a timer, then I will be quite surprised as it's not typical for a turbine trip from the generator control panel to be blocked with a timer, but I'm just guessing as to what logic is driving the timer.

I think we covered the Z signal name suffix when we talked about L4Z, which is is a timer to L4, that is, it is a logic "1" some time after L4 is a logic "1" (1 second, if I recall correctly). So, I'm SWAGging that L86TG1Z is a logic "1" some time after l68tg1 is a logic "1", but, again, that's pretty unusual for any turbine I've ever worked on--so I'm extremely curious about L86TG1Z, and what purpose it serves.

l86tg1 is coming from a lock-out relay in the Generator Control Panel, and usually any of several generator protective relays can actuate the lock-out relay. You're not expected to know (at this point in your career) what actuates 86G-1, but, as a technician you should get a copy of the generator protection elementaries (schematic drawings) and find 86G-1 and write down all the things that can trip 86G-1--because those are all things that can trip the turbine, too! It's all part of being a good instrument technician--and <b><i>everyone in the plant</b></i> relies on the instrument tech to know what trips the turbine (though they all have their own perceptions of what does--and shouldn't--trip the turbine, you have to be the bearer of the news of what actually trips--and doesn't--the turbine, so at some point you need to work through this because it's not in ToolboxST).

<b>L5ESTOP1_FZA</b><pre>
L5ESTOP1_FBZ L5ESTOP1_FZA
----|/|--------------( )------</pre>
5: STOPPING DEVICE E: emergency
L5ESTOP1_FZA = VPRO E-STOP PB Circuit Open

You wrote:

> So when L5ESTOP1_FBZ is logic "1",
>then L5ESTOP1_FZA is logic 1. I think if
>L5ESTOP1_FZA is logic 1, it means the
>emergency pb is pushed down.

Please re-consider and then re-write your statement. Also, please see if L5ESTOP1_FZA is used anywhere else in the application code in ToolboxST. (I'm just curious here as I've never seen this signal before.)

Also, you might want to take a look at the Mark VIe System Guide, GEH-6721, in the section on the TREG card, and have a look at the E-Stop P/B circuit. I will tell you that E-Stop P/Bs (push-buttons) are always (in GE-design heavy duty gas turbine philosophy and practice) manually-operated, latched assemblies with NC contact that open when pressed. (I think there's some EU "standard" that says E-Stops are now NOT supposed to be latching (latched open when pressed), and that may be some reason for this L5ESTOP1_FZA, but I'm probably wrong because there's no Master Reset latch on this rung. So, again, another reason for my curiosity.)

I hope that later we can go over the TREG and TRPG circuits as they are VERY important parts of the turbine trip circuit, which are hardware portions as opposed to software we are talking about now (application code software that runs in the control processors).

Anyway, I have another request: Ignore the L63CSHH and L63ETH contacts in L4PSTX1 and then re-write your statement about L4PSTX1.

And, I also want you to tell me what you see about L4PSTX1, and L4PSTX2 and any other L4PSTXn contacts that drive L4PSTX. They are all similar in one respect. And, there are multiple L4PSTXn rungs, again, because of the old limitation of the number of elements in a horizontal rung (and, by the way, that restriction no longer exists in Mark VIe, but GE continues as if it did--sometimes! Belfort does and doesn't, and it's maddening for some of us--as most things Belfort does and doesn't do).

I'm sorry to seem to be so hard, here, about what is being overlooked and missed. I know you have a full-time job and this; that's why I don't push. I, too, have a full-time job, and I've recently been traveling on business and will be again in a couple of weeks and will be out of contact for a week-and-a-half (I will have Internet access, but it's limited to business-related email, and the Customer is VERY stringent about this). Just a heads-up in advance.

Also, I took some time to do the inversion masking stuff which I didn't spend as much time on with this thread as perhaps I should have--which is why I took more time with it in the other thread. I hope you've been following that, and that it was helpful and informative.

We can talk about Start-up Fuel Flow Trip after we get this L4PSTX1 completed, but, I am curious--you asked what would happen if the unit didn't trip on excessive fuel flow during start-up. Are you asking why the logic is even in the application code? Or, what if someone forced the logic to "0" during a start-up.?.?.? So, when we finish L4PSTX1, we need to deal with this question as we work through L4PSTX2.

Looking forward to hearing from you, Neo!
 
At this point, this author would like to add a small description of Generator Differential Protection.

Generator differential protection is the most important protection (at least in this author’s opinion).

This protection is for generator stator winding. According to generator design, current flow through all three phases of generator should be equal. If there is less current flow in a phase as compared to other two phases, it means there is restriction to the flow of current in that phase. This indicates that the resistance of that phase is higher than other two phases. This high resistance will cause overheating and burning of the conductor eventually. This high resistance can be due to damaged conductor (in case of damaged conductor, the area for current flow will decrease, thus resistance will increase, current will decrease). In order to avoid such damage to generator stator winding (which is hardly repaired on-site) and save your money, it’s important to trip the generator and resolve the issue.

How to “sense” this condition and trip the generator in time to avoid the said damage?

Separate CTs (current transformers) mounted on individual phase give their output to a relay (relay name starting with “87” in accordance with ANSI device number standards). This relay monitors the difference in the currents of each phase and initiates a trip when abnormal condition is sensed.

It is expected that CSA and other MVPs will provide their valuable input to elaborate the understanding of the community on this topic.

Hope this helps!
 
> And, I also want you to tell me what you see about L4PSTX1, and L4PSTX2 and any other L4PSTXn contacts that drive L4PSTX.

CSA, They are all NC contacts!

What is the reason for pointing out sense of this contacts CSA? Now please enlighten us by explaining the reason for this till Neo prepares a response.

(I'm reading and re-reading this thread to build my understanding of GE-design heavy duty Gas Turbine control system).
 
SB,

My main purpose in pointing out that the contacts are all NC (Normally Closed) is that it's related to the whole inversion masking philosophy--that logic signals are a logic "1" when the unit is to be tripped, not when the condition is "normal." If the trip logic signal is derived from a discrete (contact) input, the discrete input circuit is closed when the condition is normal (such as when the L.O. Pressure is not below the trip setpoint, or when the L.O. Header Temperature is not above the high temperature trip setpoint), and the circuit goes open when the pressure drops or the temperature increases, respectively. And, the inversion mask makes the logic signal a logic "0" when the condition is normal--and the signal name is chosen such that when the logic signal is a logic "1" the turbine should be tripped.

Now, the way that GE uses NC contacts in a series string has always seemed kind of odd and I've never gotten a good answer when asking about this particular practice--but it's still worth pointing out. If people add trips in the field (at the site) they should be aware of how other trips are accomplished and follow the practice to be uniform. There's almost nothing more maddening when troubleshooting that running across a mish-mash of programming practices--NOTHING.

I've seen some very excellent programming in other vendor's control system packages, but usually it's not consistent because there was more than one programmer and no one to oversee or keep things uniform. Which is becoming the case in GE with responsibility for various machines decentralizing to various parts of the world and no written set of philosophies and standards to follow.

I wonder if I'm being too hard on Neo; in the beginning I overlooked the problems and just re-wrote the statements for the rungs. But, I was hoping that we had reached the point where at least the statements would reflect the sense of the contacts used in the rungs--and that if more information was required about the signals and how they are derived and intended that that information could be added. Perhaps I need to revert to the earlier practice to keep this journey moving forward.

Anyway, if you have questions or need clarification, ask away. This has been a good brush-up for me, and hopefully a good learning experience for others.

By the way, did you follow the inversion masking stuff in http://www.control.com/thread/1387648847#1406929406? If so, was it helpful? I'm trying to find ways to explain inversion masking--it's much more than making commissioning engineer's lives easier, and much more important and critical to reliability than making commissioning engineer's lives easier. I'd appreciate any constructive criticism.
 
CSA

I am honored that you give me an assignment, and i need time to prepare.

You taught me the concept of inversion mask in previous thread, and i think sometimes we should make life easier.

Best regards!
Neo
 
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