MARKVE Getting a Better Understanding of Gas Turbine Control 1 2 3

Getting a better understanding of gas turbine control

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Posted by Neo

on 5 May, 2014 - 8:28 am

I'm a rookie in gas turbine using GE MARK VI control system. I see there were a lot of threads replied by CSA, and i found him very knowledgeable. k nowledgeable. I was wondering how can a rookie like me to have a better understanding of gas turbine control. In one thread, CSA advised to read Control Sequence Programs (CSPs) and Control Specification. what is Control Specification? how can i find it? Thank you. Reply to this post...


Posted by saadh on 5 May, 2014 - 9:40 am

Hi GAS TURBINE CONTROLS ARE ; 1) STARTER CONTROL SYSTEM 2) STARTUP SEQUENCE AND SHUT DOWN CONTROL SYSTEM 3) COMBUSTION CONTROL SYSTEM 4) HP SPEED CONTROL SYSTEM 5) Lp speed control system 6) exhaust temperature control system 7) 2 nd stage s tage Nozzle control system 8) Lube oil and cooling system s ystem Best regards saradhi Reply to this post...


Posted by CSA

on 5 May, 2014 - 10:48 am

Neo, Welcome to the business. Mark V turbine control panels employ what's formally known as the CSP-Control Sequence Program. Mark VIs (and Mark VIes) employ what's formally known as "application code." Both are terms for the application-specific sequencing, the "logic", that's gets downloaded to the turbine control to make it particular for a specific application and site. "Reading" the CSP or application code involves learning a new language--r language--relay elay ladder diagram language.

In the case of the Mark VI and the Mark VIe they use function blocks to perform the same operations that rungs used to do in relay ladder logic, but they still use a similar graphical representation to relay ladder diagram logic. The Mark V CSP can be printed, and so can the Mark VI/VIe application code--but printed application code looks almost nothing like what one sees in Toolbox/ToolboxST and it consumes reams of paper and is usually considered a waste of time and natural resources to print it. Myself, I use MS-Windows screen printing capability to capture capture bits of code I need need to make notes on and study study to a MS-Word or MSMSWordpad document, and then print them. I would be very happy to work through the single most important rung in the GE-design heavy duty gas turbine world: L4. If you have some patience, we can cover everything from what trips your turbine, to all of the start-check permissives required to get L4 to pick up. It's a great way to learn how GE SHOULD name signals and how to look at signals and quickly determine when the logic signal is a logic "1" or "0", and even if it's a timer ti mer or an inverse timer or associated with a physical input or output. The Control Specification is a document that is provided with the Speedtronic turbine control panel. A Control Specification is specific to every turbine (or group of turbines installed and commissioned at the same time on a site). In the old days, GE used to provide the Control Specification, and the Piping Schematics (everyone else in the world calls them P&IDs) in Vol. III of the Service Manuals provided with the turbine and auxiliaries. But, they couldn't leave well enough alone, and it's changes several times over the last decade-and-a-half (which volume of the manual they provide it in). It's a very good document for most things, but I've seen some glaring errors in the Control Specification, such as Control Spec.'s which say the turbine has a diesel starting motor when it has an electric starting motor, and vice versa. So, read it for "intent", not "content"--meaning the description of the starting sequence, in this case, should talk about purging, firing, warm-up, warm-up, and acceleration. acceleration. That has to be done regardless regardless of the type of starting starting means. Also, many people find the Control Specification years after the unit was commissioned and think the Control Constant values listed in the Control Specification are GOSPEL and start changing the as-running values to match the Control Specification, and that' when the real "fun" begins. If the turbine's been running fine for months or even years, the Control Constant values in the Mark VI are probably just fine, though some could probably use a little "tuning." J ust as with hardware ("Berg") jumpers, the positions you find them in on a card which has been working but is suspect are most likely the correct ones--not what some piece of paper says. says. So, if you want to work on L4 in this forum, just let me know. It won't be the quickest thing we've every done, but it will be a good and valuable learning experience--I promise. And, don't neglect the P&IDs--the Piping Schematic drawings. Those are about the single most important group of drawing a technician or operator can have. Every technician, and every operator, should have their own copy, with their own notes and markings. Finally, one thing I'm coming to understand about newbies is that they don't have a good grasp of how field devices and instruments work. RTDs, in particular, but even thermocouples and pressure switches and temperature switches and limit switches and pressure transmitters--not to mention electro-hydraulic servovalves and LVDTs. RTDs and T/Cs (thermocouples) have been covered in some detail on control.com. And none of them are particularly difficult to understand--but wiring them to any control system can require some basic knowledge which most people don't have and seem to believe isn't really important. So, if you have any questions about field devices and instruments, open a new thread and we can talk about them, if necessary--after you've researched the control.com archives (past threads, using the 'Search' feature) and if you have any questions. Looking forward to working with you, Neo. Reply to this post...


In the case of the Mark VI and the Mark VIe they use function blocks to perform the same operations that rungs used to do in relay ladder logic, but they still use a similar graphical representation to relay ladder diagram logic. The Mark V CSP can be printed, and so can the Mark VI/VIe application code--but printed application code looks almost nothing like what one sees in Toolbox/ToolboxST and it consumes reams of paper and is usually considered a waste of time and natural resources to print it. Myself, I use MS-Windows screen printing capability to capture capture bits of code I need need to make notes on and study study to a MS-Word or MSMSWordpad document, and then print them. I would be very happy to work through the single most important rung in the GE-design heavy duty gas turbine world: L4. If you have some patience, we can cover everything from what trips your turbine, to all of the start-check permissives required to get L4 to pick up. It's a great way to learn how GE SHOULD name signals and how to look at signals and quickly determine when the logic signal is a logic "1" or "0", and even if it's a timer ti mer or an inverse timer or associated with a physical input or output. The Control Specification is a document that is provided with the Speedtronic turbine control panel. A Control Specification is specific to every turbine (or group of turbines installed and commissioned at the same time on a site). In the old days, GE used to provide the Control Specification, and the Piping Schematics (everyone else in the world calls them P&IDs) in Vol. III of the Service Manuals provided with the turbine and auxiliaries. But, they couldn't leave well enough alone, and it's changes several times over the last decade-and-a-half (which volume of the manual they provide it in). It's a very good document for most things, but I've seen some glaring errors in the Control Specification, such as Control Spec.'s which say the turbine has a diesel starting motor when it has an electric starting motor, and vice versa. So, read it for "intent", not "content"--meaning the description of the starting sequence, in this case, should talk about purging, firing, warm-up, warm-up, and acceleration. acceleration. That has to be done regardless regardless of the type of starting starting means. Also, many people find the Control Specification years after the unit was commissioned and think the Control Constant values listed in the Control Specification are GOSPEL and start changing the as-running values to match the Control Specification, and that' when the real "fun" begins. If the turbine's been running fine for months or even years, the Control Constant values in the Mark VI are probably just fine, though some could probably use a little "tuning." J ust as with hardware ("Berg") jumpers, the positions you find them in on a card which has been working but is suspect are most likely the correct ones--not what some piece of paper says. says. So, if you want to work on L4 in this forum, just let me know. It won't be the quickest thing we've every done, but it will be a good and valuable learning experience--I promise. And, don't neglect the P&IDs--the Piping Schematic drawings. Those are about the single most important group of drawing a technician or operator can have. Every technician, and every operator, should have their own copy, with their own notes and markings. Finally, one thing I'm coming to understand about newbies is that they don't have a good grasp of how field devices and instruments work. RTDs, in particular, but even thermocouples and pressure switches and temperature switches and limit switches and pressure transmitters--not to mention electro-hydraulic servovalves and LVDTs. RTDs and T/Cs (thermocouples) have been covered in some detail on control.com. And none of them are particularly difficult to understand--but wiring them to any control system can require some basic knowledge which most people don't have and seem to believe isn't really important. So, if you have any questions about field devices and instruments, open a new thread and we can talk about them, if necessary--after you've researched the control.com archives (past threads, using the 'Search' feature) and if you have any questions. Looking forward to working with you, Neo. Reply to this post...


Posted by Neo

on 6 May, 2014 - 12:54 am

CSA, thanks for your detailed reply. It would be great if i have an opportunity to work with you. As i am confused about how to start, i think working on L4 is a good choice. And i am interested in of gas turbine control. But what should i do exactly? Can you give me guidance and told me what specific i should do. I am willing to spend several hours a day working on it. Reply to this post...


Posted by CSA

on 6 May, 2014 - 3:01 pm

Neo, Okay! Let's get started. First, some "back-room" stuff. In order to post rungs so that they're legible on control.com we have to use HTML tags, specifically, the 'pre' and '/pre' tags (enclosed by the < and > characters). The 'pre' HTML tag needs to be added to the reply Text immediately before the rung, and then the '/pre' HTML tag needs to be added immediately after the rung--this is necessary to put the forum software into fixed-pitch font mode. (You can usually see the HTML tags in the body of replies.) So, by putting a 'pre' (with the < and > characters-characters--which which won't show in this reply properly on the main pages of control.com--before control.com--before the L4 L4 rung and then following it with with the '/pre' (with the < and > characters) characters) we can display the L4 rung: L4S L94T L4T L4 -----| |-----------|/|----------|/|------------( ) | | L4 | -----| |------

Also, at least in the web browser that I use one can grab the lower right corner of the control.com Text box and drag it to the right (and down) to get more horizontal (and vertical) space when replying. This will be useful when logic signal names are long, and when there are as many as eight horizontal elements in a rung. You can always use the 'Preview' and 'Edit' buttons to see how your post appears before submitting it. Also, let's talk about how GE is supposed to to write and choose logic signal names (per their own standard-realize that every company has its own standard, and we're just talking about GE here). In the early days of digital Speedtronic turbine control systems it was decided to make the signal name describe when the logic was a "1", or when it was "True." In general, this has been followed over the years, but it's not always followed and that's a real shame, because it's very useful when it is. Next, we need to be sure sure everyone (you, Neo, and me) is clear about what normally normally open and normally normally closed means. A normally open contact associated with a logic signal will be OPEN when the associated

logic is "0" and will be CLOSED when the associated logic is "1". A normally closed contact associated with a logic signal will be CLOSED when the associated logic is "0" and will be OPEN when the associated logic is "1". To get a logic signal to be a logic "1" it's necessary for power to flow through a series-parallel string to the "coil" of the logic signal, so that means that the logic signals of normally open contacts must be a logic "1" and the logic signals of normally closed contacts must be a logic "0". As an example, let's "read" the L4 rung (because it is, in fact, a sentence). "When L4S IS a logic "1" OR when L4 IS a logic "1", AND when L94T IS NOT a logic "1" AND when L4T IS NOT a logic "1", then L4 will be a logic "1"."

So, when L4S is a logic "1" its associated normally open contacts will be CLOSED, and when L4 is a logic "1" its associated normally open contacts will be C LOSED, and when L94T is NOT a logic "1" (that is, when it IS a logic "0") its associated normally closed contacts will be CLOSED, and when L4T IS NOT a logic "1" (that is, when it IS a logic "0") its associated normally closed contacts will be CLOSED. And when either L4 or L4S is a logic "1", and when both L94T and L4T are NOT logic "1"s, then L4 will be a logic "1". I find it easiest to "read" rungs in this fashion--"imagining" what state the associated logic signals of normally open and normally closed contacts have to be in in order for power to flow through the normally open or normally closed contacts to "energize" the logic signal coil(s) at the right end of the rung. Others like to read them in different fashions--possibly like this: When L4S is TRUE OR when L4 is TRUE, AND when L94T is FALSE AND L4T is FALSE then L4 will be TRUE. But, it's the same thing--TRUE and FALSE are another way of describing when logic signals are "1" or "0" and which state the logic signals need to be in in order for power to flow through them to energize the rung's logic signal coil. There are lots of ways to read and interpret rungs--lets' just stick with this one for this discussion, and hopefully it will become clearer why this way works best for GE logic (application code in the Mark VI). So, from the longname descriptions of signal names in Toolbox, we can see that L4S stands for "L4 Set" (or sometimes called "L4 Start"). It will be a logic "1" (True) when all of the start-check permissives are met and when all of the other final start-checks are completed when a START is initiated. (Don't worry; we'll go over all of them in due time--presuming you have the patience.) Now, let's continue with the descriptions of the other names of elements of the L4 rung. L94T will be a logic "1" when a normal shutdown is in progress and the fuel is to be shut off in two of the three control processors, , and for a TMR control panel--or just in for a SIMPLEX control panel . L4T will be a logic "1" when any condition which trips the turbine in two of the threee control processors, , and for a TMR control panel--or just in for a SIMPLEX control panel . (There are MANY sub-rungs for L4T, and we'll go over all of them.) So, what does this tell us about L4? In order to get L4 to go to a logic "1" (to "pick up"), L4S needs to be a logic "1" and L94T and L4T both need to be logic "0"s, and then L4 will also go to logic "1" which will close the normally open contact in parallel with L4S and "latch" or "seal-in" the rung--so that if EITHER L94T goes to a logic "1" OR L4T goes to a logic "1" L4 will "drop out", or go to a logic "0". It should also be clear that it's necessary for L4S to go to a logic "1" to get L4 to also go to a logic "1", but that once L4 is a logic "1" that L4S does NOT need to remain a logic "1" for L4 to remain a logic "1"--as long as both L94T and L4T both remain logic "0". That's it. Once L4 is a logic "1" there are only two conditions which can "drop out" L4 (make it go to a logic "0")--L94T going to a logic "1" or L4T going to a logic "1". And in order to start, run and shutdown (normal shutdown) the turbine, L4 MUST be a logic "1", and if L4 transitions from logic "1" to logic "0" while the turbine is starting or running or shutting down then the fuel stop valve(s) will be commanded to close and the turbine will be tripped. (Fuel stop valves are not open during purging and prior to firing, but L4 is required to be a logic "1" in order to open fuel stop valves when necessary, and for them to remain open.)

And--presuming that both L94T and L4T are BOTH logic "0"s, which they must be in order to initiate a START--there is only one condition that will allow L4 to pick up (go to a logic "1")and that is when L4S goes to a logic "1". (That's because prior to a START, when a READY to START is indicated to the operator, L4 is a logic "0". This can be seen in the 'Start Check Permissive' display.) Hopefully you can begin to see how the signal name being chosen to describe when the signal is a logic "1" can be helpful. And hopefully you can also begin to see how knowing how to read signal names (most of them--unfortunately not all, because standards aren't always adhered to) can be very beneficial to quickly reading and interpreting rungs and logic (application code in the Mark VI). There are some little "tricks"-which aren't documented anywhere, not even in GE (sad, but true)--which we will discover on this journey. So, your assignment, Neo, is to post the L4S rung to this thread (using the HTML tags). And, then, please "read" (write the sentence) that describes when L4S will be a logic "1". Also, please post the longnames for each of the logic signals in the rung. Here's an example: L4 = Master Protective ("1" to Run) L4S = L4 Set L4T = Master Protective Trip ("1" to Trip) L94T = Normal Shutdown Trip (I believe that if you hover the cursor over a signal name in Toolbox the longname description will appear at the lower left corner of the Toolbox window.The longnames I wrote were exact quotes from a Mark VI site; they are not the same for every job. Just post what it says in your application code from Toolbox. Sometimes, there is no longname; and worse, criminally, the longname is wrong. That's life, though. We learn to deal with it.) We will go through each element of the L4S rung (which has several "sub-rungs", and the L4T rung, which has MANY sub-rungs) so you will get very proficient at u sing the HTML tags--and "reading" signal names. We'll go over the L94T rung, too. And, we will discuss the various other types of proper (and possibly improper) GE signal names, as well as understand the conditions and permissives. You're going to have to look up Control Constant values, and various device settings (from the Device Summary document provided with every GE-design heavy duty gas turbine). So, you will need to find the Device Summary document (it also used be in Vol. III, but who knows where "they" put it now...). If you have any questions or comments on the above, let's deal with those first. If I introduce words or terms you're unfamiliar with, ask for clarification. If you're having some trouble with normally open vs. normally closed contacts, just be patient with yourself. It will begin to become clearer soon. Best not to get caught up in that discussion because it does get very clear after a while--it just takes longer for some people than others, but be patient. This is going to be a joint effort, but to be of the most benefit to you we are going to use the exact rungs and signals in your Mark VI application code so that it's specific to your turbine and auxiliaries. Your job is to provide requested information--rungs, Control Constant values, pressure switch or temperature switch settings, etc.--and the rest we will sort out as we continue on this journey of discovery. Remember, relay ladder logic is just another "language"--and it has "sentences" with verbs and predicates and subjects just like any other language. And it's nothing more than logic, sequencing. By learning how to "anticipate" when a logic signal will be a logic "1" (and by inference, when it won't be a logic "1"--that is, when it will be a logic "0") one can more easily read the rungs and begin to understand what is to be happening so that one can understand GE-design heavy duty gas turbine control and GE-design heavy duty gas turbine control philosophy. Finally, L4 is just one way the turbine can be tripped--from the application code running in the control processors. There is also tripping which can be done through the
core and associated inputs to the
core--and we'll get to that to as we finish this discussion. Because it's important to understand this isn't the

only way a turbine can be tripped--GE has several. Be patient, and we'll cover them all, and in the process learn more about the Mark VI. I'm looking forward to this journey! Let's keep moving and we're going to "see" some amazing things. "Learning is finding out what you already knew," is one of my favourite quotes. When presented correctly, it's exactly what happens--one says to himself (or herself), "I knew that!" It's just that you hadn't thought it about it that way before. And with a few little hints, tips and tricks it can be very easy--and intuitive, which means, well, you already knew that! By the way, I'm going to apologize in advance for making a few mistakes along the way. I'm not a good person to proofread my own writing (most people aren't good at proofreading their own writing), and I'm doing this in my spare time, and so I do--and will--make mistakes. Just hopefully, not too many of them. Please be patient with me. Reply to this post...


Posted by Neo

on 7 May, 2014 - 9:21 am

CSA, Thank you for your reply.I am excited too, feeling i'm on a mysterious trip with you. This time my assignment is L4S right? If there are some mistakes and drawbacks or you have advice just let me know,and i'll try to do better next time. I hope to have a long and exciting journey with you. Here comes the L4S: L4SX L14HR L14Y L4s -----||-----------||----------||------------()

where: L4SX = Master protective set auxiliary logic(confusing) L14HR = HP zero speed signal L14Y = time delay loss of master protective(not sure if it is needed) So, if L4SX, L14HR and L14Y are 1, then L4s is 1, otherwise L14 remains 0. Should i make further classification? But it is hard for me. I think L14SX is relatively important, so i dig deeper. Here comes the L14SX; L3RS L1X L33cse L63QT L4SX -----||----------||----------||----------|/|----------()

L3RS = Start up check present(not sure) L1X = startup check stop master control-startup permiss(confusing) L33cse = starting means cluth engaged L63QT = lube oil gen low pressure voted So, if L3RS, L1X, and L33cse are 1, and L63QT is 0, then the L4SX is 1. Is it enough for this time? It seems that the logic is endless if i go deeper.

I have questions, and some of them are foolish to you. 1) I think L means the type of variables is logic, and do the number,like 4,14 means something? 2) I am a little confused L4, can you give me some specigication. 3) How is my assignment? I am not sure whether i do it in the way you ask. Best regards,Neo. Reply to this post...


Posted by CSA

on 7 May, 2014 - 3:36 pm

Neo, This is a good start. Please do be careful when "copying" signal names; if the signal names is in all capital letters in Toolbox, you should use all capitals in your post. If the signal name is in lower-case letters, you should use lower-case letters in your post. And, please double-check to make sure you are t yping the proper signal names (see below). Yes. "L" means the signal is a logic--usually; GE violates that standard occasionally, too, but not very often, fortunately. And, the numbers--they are VERY important. They correspond to GE's interpretation of the ANSI Device Numbering standard, and GE's interpretation is very close to the ANSI standard. For example, a "4" device is a 'master protective' or 'master control' element/device. A "14" is a speed level element/device. A "33" is a limit switch element/device. A "63" is a pressure sensing element/device (a pressure switch). A "94" is a shutdown (normal shutdown--not emergency shutdown, trip) element/device. A "5" is an emergency shutdown element/device (like an emergency stop pushbutton). It's VERY helpful to commit the ANSI device number standard to memory--or at least have a copy available when you are reading application code. It's critical, actually, and as you get more familiar with the device numbers you will begin to recognize certain functions/signals. You can find lots of ANSI lists on the world wide web with your preferred Internet search engine. Please be very careful when copying information from Toolbox: >Here comes the L4S: > L4SX L14HR L14Y L4s >-----||-----------||----------||------------( )

>where: >L4SX = Master protective set auxiliary >logic(confusing) >L14HR = HP zero speed signal >L14Y = time delay loss of master >protective(not sure if it is needed) It should be: L4SX L14HR L4S L4Y -----||-----------||----------||------------( )

where: L4SX = Master protective set auxiliary logic L14HR = HP zero speed signal L4Y = time delay loss of master protective Let's deal with the L14HR signal. "14" means it's a speed level signal, "H" means it's related to the HP shaft (and since your turbine is a single-shaft, I presume) the shaft is the HP shaft, and "R" means the shaft is 'at rest' or, 'at zero speed.' So, L14HR is a logic "1" when the turbine-generator shaft is at rest, or at zero speed. L4SX, as you rightly noted, is important. In this case the "X" means it's a 'permissive' or 'auxiliary' to L4S. In earlier versions of GE digital Speedtronic turbine control systems, there was a limit of eight "elements" horizontal string in a rung. That means there could be no more than seven contacts (normally open and/or normally closed) and one coil--for a total of eight. So, if there were more than seven contacts necessary it was required to split the rung into multiple rungs, and name the "permissive" rungs by applying an "X" suffix to the main logic signal name. Since most of the application code was copied from earlier control systems, this was continued. And on some turbines, there may be additional contacts in either or both of the L4SX and L4S rungs. So, in your mind you could envision the following: L3RS L1X L33CSE L63QT L14HR L4Y L4 ---| |---| |----| |------|/|-----| |----| |-----( )

because it's exactly the same as the combination of L4SX and L4S. Let's tackle L4Y. When you see a "Y" suffix on a signal name it almost always means an "inverse time delay" to its namesake, in this case L4. If you look up L4Y in Toolbox, it will look like this: L4 L4Y -----|/|-------------------------(T) 1.0 sec

By "inverse time delay" you can see that 1.0 second after L4 transitions from a logic "1" to a logic "0" (which is the inverse of a logic "1") that L4Y will be a logic "1". Or: "1.0 second after L4 is NOT a logic "1", L4Y will be a logic "1"." [If you look up L4Z, it will look like this: L4 L4Z -----| |-------------------------(T) 1.0 sec

A "Z" suffix almost always means a "time delay" to its namesake, in this case L4. L4Z is read: "1.0 second AFTER L4 IS a logic "1", L4Z will be a logic "1"."] Let's read the combined L4SX/L4 rung: "When L3RS is a logic "1" AND L1X is a logic "1" AND L33CSE is a logic "1" AND L63QT is NOT a logic "1" AND L14HR is a logic "1" AND L4Y is a logic "1", then L4S will be a logic "1"."

L3RS = Ready to Start L1X = Auxiliary to START command l33cse = Clutch-Starting Engaged (driven by a discrete (contact) input L63QT = Low L.O. Pressure TRIP L14HR = HP Shaft at Rest L4Y = L4 Inverse Time Delay I think (I hope!) that the signal you wrote as L33CSE was actually l33cse (all lower-case alpha characters), because that's GE's "standard" for signals that associated with inputs and outputs--to express the signal names in lower-case characters. It's not required--but it's intended to be helpful to people reading the application code to let them know those particular signal names with lower-case alpha characters are associated with physical inputs or outputs. (Again, GE doesn't always follow their o wn standards. But we learn to live with it.) So, now, let's re-read the combined L4SX/L4S rung: "1.0 seconds after L4 goes to a logic "0" AND the 'Ready to Start' signal is a logic "1" AND the START command auxiliary is a logic "1" and the Starting Clutch is engaged AND there is NOT a Low L.O. Pressure Trip and the shaft is at zero speed, then L4S will be a logic "1"." In order to be able to start a GE-design heavy duty gas turbine, the operator interface must display a "READY TO START" indication. Most HMIs have a "Start-Check Permissive Display which can be used to determine why a Ready to Start indication is not being displayed. (We are going to go through all of that-just be patient.) Part of the 'Ready to Start' indication is that there are no turbine trips (L4T is a logic "0")-remember L4T from the L4 rung. (A "3" is a complete sequence element/device. In this case, the ready to start sequence is complete.) L3RS will be a logic "1" when the start-check (" R eady to Start) sequence is complete. When the "READY TO START" indication is seen AND when the operator selects START and executes the command then L1X will pick up (a "1" is a starting element/device per ANSI & GE). When L1X picks up, that starts several auxiliaries, including the Aux. L.O. Pump, which pressurizes the L.O. system after a few seconds (if the Aux. L.O. Pump is not already running). L1X is an auxiliary signal that is a logic "1" when a turbine START is active. Also, L1X usually starts the Hydraulic Ratchet pump to engage the starting clutch, which should cause actuate limit switch 33CS-1 after the clutch halves are engaged to make l33cse go to a logic "1". The signal name tells you when it's going to be a logic "1"--when the starting clutch (the jaw clutch on most machines; a SSS clutch on some units) is Engaged. When the low L.O. pressure switches at the collector end of the generator (the furthest point away from the L.O. pumps) are actuated--meaning they have sensed minimal L.O. pressure--then logic signal L63QT will go to a logic "0". A 63 is a pressure sensing element/device, mostly a pressure switch per GE's interpretation. When you see a "Q" in a logic signal name it means oil, or flow. In this case it means L.O., and the "T" means 'Trip.' L63QT will be a logic "1" when the L.O. bearing header pressure--as sensed by the switches at the collector end of the generator--is below the minimum pressure required to protect the bearings. Again, the signal name tells you when it's going to be a logic "1"--when the L.O. Bearing Header pressure is low enough to initiate a turbine trip. In this case, we want it to be a logic "0" (because we need the normally closed contact to be closed to get power flow through the contact) so we want L63QT to be NOT a logic "1"--which is the same as saying when the L.O. pressure is NOT low enough to initiate a turbine trip. And, again, that will happen several seconds after the Aux. L.O. pump starts and pressurizes the bearing header and the pressure switches at the collector end of the generator are all actuated. L14HR is a logic "1" when the HP shaft is at R est. L4Y is a logic "1" 1.0 seconds after L4 is NOT a logic "1". And that's L4S (and L4SX).

Regarding your confusion about L4, it's the signal that says "It's okay to run the turbine" when it's a logic "1". And when it's NOT a logic "1" (when it's a logic "0"), then the turbine is to be tripped. If you look at how many places in the application code L4 is used, you will--it's a LOT! Probably the most used s ignal, because it's the permissive to start run a lot of auxiliaries, to energize a lot of solenoids, to permit fuel to flow, and on and on. L4 must be a logic "1" to burn fuel in the turbine, and if it changes from logic "1" to logic "0" the fuel flow-rate will be stopped--tripping the turbine. This logic signal, L4, should >>>NEVER<<< be forced to a logic "1". Never. Ever. NEVER. Not even when the turbine is at zero speed. If this signal is forced to a logic "1" when the turbine is not running, a lot of auxiliaries may start and run, and a LOT of alarms will be annunciated, and in the worst case, fuel might be accidentally admitted to the combustors. It's just not ever permissible to force L4. Even if some GE document tells you to do so--it's wrong. And, it should absolutely NEVER be forced to a logic "1" when the turbine is running--because if L4T is picked up (by, say, l ow L.O. pressure, or high vibration, or loss of flame, or exhaust overtemperature, etc.) the turbine will NOT trip. So, to anyone reading this: Never force L4 to a logic "1"--whether the turbine is running or not. I hope it's becoming clearer how to "read" logic signal names. In general, the signal name tells you when the logic is going to be "1". And, armed with this information, it should be easier to read application code. Don't try to think that you have to learn everything right now. You have this information, you can print it, and you can review it any time you wish. And, it's always available on control.com. Reply to this post...

Posted by Batman

on 10 July, 2014 - 3:22 am

Dear CSA, I am a mechanical engineer by qualification, trying to understand GE 9FA control system. I have a question on L4 & L4Y commands. How both of them can be a logical state "1" si multaneously? As you mentioned L4 needs to be "1" for getting start permissive and apparently L4Y too needs to be "1" in L4S loop. This is a bit confusing. Sorry in advance if it's a stupid question. Reply to this post...


Posted by CSA

on 10 July, 2014 - 11:41 am

Batman, Good on you for expanding your knowledge; it's very helpful for mechanical engineers to understand how turbines operate, too, not just to know how to turn a wrench or orient an orifice plate. I believe you found a typographical error in my post (something I had just chided Neo for making... and then I made a serious one!). The rungs in questions are: L3RS L1X L33CSE L63QT L4SX -----| |-----| |-----| |-----|/|------------( ) L4SX L14HR L4Y L4S -----| |---------| |---------| |------------( )

The first, L4SX, is an "auxiliary" to L4S, made necessary because a sequence editor can't have more than

eight (8) elements, so it was broken into two rungs by making the first an "auxiliary" and then including the auxiliary in the "actual" rung. The resulting rung (which I mistyped) would look like this: L3RS L1X L33CSE L63QT L14HR L4Y L4S ---| |---| |----| |------|/|-----| |----| |-----( )

Hopefully this part was clear: >L4Y is a logic "1" 1.0 seconds after L4 is NOT a logic "1". So, the rung which I mistakenly put L4 over the coil, should have been L4S, and this should help clear your doubt. The rung for L4 is always: L4S L4T L94T L4 ----| |--------|/|-------|/|----------( ) | L4 | ----| |-----

Does this help? Sorry for any confusion--and there is no such thing as a stupid question when one is trying to learn something new. Just dumb answers. Reply to this post...

Posted by Batman

on 11 July, 2014 - 4:04 am

Thank you CSA for the quick reply in spite of your busy schedule. I'll summarize what I understand (about L4Y), then I'll ask you a question. 1) L4 is a master protective signal, which is normally "1", when everything is fine. 2) But, just before start up, it is "0", so that L4Y which is used in STCK2 is "1" which makes L4S "1" if all other conditions are met. 3)Once after L4S is "1", L4 changes its state from "0" to "1" if L94T & L4T are "0", and it remains "1" until L94T or L4T change their state. Now I have a question (Assuming my comprehension is correct so far) Why time delay for L4Y is only one sec, if it's used to block an immediate start attempt followed by a trip/shutdown? One second seems to be little impractical. I guess it's main purpose is to avoid a start attempt when L4 is "1", but not convinced with the time delay. Please correct me if I miss something here. Reply to this post...


Posted by CSA

Batman,

on 11 July, 2014 - 9:29 am

L4Y is used in other rungs, not just L4S. The reason there is a timer at all is to prevent what's called a "relay race" during very "busy" times when L4 is changing state from "1" to "0". I honestly don't know why it's set for 1.0 seconds, but I know it works. And I know that changing things like this without understanding all the knock-on effects (in all the other rungs that L4Y is used in) can have very bad effects. A lot of the application code in Speedtronic turbine control panels are artifacts from the days of electromechanical relays. That's one of the things that makes Speedtronic panels unique--every time a new Speedtronic panel comes out GE doesn't reinvent the way it controls the turbine. And, for sites/Customers that buy new turbines with Speedtronic turbine control panels, or technicians with experience and knowledge from older versions of Speedtronic turbine control panels, it's very easy to troubleshoot and understand the way the turbine is being controlled. There was one exception to this--Mark II Speedtronic--when GE went away from relay ladder logic and diagrams to a "logic gate" type of depiction. A lot of people really didn't like that format, even though it was "modern" and functionally exactly like Mark I (the turbine operated in virtually the same way). A LOT of Mark II-equipped turbines were sold around the world (and a LOT of Mark IIs were still in service), but a lot of Customers with older Speedtronic turbine control panels complained, and when GE developed the Mark IV it went back to relay ladder logic/diagrams. The upshot of all this is: a time delay may not be necessary for today's digital control systems. But, why fix something that isn't broken? It may not seem that L4S needs a time delay, but other rungs/functions probably do. Reply to this post...


Posted by otised on 11 July, 2014 - 3:25 pm

> I honestly don't know why it's set for 1.0 seconds, but I know it works. Engineering inertia is the reason the time delay on L4Y is set to 1.0 second. Back in the days of Mark I, 4Y was a time delay dropout relay (electromechanical), and I believe 1 second was about the minimum setting on the device. Basically, it's always been that way, it works, why change it? Reply to this post...

Posted by CSA

on 12 July, 2014 - 7:26 pm

otised, I'm going to use 'Engineering Inertia' in the future, probably many times. You're so PC (Politically Correct)! Reply to this post...


Posted by CSA

on 11 July, 2014 - 11:56 am

Batman, I likely didn't address your explanation of what's happening--but it's basically correct. 1) L4 must go to a logic "1" in order to start the turbine, and it must remain a logic "1" in order to keep fuel flowing to the turbine once flame is established. 2) When the unit is at rest or when it's on Cooldown (ratchet; turning gear; etc.) L4 is a logic "0". And it doesn't go to a logic "1" until an operator puts the unit into some mode other than OFF and initiates a START (and all the other permissives are met). 3) Yes; L4 remains "1" until L4T or L94T changes state. L4T goes to "1" when the control processors detect a condition that requires an immediate shut-off of fuel (and emergency trip). L94T goes to a logic "1" (during normal operation) when flame is lost during deceleration, or the unit drops "blow-out" speed for a specified period of time, or when the unit hasn't reached "blow-out" speed within a certain period of time after a STOP was initiated. So, with a few qualifications, your comprehension is correct. Reply to this post...

Posted by Batman

on 11 July, 2014 - 11:02 pm

Thank you CSA. your explanation made me understand L4Y better, will start focusing on rest of the control signals. Reply to this post...

Posted by CSA

on 13 July, 2014 - 5:59 am

Batman, You're very welcome. Thanks for the feedback! Reply to this post...


Posted by CSA

on 7 May, 2014 - 4:11 pm

Neo, I don't believe you've told us what turbine you are working on at your site.... And what fuel(s) it burns.... And what kind of starting means it has.... Your next assignment is to examine L3RS. Post the rung, and the logic signal names from Toolbox, and write your sentence of how the rung works. One of the contacts should be L3STCK, and the L3STCK rung should have several contacts like L3STCK0, L3STCK1, L3STCK2, etc. Please post the L3STCK rung from your Toolbox file. Reply to this post...

Posted by Neo

on 11 May, 2014 - 9:46 am

CSA, Should i wait for you comment and guidance or just continue to examine the signal L3RS? Best regards. Reply to this post...


Posted by CSA

on 11 May, 2014 - 1:04 pm

Neo, I am working on my response; L3STCK0 is a fairly extensive rung. Please check the "sense" of L45FP_STCK (normally closed or normally open). It is confusing me. It might be a good idea to put the rung in your reply. Please take your time and be certain of the case of signal names and the sense of contacts. Reply to this post...


Posted by Neo

on 9 May, 2014 - 8:54 am

CSA, Thank you sincerely for your detailed reply. Your comment makes it easier for me to read application code. Firstly, i should make some clarifications: 1) The gas turbine is MS6001B,burning syngas. 2) The signal name of l33cse is in lower case letter. This time my assignment is to examine L3RS, and i find it a little complicated. Here comes the L3RS: L3RS1 L3RS2 L5VPRO_LATCH L3RS ----------||----------||----------|/|-----------()

Where: L3RS1 = Start check stop ready to start logic1; L3RS2 = Start check stop ready to start logic2; L5VPRO_LATCH = Protective VPRO card trip_latch(Never heard it before) SO,when Ready To Start 1 signal(L3RS1)and Ready To Start 2 signal (L3RS2) are logic 1,and L5VPRO_LATCH is 0, the L3RS will be logic 1.

It will be necessary to examine L3RS1 and L3RS2, and this time i'll examine L3RS1. L3STCK L3RS1 ------------||------------()

Where: L3STCK = Startup check stop stop start check permissive. And the signal L3STCK:

L3STCK0 L3STCK1 L3STCK2 L3STCK3 ----------||----------||----------||-----------||----------()

L3STCK0 = Startup check stop start check logic 0; L3STCK1 = Startup check stop start check logic 1; L3STCK2 = Startup check stop start check logic 2; L3STCK3 = Startup check stop start check logic 3; In conclusion, the L3RS is divided in L3RS1 and L3RS2, and L3RS1 is devided in L3STCK0, L3STCK1 ,L3STCK2 and L3STCK3. I was wondering what kind of signal will be grouped in L3STCK0, L3STCK1, L3STCK2 and L3STCK3 respectively. L3STCK0(start check logic 0 for units without third fuel and no HRSG by pass)(?) L27BN l3cp L86TCI L3IGVFLT L5WSTOP L5ESTOP1 L45FP_STCK L3STCK0 -------||----------||----------|/|----------|/|----------|/|------- |/|------|/|------------( ) | | | | L27BZ | TRUE | -------||---------||-------

Where: L27BN = AC BUS normal; L27BZ = AC BUS undervoltage(confusing); l3cp = startup check stop customer permissive to start (difference between l3cp and L1X?); L86TCI = compressor inlet thermocouple disagree (not clear); L3IGVFLT = IGV valve position servo trouble; L86MP = startup check stop master prot startup lockout (not sure); L5ESTOP1 = state of E-STOP 1 (confusing); L45FP_STCK = Fire protection start permissive (not clear); SO, if any of L27BN and L27BZ is logic 1, AND l3cp is logic 1, whenL86TCI, L3IGVFLT, L5WSTOP, L5ESTOP1and L45FP_STCK are logic 0, then L3STCK is logic 1. I'll start with the signal L3IGVFLT. The L3IGVFT : L3IGVF1 L3IGVFLT --------||------------( ) | L3IGVF2 | --------||---------

The signal L3IGVF1 and L3IGVF are outputs from L86GVTV2 block,and my interpretation is when the

csgv is <31 and >35, the L3IGVFLT is logic 1. It seems that the L3IGVFT signal will function only before gas turbine startup. (am not sure for i cannot figure out the signal L3IGV). I am poor in electric knowledge, so the other signals are not easy for me. But i did what i can, i looked up the ANSI device numbers; 27: undervoltage relay 86: lockout relay 1. Does that mean signal names with 27/86 are related to the status of certain relay? And what's the difference between undervoltage relay and lockout relay? 2. Can you explain the word lockout for me ,because it's hard for me to understand. If the above questions are too easy, just let me know, and i'll try to find answer on my own. I would like to continue next time,is it ok? Because it is not easy for me :} And i'll try to do better next time. Reply to this post...


Posted by CSA

on 11 May, 2014 - 5:02 pm

Neo, Thanks for the information about the turbine at your site. What is the source of the syngas? Does the unit start and stop on syngas, also, or does it use another fuel (natural gas or liquid fuel (distillate) for starting and stopping and you have to transfer to syngas at some speed/load? As for questions being too easy, sometimes the easiest ones are the hardest ones to answer. I learn a lot from teaching, and I like to say, "There is no such thing as a dumb question--just dumb answers." A 27 may be related to a protective relay, or it might be related to the presence/absence of voltage in one of the MCCs or the battery charger. Undervoltage is undervoltage; it indicates the loss of or the lack of a minimum level of voltage for some condition. A lock-out condition is one that requires some manual intervention to reset. The intent is to make certain that someone is aware of the problem and has taken appropriate action to resolve the condition before the alarm condition is unlatched, and many times before the turbine can be re-started. An 86 device is a lock-out--which may be a relay, or it may be a latched alarm/trip condition as described above. An 86 lock-out relay is a relay that must be manually latched (against spring pressure that would otherwise open the latch). When one of several other relays operates (when a serious condition is detected), it operates an electric coil that unlatches the relay. There are many different generator/transformer protective relays or relay functions each with its own unique ANSI device number. So, if 2 of the 3 the VPROs in the
core initiate a trip, from the signal name L5VPRO_LATCH I would presume they are latched in the trip condition and L5VPRO_LATCH would go to a logic "1". Once the trip condition is resolved and cleared to reset the alarm and unlatch the trip one probably has to issue a 'Master Reset' from the HMI to make L5VPRO_LATCH to go back to logic "0"--which is the good condition.

When L5VPRO_LATCH is a logic "1" the "READY TO START" indication can't be achieved. Yes; the next logical rung would be L3RS1, which is "driven by" L3STCK, which is driven by the four start-check rungs: L3STCK0, L3STCK1, L3STCK2 and L3STCK3 (for your machine). If there wasn't a limit to the number of horizontal rung elements there would only need to be a single rung--probably L3STCK, but since there are well more than seven start-check permissives there has to be more than one rung, with "auxiliary" rungs used to get all the start-checks to finally pick up L3STCK. And the next logical step would be to analyze L3STCK0. Though, at one point you lis ted L3STCK0 as "Startup check stop start check logic 0" and in another place you listed it as "start check logic 0 for units without third fuel and no HRSG by pass". Where did you find the two descriptions? (I guess the second description was from a 'Comment' in the application code.?.?.?) I think you might have been in a great hurry when typing your response.... I think the L27BN and L27BZ should have been l27bn and l27bz and the contact for L45FP_STCK should have been normally open, not normally closed. This is because both l27bn and l27bz are usually associated with individual discrete (contact) inputs from relays in the generator protection panel. And, if the signal name L45FP_STCK was chosen correctly, then it should be a logic "1" when the Fire Protection System is capable of detecting a fire, tripping the turbine, and discharging fire extinguishing agent. And we want the Fire Protection system to be capable of all of the above. If L45FP_STCK is a logic "1" when it's "ready" then the normally closed contact you drew would be open, and L3STCK0 would not got to a logic "1"--which is what we need to get a READY TO START. l27bn = is a logic "1" when the Bus Voltage is Normal l27bz = is a logic "1" when the Bus Voltage is NOT Normal (the "Z" in this case means 'inverse') l3cp = logic "1" when the 'Customer Permissive' to START is a logic "1" TRUE = ??? This is one I'm not familiar with, but I think it's always a logic "1"--ALWAYS L86TCI = is a logic "1" when the redundant axial compressor inlet thermocouples disagree (have a wide discrepancy) by more than a setpoint L3IGVFLT = is a logic "1" when an IGV Fault has been detected L5WSTOP = (you didn't provide a description, and I'm not familiar with this one--at all) L5SETOP1 = is a logic "1" when one of the E-STOP Push-button inputs to the
core is actuated (open) L45FP_STCK = is (should be) a logic "1" when the Fire Protection Start-check Permissive is satisfied (unless the signal name was chosen incorrectly) So, let's read the rung: "If the bus voltage IS normal OR the bus voltage is NOT normal, AND if the Customer Permissive to Start is a logic "1" OR TRUE is a logic "1", AND the compressor inlet thermocouples DONOT disagree with each other AND there is NOT an IGV fault AND there is NOT an L5WSTOP AND the first E-Stop input to the
core is NOT actuated AND the Fire Protection Start-check Permissive is NOT [???] satisfied, then L3STCK0 will be a logic "1". The l27bn/l27bz parallel combination is a way to be sure the bus PTs are both sensing voltage or both NOT sensing voltage. (The "bus" is the voltage on the other side of the generator breaker--the grid voltage, the "running" voltage as it's often called.) The two logic signals should each be driven by separate discrete inputs (which is why I put the signals names in lower-case letters) from a bus under-voltage relay that is picked up when both PTs sense bus voltage, or when both PTs DO NOT sense bus voltage. If there is a problem sensing bus voltage there should be a Process Alarm to alert the operator to the condition. Note that a complete lack of bus voltage does not prevent a start; many times for testing there is no bus voltage when a turbine is started, or s ome turbines have the ability to close on to a dead bus. So the lack of bus voltage does not prevent a start; but when there is no bus voltage (a complete lack of bus voltage) there is a process alarm for that to alert the operator to the condition, but, again it does not prevent a start. A recent thread on control.com indicated some turbines start with a dead bus, and then close on the bus with a "dead" generator, and then apply excitation and slowly increase generator terminal voltage to "charge the

line" (the "bus" line). And, this is a good time to mention that every start-check permissive should be accompanied by a Process Alarm to alert the operator why a 'READY TO START' is not being displayed--EXCEPTone signal. And we'll get to that one soon enough. The l3cp/TRUE parallel combination is a way to bypass a 'Customer Permissive to Start' discrete input which usually exists in most all Speedtronic systems. It might be from the DCS saying the HRSG drums are full and heat can be applied to the HRSG from the gas turbine exhaust, or it just might an operator selection from the DCS saying they are prepared for a gas turbine start. (This signal does not trip the turbine when the turbine is running if it goes to a logic "0"; it just must be a logic "1" to start the turbine. If it's not, there should be a Process Alarm to alert the operator there is no Customer Permissive to Start.) The TRUE is the software "bypass" to l3cp; if there is no discrete input connected to the Speedtronic it will never change state, so the software TRUE (which is ALWAYS a logic "1") is used to bypass l3cp when there is no signal from the "Customer." In the "old" days, we used to just put a hardwire jumper on the l3cp discrete input terminals to permanently make l3cp a logic "1"; this is just a software equivalent of that. The signal could have been just deleted from the rung; TRUE completely baffles some people since it's not explained in any GE documentation--anywhere.) L86TCI a logic signal that warns the operator of a problem with the axial compressor inlet thermocouples, usually signal CTIF-1, CTIF-2 and sometimes CTIF-3 (Compressor Temperature-Inlet, Flange 1, -2 or -3). There is some logic in the application code that checks to make sure the three signals are within an allowable range of each other; if not, then a gas turbine start is not permitted. This is because axial compressor inlet temperature is used for biasing HP shaft speed for s ome very important functions (the resultant signal is TNHCOR, Turbine Speed-HP Shaft, Corrected). So, if the temperature measurements are not reasonably close to each other then there is a good possibility that TNHCOR can be adversely impacted which could affect turbine operation. The "86" in the signal name is an indication that the condition requires a Master R eset to unlatch the alarm once the condition has been corrected. Signals with "86" in the name are generally called "lock-out" signals. Most do require a Master Reset; some do not (unfortunately; another occasion when GE doesn't adhere to its own standard). L3IGVFLT is a logic signal that we can spend more time on if you wish. As you noted, it's checking to make sure the IGVs are within reasonable limits of where they should be prior to starting. The minimum mechanical stop on the IGV ring is set for approximately 32 DGA, so the lower limit s hould be something slightly less than that--and 31 DGA is a reasonable number. The minimum operating angle during starting is 34 DGA and the IGVs shouldn't be much more open that prior to a start, so 35 DGA is also a reasonable number. This is just a check to make sure the IGVs are in a reasonable position prior to starting (presuming the LVDT feedback is properly calibrated). The IGVs are one method to limit axial compressor surge/stall during starting by keeping them "closed" (34 DGA or so is considered closed). (Axial compressors are very unusual and have some very unique requirements.) The description you provided, probably from Toolbox, can be misleading. A servo problem might be the cause of this logic signal being "1", but, it might just be that the IGVs were left in some position other than what they should be after a maintenance outage, or the IGV LVDT calibration is inaccurate (this happens a LOT, unfortunately)--which is NOT a servo-valve problem, it's a human problem. Sometimes, the IGV minimum mechanical stop is also not set correctly after a maintenance outage when the IGVs have been worked on, resulting in the IGVs going to 30.9 or 30.8 DGA--which is not horrible, but is approaching the limits of acceptability. When a START signal is initiated, the IGV Trip Solenoid, 20TV-1 will be energize and hydraulic pressure will move the IGVs to the minimum operating condition (34 DGA). So, if personnel are CERTAIN the IGV LVDTs are properly calibrated AND that the mechanical stop has not be properly set it's sometimes permissible to change the limit to prevent the alarm. But, any value less than approximately 30.5 DGA means the minimum mechanical stop should be repositioned (it was moved) or the IGV LVDTs have not been properly calibrated--which, again, is NOT a servo-valve problem; it's a measurement and calibration procedure problem which should be corrected before starting.

Also, I would be interested to know if the application code for your turbine requires a Master Reset to unlatch L3IGVF1 and L3IGVF2 once the condition has been resolved. If so, this would be an example of a lockout that doesn't have "86" in the name. (Isn't this fun?) I would like to see the rung for L5WSTOP, as it's not something I'm familiar with. So, if you would, please, post it to your next reply. L5SETOP1 is a logic signal that comes from the
core when one of E-Stop P/B (Pushbutton) circuits is NOT closed. (E-Stop P/B circuits are normally closed, and when the circuit opens (by pressing the the EStop P/B) the turbine is tripped. There are a couple, if I recall correctly, E-Stop P/B inputs so it 's easier to identify which E-Stop P/B has been actuated (or possibly a wire in the circuit has come loose--it does happen!). Note again--this comes from
core. It is a hardware trip, as opposed to a software trip. It's meant to be a "positive" means of tripping the turbine (by opening the circuit) without having to go through software to trip the turbine. (There are also software trips, but I believe many insurance companies and some technical regulations and standards require a hardware method of tripping the turbine.) Hopefully, we will remember to cover this when we get to the L4T rungs, and other ways to trip the turbine. L45FP_STCK; this one I believe is either an incorrectly chosen signal name, a typo, or the contact sense (normally open vs. normally closed) is typed wrong. The signal name indicates this signal will be a logic "1" when the fire protection circuit is "ready" to detect a fire, trip the turbine and discharge fire extinguishing agent (CO2 or water sprays). If the signal name is correct--the logic is "1" when it's active and in a "ready" condition then the contact sense as shown is wrong. If the contact sense is correct (from the application code), then this is an example of someone not choosing a signal name correctly.... Let's work on L3STCK1 next, but, also please post the L5WSTOP rung, and if the sense of the L45FP_STCK contact is correct as you have typed it, please post the L45FP_STCK rung, also. And, please check on the case of signals l27bn and l27bz; if they are indeed all capitals, then please check to see if they are driven by discrete inputs; this could also be another example of GE not adhering to their own standards.... (What's the purpose of having standards, eh?) Reply to this post...


Posted by Neo

on 12 May, 2014 - 11:10 am

CSA, Glad to continue this finding journey, and thank you angain for your detailed reply. First i have to apologize to you for several unnecessary mistakes i made. So, i'll start with some clarification: 1)The sense of L45FP_STCK is normally open. 2)There is no signal named L5WSTOP,it should be L86MP.(weird mistake,sorry again) But the signal L27BN and L27BZ do in capital letter. SO the L3STCK0 rung should be: L27BN l3cp L86TCI L3IGVFLT L86MP L5ESTOP1 L45FP_STCK L3STCK0 -------||----------||----------|/|----------|/|----------|/|------- |/|------||------------() | | | |

L27BZ | TRUE | -------||---------||-------

Where: L27BN = AC BUS normal; L27BZ = AC BUS undervoltage; l3cp = startup check stop customer permissive to start ; L86TCI = compressor inlet thermocouple disagree ; L3IGVFLT = IGV valve position servo trouble; L86MP = startup check stop master prot startup lockout(confusing) ; L5ESTOP1 = state of E-STOP 1; L45FP_STCK = Fire protection start permissive ; I Checked the source of signal true l27bn1---------||---------L27BN;

true l27bz1---------||---------L27BZ;

In your reply, you mentioned if the s ignal is driven by a discrete(contact) input it should be in lower case letter. I am confused about the meaning of the word 'discrete'. Do you mean that if one signal is directed from sensors it's name should be in lower case letter? I am still a little confused about relay, as my understanding, a relay functions like a switch,when DO is logic 1, then it closed and the circuit is powered with electricity. The (undervoltage) relay and (lockout) relay confuse me. Take signal L27BN as an example, how does a undervoltage relay related to L27BN? Yeah, the application code in my turbine requires a Master Reset to unlock L32IGVF1 and L3IGVF2. Last thing to clarify the second description of LSTCK0 do comes from Toolbox,and i find it misleading. ------------------------------------------------------------------- -----------------------------------Here comes the LSTCK1: l26qn

L28FDSCK

L430

L14HR

L86HD

L3STCK1 -----------||---------||--------|/|---------||------------|/|----------()

l12hblt ---|\|-

Where: l26qn=Lube oil tank temperature low low; L28FDSCK=Flame detector trouble; L430=Off modo selected; L14HR=HP zero speed signal; L86HD=Hydraulic protective trouble; l12hblt=overspeed bolt trip; If the 'lube oil tank temperature is lower than setpoint' AND 'any one of the flame detector detect no signal of flame before start AND 'off MODE' is not selected'AND'the HP-shaft' is at rest AND 'Hydraulic protective is not logic 1 'ANd'overspeed bolt trip is not logic 1', then L3STCK will be logic 1. As to signal l26qn, does it from a temperature switch which outputs 1 when the temperature is lower than setpoint? I think the temperature of lube oil affect its performance. It seems the signal is related to the fuel servo system ,and i think it is important. Should i examine it next time?

I am confused about L430 signal, does it an input from HMI? And just to normally shutdown gas turbine? Up to now, i was confronted a lot of signals and i find it hard to sort it out? What should i focus on through this journey? Reply to this post...


Posted by Neo

on 12 May, 2014 - 11:27 am

CSA, I will give a brief introduction of gas turbine on my site some time later. I will prepare it. Best regards. Neo Reply to this post...


Posted by Neo

on 12 May, 2014 - 11:45 pm

CSA, I reread the your response below. "The l27bn/l27bz parallel combination is a way to be sure the bus PTs are both sensing voltage or both NOT sensing voltage. (The "bus" is the voltage on the other side of the generator breaker--the grid voltage, the "running" voltage as it's often called.) The two logic signals should each be driven by separate discrete inputs (which is why I put the signals names in lower-case letters) from a bus under-voltage relay that is picked up when both PTs sense bus voltage, or when both PTs DO NOT sense bus voltage. If there is a problem sensing bus voltage there should be a Process Alarm to alert the operator to the condition." I think there are two PTs measuring the bus voltage,both of them output its logic signal through the status of a relay. The relay outputs signal l27bn is closed when the bus voltage is normal and the other relay that outputs signal l27bz is closed when the bus voltage is below setpoint. So it is the hardware way of judging the status of bus voltage. It can also be done in software way by implementing the compare block. Is it right? Best regards Neo Reply to this post...


Posted by CSA

on 13 May, 2014 - 10:00 am

Neo, Whoa, there. Let's not get too far ahead of ourselves. You had asked about relays and discrete inputs (and by extension, discrete outputs) and you're talking about relays here like you have a good understanding of them. A discrete input (or output) to a programmable control system (and the Mark VI is a purpose-built programmable control system--built, primarily, for the purpose of controlling GE-design heavy duty gas turbines) is one that is either "on" or "off", "1" or "0", "true" or "false", "energized" or "de-energized", "picked up" or "dropped out", "close" or "open", and so on. It has only one of two possible states. A relay is simply a device for conveying information via contacts, that are either open or closed, when the relay is energized or de-energized. Relays usually have more than one set of contacts. The contacts can be electrically separate (have no common electrical circuits), or they can have electrically common contacts (so-called "c-form" contacts that have a normally open and normally closed terminal and share a COMmon terminal). In the case of an undervoltage relay, it is sending a discrete signal to the Speedtronic about the presence, or absence, of voltage. Additional contacts of the undervoltage relay may be used in other circuits for the same purpose (to indicate the presence or absence of voltage). Relays are pretty simple devices, however, they require a power source (110/220 VAC; 24 VAC; 24 VDC; 125 VDC; and many others depending on the manufacturer and application). They are electromechanical devices, and as such, they can fail when the electric coil fails, or when the contacts weld closed or the spring fails. Now to your present question about L27BN and L27BZ. GE and it's packagers typically use two PTs to sense bus voltage, and two PTs to sense generator terminal voltage--both arranged in what's called an opendelta configuration. If any phase voltage is lost, or if there is a failure of any single PT then, in this case (the bus voltage) l27bn1 (I believe you said it was at your site, that drives L27BN) will not pick up. Conversely, both PTs have to indicate there is NO bus voltage before l27bz (which I believe you said drives L27BZ at your site) will indicate a complete loss of bus voltage. There really is no point in starting a gas turbine that drives a generator if there is a problem with the bus voltage because it is very likely that the gas turbine will have to be stopped to sort the problem. As for whether or not the checks could be done with a COMPare block, well, yes. But then one would need to have additional AC voltage input circuits (at additional cost and complexity) when simple relays will do the job more than adequately by providing discrete inputs. Discrete inputs have historically been much cheaper to implement than analog inputs (voltages; currents). Unfortunately, sometimes discrete inputs don't have as much "information" available (such as the actual voltage levels, versus a minimum or zero voltage level, or even a maximum voltage level in some cases). Also, historically it was much easier to predict the failure mode of most types of discrete input devices (pressure switches; temperature switches; etc.). And GE is all about reliability and in the past transmitters weren't so reliable and could fail full on as well as full off. Also, historically providing power (24 VDC or 110/220 VAC) for transmitters was expensive, as were transmitters, themselves. As was the cost and complexity of analog input circuits. For reliability, it would be necessary to have redundant analog inputs which would also increase cost and complexity. So, mostly discrete inputs were used--and very successfully, too. Older Speedtronic panels (pre-digital versions) only had limited analog inputs and outputs: speed (frequency, and prior to that voltage); temperature (thermocouples--more reliable than RTDs and don't require additional power supplies, though they did require cold junction compensation circuits (be VERY thankful we don't have to do THAT any more!); one or two pressure transmitters (fuel gas intervalve (P2) pressure and axial compressor discharge pressure (CPD: Compressor-Pressure, Discharge); LVDTs; servo-valve outputs. Almost every other signal was a discrete input or -output.

And this brings me to say things need to slow down just a little, well, maybe a little more than that. I have just been given a rush assignment at work and I need to devote time to that (since I get paid at work, and I don't get paid for this endeavour). Also, you have asked several questions about terms and words and we haven't had a chance to cover them in any detail yet. We need to keep some focus here so that we don't get ahead of ourselves. We need to be sure that all questions get answered before we jump to another topic or rung. Control systems have gotten more and more sophisticated over the last few decades. And they have gotten both cheaper--and more expensive. I can recall when USD140,000.00 for a Mark IV Speedtronic turbine control panel was a LOT of money--and it wasn't all that capable as a programmable control system. Now, Mark VIes are nearly two- to three times as much, but they do have a LOT more capability, and they are much more expandable (inputs or outputs can be "easily" added to the control system (easily is a relative term--much easier than the Mark IV!). But, one has to remember that as the control systems changed and improved over the decades, GE-design heavy duty gas turbines basically remained the same. The turbine designers and packagers were loathe to change inputs and outputs (lots of changes to layout drawings, and schematics, and manufacturing practices and sourcing and warehousing and parts lists and manuals). It can become VERY expensive to change inputs and outputs just because the control system capability has improved. And, it's one of the things that have made GE-design heavy duty gas turbines so reliable and so desirable: They don't change very much. They are pretty constant things in a very fast-changing world. They are RELIABLE--when they are operated and maintained properly by people who are properly trained and have access to quality parts and services. The control philosophies GE has employed over the years have proven to be very robust and very scalable (meaning that as G E-design heavy duty gas turbines have gotten larger and more powerful the control systems were able to be expanded to maintain similar operation and protection philosophies and methods). So, when you ask, "Couldn't this be done with a COMPare block?" one has to think back to how things have evolved to the present condition when someone can ask a question like that. Imagine how many wires would be have to be used to interconnect all these devices to a single control system. Imagine how complicated and large such a control system would have to be. I don't know about you, but I LOATHE European-style, high-density terminal boards--even when appropriate sized wires are used on them. I prefer to have terminal boards that have to use a voltmeter easily and without fear of shorting or grounding, and where I can see terminations visually and where I can handle wires for troubleshooting and repair purposes. And, you're proposing even more wires and more terminal boards and more printed circuit cards and more complexity. Anyway, I'm enjoying our time and this journey, but I have to limit my time for the next couple of weeks. As I said before--don't try to ingest all of this right now, immediately. That's the great thing about this forum: it will be here for a long time. And the things that are written here will be here for a long time. And you can refer to them as your understanding grows. And you should be reading and re-reading them over time as your knowledge and experience grows. It's a LOT of information to try to take in all at once--we haven't even touched on inversion masking! And we haven't finished the start-check permissives. And we haven't started the trips! So, let's dial it back a little bit, and let me get caught back up at my day job, and finish one rung before we start another. There's always time for more questions. Reply to this post...


Posted by CSA

on 14 May, 2014 - 12:10 pm

Neo, As for that second description of L3STCK0, GE is trying to use the same sequencing with slight modifications for all heavy duty gas turbines. Makes sense, right? If it works, why change it? And it works. Has for decades. Again, it's one of the things that make GE units so desirable and so reliable--the operation and control philosophies have not changed much over the years and it's very reliable. That Comment from the application code is supposed to be for the requisition engineers who put the application code together in the factory. Sometimes (often) those engineers don't really have any field experience at all, and they make silly Comments. That's a silly Comment. As for L3STCK1. You made a pretty huge mistake on the first signal, l26qn. Why would you want to start a turbine if: "the lube oil tank temperature is lower than setpoint" (your words from the sentence for L3STCK1)? l26qn is a logic "1" when the L.O. Tank temperature is normal. It's driven by a discrete input from a temperature switch, 26QN-1. The switch contacts are closed when the tank temperature is "normal" (whatever the switch setpoint is from the Device Summary drawing, usually above approximately 60 deg F). And when the switch contacts are closed, l26qn will be a logic "1". This discrete input is NOT inverted. (We'll get to inversion masks shortly, but I want to get you started thinking about and anticipating the concept.) There will be a Process Alarm to indicate the L.O. Tank Temperature is Low. L28FDSCK is a signal that is a logic "1" when none of the flame detectors is indicating flame when the unit is not running. And, one doesn't want to start a turbine when one or more of the flame detectors indicates flame when fuel isn't flowing.... There will be a Process Alarm to say the flame detectors are not in a readyto-start condition. L43O. The contact is normally closed, and L43O is a logic "1" when OFF mode is selected, so to have power flow through the normally closed contact L43O would have to a logic "0", or when OFF mode is NOT selected. Here's the ONLY start-check permissive that doesn't have a Process Alarm to alert the operator. Why? Because one doesn't need a READY TO START indication if the unit is in OFF mode. In other words, to get a READY TO START indication the operator has to select CRANK, FIRE, AUTO or one of the other available modes, but when OFF is selected the unit can't be started anyway. It's not a alarm condition when OFF mode is selected. So, operators just have to know: When they want or need a READY TO START they have to be in some mode other than OFF. L43O doesn't come from the HMI. The HMI sends a command to the Speedtronic to switch to OFF mode, and if all of the permissives are satisfied to allow OFF mode to be selected then logic signal L43O is set to a logic "1". The HMI doesn't do any control or protection--it just sends commands to the Speedtronic, and monitors the operation of the unit (via signals from the Speedtronic), and, of course--it displays alarms from the Speedtronic. LOTS of alarms. Too many alarms, most would say--but that's because of poor configuration and/or poor maintenance or lack of understanding or just lack of response to alarms. Most operators, and their supervisors/managers, just don't pay any attention to any alarms as long as the turbine runs and doesn't trip. They think the Speedtronic will protect the turbine and trip it if it's necessary--and for the most part, it will. But there are some conditions that require operator action, and most operators (and technicians--and operations supervisors/managers) don't know when an alarm is indicative of a possibly larger problem. And, that's just poor training--and lack of personal motivation--both of which are permitted in too many plants. L14HR is a logic "1" when the unit is at rest, or when it's at zero speed. MANY people look at the logic that drives L14HR and they see that it doesn't actually change state at 0.000 percent speed, but something slightly higher, and they think that's wrong (??!!!??!) and so they change it to 0.000% and then the Speedtronic doesn't work. Passive speed pick-ups aren't very good at very low RPMs and that's why the speed level isn't set at exactly 0.000% (0 RPM). I think it's set for something like 3 RPM, which is just fine for this purpose--which is to protect the jaw clutch from being damaged if it's engaged when the turbine shaft is spinning. That's (probably) why your unit has to wait to get down to "zero" speed to start--because it has a jaw clutch which shouldn't be engaged when the turbine shaft is still spinning (and 3 RPM isn't very

fast!). L86HD. This is a condition and Process Alarm that confuses many people--because of the alarm message text: Hydraulic Protective Trouble. For present-day GE-design heavy duty gas turbines this alarm has NOTHING to do with the Hydraulic System. It is related to the Trip Oil system, and the presence of Trip Oil pressure in the system when there should NOT be pressure. It is a lock-out--signified by the "86" in the signal name, which means that when the Trip Oil pressure condition is resolved a Master Reset is required to unlatch the alarm, and permit a READY TO START. l12hblt is driven by a discrete input (the signal name is all in lower-case letters), and it's a logic "1" when the mechanical overspeed bolt is actuated. This input IS inverted, which means it is a l ogic "1" when the contacts of the overspeed bolt are open. As explained, the contacts of the L.O. Tank temperature switch, 26QN-1, are closed when the tank temperature is normal, and l26qn is a logic "1". It is NOT an inverted input. In this case, when the contacts of 12HBLT are open l12hblt is a logic "1"--which is the opposite (inverted) of what one would expect would happen. Why does GE use inverted logic? It's a poor-man's method of something called "contact supervision." What's contact supervision? It's a method whereby the control system monitors discrete input circuits to ensure a wire in the circuit has not come loose, or has not been cut/damaged. Most contact supervision circuits use "end-of-line" resistors placed across the physical switch contact terminals and the control system is always checking to see if there is current flowing in the circuit--whether or not the switch contacts are open or closed. More current flows when the switch contacts are closed, and only a small amount of current flows when the switch contacts are open, and when no current is flowing the control system alarms to alert the operator to a bad circuit/wiring. GE decided decades ago to standardize on circuits that were closed under normal operating circumstances, and opened to alarm or trip the turbine. To detect a closed contact, the circuit has to be intact (the wiring has to be good; the terminations have to be good) in order for current to flow--that's how the control system detects closed contacts. Open contacts result in no current flow. Let's say the overspeed bolt limit switch contacts were configured to close when the overspeed bolt actuated (because of a turbine overspeed). And, let's say that one of the wires of that circuit had come loose from its crimp and had fallen away from the terminal. If the turbine oversped and the bolt limit switch contacts closed the control system would never detect the contact had closed--because of the disconnected wire. No current would flow in the circuit when the overspeed bolt contacts closed, so the control system would never know the contacts had closed. NOT good. Now, let's say the overspeed bolt limit switch contacts were configured to open when the overspeed bolt actuated. Under normal circumstances, when the overspeed bolt limit switch contacts were closed current is always flowing in the circuit and the turbine thinks everything is just fine. And, let's say the turbine is running just fine at 73.4% of rated load, and suddenly one of the wires in that circuit vibrated loose from its crimp and became disconnected (it doesn't have to be a sudden disconnection--it just sounds better to say "suddenly"...). Even though the overspeed bolt limit switch contacts are still closed (there was no overspeed), because the circuit is now open there is no current flowing--just like if the switch contacts had opened. If the control system interprets no current flow as bad then it can take appropriate action, alarm and/or trip. In this way, the operator, and the technician, are aware of a bad circuit--could be a failed switch, just as easily as a loose wire, but the circuit is not intact and that's not a good condition under any circumstances. So, GE's answer to ensuring that circuits are in good condition (before there was even contact supervision available in any programmable control system) was to "invert" the input. In this way, the signal goes to a logic "1" when the external circuit is open (no current flowing). The signal names are generally chosen to indicate when there is a problem (alarm or trip), and this matches the inversion philosophy--a logic "1" when the external circuit is open. This is big one: inversion masking. Lots of people--myself included for years--used to say it was done to be "fail-safe." That's one way to think of it (not a good way in my opinion, because it doesn't really describe

how or why--it's just a quick answer that sounds good). Now, some people will say, "Well--if the turbine alarms or trips every time a wire comes loose, that's not very reliable!" And, they would be right. Wires should not come loose, but they do. Switches should not fail, but they do. So, GE's answer to that was to use redundant switches. It's not likely that two wires will come loose at the same time, or two switches will fail at the same time. But, if either did happen, then that's certainly a condition that should be resolved. But, if a wire comes loose or a switch contact fails in one of two redundant circuits and the logic (application code) requires two open circuits to alarm or trip the turbine on a serious fault then the turbine won't trip. GE also wrote logic to alert the operator/technician to a "disagreement" between redundant discrete inputs so the problem could be investigated and resolved. So, it's about reliability. Making sure that circuits and switch contacts are serviceable and can and will alarm or trip on serious trouble. Inversion masking is so mething that generally takes some time to "absorb" and comprehend, but once one internalizes the concept and the practice its something that helps understand and improve lots of other aspects of control and automation. And, can help explain a lot of nuisance alarms and trips on other systems where a standard wasn't adopted and followed (and it happens a LOT in many control systems!). Re-stating the sentence for L3STCK1: "When the L.O. Tank Temperature IS normal AND when the flame detectors ARE in a ready-to-start condition AND when OFF mode is NOT selected AND when the turbine shaft IS at zero speed (at rest) AND when there is NOT a Trip Oil pressure problem AND when the mechanical overspeed bolt limit switch is NOT de-actuated THEN L3STCK1 will be a logic "1"." That should take care of L3STCK1. One more comment about l2hblt--it doesn't trip the turbine. This logic signal does NOT (and SHOULD NOT) trip the turbine. It's simply a limit switch that indicates when the mechanical overspeed bolt has been actuated (which de-actuates the limit switch). The mechanical overspeed bolt will "dump" Trip Oil pressure--which is what trips the turbine. The limit switch just says, "The mechanical overspeed bolt is NOT actuated," or, "The mechanical overspeed bolt is in the RESET position, ready to indicate when the bolt has been actuated." Which is the position the mechanical overspeed bolt needs to be in to start the turbine. Why shouldn't this limit switch be used to trip the turbine in the Speedtronic turbine control panel? Because, it's a single limit switch--there's no redundancy. If it fails, vibrates loose, or a wire is disconnected, then if this input is used to trip the turbine--it will trip the turbine. It's extremely rare that a single discrete input will be used to trip the turbine--extremely rare. It reduces reliability (using a single switch). The only purpose of this switch is to indicate the overspeed bolt has been actuated--or, that is has not, as it's being used in the L3STCK1 rung. Now, have we satisfied all your queries about relays and lock-outs and such? Do you want to spend any more time on L3STCK1 before proceeding to L3STCK2? If not, let's continue. Do you have any questions about inversion masking? (You can have questions about it later, too. But if you have them now, let's try to answer them now. It's a very important concept, and it's key to troubleshooting and understanding GE turbine control systems--at least the digital ones.) Let me know if you're okay with what we're doing here. Is there a way to make it easier? Or better? Reply to this post...


Posted by Neo

on 15 May, 2014 - 9:16 am

CSA, Very glad to receive your response. I appreciate your patient and detailed reply. I have been enjoying this journey with you as your comment is always enlightening and helpful. You are a very patient and excellent teacher indeed. You asked me whether i am okay with what we are doing, and my answer is yes,certainly. And you asked me if there is a way to make things to make things easier. I think i should do some adjustments to make this journey easier for you. 1) I think i should focus on the main line,like present i should focus on L4S. I should set some questions that are not important at present aside, as we will have opportunity to discuss those questions latter (I wish:)) 2) If your comment wanna to cover every side of a signal ,it will take a lot of time and effort of you, and i think it will disturb your day work. In order to avoid this situation, i think it will be better if you just comment the important information i should know at this present. 3) We could keep in touch every day, but just examine no more than one rung. And i will split my response my reply in several section, and if you are busy, you can just reply one of them,and continue next time. In general, I think this journey is vary exciting, but it is difficult to start, but i think it will be easier if we continue. And thanks again for what you have done as i and this forum don't pay :) ------------------------------------------------------------------- ---------------------------------1) As to L3STCK1,I made a pretty mistake about l26qn. I thought that the toolbox description refers to the logic 1 situation. l26qn=Lube oil tank temperature low. l26qn L3STCK1 -------||--------......------() So i think when lube oil temperature is lower than set point ,it will be logic 1. 2) I do have questions about inversion masking, like when we should use inversion masking.Why l26qn is not inversed when l12hblt has to be inverted??? Does it related to the type of relay,NC or NO.How it helps us to read application code. I think take examples would make things easier to understand. ------------------------------------------------------------------- --------------------------------I think we should keep on moving, and i'll just write down the rung and examine it next time. L86CB L4Y L3BHSTCK L30CC_STCK l33cl1 l45fp1 l27f --------|/|-------||---------||---------|/|------|/|-------|/|----- |/|--------() || || -------------------true L86CB = Surge protection trouble startup lockout; L3BHSTCK = Comp operating limit BH start check perm logic;

L30CC_STCK = Fire protection trouble-GT start inhibited; l33cl1 = Fire protection aux/turb/laod compt CO2 locked; l45fp1 = Fire protection aux/turb/laod compt fire pre-detec; l27f = Fire protection trip relay undervoltage; ------------------------------------------------------------------- --------------------------------Best regards Neo Reply to this post...


Posted by CSA

on 16 May, 2014 - 11:56 am

Neo, >1) I think i should focus on the main >line,like present i should focus on L4S. >I should set some questions that are not >important at present aside, as we will >have opportunity to discuss those >questions latter (I wish:)) If you have questions, let's try to answer them. If we need to come back to them later, we can. I do believe, though, that the more we continue the more things will become clearer--but, if the questions are preventing you from understanding something let's try to answer them. >2) If your comment wanna to cover every >side of a signal ,it will take a lot of >time and effort of you, and i think it >will disturb your day work. In order to >avoid this situation, i think it will be >better if you just comment the important >information i should know at this >present. I think the important thing to get out of this exercise is how to "read" signal names and logic (rungs). DO NOT trust the longname description from Toolbox--just as with l26qn. When you wrote the sentence for the rung, it doesn't make sense to start the turbine with low lube oil tank temperature. You're saying, "If I can't trust the longname description in Toolbox, what can I trust?" Well, you have to analyze the information in front of you, and use any other resources you have to make sense of the situation. For example, if you went to the VCRC input where 26QN-1 is connected, you would see the input is NOT inverted (it's "Normal"). And, if you went to the Device Summary document, which lists the setpoints for most of the devices provided with the turbine and auxiliaries (but, unfortunately, not all of them....) you would see the switch is (likely) set for 60 deg F (approx 16 deg C) INCreasing, and the NO (Normally Open) contacts of the device are to be used for the indication. This means that as the L.O. Tank Temperature increases above approximately 60 deg F the NO contacts will close. (The Device Summary should also list the DECreasing setpoint, something around 50 deg F, for a deadband on the switch of approx. 10 deg F. This means that once the L.O. Tank temperature had risen above 60 deg F, closing the NO contacts, that the L.O. Tank temperature would have to drop below approx. 50 deg F to cause the NO contacts to open, or "reset" as many people like to say--meaning go back to the "un-actuated" state.) So, knowing that the input is NOT inverted, and that the switch contacts are closed above approximately 60 deg F, one can deduce that the longname description of the signal is wrong--that is, it does NOT describe

when the signal name is going to be a logic "1". You asked why this input is not inverted, but l12hblt is inverted. The input could have been inverted, and it would work just fine. Of course, the signal name would be exactly opposite of what it should be because it would be a logic "1" when the L.O. Tank temperature was less than normal. Sometimes these things, even though they could go one way or the other (with a signal name change to make it easier) are just continued for decades--and this is one of them. I believe if you will post the L26QN_ALM rung (I'm guessing at the alarm signal name; it will likely be different--unless I am very lucky today) you will see it looks something like this: l26qn L26QN_ALM -----|/|-------------( ) This rung, if it matches your application code, is a violation of another one of GE's control philosophies: That the logic that drives an alarm should be a logic "1" to make the alarm active. Do two wrongs make a right? In this case, it seems to. ;-) We learn to live with it. A former colleague of mine used to say, "This ain't rocket science." And, it's not. Does it have to be exact? No. Should it be exact? It would certainly help. Is it critical to proper operation of the unit? No. Would it take much to fix it? No--but, at GE there is no one who really understands all of stuff and is in charge or reviewing it to be sure it's accurate and consistent and so long-standing mistakes like this just keep getting repeated, decade after decade. Even if someone realizes it should be changed, that person likely is afraid to do so--because most of the people writing the application code have little or no hands-on, field experience. And yet, someone has changed the longname signal description--because for decades it was always "Lube Tank Temperature Normal", and in the application code at your site it's "Lube oil tank temperature low" (which is the alarmed condition of the input--the one that will prevent a READY TO START....). Again, the people who really do understand this stuff at GE realize--it's not critical. It's always been that way. Should it be changed? Probably. But, "If it ain't broke, don't fix it." The circuit has worked for decades even if it's not exactly as per philosophy, so it just gets neglected. Anyway, I can't read the next rung as you wrote it --you clicked on 'Submit Post' with a mistake in the html tags (you used /pre BEFORE and after the text; it needs to be pre before, and /pre after). Please correct the text and re-submit. You also forgot to put L4Y's longname description in the list of signals in the rung. One of the reasons I'm spending a little more time on signal descriptions is that a lot of other people read these posts, and it might help them to understand GE-design heavy duty gas turbine operation and control philosophy if there is a little more detail. So, please be patient with me. Reply to this post...


Posted by Neo

on 17 May, 2014 - 9:12 am

CSA, You said "I think the important thing to get out of this exercise is how to "read" signal names and logic (rungs)." Ok, i will keep this in my mind. ------------------------------------------------------------------- ----------------------------------I'm still confused about the concept of inversion masking. You said "So, GE's answer to ensuring that circuits are in good condition (before there was even contact supervision available in any programmable control system) was to "invert" the input."

Just take the signal l26qn for example, the temperature switch contact is closed(logic 1) under normal operating circumstances,and when the circuit fails, l26qn will turn to logic 0. So, it has the function of circuit supervision. So why inversion masking. As the same to signal l12hblt,if the circuit fails,it will become logic 0. Again why should the l12hblt be inverted. "GE decided decades ago to standardize on circuits that were closed under normal operating circumstances, and opened to alarm or trip the turbine." Does that mean logic 1 refers to normal operating circumstance, and logic 0 to alarm or trip the turbine. "For example, if you went to the VCRC input where 26QN-1 is connected, you would see the input is NOT inverted (it's "Normal"). How is one signal inverted,in hardware way or software way. If it is in software one, a signal can be inverted like this: prestate poststate ( )---------|/|-------( )

------------------------------------------------------------------- ----------------------------------"You asked why this input is not inverted, but l12hblt is inverted. The input could have been inverted, and it would work just fine. Of course, the "signal name" would be exactly opposite of what it should be because it would be a logic "1" when the L.O. Tank temperature was less than normal. Sometimes these things,even though they could go one way or the other (with a signal name change to make it easier) are just continued for decades--and this is one of them." I am confused about "sigal name",the name of signal? If does mean name of signal, i think whether or not the signal is inverted, is has no effect on signal name,just a name. So, this confuses me . ------------------------------------------------------------------- ----------------------------------In one reply, i typed one rung below: L45FP_STCK L3STCK ---.....------|/|---------()

The contact sense of L45FP_STCK is typed wrong,Which should be: L45FP_STCK L3STCK ---.....------||---------()

You found that mistake,and deduced that either an incorrectly chosen name or the contact sense is t yped wrong. How did deduce it? And you said the signal name indicates this signal will be a logic "1" when the fire protection circuit is ready to detect a fire. How did you know it is a logic "1" not a logic "0" when the fire protection circuit is ready to detect a fire? Those are the questions bother me a lot, and maybe it is good to deal those questions right now.And i hope

it will not bother you too much as some of them are silly. ------------------------------------------------------------------- ----------------------------------L86CB L4Y L3BHSTCK L30CC_STCK l33cl1 l45fp1 l27f L2STCK2 --------|/|-------||---------||---------|/|------|/|-------|/|----- |/|-------( ) | | | true | --------------------

L86CB = Surge protection trouble startup lockout; L3BHSTCK = Comp operating limit BH start check perm logic; L30CC_STCK = Fire protection trouble-GT start inhibited; l33cl1 = Fire protection aux/turb/laod compt CO2 locked; l45fp1 = Fire protection aux/turb/laod compt fire pre-detec; l27f = Fire protection trip relay undervoltage; I will examine this rung next time. Best regards Neo Reply to this post...


Posted by CSA

on 18 May, 2014 - 12:46 pm

Neo, It would seem after you most recent post that inversion masking is becoming clearer to you. Yes; the exact purpose of inversion masking is to make the logic signal associated with a discrete input (DI) a logic "1" when the contact--or the circuit--is open. And, if the signal name is chosen correctly it will describe the condition when the contact is open. And, yes, you are correct--l26qn is a violation of that philosophy and could have been configured to be inverted IF the signal name had been chosen to be something like 'l26ql' (except, that signal name is used on many older turbines.... so it would have had to be something similar, but different). And then the L3STCK1 rung could have been written: l26ql L3STCK1 ------|/|------ - - - ----( ) and the Low L.O. Tank Temp Low alarm rung could have been written: l26ql L26QN_ALM ------| |-----------------( )

I presume you used 'View | Reports... | I/O Report' to find the information you posted with the inversion mask and the description.?.?.? (Though I don't know where that description came from in Toolbox.... it's very odd, indeed. But, stranger things have been coming out of Belfort and Hyderabad--much stranger things.) For the Mark VI and Mark VIe, that report works fine because it actually looks at every I/O point and correctly reports the configuration (inversion mask; signal scaling; etc.). But--it does NOT work for the Mark V. The I/O Report is >>>NOT<<< only looks at the actual I/O Configuration when the report is first created--and after that, if any changes are made to I/O Configuration or location a conscientious person has to manually edit TC2KREPT.TXT to make the appropriate changes. While the Mark V I/O

Report is probably 97.9% correct, it always seem like when it 's late on a Saturday night and someone is relying on it for proper information--it's usually not right for the I/O point being worked on. (Sorry; I needed to do that for the people with Mark Vs reading this.) It should also be noted that an input is NOT configured to be inverted or normal via this report. It is done at the I/O card level (usually a VCRC for a Mark VI). But, you do seem to be getting the correct idea here. When you find what you believe to be a violation of GE's control philosophy, should you make the appropriate modifications to make it comply with GE's control philosophy? No. NO. NO. Emphatically, NO! You use GE's fall-back control philosophy: "If it's not broken, don't break it." I'm still confused by the 'true' "element" in parallel with l33cl1 and l45fp1. Is it a normally open contact that is in parallel with the two DIs? If so, it's a really SAD and shameful method of "deleting" the two contacts from the start-check rung. Perhaps it was done temporarily (I'm trying to give the commissioning engineer the benefit of the doubt here), but it's still very, very sad. I wonder what the alarm rungs for those DIs look like??? Are there normally open 'false's in those rungs, or normally-closed 'true's? Do the rungs even exist? Anyway, you didn't write your sentence for the rung.... As for how I deduced (makes it sound very sleuth-like!) the errors in signal naming or contact sense, it is really just experience--and lucky guessing. A very well-respected person who retired from GE many years ago said at his retirement dinner in response to questions about how he'd been so successful, "The harder I worked, the luckier I was. And, I'd rather be lucky than good." That's kind of how I feel--one can be good and unlucky, and that can be fatal. I'd rather be lucky, and be thought good--and the way to be luckier is to work hard, study hard, reflection, and constant review and reflection (kind of like continual process improvement in many manufacturing/quality programs. I think reflection is one of the most often overlooked qualities of success--in the olde days, people used to keep journals. If you've ever read the journals of famous people (who were considered successful and pre-eminent in their field) those journals describe lots of mistakes, reflection, successes, and reflection, and ponderment, and reflection. A quiet place to reflect, to consider what was and what could have been and what could be is really inspiring, invigorating and critical to getting lucky (improvement and "goodness"). So, again, as I've suggested in the past: Continue to look at this post, and others, and continue to develop your understanding based on your experience working with the equipment. Your understanding will grow, exponentially at first (though it seems difficult), and the respect of your peers and supervisors will also grow. The mistake that happens in a lot of places is that when someone gets technically good in their job they get promoted--and they don't mentor people who are coming up behind them to pass along the benefit of their knowledge. Too many people think, "Why should I make it easy for them; I had to struggle to get to where I was--no one made it easy for me. I made a lot of mistakes along the way, and I learned from those mistakes. Let others do the same." I'm paying back what I was fortunate to have been the beneficiary of decades ago. Please do the same, Neo. Maybe not this particular field, but pay it back. It really is a good feeling. So, write your sentence and ask your questions. We've still got quite a distance to cover here. Reply to this post...


Posted by Neo

on 18 May, 2014 - 8:13 pm

CSA, "The mistake that happens in a lot of places is that when someone gets technically good in their job they get promoted--and they don't mentor people who are coming up behind them to pass along the benefit of their knowledge. Too many people think, "Why should I make it easy for them; I had to struggle to get to where I was--no one made it easy for me. I made a lot of mistakes along the way, and I learned from those mistakes. Let others do the same." I appreciate what you said above,and you are a good teacher not only technically. From this point, i am lucky :) Last time i didn't write the rung, because i am afraid it will disturb your day work if too much things you have to deal with. I'll try to write sentence in several hours, and be patient with me. :) Best regards. Neo Reply to this post...


Posted by Neo

on 19 May, 2014 - 4:24 am

CSA, Here comses the L3STCK2: L86CB L4Y L3BHSTCK L30CC_STCK l33cl1 l45fp1 l27f L3STCK2 --------|/|-------||---------||---------|/|------|/|-------|/|----- |/|-------( ) | | | true | --------------------

L86CB = Surge protection trouble startup lockout; L3BHSTCK = Comp operating limit BH start check perm logic; L30CC_STCK = Fire protection trouble-GT start inhibited; l33cl1 = Fire protection aux/turb/laod compt CO2 locked; l45fp1 = Fire protection aux/turb/laod compt fire pre-detec; l27f = Fire protection trip relay undervoltage; ------------------------------------------------------------------- ------------------------L86CB is a logic signal that warns the operator a problem with the surge protection system: 1.IGV 2.Compressor Bleed Valve L86CBA L86CB --------||----------|------( ) | L86TV | --------||----------| | L30CBC_AL |

--------||----------|

L4 L14HS L520ONLINE L20CBX L20CBZ -------||---------||---------||------------( )---------------(T)

l33cblO L86CBZ L20CBA --------||--------|------||-------( ) l33cb2O | --------||--------|

L20CBZ is a logic 1 when the gas turbine is under normal condition(TNH>97% rated speed),and i think it is a command to close compressor bleed valve when it is logic 1.And if the valve is still open when L20CBZ is logic 1, then L20CBA is logic 1. The same to L86CBC_AL. When the compressor bleed valve is required to open(L20CBZ is logic 0), but it is still closed , then L86CBC_ALM is logic 1. I deduce it from the knowledge that the compressor bleed suction works when the gas turbine is under part load to prevent the compressor from surge. If i knew nothing about surge protection, how can i know what does it mean when l33cb1o is logic 1,whether it refers the valve is open or closed? Or when L86CB is logic 1, it is a command to close the valve or open the valve? From signal name and description form toolbox(but sometimes it is misleading)? As to L86TV, it is a little weird. L3IGVF2 L14HA L83BW L86TV -------||--------||---------|/|---------( )

It means when the TNH >50% rated speed, csgv>35deg , and L83BW is logic 0,then L86TV is logic 1. I am confused about L86TV,what deos it mean when it is logic 1.And is it related to surge protection. Besides, we had checked L3IGVF2 in L3IGVFLT in L2STCK0. ------------------------------------------------------------------- -----------------------------L3BHSTCK is a logic 1 when IBH system is in trouble. L3BHF1 L3BHF3 L3BHSTCK ----------|/|-----------|/|-----------( )

L3BHF1(bleed heat feedback trouble alarm) is not difficult to understand,for it is just like command not following. L3BHF3 is a little complicated. L3CPRAH L3BHF3 --------------||----------------|------( ) | L3BHF1 L3BHF2 L14HS | --------||-------||--------||---| | LCPRERR | --------------||----------------|

The lockout logic is left out. L3CPRAH = Ambient pressure indication high logic. LCPRERR = Compressor operating limit control falut. So when the inlet pressure is higher than the set point OR L3BHF1 and L3BHF2 is logic i when THN>97% rated speed OR CPR is reaching its max limit, then the L3BHF3 is logic 1. Can you explain The L3BHF3 for me, am confused about it? How are L3CPRAH and LCPERR are related to IBH? ------------------------------------------------------------------- ----------------------------L30CC_STCK is logic 1 when there is a problem in fire protection system. l27f is a logic 1 when its voltage is low. -----------------------------I------------------------------------- -----------------------------In conclusion,when surge protection system is normal, AND IBH system is normal,AND fire protecion trip relay is not undervoltage,And fire protection system is normal,then the L3STCK2 will be a logic 1. Best regards. Neo Reply to this post...

Posted by CSA

on 21 May, 2014 - 12:45 pm

Neo, I think there are some errors in the rungs and the explanations. Please review them and let us know what you find. I'll get back when I can devote the required amount of time and the errors have been corrected. Thanks! Reply to this post...


Posted by Neo

on 23 May, 2014 - 7:28 am

>CSA, > >Here comes the L3STCK2: > L86CB L4Y L3BHSTCK L30CC_STCK l33cl1 l45fp1 l27f L3STCK2 >--------|/|-------||---------||---------|/|------|/|-------|/|- ----|/|-------( ) > | | > | true | > --------------------

>L86CB = Surge protection trouble startup lockout; >L3BHSTCK = Comp operating limit BH start check perm logic; >L30CC_STCK = Fire protection trouble-GT start inhibited; >l33cl1 = Fire protection aux/turb/load compt CO2 locked; >l45fp1 = Fire protection aux/turb/load compt fire pre-detec; >l27f = Fire protection trip relay undervoltage; >--------------------------------------------------------------- ----------------------------> >L86CB is a logic signal that warns the operator there is a problem with the surge protection system: >1.IGV 2.Compressor Bleed Valve > L86CBA L86CB >--------||----------|------( ) > | > L86TV | >--------||----------| > | > L30CBC_AL | >--------||----------|

L86CBA = Cool seal air comp bleed/valve pos trouble close (what is cool seal air) L86TV = Inlet guide control troubles L30CBC_AL=Comp bld valves failure to open > L4 L14HS L520ONLINE L20CBX L20CBZ >-------||---------||---------||------------()---------------(T) (PS:I made some simplifications.)

L520ONLINE = Unit online (confusing) L20CBX = Cool seal air Air comp bleed 3 way valve ctrl signal

l33cblo L86CBZ L20CBA --------||-------- |------||-------( ) l33cb2o | --------||---------|

l33cb1o = cool seal air comp bleed valve#1 pos switch open l33cb2o = cool seal air comp bleed valve#2 pos switch open L20CBZ is a logic 1 when the gas turbine is under normal condition (TNH>97% rated speed), and i think it is a command to close compressor bleed valve when it is logic 1. And if the valve is still open when L20CBZ is logic 1, then L20CBA is logic 1. When the compressor bleed valve is required to open(L20CBZ is logic 0) while it is still closed, then L86CBC_ALM is logic 1. I deduce it from the knowledge that the compressor bleed suction works when the gas turbine is under part load. And it is one means to prevent the compressor from surge.If i knew nothing about surge protection, how can i know what does it mean when l33cb1o is logic 1,whether it refers to the valve is open or closed? As to L86TV, it is a little weird. > L3IGVF2 L14HA L83BW L86TV >-------||--------||---------|/|---------( )

L3IGVF2 = IGV-Vanes open alarm L83BW = water wash offline washing start check L14HA = HP accelerating speed signal

It means when TNH is above 50% rated speed,csgv>35deg , and L83BW is logic 0,then L86TV is logic 1. I am confused about L86TV,what oes it mean when it is logic 1.And how is it related to surge protection. Besides, we had checked L3IGVF2 in L3IGVFLT in L2STCK0. >--------------------------------------------------------------- --------------------------------->L3BHSTCK is a logic 1 when IBH system is in trouble. > L3BHF1 L3BHF3 L3BHSTCK >----------|/|-----------|/|-----------( )

L3BHF1 (bleed heat feedback trouble alarm) is not difficult to understand,for it is just like command not following. L3BHF3 is a little complicated. > L3CPRAH L3BHF3 >--------------||----------------|------() > | > L3BHF1 L3BHF2 L14HS | >--------||-------||--------||---| > | > LCPRERR | >--------------||----------------|

>The lockout logic is left out. >L3CPRAH = Ambient pressure indication high logic. >LCPRERR = Compressor operating limit control at max error. >So when the inlet pressure is higher than the set point OR L3BHF1 >and L3BHF2 is logic 1 when THN>97% rated speed OR CPR is reaching >its max limit, then the L3BHF3 is logic 1.Can you explain L3BHF3 for >me, I am confused about it? How are L3CPRAH and LCPERR related to IBH? >--------------------------------------------------------------- -------------------------------->L30CC_STCK is logic 1 when there is a problem in fire protection system. >l27f is a logic 1 when its voltage is low. >-----------------------------I--------------------------------- --------------------------------->In conclusion,when surge protection system is normal, AND IBH system is normal,AND fire protection >trip relay is not undervoltage,And fire protection system is normal,then the L3STCK2 will be a logic 1. Best regards. Neo Reply to this post...


Posted by CSA

on 27 May, 2014 - 11:56 am

Neo, I don't see much in the way of correction; the 'ltrue' still doesn't seem to have a contact (NO or NC). L4Y is not listed. The axial compressor bleed valves MUST be open prior to a start of the gas turbine, otherwise it's likely the unit will suffer extremely high vibrations as a result of compressor problems during starting which could even result in damage to axial compressor blading (stationary and rotating). The condition that can occur during starting--and shutdown--of the axial compressor is commonly referred to as surge and/or stall and occurs when the air flow through the compressor doesn't move as it should--as if it's blocked. This is true of

most axial compressors, not just those of GE-design heavy duty gas turbines. The limit switches on the bleed valves are designed to be actuated when the bleed valves is fully open. When the bleed valves are commanded to open there is a timer (usually 11 seconds) that starts, and if both bleed valves are not fully open by the end of the timer then the turbine is tripped and a start is prevented until the condition is corrected and a Master Reset is initiated. (The same is true of closing the compressor bleed valves--there is a timer that starts when they are commanded to close and if neither of them moves from the open position then there is an alarm, and on most DLN combustor-equipped units there is also a trip (which requires a Master Reset to clear once the condition has been resolved). Some newer units (especially the F-class turbines) have limit switches for BOTH the open and the closed positions. I was going to write that the signal name descriptions are getting very strange, but then I remembered this unit is a Frame 6B which means the Belfort Bunch has their brand all over the "logic."'Cool seal air' probably refers to 'Cooling and Sealing Air' which is the P&ID that the axial compressor bleed valves are shown on. But, the axial compressor bleed valves have little (if anything) to do with th e cooling and sealing air system. Once again, instead of clarifying things, Belfort is actively making them les s clear and more confusing--needlessly. "If it's not broke, break it," seems to be their driving philosophy. Or, probably, more truly, "If it's clear, de-clarify it; if it's simple, complicate it." L4Y is a timer that is a logic "1" one second AFTER L4 i s NOT a logic "1" (an "inverse" timer). It's used here just to provide at least 1 second after a trip during starting before another start might be initiated--and it also prevents a start if L4 is already a logic "1". The L3BHSTCK logic is also something which seems to have been "improved" by the Belfort Bunch. An excellent example of this is confusion created by the L3BHF3 rung you are experiencing. I don't believe the 96AP-n transmitters are used for IBH (I believe they are used to trigger the L3CPRAH logic), and L3CPRERR used to be used to detect a problem with the CPR calculation--which isn't directly related to IBH, either--just to the calculation of the axial compressor pressure ratio which is used to determine exhaust temperature control limit and protection. Inlet Bleed Heat (IBH) is a very poor name for the function it provides--compressor protection when the IGVs are operating at reduced angles so the turbine can operate in Premix Steady-state combustion mode at lower loads than would otherwise be possible. So, without being able to see the logic driving both signals (L3CPRAH and L3CPRERR) it's not possible to say for sure exactly what is being attempted with those two conditions driving L3BHF3. The other parallel string, L3BHF1 and L3BHF2 are blocked from actuating L3BHF3 below 95% speed by the L14HS logic, so, it just adds to the complication and muddling of the rung and it's use in the L3BHSTCK rung. It's understandable that the turbine should not be started if the ambient pressure transmitters are not working properly (the L3CPRAH function, I believe), but previously the L3CPRERR was also not enabled below 14HS (may still be), but the whole thing is just a mess to decipher and make sense of and try to explain. Sorry; I wish it weren't so, but this is a perfect example of Belfort thinking and logic. L30CC_STCK is almost another Belfort kludge, except that a 30 device is the ANSI device number for an alarm relay or device so it almost makes sense that if this signal is a logic "1" the start-check should be blocked. The bad part about this signal name is the STCK at the end--which conflicts with the whole L3STCKn naming convention--but, this is the Belfort way: complicate and confuse whenever possible. The concept here is that the turbine should not be started if the fire protection system (usually a CO2 system-hence the "CC" part of the signal name) isn't capable of detecting or extinguishing a fire. The next two signals, l33cl1 and l45fp1, appear to be coming from locking devices on compartment fire protection systems--which would be a logic "1" if either of them were prevented from being operated, which should be a start-check permissive. But, someone has seemingly (because it's not clear from your "drawing" of the rung) put a ltrue (NO) around them which effectively disables this part of the fire protection system logic. If there are no physical wires connected to the discrete inputs driving l33cl1 and l45cp1 then these signals should have just been removed from the application code (freeing-up a couple of discrete inputs for possible usage at some other time) and uncomplicating the start-check "logic." But, again, this is not per the Belfort way--so, complicate and confuse drives the mess. Why l27f couldn't be incorporated into the L30CC_STCK logic is just, yet AGAIN, stupefying. 'Nuff said.

Finally, the L52ONLINE logic is a DLN relic. It usually g oes to a logic "1" sometime after the generator breaker closes AND the unit is above some "minimum" load, sometimes 5 MW, AND the axial compressor bleed valves are closed. It's kind of unnecessary if the turbine trips of the axial compressor bleed valves aren't closed when the unit is above 14HS, but it seems to have a life of its own (part of the "if it's not broke, don't break it"--because it's not understood, not because it needs complication or confusion). Wow! This rung was difficult; sorry. This is why it's really necessary to have paper copies of rungs with hand-written notes on them to help remember what these things are when one has to try to understand them--and if one has to go back to them in future years. Trying to figure this stuff out months or years later can be just as difficult as the figuring it out the first time--so notes are really helpful, now and in the future. PLEASE make sure you are drawing the rungs properly and completely as we progress. We haven't even finished the start-check stuff, and we still have all of the tripping stuff to go through. So, clarity and accuracy is crucial to keeping on track. Reply to this post...

Posted by Neo

on 28 May, 2014 - 12:09 am

CSA: Thank you for your detailed reply. 1)We have dealt with L4Y before, that's why i didn't list its definition. 2)If is 'True',it is always a NO contact. I have been occupied with work these days ,and i will reply to you as soon as possible.I hope you can comment on my understanding and answer my questions if it means something.In this way, i will get more interested in this journey. And my next assignment is L3STCK3? Best regards. Neo Reply to this post...


Posted by CSA

on 28 May, 2014 - 10:49 am

Neo, Yes; I'm busy at this time, too, so I'm not devoting as much time to this as I'd like. Yes; you're next assignment is L3STCK3. 2) I've seen some usages of 'ltrue' that were NC, not only NO. It can be either. If it's NO, then the contacts will be closed (because 'ltrue' is always a logic "1"); if it's NC then the contacts will be open. There's also an 'lfalse', that's always a logic "0", and can be NO or NC.

To your questions: a) Cooling and Sealing Air is air that's extracted from a couple of points from the axial compressor that's mostly used to cool various spaces, like wheelspaces. It's also used to pressurize other areas, such as bearing seals, in an effort to keep lube oil from leaking out of the bearings along the shaft. For more information, please refer to the Cooling & Sealing Air P&ID, as well as the System Description for the Cooling & Sealing Air system in the Service Manuals provided with the turbine and auxiliaries. For some reason, the compressor bleed valves appear on the Cooling & Sealing Air P&ID, probably because there's not really anywhere else to put them.?.?.? b) l33cb1o & l33cb2o are logic signals, driven by limit switches on the compressor bleed valves, and they are a logic "1" when the compressor bleed valves are fully open (the "o" at the end of the signal name stands for "open"). There is another very useful document provided with most GE-design heavy duty gas turbines called the Device Summary. It lists most (but not all) of the field devices and instruments provided on the turbine and auxiliaries by the packager. It typically does NOT list the devices provided with the generator (except for the low and low-low L.O. pressure switches) and exciter and generator controls, and quite often these days does not list some devices provided on skids supplied by subcontractors. But, it does have good information which can be very helpful and useful. It's most useful aspect is that it lists the settings for the majority of the pressure- and temperature- and limit switches on the unit. c) L86TV is weird in the context shown, and it violates the concept of a lock-out device since it has no seal-in and doesn't use a Master Reset to unlatch the signal. L83BW is a logic signal that's a logic "1" when a water wash is being performed--usually an off-line water wash, but has been used for on-line water wash indication as well. Again, there are some messy logic signals in many Speedtronic control panels, and this appears to be another one. (I had no idea we were going to encounter so many on this journey! But, it's probably just as well since it's a journey of discovery and one discovers good things and bad things on most journeys, right?) I think that covers most of the questions, or are there others I've missed? Reply to this post...

Posted by Neo

on 9 June, 2014 - 8:20 am

CSA, I am back :) I will do my assignment as soon as possible. Neo. Reply to this post...


Posted by Neo

on 10 June, 2014 - 10:06 pm

CSA, Sorry for be absent for more than a week.

In the last rung, you explained that: LCPRERR used to be used to detect a problem with the CPR calculation--which isn't directly related to IBH, either--just to the calculation of the axial compressor pressure ratio which is used to determine exhaust temperature control limit and protection. It seems that LCPRERR is more related to tell whether the CPR is approaching the Cprlim. ------------------------------------------------------------------- ------------------------------------------Here comes the L3STCK3: L4T L39VD3 L3TFLT LAUXGAS_PT L30IPFLT2 L3IPSTCK L3STCK3 ------|/|------|/|---------|/|---------|/|----------|/|--------|/|- -------( )

L4T = Master protective trip; L39VD3 = Vibration start inhibit; L3TFLT = Compressor discharge pressure fault alarm; LAUXGAS_PT = Auxgas Press or Temp Detected at Meter Tube; L30IPFLT2 = IP fault no flow detected-during transfer off aux; L3IPSTCK=Inert purge system system start check; I think L4T is an important signal name, but i have little knowledge about it. All i know is that if L4T is logic 1, then the gas turbine trips. So i think all signals that will trip a gas turbine will finally go to L4T.And i think there is a connection between L4 and L4T. L14HS L4 L14HSX ---------||--------------||-----( ) | L14HSX L94X | ------||------|/|----

L94X = Startup check stop GT normal shutdown; L14HS = HP operating speed signal; A>B----| | L14HSX L3TFLT ---------| |---------||-----------( )

A = CAKCPD(35psi) B = CPD L14HSX = Auxiliary signal to L14HS If CPD is less than 35psi when gas turbine is under normal operation (L14HS is logic 1), then L3TFLT is logic 1 (indicates the pressure transducer is in fault?) I was wondering the function of the L14HSX signal, and can L14HSX in the L3TFLT rung be replaced by L14HS? I am confused with the signal L94X. In the toolbox, its description is: Startup check stop GT normal shutdown (startup or shutdown?). And i found 94 is related to tripping or trip-free relay in ANSI device number. L39VD3_GT L39VD3 --------||------------( ) | L39VD3_GEN | --------||-----

L39VD3_LG --------||-----

| |

According to the above rung,there are three groups of vibration sensors in this unit: one for gas turbine, one for generator and the last one for load gear. And if anyone of the sensor groups is faulty or disabled (qty of sensors in group faulty or disabled > = 1; > = (#sensors+1)/2; both sensors in any pair faulty or disabled.), then L39VD3 is logic 1. I referred to the L39VV7 block, and was confused about the difference with faulty and disabled. Whether a vibration sensor is fault or not is decided by HLTHn, while disabled or not is decided by ENABLEn. LAUXGAS_PT LFPAG0LL LAUXGAS_PT -------|/|------------------( ) | LFPAG0 | -------||----------| LFTAGI false | -------||------||--| CA43P2 false | -------||------||---

LFPAG0LL = auxgas supply pressure low low; LFPAG0 = auxgas supply pressure detected; LFTAGI = auxgas supply temperture detected; CA43P2 = initiate P2 cavity blocking; If the LAUXGAS_PT is logic 1, then there is a problem in the auxgas supply system. According the above rung, if the pressure is lower or higher than the setpoint, then it is presumed that the auxgas supply system has a problem. I think auxgas refers to the gas fuel, right? And FPAG in the signal name stands for something? L30IPFLT2 and L3IPSTCK are related to purge system. As to my understanding, there is a need to purge before start a gas turbine in order to clear away the residual gas fuel in combustor. In conclusion, if L4T is logic 0, and the vibration sensors works well, and CPD is more than 35 pisg when under normal operation, and there is no problem in auxgas supply system and inert purge system, then L3STCK3 is logic 1. Reply to this post...

Posted by Neo

CSA, I am waiting for your reply:) Best regards! Reply to this post...

on 17 June, 2014 - 5:57 am

Posted by CSA

on 17 June, 2014 - 10:00 am

Neo, Sorry, I missed your post. I also believe that the unit you are operating may be burning more than one gas fuel, based on some of the logic signals in the post (_IP--Inert Purge, for one). You didn't tell us about that. Give me some more time to review your post. Reply to this post...


Posted by CSA

on 17 June, 2014 - 4:43 pm

Neo, You are reading the Longname description for LCRPERR very literally--and that can be a mistake sometimes. As we've learned. If that logic signal has a rung, can you post it? Your sentence for L3STCK3 is correct. And you are also right: L4T is VERY important (we're headed there soon!). But, you are NOT correct in that every trip is not run to/through L4T--because there can be trips connected to
and from
(remember the overspeed/rate of speed change trips that is
's primary function!). L4T is all of the turbine trips that come from (, and )) and the application code running in and the trip inputs connected to . The "connection" between L4 and L4T is: L4S L4T L94T L4 ---| |-----|/|------|/|----------( ) | L4 | ---| |---

Remember? That's where we started: L4. We're now working on how L4S gets to be a logic "1" and when L4T is NOT a logic "1" and L94T is NOT a logic "1" then L4 will be a logic "1" (when L4S goes to a logic "1"--which it does for a few seconds at most). Again, the whole FPAG (Fuel Pressure - Aux Gas) seems to be related to a second gas fuel, perhaps an "off-gas" from some process nearby that has some heat content that can be burned in the gas turbine--but the turbine can't be started on the aux gas, and the aux gas piping needs purging.?.?.? I wouldn't be too shocked to find this is "max-case" logic meant for machines with dual gas fuel capability-and your unit doesn't have it, or maybe it was supplied with the intent of having it some day.?.?.? But, this is where I'm coming up with the aux gas stuff--these signals seem to be indicating that you didn't tell us about a second gas fuel capability, OR (perhaps more likely) it doesn't exist and was (sadly and almost criminally) left in the application code. Hope this helps! If you're questions about L3STCK3 have been answered, we can move on. Otherwise, let's get them

answered to your satisfaction before we do (move on). And if you have other questions (related) that have come up recently, let's deal with those here, too, and now. I don't understand why you posted L14HSX, and then didn't discuss it all.... Reply to this post...


Posted by Neo

on 18 June, 2014 - 9:05 pm

CSA, Thank you for your reply,and you reply is always enlightening. It seems that you know every thing, and most of your guess about this unit is right! This is a PG6561B-L(MS6001B) gas turbine, and i think L is for low heat content fuel. When it is under normal operation it burns BFG(Blast Furnace Gas) and COG (coal oven gas), BFG and COG do are "off-gas" from nearby steel plant. And BFG and COG are premixed(syngas). And this unit starts on light diesel oil.We can choose fuel in HMI from "syngas,distillate fuel and gas/distillate fuel mix". And there is a IGCC module in toolbox,and i think it is related to the gas fuel system. I have several questions: How did you deduce these information from siganl names? What is IP stands for in L30IPFLT2? Why this unit have to start on liquid fuel,low heat content? If we chosen syngas on gas turbine start by mistake, what will happen? You said "but the turbine can't be started on the aux gas, and the aux gas piping needs purging". What does the purging system for? I found this unit is equipped gas fuel and liquid fuel purging system. I think the auxgas in application code is sygas,right? And it is weird, where is the primary gas? Sorry for bothering you with so many questions,but it really haunts me. Thank you. Best regards! Neo. Reply to this post...

Posted by Neo

on 18 June, 2014 - 9:27 pm

CSA, I find it is not convenient to print CSP. CSP will be split by page marker and the page is not fit into A4.

Best regards! Neo Reply to this post...

Posted by Neo on 22 June, 2014 - 7:49 pm

CSA , It seems that you do not respond as soon as before :( What's wrong? If you do not wanna go on this journey, you can just let me know. That't ok. Neo Best regards. Reply to this post...


Posted by CSA

on 23 June, 2014 - 10:38 am

Neo, I've been having computer hardware issues with my old and trusted desktop--which is the computer I use for writing the long missives for this thread. (It's too difficult to respond to this thread using a tablet--I don't have a keyboard for the tablet.) I'm still keen to continue--and complete the journey--but I do, also, have a paying job that I must devote attention to. In this business one can never anticipate when something will break or someone will decide they want to upgrade their equipment this week--only to decide next week that it's too expensive and they want to keep their current equipment without doing any maintenance. I don't understand the comment about printing the CSP. The designers of Toolbox never envisioned anyone would want to print the application code (it's CSP for the Mark V; sequencing for the Mark IV; and application code for the Mark VI and Mark VIe--isn't this fun?). So, while they made a half-hearted attempt at a Print function, they didn't do a very good job of it. As I said, I use the MS-Windows capture hot-key sequences--and with Win7 and Win8.1 there's the 'Snippet' tool--to "grab" what's in Toolbox display and copy it to the Clipboard and then past the contents in a MS-Word or Wordpad document and then print that to make notes on. There is just so much empty "white space" (wasted space) in the Toolbox and ToolboxST printouts and the way elements are displayed can be extremely confusing (again because of the half-hearted printing routine used in Toolbox and ToolboxST) that it's just not worth the effort unless one has LOTS of time, toner cartridges, and reams of paper. As for the comments about how did I know the unit burned low-BTU gas fuel, well, from the Longname descriptions you provided which included the Inert Purge term. Natural gas will always be the "primary gas fuel" even if the unit doesn't burn natural gas. Any other gas fuel--for the time being--will be the "aux" gas, and sometimes referred to as "syngas." I believe that

portions of the purging sequence sequence in your machine machine were likely copied-and-pasted copied-and-pasted from the IGCC IGCC unit control schemes (Integrated, Gasified Combined Cycle--the test units for trying coal gasification) as they use purging quite extensively in the gas fuel system(s). Generally, the reason most turbines are started on "conventional" fuels is that there simply isn't enough heat content in the secondary fuel(s) ("aux" gas, in your case) to reliably start the unit. It works one day, but not the next--and usually because the heat content of the secondary fuel isn't consistent. So, the decision is made to start on a more consistent (conventional) fuel for reliability. If the application code is written correctly, if you try to start on "aux" gas, it just won't allow the START to be initiated--most likely. And if if it did, again, it might start today but then might not start tomorrow tomorrow or next week on the "aux" gas. Gas fuel purging is to remove the "aux" gas from the piping, usually for safety's sake--and ALSO to keep hot combustion gases from the other fuel (liquid fuel in your case) from entering the gas fuel passages and causing problems when running on liquid fuel. Liquid fuel purging is also done for two reasons--to remove the liquid fuel from the fuel nozzles to prevent coking (carbonization of the liquid fuel by the heat from hot combustion gases when running on the "aux" gas), and also to ensure hot combustion gases don't enter the liquid fuel nozzles or atomizing air passages when running on "aux" gas. GE is consistently inconsistent with it's use of words and terms--as are most other manufacturers in the world. Frankly, there are just too many people working on various parts of the gas turbine, the control system, and the auxiliaries and there's no one person or group that's making sure consistent words and terms are used throughout the documentation (including comments in the application code, the Control Specification, and System Descriptions, etc.). The interesting thing to note here is that GE and packagers of its turbines sell a LOT aeroderivative gas turbines to military organizations around the world. And they have to provide documentation that is consistent and explicit. The US government, for example, will insist on seeing the documentation (training manuals; system descriptions; maintenance and parts manuals) BEFORE they will start receiving and inspecting equipment. This is because they want to be sure that operators, technicians and repair personnel have good-to-excellent good-to-excellent documentation to work from when servicing this equipment at sea, or while on the ground (for aircraft)--especially aircraft)--especially in times of conflict. They don't call for a service person to come to fix the equipment; they have trained personnel to do that and they want to make sure the manuals and documentation their personnel have are very, very good. Too bad the same thing doesn't happen for heavy duty gas turbines.... It's really too bad it doesn't. Their lives (GE field service personnel), the experiences of operators and technicians, and the work of mechanics would all be SO MUCH easier if the heavy duty units had manuals and documentation that's even half as good as the military documentation. But, I digress. What rung are you going to document next on our journey? (Realizing we both have jobs and lives, of course.) Reply to this post...

Posted by Neo

on 28 June, 2014 - 7:53 am

CSA, "As for the comments about how did I know the unit burned low-BTU gas fuel, well, from the Longname

descriptions you provided which included the Inert Purge term." Is the Inert Purge term special for low-BTU system? If one unit burns natural gas,purge system is still needed,right? I happened to see a test bench application code. The test bench application does't have IGCC module,and its GAS_LIQ_PURGE module has LIQ_NO_DLN and GAS tasks,while our application has IGCC module,but only LIQ_NO_DLN task in GAS_LIQ_PURGE GAS_LIQ_PURG E module. So i think you deduction "that portions of the purging sequence in your machine were likely copied-and pasted from the IGCC IGCC unit control schemes as they use purging quite extensively in the gas fuel system(s)" is right. I wondered that if an IGCC unit has an unique purge system? And for our unit that burns low-BTU gas fuel, should its purge system be different from those that burns natural gas? Maybe these questions are very boring, but i am still curious. May it not bother you. Best regards! Neo. Reply to this post...


Posted by CSA

on 29 June, 2014 - 1:27 pm

Neo, Usually, whenever a GE-design heavy duty gas turbine burns multiple fuels (even two different gaseous fuels) there are fuel purge systems. This primarily to ensure that there is no fuel in the system which is not in service which can accidentally ignite, and also one of the primary purposes of the purge system is to provide a flow of cooling cooling air through the fuel system system not in service. Another benefit of this flow of air through the fuel system which is not in service is that it prevents the backflow of hot combustion gases into the fuel system which is not in service and which can cause very serious damage to piping and components (especially fuel nozzles and flexible piping section). Some fuels are very dangerous if exposed to oxygen, even atmospheric oxygen, so the purge is used to ensure that no unburned fuel is ever present in the piping. A fuel purge system is a fuel purge system in my opinion. I don't think one fuel or process has a purge system that is that much different than any other--except when some inert gas is required to purge the fuel to avoid coming into contact with ox ygen. These systems will be more complicated, necessarily so, because of the additional piping and regulators and valves and solenoids and such. I don't know if the low-BTU fuel at your site qualifies as such, but it could. Gas turbines are burning a lot of different fuels these days as people are looking to prevent prevent flaring off-gases off-gases to reduce emissions--and emissions--and to increase the efficiency efficiency of the process by utilizing available available energy from from hydrocarbons instead of just burning it or venting it. Hope this helps! Next rung in the L4 Journey, Journey, please? Reply to this post...


Posted by Neo

on 25 June, 2014 - 5:54 am

CSA. Very glad to receive your reply,and thank you sincerely for your engagement.I am not rich,or i am willing to pay you for this interesting journey:) And if you are busy,just let me know. You know waiting is miserable. I hate to quit and i wanna to go on this journey and finish it. Thank you again for your help. ------------------------------------------------------------------- ---------------------------------------You missed this quetion below:

A>B----| | L14HSX L3TFLT ---------| |---------||-----------( )

A=CAKCPD(35psi) B=CPD L14HSX=Auxiliary signal to L14HS And i tried to find the differece between L14HS and L14HSX.

L14HS L4 L14HSX ---------||--------------||-----( ) | L14HSX L94X | ------||------|/|---L94X=Startup check stop GT normal shutdown; L14HS=HP operating speed signal;

As for L3TFLT,if CPD is less than 35psi when gas turbine is under normal operation,then L3TFLT is logic 1. I was wondering the function of the L14HSX,and whether whether can L14HSX in the L3TFLT rung be replaced by L14HS. I am confused about L94X.In the toolbox, its description is :Startup check stop GT normal shutdown. ------------------------------------------------------------------- --------------------------------------L3RS1 L3RS2 L5VPRO_LATCH L3RS -------||----------||----------||---------||------------|/|------------|/|----------( -----( ) L3RS1=Startup check stop ready to start 1; L3RS2=Startup check stop ready to start 2; L5VPRO_LATCH=Protective L5VPRO_LATCH=Prot ective VPRO card trip-latch; As we just finished L3RS1,i think L3RS2 is my assugnment this time.

L52ONLINE L3COMM_IO L3ACS L3RS2 ------|/|---------||-------||------( ) L52ONLINE= Unit online ; L3COMM_IO=VCMI state changes for ,, OK; L3ACS=Auxiliary check servos; I find L3ACS is not easy,so i decide to deal this sigal this time. L3GFLT L3LFLT L62TT2 L3ACS ----|/|-----|/|------|/|--------( ) | | L84TL | L84TG | -----||------||---L3GFLT=Gas fuel control fault; L3LFL=Liquid fuel control fault; L84TL=On total liquid fuel; L84TG=On total gas fuel; L62TT2=startup check stop mutiple start counter;

let me start with L62TT2:
Timer_sec _Counter L2FZ(log_in) (log_out)L62TT-----------L62TT(INC) (AT_CNT)L63TT2 K62TT(pu_del) K62TT2(MAX_CNT) L1XY(RESET) L2FZ=startup check stop multiple starts permissive; K62TT=startup check stop multiple start time delay(5s); L62TT=startup check stop multiple start and atuo refire; K62TT=startup check stop multiple start count(2); L1XY=startup check stop aux to master contr-stup perm; When the number of pulse(L62TT signal) is less than 2(K62TT2),than L63TT2 is logic 0. There are several combinations which will make L3ACS logic 1 when L63TT2 is logic 0: 1.L84TL=1,L3LFLT=0; The gas turbine is on total liquid fuel,and the liquid fuel control is not in fault. 2.L84TG=1,L3GFLT=0; The gas turbine is on total gas fuel,and the gas fuel control is not in fault. 3.L3GFLT=0,L3LFLT=0; The fuel control system is not in fault. CSA,I am confused about L62TT2,and can you explain it briefly. According to the above combination,the gas turbine can start up when one of the fuel control systems is fault,and is it reliable? Reply to this post...


Posted by Neo

on 25 June, 2014 - 10:34 am

CSA. Very glad to receive your reply,and thank you sincerely for your engagement.I am not rich,or i am willing to pay you for this interesting journey:) And if you are busy,just let me know. You know waiting is miserable. I hate to quit and i wanna to go on this journey and finish it.

Thank you again for your help. ------------------------------------------------------------------You missed this question below:

-------------------------------------------------------------

A>B----| | L14HSX L3TFLT ---------| |---------||-----------( )

A=CAKCPD(35psi) B=CPD L14HSX=Auxiliary signal to L14HS And i tried to find the differebce between L14HS and L14HSX.

L14HS L4 L14HSX ---------||--------------||-----( ) | L14HSX L94X | ------||------|/|---L94X=Startup check stop GT normal shutdown; L14HS=HP operating speed signal;

As for L3TFLT,if CPD is less than 35psi when gas turbine is under normal operation,then L3TFLT is logic 1. I was wondering the function of the L14HSX,and whether can L14HSX in the L3TFLT rung be replaced by L14HS. I am confused about L94X.In the toolbox, its description is :Startup check stop GT normal shutdown. ------------------------------------------------------------------- --------------------------------------L3RS1 L3RS2 L5VPRO_LATCH L3RS -------||----------||------------|/|----------( ) L3RS1=Startup check stop ready to start 1; L3RS2=Startup check stop ready to start 2; L5VPRO_LATCH=Protective VPRO card trip-latch; As we just finished L3RS1,i think L3RS2 is my assugnment this time.

L52ONLINE L3COMM_IO L3ACS L3RS2 ------|/|---------||-------||------( ) L52ONLINE= Unit online ; L3COMM_IO=VCMI state changes for ,, OK; L3ACS=Auxiliary check servos;

L3GFLT L3LFLT L62TT2 L3ACS ----|/|-----|/|------|/|--------( ) | |

L84TL | L84TG | -----||------||----

L3GFLT=Gas fuel control fault; L3LFL=Liquid fuel control fault; L84TL=On total liquid fuel; L84TG=On total gas fuel; L62TT2=startup check stop mutiple start counter; let me start with L62TT2:

Timer_sec _Counter L2FZ(log_in) (log_out)L62TT-----------L62TT(INC) K62TT(pu_del) K62TT2(MAX_CNT) L1XY(RESET)

(AT_CNT)L63TT2

L2FZ=startup check stop multiple starts permissive; K62TT=startup check stop multiple start time delay(5s); L62TT=startup check stop multiple start and atuo refire; K62TT=startup check stop multiple start count(2); L1XY=startup check stop aux to master contr-stup perm; When the number of pulse(L62TT signal) is less than 2(K62TT2),than L63TT2 is logic 0. There are several combinations which will make L3ACS logic 1 when L63TT2 is logic 0: 1.L84TL=1,L3LFLT=0; The gas turbine is on total liquid fuel,and the liquid fuel control is not in fault. 2.L84TG=1,L3GFLT=0; The gas turbine is on total gas fuel,and the gas fuel control is not in fault. 3.L3GFLT=0,L3LFLT=0; The fuel control system is not in fault. CSA,I am confused about L62TT2,and can you explain it briefly. According to the above combination,the gas turbine can start up when one of the fuel control systems is fault,and is it reliable? Reply to this post...


Posted by CSA

on 25 June, 2014 - 1:03 pm

Neo, I'm not quite sure what the question is, but let's try this. The comparator is checking to make sure the median value of CPD is greater than 35 psig; if it's not then when the unit is above 14HS and running (we'll get to that in a minute) then L3TFLT is a logic "1" and usually, these days, that means a turbine trip-especially for machines with DLN combustors (because CPD is very important for exhaust temperature control--VERY important). L14HSX is a unique L14HS in that, as you can seem from the rung once the unit is running (L4 is a logic "1") and the unit gets above 14HS (usually 95% TNH), then L14HSX latches in (through the L94X/L14HSX parallel part of the rung). L94X is a very important signal--a 94 device is a shutdown device, not a TRIP, but a normal, orderly shutdown. As, in an operator selects STOP and the unit starts unloading, the breaker opens, and the unit goes into a fired shutdown until is reaches Cooldown. Some other operating conditions can also initiate an "automatic" shutdown (sometimes high-high inlet air filter differential pressure, or similar) can do the same thing--through L94AX which drives L94X (have a look at the application code in your machine).

So, if the turbine trips, L4 goes to a logic "0" and at whatever speed it's at then L14HSX will go to a logic "0". BUT, if the unit goes below 14HS (usually 94.5% speed) when it's operating (that means the grid frequency is more than 5.5% below normal!!!) then L14HSX will remain a logic "1", and in the case of L3TFLT the rung can still activate if CPD drops below 35 psig. Kind of confusing, but not really. (I hope!) L3RS2 would be the next logical progression; yes. And the important logic signal in L3RS2 is L3ACS--another signal which should be relatively straightforward but which has become somewhat perverted over the years. L62TT2 stands for "Turbine Tried Twice to Start". It's a "relic" (old) bit of logic that causes a LOT of problems. It was put into GE logic way back when a lot of GE-design heavy duty gas turbines were being used for peaker units (during times of high electrical demand) and natural gas compressor drive, and a lot of these sites were unmanned. So, if a START was initiated from a remote location (say 250 km away) and something not too critical interrupted the START sequence, a second START would automatically be initiated by the Speedtronic panel without any operator intervention. (This was long before the days of SCADA and Ethernet and HMIs, so alarms were grouped into critical and non-critical bunches and the only alarm the remote operator would get would be a "Group1" or "Critical" alarm, so it wasn't much help.) If the turbine still failed to start and accelerate to FSNL on the second, automatic attempt L62TT2 would go to a logic "1" and then someone would have to go to site to check on the unit. Sometimes, the remote operator could just initiate another START if it failed the second automatic start, but usually, once L62TT2 picked up starting was prevented until someone went to site and initiated a MASTER RESET--which was the mechanism for requiring a human to reset the Speedtronic in the event of a critical problem before the turbine could be re-started. So, that's a little history of the signal. It has, unfortunately, remained in the logic even for combined cycle power plants--even though it has caused a lot of problems. For example, if a START is unsuccessful for some minor reason and a FAILURE to START alarm is annunciated, while the operators are scratching their heads about what went wrong the Speedtronic will automatically--without operator intervention--initiate another START sequence, at which point everyone is shocked and surprised. And this is because of L62TT2 being left in the control scheme even for combined cycle power plants--which are almost NEVER unmanned. Another problem that occurs is when the turbine is STOPped before the generator breaker synchronizes (which is usually Complete Sequence these days), which increments L62TT2 once, and when the unit gets back down to zero or minimum firing speed (depending on the machine) it will automatically START again--which also causes quite a lot of surprise and consternation. I wish GE would stop shipping application code with that logic to manned sites, and only add it if the site is converted to unmanned, or block it with a NO 'false' or something like that, because it really causes a lot of grief and can be very scary. But, since most of the engineers at GE don't understand how the signal came to be and aren't capable of critical thinking they just leave the signal in--and, it usually results in at least one problem during commissioning, and again afterwards--when no one is expecting the unit to automatically re-start, but it does. So, except for certain unfortunate circumstances you can presume that L62TT2 is always a logic "0". And, unfortunately, without being able to see all of the application code in the machine at your plant it's impossible to say precisely what those certain unfortunate circumstances are.... Thank you, Belfort, yet again. AAARRRGGGHHH!!! The L3COMM_IO is one of the ways that the Speedtronic checks to make sure that all three control processors (, and ) are healthy and communicating with each other. I have, unfortunately, heard of people being able to force this logic to be able to TRY to start the machine when there is a problem with one of the VCMI cards and then when the unit won't start they are furious, to say the least. Because of the way the Mark VI (and VIe) are configured, it might be possible for a start to actually be successful--but it shouldn't, and I believe that most Mark VI firmware has been "fixed" to stop this from

being even an unlikely possibility. So, write the sentence for L3RS2--and for L3ACS, Neo. Yes; if the unit is not on Total Gas (L84TG is NOT a logic "1") and there is a fault with the gas fuel system the unit can still be started. Will it be "reliable"? What's your definition of "reliable"? Reply to this post...

Posted by Neo

on 28 June, 2014 - 3:35 am

CSA, Thank you for your detailed and enlightening comment on L14HSX, L62TT2 and L30COMM_IO. When the selected fuel control system is not in fault(L84TL=1,L3LFLT=0 or L84TG=1,L3GFLT=0) and L62TT2 is logic 0, then L3ACS will go to logic 1. 2222222222222PAAAAAAAAAAAAAAAARTIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Getting a better understanding of GT control PART 2

Posted by Neo

on 11 July, 2014 - 10:48 pm

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. 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.

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. 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.

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.

(TNH>K60RB)---| L28FDY L60RB ------------| |-----|/|--------( )

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

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

(TNH>K60RB)---| L60RB ------------| |------( )

L60RB L94SD L83RB ---------|/|--------||----------( ) L83RB L94T ---------|/|------------------( ) 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. ------------------------------------------------------------------- ------------------------------------L63QTX L45FTX L5ESTOP1_FZA L86GT L63ETH L63CSHH L4PSTX1 ------|/|------|/|------|/|-------|/|-------|/|-------|/|-----( )

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 L63QTX 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. L63QT L4 L63QTX -------||--------||---------( )

L63QTX L4Y | -------||--------|/|-------

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; L63QT L4 L63QTX -------||--------||---------( ) L63QTX | -------||-------

Or just below: L63QT L4 L63QTX -------||--------||---------( )

Best regards Neo Reply to this post...


Posted by CSA

on 13 July, 2014 - 7:08 am

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. Reply to this post...

Posted by Neo on 13 July, 2014 - 9:20 am

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 Reply to this post...

Posted by Amr karam24 on 17 July, 2014 - 3:58 am

Have a nice time CSA... All waitting for you... Reply to this post...


Posted by CSA

on 21 July, 2014 - 9:27 am

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 problems 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 pi cking 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"? > L63QT L4 L63QTX >-------||--------||---------( ) > L63QTX L4Y | >-------||--------|/|-------

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. Reply to this post...


Posted by Neo

on 22 July, 2014 - 9:39 am

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. L63QT L4 L63QTX -------||--------||---------( ) L63QTX L4Y | -------||--------|/|-------

"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"?" L63QT;

----------(1)

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

(1) ---------| -------------(0)

----------(1) | L4Y (0) -----------------(1) | | L63QTX(0)---------------------(0)

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 Reply to this post...


Posted by CSA

on 25 July, 2014 - 9:50 am

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 in accurate 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 s traying is fine, but we need to finish this journey, don't you think? Reply to this post...

Posted by Neo on 25 July, 2014 - 7:41 pm

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 Reply to this post...

Posted by Neo

on 25 July, 2014 - 11:59 pm

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! ------------------------------------------------------------------- ----------------------------------------L63QTX L45FTX L5ESTOP1_FZA L86GT L63ETH L63CSHH L4PSTX1 ------|/|------|/|------|/|-------|/|-------|/|-------|/|-----( )

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

L45FTX l45ftx1 L45FTX -----||------------( ) | l45ftx2 | -----||------| | l94f1b false| ----||---||--

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. L63ETH l63et1h l63eah false L63ETH ------||-----||------||-----( ) l63et2h | | ------||--| l63et1h l63et2h | ------||----||----

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. L63CSHH l63cs2ahh l63cs1h false L63CSHH ------||-----||------||-----( )

l63cs2bhh | | ------||---| l63cs2ahh l63cs2bhh | ------||----||----

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 Reply to this post...

Posted by SB

on 29 July, 2014 - 3:08 am

______________________________________________________________________ ___ 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). Reply to this post...

Posted by CSA

on 29 July, 2014 - 11:31 am

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: l63et1h l63eah false L63ETH ------||-----||------||-----( ) l63et2h | | ------||---| l63et1h l63et2h | ------||----||-----l63cs2ahh l63cs1h false L63CSHH ------||-----||--------||-----( ) l63cs2bhh | | ------||----| l63cs2ahh l63cs2bhh | ------||----||-------

What the normally open false contact in both those rungs says to me is: Both of these functions are disabled. false is always a logic "0", and so the normally open false 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 false contacts that the logic coils of either of the two rungs will never be logic "1". So, any time one finds a normally open false 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 false 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. Reply to this post...


Posted by SB

on 29 July, 2014 - 9:11 pm

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 GEdesign heavy duty gas turbines. Thanks for contributing! Reply to this post...

Posted by Neo

on 30 July, 2014 - 8:14 am

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 Reply to this post...

Posted by Neo

on 31 July, 2014 - 7:59 am

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. ------------------------------------------------------------------- -------------------------------------------L63QTX L45FTX L5ESTOP1_FZA L86GT L63ETH L63CSHH L4PSTX1 ------|/|------|/|------|/|-------|/|-------|/|-------|/|-----( )

L5ESTOP1_FZA = VPRO E-STOP PB Circuit Open L86GT = Generator Protective Trip

L86GT

l86tgt1 L86TGT1Z L86GT ----|/|--------( )------( )

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. L5ESTOP1_FZA L5ESTOP1_FBZ L5ESTOP1_FZA ----|/|--------------( )------

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. ------------------------------------------------------------------- ----------------------------------------L39VT L2SFT L12H_FLT l4ct L45HA_T L45HT_T L4PSTX2 --------|/|------|/|--------|/|--------|/|--------|/|------|/|----- ---( )

L39VT = Vibration trip L2SFT = Startup Fuel Flow Excessive Trip L12H_FLT = Loss of Protective HP Speed Inputs L39VT 39 (MECHANICAL CONDITION MONITOR) V: Vibration T:Trip L39VT = (L39VDIFF_GT+L39VDIFF_GEN+L39VDIFF_LG) L2SFT 2: SEQUENCE TIMER(?) S: Startup F: Fuel T: Trip L60FFLH L14HA L2WX L2SFTL --------||-------|/|--------|/|--------( ) 2s

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 Reply to this post...

Posted by CSA

on 3 August, 2014 - 9:37 am

Neo, I'm working on a response. Got sidetracked with inversion masking; sorry. Reply to this post...


Posted by CSA

on 3 August, 2014 - 6:59 pm

Neo, We're just learning here, so it's understandable if you miss the false contacts in the rungs. There was also a false in one of the parallel strings of the fire protection rung (L45FTX). I don't know why we're missing s o many things here, but we are. L86GT l86tgt1 L86TGT1Z L86GT ----|/|--------( )------( )

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 everyone in the plant 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). L5ESTOP1_FZA L5ESTOP1_FBZ L5ESTOP1_FZA ----|/|--------------( )------

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 rewrite 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 fulltime 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! Reply to this post...

Posted by SB

on 4 August, 2014 - 9:55 am

> 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). Reply to this post...

Posted by CSA

on 5 August, 2014 - 1:14 pm

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. Reply to this post...

Posted by Neo

on 5 August, 2014 - 9:23 pm

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 Reply to this post...

Posted by SB

CSA,

on 6 August, 2014 - 6:39 am

Thanks for being patient regarding this thread and our questions, I appreciate your persistence to help others. And sorry for such a simple question (not dumb--as there are no dumb questions, right?). While waiting for your response, I reconsidered my question and the conditions of the contacts in the rungs, in order to keep the machine running or trip it. I realized that it is related to "inversion masking" that you explained in first part of this thread. I think it is quite natural for the one devoting his energy and time to explain things to others to expect that mistakes that has been pointed out and clarified should not be repeated. But Neo seems to be busy this days and I can't add anything to the stuff regarding cards as I'm from Mechanical background. And regarding the other thread, I'm following it but I haven't read it more than once for now, I'll surely read the thread again and respond. By the way I've read this threadhttp://www.control.com/thread/1026245600#1026245640 and it is very helpful. You helped a LOT in developing my understanding of GE-design heavy duty Gas Turbine control system. Thank you for making things simpler for us. Reply to this post...

Posted by CSA

on 6 August, 2014 - 10:05 am

SB, Some of the best controls TAs (Technical Advisors) I've ever worked with started as mechanical TAs. The control system isn't just the Mark [whatever]--it includes valves (control and manual!), and solenoids, and pumps and fans and fuel nozzles and spark plugs. And, before one can be a good controls technician one really needs to be a good operator--to know what's supposed to happen when, and how that happens (systems and components, included). So, stop putting yourself down because you're not a "controls engineer" or that you don't have a controls background. There's not a university (except for possibly one in the UK) where one can really study and become a gas turbine controls engineer. That happens with OJT--On-The-Job training and experience. GE does offer some internal training courses for their design engineers, but it's pretty specialized. Continue trying to learn controls and operation, and eventually you will reach your goal. Hopefully you're leaning a lot here on control.com. You're more than welcome to open your own threads to ask questions or get information. Reply to this post...

Posted by SB

on 7 August, 2014 - 12:58 pm

CSA, Thanks for the encouragement. Yes, I'm learning a lot here. This is such a great platform. I've a good idea of field devices due to my Mechanical background and I'll continue to learn GE-design heavy duty gas turbine operation and control. Reply to this post...

Posted by Neo

on 6 August, 2014 - 8:57 am

CSA: Always glad to receive your response. L86GT

l86tgt1 L86TGT1Z L86GT ----|/|--------( )------( )

l86tgt1 = Generator Differential Trip Chan 1 L86TGT1Z = inverted signal for l86tgt1 There is no rung for L86TGT1Z,and L86TGT1Z is just the inverted signal for l86tgt1. And i think information below may help: J3:IS200TREG 1D5-Contact3-G1\l86tgt1 So it seems that l86tgt1 signal comes from hardware, and it is inverted in toolbox to meet GE's philosophy. I think we need your comment about this, and the suffix Z in the L86TGT1Z signal name is confusing. CSA, can i ask one basic question:What exactly is the Lock Relay? And where can i find generator protection elementaries (schematic drawings) to know all the things that can trip 86G-1? ------------------------------------------------------------------- --------------------------------------L5ESTOP1_FZA L5ESTOP1_FBZ L5ESTOP1_FZA ----|/|--------------( )------

So when L5ESTOP1_FBZ is logic 0, then L5ESTOP1_FZA is logic 1. I think if L5ESTOP1_FZA is logic 1, it means the emergency pb is pushed down. CSA, L5ESTOP1_FZA is only used in the L4PSTX1 rung. I checked E-Stop P/B in PPRO Backp Turbine Protection Module-TREG Turbine Emergency Trip,and do find it is a NC contact (I need to learn how to read circuits). 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). When we finish L4T:) ------------------------------------------------------------------- ---------------------------------------L63QTX L45FTX L5ESTOP1_FZA L86GT L4PSTX1 ------|/|------|/|------|/|-------|/|----------( )

When lube oil pressure is too low to protect turbo machinery (L63QT=1), or there is an fire indication in (L45FTX), or the VPRO E-STOP PB is depressed (L5ESTOP1_FZA=1), or the current in three phases is different, then L4PSTX1 goes to logic 0, L4T goes to logic 1 ,L4 goes to logic 0, AND the GT trips. Thanks to SB, he points out that signals in L4PSTXn rungs are NC contacts, that is the signal is logic 1 when it trips the GT. CSA, i have seen the thread,and i respect your efforts. As for Start-up Fuel Flow Trip, i am just wondered the causes and consequences of it.

------------------------------------------------------------------I hope it is OK.

--------------------------------------------



Posted by CSA

on 6 August, 2014 - 4:07 pm

Neo, I may have completely missed something here.... You have twice typed (and I have once copied and pasted) the following? >L86GT > l86tgt1 L86TGT1Z L86GT >----|/|--------( )------( )

This is an "illegal" rung if indeed the element for L86TG1Z is a coil (as drawn) and not a normally open contact. It's also a serious problem if it's NOT a coil but it IS a normally open contact from a non-existent rung. Let's not confuse inverted discrete inputs with "inverted" logic signals; they are not the same and it can be very misleading. As was said in a prior post, a rung with a suffix of "Z" is usually a timer, as in the example we used of L4Z. L4Z was a time delay to energize--L4Z would be a logic "1" one second after L4 was a logic "1". I'm presuming I'm presuming that that L86TG1Z is a timer, ti mer, and that it will be a logic "1" some time after L86TG1 is a logic presumption. on. It would take a rung with a timer block to write to L86TG1Z--it can't "1"--but that's just a presumpti be done with the inversion inversion mask of a discrete input. If there's no rung or coil for L86TG1Z then there is a real problem. As we have noted, signals with lowercase alphabetic characters are intended to denote inputs and outputs of the Mark VIe turbine control system--and l86tg1 would appear to be that: a discrete input from a lock-out relay on the generator control panel. A lock-out relay is a panel-mounted (or door-mounted) device with a "bat" handle, usually (it looks like a small pistol grip; I don't know why it's called a "bat" handle except that it may have looked like a bat wing in some incarnation in the past). There is a spring and a solenoid-operated latch in the device, and usually a long string of contacts (normally open and normally closed) on the back of the relay on a shaft to which the handle is also attached. When the bat handle is in the vertical position the relay is in the "RESET" position, and the spring is compressed and latched into a position that closes the normally open contacts and opens the normally closed contacts. When a signal from any of several different generator protective relays actuates, the solenoid of the lock-out relay energizes and releases the latch, and the lock-out relay spring rotates the bat handle and opens the normally open contacts of the lock-out relay and closes the normally closed contacts of the lock-out relay. The bat handle rotates slightly (usually in the anti-clockwise direction, or to the right, and the handle is no longer vertical--which is one visual indication that the lock-out relay has been actuated--that it has bee "tripped"). Sometimes there is an orange "target" which is uncovered on the lockout relay cover behind the handle which indicates the lock-out relay is in the TRIPPED position. Sometimes there are green and red indicating lamps on or above the lock-out relay cover, and the green indicating lamp is lit when the relay is in the RESET position, and the red indicating lamp is lit when the lockout relay is in the TRIPPED TR IPPED position.

There are a couple of purposes for using a lock-out relay. First, it requires a human to reset it--that prevents re-starting the unit until someone has resolved the problem and manually reset the relay. Second, one contact from one relay can be used to change the state of several contacts on the lock-out relay, which can be used to open the generator generator breaker, trip trip the turbine, provide alarm alarm annunciation, and block block other operations (by opening normally opened contacts in other strings). Lock-out relays are a VERY important part of the protection of the unit--turbine and generator. Some generator lock-out relays are used to trip the turbine AND the generator; some lock-out relays are used to trip only the generator breaker, or some other device--but not the turbine. It all depends on how the generator protection is set up. Usually, the "main" lockout relay for the generator is called 86G-1, and sometimes it drives the discrete input l86g1. I've also seen it called 86TG-1, driving l86tg1 (with Belfort, we never know what they're going to do or name signals and devices). So, let's just say the main generator lockout relay is called 86TGT-1, and it drives l86tgt1. A normally open contact of 86TGT-1 would be wired to the discrete input l86tgt1. The normally open contact would be closed when the lock-out relay was in the RESET position, and typically, l86tg1 is inverted in the IOPACK for the discrete input. It would look like this in my version of "drawing": INVERTED NO 86TGT-1 Discrete Input to Digital Speedtronic Turbine Control Panel (86TGT-1 Changes State (Opens) on a Differential Trip) Hardware --------

| Software | -------| Physical | Contact | 86TGT-1 Input Screw l86tgt1 ---| |----------o------------------(I)--| | l86tgt1 | ---|/|---

And here's the L86GT rung from Neo's machine, presuming the element is a normally open contact, not a l86tgt1 L86TG1Z L86GT ---|/|--------| |---------------( )---

If there truly is (and I believe you, Neo!) no rung writing to L86TG1Z then l86tgt1 can never trip the turbine! Because L86TG1Z will never close if there is no logic in a rung writing to L86TG1z. Let's presume there was a rung for L86TG1Z, and let's further presume that it is indeed a timer, and let's say that it is driven by l86tgt1. It could look like this (I just put a value of 1.0 sec for the time; it could be any value): l86tgt1 L86TG1Z ---| |--------------------------(T)--1.0 sec

Now, let's analyze analyze the L86GT rung presuming presuming the existence of L86TG1Z L86TG1Z as shown above. It It would say that when there is NOT a Generator Differential Trip Chan 1 AND when there WAS a Generator Differential Trip Chan 1 for 1.0 sec then trip the turbine by making L86GT a logic "1". That's not "logical" (pun intended). If l86tgt1 goes to a logic "1" (when 86TG-1 opens), then the normally closed l86tgt1 in rung L86GT is going to open, and the normally open contact of l86tgt1 in L86TG1Z is going to close, and 1.0 seconds later L86TG1Z is going to go to a logic "1" and the normally open contact of L86TG1Z in rung L86GT is going to close. But nothing will happen because the normally closed contact of l86tgt1 is open--

and the turbine will not trip. Let's just presume, for the moment, that L86TG1Z is not a timer, and that is an "inverted" version of l86tgt1 (meaning that it's the opposite sense of l86tgt1). Then it would look like this: l86tgt1 L86TG1Z ---|/|--------------------------( )---

If this was the case, then the turbine would be tripped all the time--presuming that the "coil" we've been typing and copying is a normally open contact: l86tgt1 L86TG1Z L86GT ---|/|--------| |---------------( )---

because when l86tgt1 is NOT a logic "1" then l86TG1Z l86TG1Z WILL BE a logic "1" "1" which would close the normally open contact in rung L86GT. And, when l86tgt1 is NOT a logic "1" and when L86TG1Z IS a logic "1" (which it will be when l86tgt1 is NOT a logic "1"!) the L86GT WILL BE a logic "1" and the turbine will be tripped. In my estimation the rung L86GT is seriously flawed. Presuming 86TGT-1 drives the inverted discrete input l86tgt1, if L86TG1Z is the inverted signal of l86tgt1 then L86GT would be a logic "1" all the time. And, I'm sure the turbine starts and runs; right, Neo? So, the ONLY way the turbine can start and run is if there is no logic writing to L86TG1Z (regardless of what it's description is) so the normally open contact of L86TG1Z in rung L86GT would never close. The problem with that is that if 86TGT-1 86TGT-1 ever opens because because of a Generator Generator Differential Trip Chan 1 and l86tgt1 goes to a logic "1" then the normally closed contact of l86tgt1 in rung L86GT will open, and because L86TG1Z can never close L86GT L86GT will never go to a logic "1" "1" and the turbine will never be tripped by 86TGT-1/l86tgt1. Either there's a typing error, or there are some serious errors in the application code for L86GT. There's no two ways about it. Neo, is there a 86TGT-1 86TGT-1 trip signal on the HMI Trip Display? Is L86GT an alarm ("GENERATOR DIFFERENTIAL TRIP)? Could L86TG1Z be a discrete input (with capital alphabetic characters instead of lower-case alphabetic characters)? 'Cause something's not right here. And this should be resolved, one way or the other. Either L86GT been "disabled" by using L86TG1Z which has no rung to drive the normally open contact in rung L86GT, or there's something very wrong. -------------------------------I think we answered the question about lock-out relays above. There should be a set of schematic drawings (GE calls them "elementary" drawings) drawings) for the Generator Protection Panel--the panel where the generator protective relays are located. It has to interface with many other panels and devices (PTs and CTs and breakers and such). These days, many of the older individual electro-mechanical electro-mecha nical generator protective relays have been replaced with a single digital generator protective relay, sometimes called a DGP. Sometimes, there is a redundant DGP, and sometimes there is another digital protective device that's used for step-up transformers. But, you should be able to find a set of schematic drawings (elementaries) for the panel which houses the generator protective relay(s). There are usually ammeters and voltmeters and synchronizing lights and switches on the GPP (Generator Protection Panel).

------------------------------Well, we should go over the start-up excessive fuel flow trips; there's usually one for gas fuel, and one for liquid fuel. The purpose of them is to protect the turbine from high temperatures caused by an inability to control fuel during the firing attempt (high fuel flows during start-up). For liquid fuel, the liquid fuel flow divider feedback is used to check for excessive liquid fuel flow-rates. For gas fuel, the Stop-Ratio Valve (SRV) position is used to check for excessive gas fuel flow-rates. Yes; you read that right--SRV position. The assumption is that if the SRV has to go open past a certain point that the gas fuel flow will be excessive and so the turbine is tripped. That's right; gas fuel flow-rate feedback is not used for this trip-even though the alarm reads "Fuel flow-rate High". Again, the presumption is that the fuel flow-rate will be excessively high is the SRV is open past a certain point during firing. But, we should verify the above by looking at the L2SFT logic for both liquid and gas fuel (I think you said your unit runs on both fuels, right?). Let's get to the bottom of this lock-out trip issue, first, though, don't you think? Reply to this post...


Posted by CSA

on 6 August, 2014 - 7:37 pm

Neo, I've been thinking about this, and this would be a valid rung--though it would not work (if l86tgt1 is inverted and driven by a normally open 86TGT-1 that's open when the lock-out relay is TRIPPED): L86GT

l86tgt1 L86TGT1Z ----|/|--------( ) | | L86GT -----( )

If L86TG1Z is a coil, then it would be true that L86TG1Z was the "inverted" signal of l86tgt1. But, that would mean that L86GT would be a logic "1" when l86tgt1 was NOT a logic "1". And when L86GT is a logic "1", then L4T will be a logic "1"--which means the turbine will be tripped. Let's go back to (the abbreviated) L4PSTX1: > L63QTX L45FTX L5ESTOP1_FZA L86GT L4PSTX1 >------|/|------|/|------|/|-------|/|------( )

And L4PST: L4PSTX1 L4PST -----|/|---------------( ) | L4PSTX2 | -----|/|-----| L4PSTX3 | -----|/|-----| L4PSTX4 | -----|/|------

And here's L4T: L4PST L4T -----| |---------------( ) | L4PRET | -----| |-----| L4POST | -----| |-----| L3SMT | -----| |-----| L4IGVT | -----| |-----| LFPAUXG2LLX | -----| |-----Reply to this post...

Posted by Neo

on 7 August, 2014 - 7:30 am

CSA: I bet you don't a good sleep last night! 1) "I've been thinking about this, and this would be a valid rung--though it would not work. (if l86tgt1 is inverted and driven by a normally open 86TGT-1 that's open when the lock-out relay is TRIPPED): L86GT

l86tgt1 L86TGT1Z ----|/|--------( ) | | L86GT -----( )

If L86TG1Z is a coil, then it would be true that L86TG1Z was the "inverted" signal of l86tgt1. But, that would mean that L86GT would be a logic "1" when l86tgt1 was NOT a logic "1". And when L86GT is a logic "1", then L4T will be a logic "1"--which means the turbine will be tripped." CSA, i think you are right! "Neo, is there a 86TGT-1 trip signal on the HMI Trip Display" Yes, there is a L86TG trip signal on the HMI Trup Display. ------------------------------------------------------------------- ----------------------------------------------------------------------I checked these signals again in application code,and i think it would be better if i draw the rung as below: L86GT l86tgt1 L86TGT1Z ----|/|--------( ) |

| L86GT | |-------( ) | | L86TGT1_ALM | |-------( )

INVERTED NO 86TGT-1 Discrete Input to Digital Speedtronic Turbine Control Panel (86TGT-1 C hanges State (Opens) on a Differential Trip) Hardware --------

| Software | -------| Physical | Contact | 86TGT-1 Input Screw l86tgt1 ---| |----------o------------------(I)----| | l86tgt1 L86TGT1Z | ---|/|----------( ) | | | | L86GT | |-------( ) | | L86TGT1_ALM | |-------( )

So,if l86tgt1 is inverted and driven by a normally open 86TGT-1, then 86TGT-1 NO Contact State ------------OPEN LOSED

l86tgt1 Coil Logic State ----------"1" "0"

l86tgt1 NC Contact State ------------OPEN CLOSED

L86GT State ---------"1" TRIP "0"

But i can't find l86tgt1 is inverted or not in toolbox, nor do i make sure 86TGT-1 is NO contact. Anyone who can help? ------------------------------------------------------------------- -----------------------------------------------------------------------2) CSA, I read the thread you recommenced yesterday in a little hurry, but i find that l30sg1 is not inverted and 30SG-1 is an NO contact. 30SG-1 Diagnostic ignition exciter switch characteristics: Normal NO 125VDC l30sg1 SignalInvet Normal

Description Inversion makes signal true if Contact is open

l30sg1 l2tvx1 L30SG1_ALM ---|/|--------| |------(T)-----------( ) 1.0sec

That is weird! l30sg1 is inverted or not?

------------------------------------------------------------------------------ -------------->And L4PST:

-------------------------------------------------------------

> L4PSTX1 L4PST >-----|/|---------------( ) > | > L4PSTX2 | >-----|/|-----> | > L4PSTX3 | >-----|/|-----> | > L4PSTX4 | >-----|/|------

>And here's L4T: > L4PST L4T >-----| |---------------( ) > | > L4PRET | >-----| |-----> | > L4POST | >-----| |-----> | > L3SMT | >-----| |-----> | > L4IGVT | >-----| |-----> | > LFPAUXG2LLX | >-----| |------

L39VT L2SFT L12H_FLT l4ct L45HA_T L45HT_T L4PSTX2 --------|/|------|/|--------|/|--------|/|--------|/|------|/|----- ---( )

Next time i will interpret L12H_FLT, l4ct, L45HA_T , L45HT_T, but to what extent? As you said: Let's get to the bottom of this lock-out trip issue first, though,don't you think? Are all the Discrete Input in L4PSTXn inverted? And all the related physical contact are NO contacts? ------------------------------------------------------------------- ------------------------------------------------------------------------ -------------That is a really long response of mine, and its not my style. I think you are changing me, C SA:), and i must be careful. And i will go on a short-term trip, during that time i may not have easy access to the web. Best regards! Neo Reply to this post...

Posted by Neo

on 10 August, 2014 - 9:51 am

CSA: Thank you for your patient reply for NO/NC contact. ------------------------------------------------------------------- ---------------------------------L39VT L2SFT L12H_FLT l4ct L45HA_T L45HT_T L4PSTX2 --------|/|------|/|--------|/|--------|/|--------|/|------|/|----- ---( )

L39VT = Vibration trip L2SFT = Startup Fuel Flow Excessive Trip L12H_FLT = Loss of Protective HP Speed Inputs l4ct = Customer trip input L45HA_T = High High Gas level Det-Gas Fuel Moduel L12H_FLT L14H_ZSPD L4 L14HT L12H_FLT -----||-------||-----||----( ) L12H_FLT L86MR1 | -----||-----|/|---------

L14H_ZSPD = VPRO Zero Speed Ind L14HT = Cooldown slow roll start s peed relay So it means the speed signal is lost in VRRP card,and L4T will go logic 1. l4ct I have no idea of l4ct. IS200TBCI 1D3 contact24 L45HA_T L45HA1_T L45HA_T ------||-------() L45HA2_T | ------||----

L45HA1_T = High High Gas Level Det-Gas Compartment L45HA2_T = High High Gas Level Det-Gas Compartment Vent Disch I think when L45HA_T is logic 1,that means flammable gas is detected in DLN and other aux compartments, and for safety consideration is will trip the turbine. L45HT_T L45HT1_T L45HT_T ------||-------() L45HT2_T | ------||----

L45HT1_T = High High Gas Level GT C ompartment L45HT2_T = High High Gas Level Det-GT Compartment Vent Disch I think L145HT_T is similar to L45HA_T. ------------------------------------------------------------------- -----------------------------------So, in conclusion, when the unit has a vibration problem, or the firing fuel supply is too much, or the speed signal in VPRO card is lost,or the gas fuel in DLN compartment and GT compartment is detected, then L4PSTX2 is logic 0,and then GT trips! Is that OK?

It occurs to me that it has been more than three months since i post my first thread here asking how to get a better understanding of GT control, and you advice me to start with L4. Thank you for your help, you get me interested in GT control, and i learned a lot from this journey. Best regards! Neo Reply to this post...


Posted by CSA

on 11 August, 2014 - 11:07 am

Neo, Hope the NO/NC explanation was clear. I can sort of understand how people can be confused by this, but it's really very simple. The problem seems to be visualizing that the NO or NC contact we see on a drawing or schematic or in application code seems "fixed"--and yet it changes state based on whether or not the coil or the device is energized or actuated. And, I know a lot of people also get confused about "energized" and "de-energized" coils and contacts. But, it's really pretty simple--and it's been around since the first days of electricity. And hasn't changed much. Sure, we have "virtual" coils and contacts--but that's just another way of doing the same things that real coils and contacts do. Just without so much wire and so many relays and physical contacts. And, physical devices like pressure switches and temperature switches and limit switches and level switches and such also have actuated ("energized") and de-actuated ("de-energized") states. Anyway, back to the L4 journey, and we're on the L4PST highway right now.... In a previous post you had written L2SFT

L60FFLH L14HA L2WX L2SFTL --------||-------|/|--------|/|--------(T) 2s

L60FFLH = Liquid Fuel Flow High L14HA = HP accelerating speed signal L2WX = Turbine Warmup Complete, Increase Fuel The rung you posted was only the liquid fuel portion of L2SFT. We should also investigate the gas fuel portion of L2SFT. L12H_FLT L14H_ZSPD L4 L14HT L12H_FLT -----||-------||-----||----( ) L12H_FLT L86MR1 | -----||-----|/|---------

L14H_ZSPD = VPRO Zero Speed Ind L14HT = Cooldown slow roll start speed relay This bit of logic compares the VPRO speed signals to the (, & ) speed signals, and

generates a trip if there is a disagreement by more than one processor (, & with respect to , & --which are the names of the three independent VPRO cards in
). Referring to L45HA_T and L45HT_T, I'm kind of surprised that the signal names are not in lower-case alpha characters--which would mean they are discrete inputs from a d evice or devices outside the Mark VIe. I know that GE sometimes uses Bently-Nevada or other hazardous gas sensors directly connected to the Mark VIe, and sometimes the sensors are connected to an external monitor which is connected via discrete contacts to the Mark VIe. So, we need to investigate the two signals further to understand how and where they come from. (In the pre-Belfort days, L45HA_T and L45HT_T were signals that came from fire detectors (high-temperature switches) mounted in the Accessory- or Turbine Compartments, respectively. But, in the Belfort era, we have to investigate every signal in detail--and while it would be nice if we could trust the signal descriptions in ToolboxST, as we've seen--we need to "trust but verify.") l4ct is in lower-case alpha characters, so we can presume that it is from a discrete input to the Mark VIe. A '4' device is a master protective device, as in L4. 'CT' stands for Customer Trip. The signal is a logic "1" when the Customer Trip input is tripping the turbine.

Usually this discrete input comes from the Customer's DCS or some other control system(s)--a circuit that is closed to allow turbine operation, and opens to trip the turbine. This is a VERY important signal to investigate at your site--as it can be from a single "device" or a single contact that has multiple conditions. And, as we've seen with l3cp in the Ready to Start application code, sometimes Belfort just puts a wire jumper on the discrete input terminals. In the past this discrete input was connected to a normal discrete input terminal board to . However, I have a sneaking suspicion that it's connected to one of the TREG card Trip Inputs (similar to l86tgt1)--and if not, I don't understand why not (again, Belfort is consistently inconsistent). So, please investigate this input further. If it's a real discrete input (to either a normal discrete input terminal board--or to the TREG card) then you need to do some more investigation to understand where the signal/circuit comes from in the plant, and what causes the signal to change state. Also, if it's connected to a normal discrete input terminal board, I suspect it will be Inverted--but that's just a guess at this point. So, you have some work to do to finish up L4PSTX2. I'm learning a lot--as I usually do when I try to teach or explain. And, of course, Belfort keeps it "interesting" with their consistently inconsistent logic/application code and their use of false and true permissives/contacts. Reply to this post...

Posted by Neo

on 12 August, 2014 - 9:33 am

CSA: Your NO/NC explanation helps! I think i should keep that when the NO/NO contact is actuated it will change state in mind. Yes,i find there is gas fuel portion of L2SFT. L60FSGH L28FDY L2FSTG ------||----------||-----------( ) L2FSTG L86MR1 | ------||----------|/|-----

L28FDY = Time delayed loss of flame L60FSGH = startup gas fuel stroke high

So, when the flame is lost and SRV feedback is open past certain point, then L2FSTG will go to logic 1. L60FFLH L14HA L2WX L2SFTL --------||-------|/|--------|/|--------( ) 2s

L60FFLH = Liquid Fuel Flow High L14HA = HP accelerating speed signal L2WX = Turbine Warmup Complete, Increase Fuel I found there is a difference between L2FSTG and L2SFTL: 1) L2FSTL has a timer while L2FSTG doesn't; 2) L2FSTG has a master reset while L60FSGH doesn't; 3) There is L14HA and L2WX in the L2FDTL rung, while L27FDY in the L2SFTL; As to L45HA_T and L45HT_T,take L45HA_T for example: There are 45HA1,45HA2 and 45HA3 hazardous gas sensors directly connected to the Mark VI, and the related DI is l45ha1hh, l45ha2hh, l45ha3hh. When two of them is logic 1, then L45HA_T will go to logic 1. L14H_ZSPD: "This bit of logic compares the VPRO speed signals to the (, ~~& ) speed signals, and generates a trip if there is a disagreement by more than one processor (, ~~& with respect to , & --which are the names of the three independent VPRO cards in~~~~
)." CSA, i am not clear that how are speed signals are processed. I think there are six speed signals (1, 2, 3, 4, 5, 6), three for , three for . 1--- 2--- 3--- 4--- 5--- 6--- So 1 is compared to 4, 2 is compared to 5, 3 is compared to 6, and if two of three disagrees (how is this 2 of 3 logic achieved?), then L14H_ZSPD will go to logic 1. I am sure not sure whether am i is clear? And i am sure there are misunderstanding. As to l4ct, again, most of your guess is right! This signal comes from DCS, and it is connected to normal DI terminal board, and it is inverted. But my colleague told me that it s hould be connected to one of the TREG card. As you said the circuit of l4cp is normally closed, and DI connected to TREG can't be inverted. so if it is connected to TREG card, it should not be NC in L4PST2. Is it right? ------------------------------------------------------------------------------ -----------------------

-------------------------------------------------------------

L12HF_ALM L12HFD_C_ALM L12HFD_P_ALM L12H_P 12H_ACC L4PSTX3 --------|/|--------|/|--------|/|---------|/|--------|/|---------( )

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 I would like to investigate L4PSTX3 next time. Always best regards! Neo Reply to this post...

Posted by Neo

on 15 August, 2014 - 4:52 am

CSA I think you may miss this reply. Best regards! Neo Reply to this post...

Posted by SB

on 19 August, 2014 - 11:56 pm

CSA, Your response is much awaited. Your replies are very valuable to many of us. it helps in understanding the underlying philosophy and history of GE-design heavy duty Gas Turbine control system. Please provide us the opportunity to learn from you. SB Reply to this post...

Posted by CSA

Neo, Are you back? Reply to this post...

on 26 August, 2014 - 10:14 am

Posted by Neo on 26 August, 2014 - 7:06 pm

CSA I am back, and waiting for your reply:) best regards! Neo Reply to this post...

Posted by CSA

on 27 August, 2014 - 5:55 pm

Neo, This thread is getting very long--and very disorganized.... L2SFTG L60FSGH

L28FDY

L2FSTG

------||----------||-----------( ) L2FSTG L86MR1 | ------||----------|/|-----

L28FDY = Time delayed loss of flame L60FSGH = startup gas fuel stroke high Let's go back to the L4, L4Y & L4Z logic signal/suffix example. L4 is the main, or "namesake" signal for this group. L4Y is a logic "1" some time AFTER L4 is a logic "0", and L4Z is a logic "1" some time after L4 is a logic "1". MOST logic signals with a suffix of Y are inverse time delay signals--they are a logic "1" some time after the main, or namesake, signal is a logic "0." MOST logic signals with a suffix of Z are time delay signals--they are a logic "1" some time after the main, or namesake, signal is a logic "1." I've never really understood why the designers used an inverse time delay L28FDY in L2SFTG because L2SFTG is checking for "excessive gas fuel flow" (and we'll get to that bit in a minute) during firing (starting). L28FD must be a logic "0" during starting (as we've seen from the Start-Check permissive discussion)--so L28FDY will be a logic "1" some time after flame was lost, either after a turbine trip or after a normal shutdown. In other words, flame will have been lost for a very long time before the turbine can be re-started, so I've never quite understood why L28FDY was used; a NC L28FD could have been used with the same results--because this 'permissive' is only saying, "Check for "excessive gas fuel flow" only when there is NO flame, and once flame has been established stop checking for "excessive gas fuel flow."" Now--about that "excessive gas fuel flow" bit.... As you correctly noted, L60FSGH is only looking at SRV position--NOT gas fuel flow. The assumption is that there will be excessive gas fuel flow if the SRV is above a certain position--but that's an assumption. I've seen many sites forget to open a manual isolation valve upstream of the SRV when starting the turbine and get this alarm--because when there is little or no gas fuel pressure upstream of the SRV then the SRV will open very far trying to make actual P2 pressure equal to the P2 pressure reference. So, the alarm text message is very misleading because it's not actually looking at gas fuel flow--it's only looking at SRV position and assuming that if the SRV position is higher than a Control Constant value that gas fuel flow will be higher than it should be. And that is an assumption. I've also seen several sites that have low gas fuel pressure upstream of the SRV until there is flame in the

gas turbine (mandated by local regulations!) so the SRV occasionally goes "high" trying to make P2 equal to the P2 pressure reference--and this alarm/trip is annunciated. (Remember: When L2SFTG goes to a logic "1" L4PSTX2 picks up, which picks up L4T and trips the turbine by dropping out L4.) It's been the very rare occasion that the SRV has been unable to control P2 pressure during starting and gone too far open actually causing gas fuel flow to be excessive. (And with most new GE turbine control systems, there is P2 pressure test during purging to check that the SRV can actually control P2 pressure before opening the GCV and sending gas fuel to the combustors.) The point of this is: Some alarm/trip text messages can be very misleading. One MUST take the time to read and understand the application code (logic; sequencing) for any alarm to be able to properly understand what the alarm message is trying to indicate--and it's also necessary to understand P&IDs (Piping Schematics) to know how the components work and what can happen under abnormal situations. The sites that had forgotten to open the gas fuel isolation valves prior to the start and got this alarm/trip were very angry--and embarrassed--when they found out they'd left the valve closed and had been chasing the wrong condition/sensor (calibrating and re-calibrating and re-re-calibrating the gas fuel flow dp sensors!). Okay; enough about L2SFTG and it's misleading alarm text message. L2SFTL L60FFLH L14HA L2WX L2SFTL --------||-------|/|--------|/|--------( ) 2s

You wrote: > I found there is a difference between > L2FSTG and L2SFTL: > 1) L2FSTL has a timer while L2FSTG doesn't; > 2) L2FSTG has a master reset while L60FSGH doesn't; > 3) There is L14HA and L2WX in theL2SFTL rung, while L28FDY in the L2SFTL All good catches; good on you! First, the presence of a timer on L2SFTL and the absence of a timer on L2SFTG. A "2" device is, by definition, a timer. There's only one reason I can explain why there's a timer on high start-up liquid fuel flow and not on high start-up gas fuel flow is that someone felt that because of common liquid fuel supply pressure fluctuations during firing which can erroneously cause high liquid fuel flows that a timer was appropriate to prevent nuisance trips during starting on liquid fuel. Many times the liquid fuel supply (forwarding) system is not in GE's scope of supply, and if the system is not properly designed or configured then large pressure/flow fluctuations can occur and GE always gets the blame for these kinds of problems, so it's l ikely that in order to avoid these kinds of problems (and to avoid forcing the supplier of the liquid fuel supply system to fix their system) someone in GE just decided to put a twosecond timer on the signal to avoid nuisance trips and blame and finger-pointing. To my mind there's no difference between too much liquid fuel during starting and too much gas fuel during starting--they're both equally dangerous conditions. But, since gas fuel flow isn't actually being measured, ..., well, ..., anyway, some things will always b e a mystery. I do completely understand the whole liquid fuel supply pressure problem thing, though, having been in the unenviable position of having to tell several project managers that the systems were inadequate--and being told that the problem was GE's problem and that GE had to fix the problem. The L14HA has been kind of a mystery to me, also, because it usually goes to a logic "1" on a GE-design Frame 6B heavy duty gas turbine at 50% speed, and L2WX usually goes to a logic "1" at about 20-30% speed. These two permissives allow high liquid fuel flow to be detected until the turbine warm-up time is complete--in other words, after flame has been detected; but not after the warm-up is complete, and in no scenario after 50% speed (which is kind of useless).

Enough about these; again, some things will forever remain a mystery and have little or no effect on normal turbine operation. As for speed signals, I dislike it when you say: > I think there are six speed signals (1, 2, 3, 4, 5, 6), > three for , three for . You should be CERTAIN, and to be certain, you need to look at the documentation and drawings provided with the turbine and control system. For most new turbines (new since about 1990) with TMR control systems there are, indeed, six shaft speed pick-ups (for a single-shaft turbine). 77NH-1, -2 & -3 are usually connected to , & , respectively, and 77NT-1, -2 & -3 are usually connected to , & , respectively. They are all identical speed pick-ups, three used for "control" (and Primary Overspeed Detection), and three used for overspeed detection (Emergency, or Back-up, Overspeed Detection). Speed detection is kind of a special case in TMR panels, and how it's done is usually dependent on the version of the panel. But, you're basically correct--each control processor checks it's speed signal against it's associated Protective Processor's speed signal, and if two control processors and their Protective Processors disagree, then there's a trip because of the disagreement. The differences in how speed signals are processed between Mark IV, Mark V, Mark VI and Mark VIe would make your head SPIN VERY FAST! (It does mine whenever I have to try to explain it because it's all kind of a background thing which one should never have to worry about--and it got more reliable with each newer version of Speedtronic.) As for the l4ct input, I would argue that it should have been connected to the TREG card and not the l86tgt input. But, you are right; it's contact sense would have to be changed--and that would also make "reading" the signal from its name problematic, also (like the l86tgt signal confusion!!!). But, I never recommend changing signal assignments without GE's approval--especially critical signals like this. Anyway, that's all the time I have for today. More later! Good to have you back! Reply to this post...

Posted by Neo

on 30 August, 2014 - 8:02 pm

CSA: I opened a new thread for this one is a little long and disorganized. http://www.control.com/thread/1409237312


Posted by CSA

on 7 August, 2014 - 11:32 am

Neo, I've been re-reading your previous post, and now I see that l86tgt1 comes from one of the discrete inputs to

the TREG card--not a normal DI or DI/DO card: J3:IS200TREG 1D5-Contact3-G1\l86tgt1 And this is where I'm making my mistake--the TREG discrete inputs can't be inverted. So, now everything works out--thought it's not a pretty sight. l86tgt1 L86TGT1Z ----|/|--------( ) | | L86GT -----( )

OR: l86tgt1 L86TGT1Z ----|/|--------( ) L86TGT1Z L86GT ----| |--------( ) | | L86TGT1_ALM -----( )

Yep; this works--but it's really ugly. REALLY UGLY. In this case, a normally open 86TG-1 (that is closed when the lock-out relay is RESET, and open when the lock-out relay is TRIPPED) will drive a discrete input of the TREG card (which cannot be inverted), l86tgt1. So, l86tgt1 will be a logic "1" when there is NOT a lock-out relay trip, and will be a logic "0" when there IS a lock-out relay trip. Again, this violates the concept that logic signals will be a logic "1" when in alarm or trip condition. Which is why they are "inverting" l86tgt1 with L86TGT1Z.... L86TGT1Z will be a logic "0" when there isNO lock-out relay trip, and a logic "1" when there IS a lock-out relay trip. Lock-out Relay Condition State --------RESET TRIPPED

86TGT-1 NO Contact State

l86tgt1 Logic Coil State

l86tgt1 NC Contact State

L86TGT1Z Logic Coil State

L86GT Logic Coil

------------

-------------

----------

----------

---------

CLOSED OPEN

"1" "0"

OPEN CLOSED

"0" "1"

"0" "1" -

TRIP!!!

So, mystery is solved. It works, but it makes reading the application extremely difficult, and just violates about every philosophy and standard that's been in place for decades. Well, we got to the TREG card a little earlier than I'd hoped, and it certainly wasn't very pretty, either. (There's still more to cover on the TRPG and TREG card--later.) Mystery solved. But I hope that people are beginning to understand that by following some simple conventions when writing application code and choosing signal names that reading and understanding application code-especially when troubleshooting--can be made much easier and simpler. And, when conventions are mixed in the same application code and configuration that it makes for some serious time-wasting exercises. For my part, I apologize for not catching the TREG reference earlier and causing so much confusion. There are seven (7) "trip interlock" inputs to the TREG card available for chosen trip conditions to be able to trip the turbine via "hardware" (as we'll see later). These inputs were originally designed for SIMPLEX panels, but it seems the Belfort Bunch have unilaterally decided to use some of them in TMR applications, and do

so with little forethought and poor description. Anyway, lets' get over it--it is what it is, as a colleague used to say. On to L4PSTX2! Have a good trip. I, too, will be on another business trip in the next few days--with no Internet or cell phone access while on site (in a mancamp environment). I would like to be able to answer that "always [this]" or "always [that]" but, as we can see it doesn't happen like it should. We can generalize, and that's helpful--but one always has to be ready for the unusual--and I wasn't ready for this one; sorry! Later! Reply to this post...

Posted by Neo on 8 August, 2014 - 6:00 am

CSA

Can i ask one basic question before we go on L4T journey? What is the definition of NO or NC of a physical contact? We usually define it based on the state of the physical contact when there is no current flowing through the coil. Best regards! Neo Reply to this post...


Posted by CSA

on 8 August, 2014 - 3:46 pm

Neo, Sure! You can ask questions--that's what we're here for. Where to start? (Why is it that the simplest things can be the most difficult to explain--especially in writing?) We can agree that a contact--whether it's a physical contact or a "virtual" contact in software--can be in one of two states, correct? That is, a contact can be either open or closed. And, that something (some force) is required to change the state of a contact. And that when that force is removed, the contact will revert back to it's "at-rest" or "normal" state. So, a contact has a "normal" or "at-rest" state, and an "actuated" or "not normal" state. The strict definition of NO and NC refers to the state of contacts when a device (pressure switch; temperature switch; limit switch; electro-mechanical relay; etc.) in its box is taken off the shelf of a storage facility (warehouse; manufacturer or store shop) when the ambient temperature is 59 deg F (15 deg C), the ambient pressure is 14.7 psia (approximately 1 bara), and the relative humidity is 60%. In this case, there is no pressure (save for atmospheric pressure), no temperature (save for ambient temperature), no current, and

no other force acting on the device. So, when that physical device is pulled off the shelf and taken out of its box at the stated conditions a normally open contact will read infinite resistance, and a normally closed contact will read zero resistance. The devices are said to be "de-actuated", and the state of the contacts in this condition (open or closed) is referred to as "normally open" or "normally closed", respectively. This is their "normal" state--their "de-actuated" or "de-energized" state. Their "energized" or "actuated" state is the opposite state (that is, closed for normally open contacts, and open for normally closed contacts). Let's remember that a software coil is a virtual representation of an electro-mechanical relay (a physical device that changes state based on whether or not current is flowing in the coil of the relay), and that both software coils and electro-mechanical relays have contacts that change state when the coil or relay is energized or de-energized. So, when virtual current is flowing in a software coil it is said to be "energized". And, when current is flowing in an electro-mechanical relay it is said to be "energized" or "actuated". And, when no virtual current is flowing in a software coil it is said to be "de-energized" or "de-actuated". The same is true of an electro-mechanical relay--when no current is flowing in the coil of the electromechanical relay coil the relay is said to be "de-energized" or "de-actuated." In the "de-energized" or "de-actuated" state normally open contacts are open--that is they WILL NOT conduct electricity (they have infinite resistance). In the "energized" or "actuated" state normally open contacts WILL conduct electricity (they have zero resistance). In the "de-energized" or "de-actuated" state normally closed contacts are closed--that is they WILL conduct electricity (they have zero resistance). In the "energized" or "actuated" state normally closed contacts WILL NOT conduct electricity (they have infinite resistance). This is true of BOTH physical devices and software coils/contacts. It's just that in the software representation, the current is "virtual", and in real physical devices it's actual electrons (amperes). Does this help? Remember, a programmable automation controller is really nothing more than a modern substitute for physical wires and physical contacts and physical electro-mechanical relays. And, t his virtual representation needs to--and does--have the characteristics as the physical devices it replaces. If you have some specific questions about normally open and normally closed contacts of specific devices, let's answer them before we continue on this L4T journey. Reply to this post...


Posted by SB

on 4 August, 2014 - 9:35 am

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! Reply to this post... 3333333333333333333333333333333333PAAAAAAAAAAAAAAAAAAAAAAAART

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 ------------------------------------------------------------------- ---------L12HF_ALM L12HFD_C_ALM L12HFD_P_ALM L12H_P L12H_ACC L4PSTX3 --------|/|--------|/|--------|/|---------|/|--------|/|---------( )

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

L12HF_ALM L12HF L12HF_ALM --------||------( )

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. L12HFD_C_ALM L12HFD_C L12HFD_C_ALM --------||--------()

L12HFD_C = HP overspeed fault - control input trouble L12HFD_C_ALM = Control speed signal trouble

L12HFD_P_ALM L12HFD_P L12HFD_P_ALM --------||--------()

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.

L12H_P

L12H_P = VPRO overspeed signal It is overspeed signal,and it comes from VPRO card. I was curious whether it should be lower case. L12H_ACC L12H_ACC = VPRO-Loss of Protective Speed Sigal

It is a signal that comes from VPRO card. In conclusion, siganls in L4PSTX3 rung are all related to speed siganls.

------------------------------------------------------------------- ------------------L3SFLT L86GCVT L86FPG2LT L4PSTX4 ------|/|-------|/|------|/|--------( )

L3SFLT = CONTROL SYSTEM FAULT TRIP; L86GCVT = GCV Not Following Reference Trip; L86FPG2LT = P2 post-ignition low pressure trip logic; Best regards! Neo Reply to this post...

Posted by CSA

on 30 August, 2014 - 5:38 pm

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 th e '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? Reply to this post...

Posted by Neo

on 31 August, 2014 - 8:20 am

L3SFLT L86GCVT L86FPG2LT L4PSTX4 ------|/|-------|/|------|/|--------( )

L3SFLT = CONTROL SYSTEM FAULT TRIP; L86GCVT = GCV Not Following Reference Trip; L86FPG2LT = P2 post-ignition low pressure trip logic; L3SFT XVCMIR0S01_A XVCMIS0S01_A L14HSX L94X L3SFLT -----|/|----------|/|-----------|/|------|/|--------( ) XVCMIT0S01_A | | -----|/|------| XVCMIR0S01_C XVCMIT0S01_A | ---|/|-----------|/|--------

L3SFLT = CONTROL SYSTEM FAULT TRIP; L14HSX = Auxiliary signal to L14HS; L94X = Startup Check Stop GT Normal Shutdown; XVCMIR0S01_A = 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 , , , 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. L86GCVT

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? L86FPG2LT (KFPG2LT>FPAG2)-------|

L84TG L2TVZ L2WX L86FPG2LT ------| |------||--------||--------|/|------( T ) 15sec

L86FPG2LT = P2 post-ignition low pressure trip logic; KFPG2LT = 24psig;

MARKVE Getting a Better Understanding of Gas Turbine Control 1 2 3

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