GE Mark V Terminal Boards and I/O Cards

Hi all,

I am new to the GE turbine control system. We have GE Mark V control system for the protection and control of gas turbine. I am just now going through the GE manuals for better understanding. Still i couldn't identify various terminology used by GE for identifying terminal boards and I/O cards, etc. For eg: I have come across with various names like TCQA, TBQC, TBQA , TBQB, etc, but didn't understand for signals this is used for. I mean for analog, digital signals how this terms are used.
Also, kindly help me to identify I/O point names in IO.ASG files as shown below;

TC01_16_31_V TC01_16_31_V TC ;Q-TBQA-VOTED Unused voted TC value #1


Q_R_POS01 FSGR PCT ;Q -TBQC-001 Position fdbck srv (high value selected) [96SR-1]

Q_R_VIB01 BB1 VIBVL ;Q -TBQB-051 Vibration sensor

Q_Q_SVO1A FAGR PCT ;TCQA-REG-CUR Speed ratio valve servo current

>For eg: I have come across with various
>names like TCQA, TBQC, TBQA , TBQB, etc, but didn't
>understand for signals this is used for. I mean for analog,
>digital signals how this terms are used.

The names you listed are printed circuit card names (the abbreviated names). They aren't associated with individual CDB point names (signal names). Sometimes they make sense (printed circuit card names, AND CDB point names!); other times they don't. I'll try.... TCQA is the main analog I/O card in each of <R>, <S> and <T> (also called, collectively, <Q>). It's the 8-1/2-inch by 11-inch printed circuit card in Location 2 (Loc. 2) of <R>, <S> and <T>. It stands for Turbine Control "A" Analog Card. (There may be an optional TCQB (Turbine Control "B" I/O Card; it would be in Loc. 3). And there is usually a TCQC, Turbine Control "C" Card, in Loc. 4.) I/O Cards are where signals are converted from analog or discrete inputs to software values, scaled if necessary, and sometimes voted, if necessary. They are 8-1/2-inch by 11-inch printed circuit cards "in" the cores.

TBQA stands for Terminal Board "A" Analog printed circuit card. It's one of the smaller terminal board cards located just below <R> (there are four terminal board cards, smaller than the I/O cards, below <R>'s group of I/O cards). TBQB is Terminal Board "B" Card; and there is usually a TBQC, Analog Terminal Board "C". (The "Q" denotes Analog for terminal boards; it can mean other things for CDB (Control Signal Database point names used in the CSP (Control Sequence Program).) I/O terminal boards have no active components on them--only passive components (like resistors, or capacitors), though the discrete input I/O terminal boards (DTBA and DTBB) do have optical isolators on them, and I guess they might be considered active components (usually, active components are integrated circuit chips and operational amplifiers and the like). I/O Terminal boards are where the inputs and outputs to and from the Mark V are terminated. Some installations have Marshaling Cabinets, which are wired to the Mark V I/O terminal boards, and the field wiring is connected to terminal boards in the Marshaling Cabinet.

Unfortunately, there is NO direct correlation between TBQA and TCQA, or TCQC and TBQC, or TBQB and TCQB. (That would have been too easy!) There are signals connected to TBQC that are associated with TCQA, and there are signals associated with QTBA that are associated with TCQA. It's just kind of "all over the place"--unfortunately.

There should be a print-out of a file on the operator interface (an <I> or a GE Mark V HMI) called the "I/O Report." The file should be in the F:\UNIT1 directory or folder, and the filename is TC2KREPT.TXT. It's an ASCII text file, and it can be viewed using any ASCII text editor, including Microsoft Windows Notepad.

The I/O Report lists most (but NOT all!!!) of the inputs and outputs connected to the Mark V, by processor (starting with <C>, then <CD>, then <P>, then <QD1>, then <R>, then <S> then <T>).

On to IO.ASG....

>Also, kindly help me to identify I/O point names in IO.ASG
>files as shown below;
>TC01_16_31_V TC01_16_31_V TC ;Q-TBQA-VOTED Unused voted
>TC value #1
>Q_R_POS01 FSGR PCT ;Q -TBQC-001 Position fdbck
>srv (high value selected) [96SR-1]
>Q_R_VIB01 BB1 VIBVL ;Q -TBQB-051 Vibration
>valve servo current

Each row in IO.ASG has three columns IO.ASG (and all .ASG files). The first column is the hardware name of the I/O channel. Q_Q_MPU2 stands for a <Q> I/O channel, the first "Q" in the abbreviation; that is terminated on <Q>, the second <Q> in the abbreviation (meaning <R>, AND <S> AND <T>--so it's a redundant input); and the input channel is MPU2 (the second magnetic speed pick-up input change).

The second column is the CDB signal name. Since the CDB signal name is the same as the I/O channel hardware name--it's not used for an input.

The third column is the scale code/type of the input. Since most speed pick-up inputs are scaled in the CSP in percent of rated speed, the scale code type is PCT. (There has to be a valid value in each of the three columns of any row; in this case since the signal is unused it can be any scale code or type. Scale codes are listed in another ASCII text file: SCLEDATA.DAT. Do NOT edit (change) SCLEDATA.DAT unless you know exactly what you're doing, or someone is directing you to edit the file. This goes for just about every ASCII text file; you can open it with a editor, but you shouldn't be making any changes--so when you close the file if it asks if you want to "Save Changes?" JUST SAY NO!!!)

There is a semicolon (;) after the scale code/type; anything after that is a comment that is ignored by any program on the operator interface (or the Mark V once the file is compiled). In the case of Q_Q_MPU2 the comment is telling the reader that ONE of the terminals associated with Q_Q_MPU2 is located on the I/O terminal board QTBA, screw number 53. (QTBA stands for Q I/O Terminal Board "A".)

The second row in your example is a little (okay; a lot) more difficult. The thermocouple (T/C) inputs to <Q> are broken up into three groups of 15 T/Cs (for a total of 45 T/C inputs). Notice how the numbering goes from 1, to 16, to 31 (by increments of 15). This is done for any triple redundant T/C inputs; you may find, if the unit has a natural gas fuel flow-rate measurement system that it has three T/Cs (triple redundant), and the CDB point name in the second column would be FTG (Fuel Temperature-Gas). In this case it tells the Mark V to take the median of the three values and display it as the CDB point name FTG. The scale code/type stands for 'Temperature-Compensated'--because T/C inputs all have cold junction compensation. (A topic much too far for this thread.) Again, in this row since the first and second columns have the same hardware name, the input is unused (as is noted in the comment after the semicolon, too). Finally, the "V" at the end of the hardware name means the input is to be a Voted input (in this case, the voting means to choose the Median of the three values).

There is another, similar, group of <Q> T/C inputs in IO.ASG, but those are for non-voted T/C inputs (even if there are multiple T/Cs in a particular area, such as the gas turbine exhaust). Voting is done differently, and sometimes not even at all, by assigning a T/C input to one of the I/O channels in the second <Q> T/C group.

The third row in your example is for a <Q> input (meaning <R>, <S> and <T>), and it is terminated on a I/O terminal board on <R> (TBQC as denoted in the comment after the semicolon), and it's Position Feedback Input Channel 1. The CDB point name for this I/O channel is FSGR (Fuel Stroke-Gas Ratio Valve). Many position feedback signals from control valves are scaled in percent of rated stroke (or travel), and so the value in the scale code/type column is PCT. And the comments is telling the reader ONE of the screws associated with this I/O channel (POS1) is on the TBQC I/O terminal board (on <R> core), screw number 1 (or, 001).

The fourth row is for a <Q> I/O channel, terminated on an I/O terminal board located on <R> core, and the I/O channel is for a vibration pick-up, #1 (or, 01). The CDB point name for this vibration pick-up is BB1, and the scale code/type is VIBVL (I'm not sure what the 'VL' portion stands for exactly; I've just always called it Vibration Value). The comment tells the reader where one of the terminals associated with this input is.

The fifth row in your list is for a <Q> I/O Channel, that is terminated on <Q> (meaning <R>, <S> and <T>--a triple redundant channel), and it's Servo Valve Output (SVO) Channel #1 Current (the 'A' stands for amperes--current). The CDB point name is FAGR, or Fuel Amperes Gas Ratio valve. The scale code/type is PCT (for Percent). And, the comments tells the reader the channel is for the Speed-ratio Valve servo current, and that it is the current associated with a regulator on the TCQA card (the #1 regulator, which another way of describing a servo-valve output (to call it a regulator--the regulators for servo-valve outputs are in the firmware of the TCQA cards...).

So, you ask some good questions--but they have long and sometimes confusing answers! Sorry I missed this old post--I was traveling for a few days and it was hectic; long days of meetings followed by airplane travel. No excuse; I just plain forgot about it.

Hope this helps! Printing the I/O Report is difficult--unless you have a printer connected to the operator interface. If you can tell me what kind of printer (if it's even working....) I can maybe help you to print the file for analyzing and making notes. But, sometimes it's about 50 or 60 pages, and if you have a dot matrix printer, well, printing a lot of pages with a dot matrix printer can be next to impossible. It's formatted in landscape mode, and the printer font is expected to be fixed pitch, 10 cpi (characters per inch), and I believe 8 vertcial lines (rows) per inch. But, having your own paper copy of the I/O Report is VERY helpful. You can make notes on it--notes YOU understand. (I would make a copy of the printout you find, and keep one untouched and pristeen, and make all your notes on the copy. If you lose the copy with notes, you would have another copy you can start over with.)

Again, NOT all I/O is listed in IO.ASG. I know for certain flame detector inputs are not listed in some IO.ASG files. And the main turbine shaft speed pick-ups are also not listed in IO.ASG (and there's a VERY good reason for that!), the MPU1 channel inputs to <Q>. The CDB point name for those inputs is hard-coded in the firmware of most Mark V turbine control panels, and should never be changed. Never. NEVER. (HINT: <b>NEVER</b>) But, most of these inputs are listed in the I/O Report. And, in the first few pages of the I/O Report is a description of how to read and interpret the information in the I/O Report. It also usually shows ALL the screws associated with an I/O channel; unfortunately, some I/O channels have three or four screws associated, but only two screws are used, and the I/O Report doesn't always indicate which two screws of the four are used. BUT, that's something that some day, when you have nothing else to do, you can make notes about in your personal copy of the I/O Report...!

Good stuff!
Good day to you.
Thanks for the detailed explanation and your patience to write here long paragraphs. It helped me a lot.

Above mentioned I/O report and IO.ASG files are same or not. I have IO.ASG files. I thought all the I/O's connected to Mark V are listed in this file. So how to get information about all I/O's connected in MarkV.

Also, please help me to decode below points<pre>
P_RLY_DRVR3 L20FG1X LOG ;P -PTBA-057 Gas fuel stop valve solenoid
TCE_REF_PTR1 L20FG1X_REF LOG ;TCEA-DIAGCHK Gas fuel stop valve control reference

Q_R_VDC1 FPG2 PRESS ;Q -TBQB-025 Interstage fuel gas press xmitter</pre> - here VDC means?
<pre>GEN_VOLTS_AB GEN_VOLTS_AB V64K ;P -PTBA-032 TCCB Gen PT Volts 1</pre>Why here in hardware name column, core name is not shown?
<pre>SVR_INTGRT_1 FPRG_INT PCT ;TCQA-SVR-INT Stop/speed ratio valve reg integrator out
SVR_ICONVG_1 FPRG_CNV PCT ;TCQA-SVR-CNV Stop/speed ratio valve reg int convergence ref</pre>
Above mentioned points are hardware I/O or is any control constants in CSP?

Also, for servo valves of GCV, SRV, IGV how many signals are associated? As per my understanding, there is 3mA output to three coils of servo valve, then 1 position feedback from LVDT, then 1 output to solenoid valve for tripping activated from PTR relay 1 to 4.

Kindly explain.

>Above mentioned I/O report and IO.ASG files are same or not.

They are NOT the same. The IO.ASG file is required for the operator interface (which are you using: <I> or GE Mark V HMI running some version of MS-Windows and CIMPLICITY?) to be able to compile downloadable files and to create the necessary files for the operator interface to be able to communicate with the Mark V.

The I/O Report is an ASCII text file that was created at the time the site-specific software was created for the turbine control panel at your site. It is very complete as regards all of the inputs and outputs connected to the Mark V--that was its primary purpose: To be a tabular list of all* inputs and outputs connected to the Mark V.

*One has to know, understand and continually remind one's self: With any GE Mark* turbine control system, there are exceptions to every "rule," and that any seeming process standard or practice most likely has an exception, and that in developing the Mark* MANY people were responsible for various bits of the total piece of equipment and there was NO ONE who was responsible for enforcing any kind of symmetry, or standard or similarity. Pretty much everyone was free to do just about whatever they could to make it work they way they thought it should. And, finally, they were consistently inconsistent in many of their documents and processes and procedures. That's just a fact, and one can spend their time working on the Mark* cussing and swearing and criticizing, or one can learn to deal with and not be upset when one encounters a non-standard bit that causes some delay or consternation and make mental note if it and move on to the next lesson--because one is going to learn a LOT of lessons along the way whilst working on Mark* turbine control systems. (NOT that it's ANY different with any other manufacturer's control system or the way the control system in implemented for a particular application. It's just that GE is a multi-national corporation and has been in the same business of turbines and turbine control for decades (and maybe for not much longer), and they developed their own purpose-built turbine control system and so had both the ability and to some degree the responsibility to be consistent and develop and follow standards that were published and could be understood by everyone--GE engineers, commissioning personnel, maintenance people, technicians, operators, mechanics, operations supervisors and power plant managers. But, they didn't do that, and aren't likely to do that now or ever. But, I digress--to try to make what you are asking more understandable and to try to help you get past many of your thoughts and concerns.

While one would assume that any changes made to IO.ASG would be "automatically" carried over to TC2KREPT.TXT, or that one could run some executable file/program/application to automatically modify TC2KREPT.TXT to match IO.ASG, one would be very, Very, VERY, <b>VERY</b> wrong. If, as often happens during commissioning and sometimes afterwards, I/O is moved or added or even deleted, the person performing the modifications rarely, if ever, edits TC2KREPT.TXT to reflect the changes. (Another excellent reason for printing your own copy(s) of the I/O Report to mark up as you find discrepancies--not that you WILL find discrepancies, but you may.

>So how to get information
>about all I/O's connected in MarkV.

You need several documents including IO.ASG, the I/O Report (TC2KREPT.TXT), the Device Summary, the P&IDs, the Generator Protection electrical schematics (GE calls them "elementary drawings), and the Control Specification Drawing. Yes; you read that right--there is NO SINGLE document or manual or drawing or book that has all the information you need. You have to search out and amass the information from various manuals and drawing archives and computer files, make your own copies, and make notes on your copies as you read, analyze and begin to understand. You can find the device number and a name for a pressure switch used to indicate low-low L.O. (Lube Oil) pressure that is connected to the Mark V, but you need the Device Summary document to understand how the pressure switch is to be calibrated to provide the proper indication(s), and you need the L.O. P&ID to be able to understand where in the system the device is located (not the ACTUAL physical location, but where in the L.O. system the device is located). And, then you need the Parts List Manual to be able to find where the device is physically located in a compartment on a section of L.O. piping. It's like a mystery--finding all of the information you need to know, and then going out and locating each and every device on the turbine, generator and auxiliaries--sometimes some inputs to and/or outputs from the Mark V are connected to a plant DCS (Distributed Control System), or boiler control system, or burner management system, or natural gas compressor control system, etc. It can be very satisfying finding all of this information and assembling it and learning how it is all necessary and how it works together--for some people. Others, ..., well, ..., they just want it to all be done for them by someone else. And they want it be easy (for them), and complete and consistent and perfect--and they expect that the great GE should have done all of this for them.

You seem to have a very good ability to spot exceptions--and sometimes they are easy to explain, but not often. Here goes....

>Also, please help me to decode below points<pre>
>P_RLY_DRVR3 L20FG1X LOG ;P -PTBA-057 Gas fuel stop
>valve solenoid</pre>
This one is for the gas fuel stop valve solenoid, 20FG-1. which is connected to <P> core, and is a physical, electro-mechanical relay output, and it is the third of four possible trip relay drivers (for the outputs). The CDB point name is L20FG1X, and the scale code/type is a LOG (for logic--it's either a "1" or "0"). The comments tells the reader that ONE wire of the gas fuel stop valve solenoid is connected to the PTBA I/O terminal board on <P> at terminal 57 (or, 057).<pre>
>valve control reference</pre>
This one is for the internal feedback checking of the TCEA and TCTG I/O cards controlling the gas fuel stop valve solenoid. It is a way for the diagnostic software on the I/O cards to know if the relay driver output is supposed to be energized or de-energized, and if it is energized or de-energized.<pre>
>Q_R_VDC1 FPG2 PRESS ;Q -TBQB-025 Interstage
>fuel gas press xmitter</pre> - here VDC means?

VDC means Volts DC (Direct Current) Older GE-design heavy duty gas turbines used pressure transmitters which had a DC voltage output for the signal to the Mark (many times it was 0-5 VDC (Volts DC)). In the Mark V the input was designed primarily at as DC voltage input, but it could also be used for a mA (milli-amp) input. And, it's actually a triple redundant input. One MORE piece of documentation you need to become very proficient at reading and understanding for the Mark V is the Mark V Application Manual, GEH-6195, Appendix D, 'Signal Flow Diagrams.' There's no way to learn it but to make your own copy of Appendix D and start going through the pages, one by one, crossing out the ones that are NOT applicable to your Mark V (like the pages with TCTS and TCTL) and making notes. No; I'm not going to try to do this over a World Wide Web forum without the ability to post pictures or drawings and try to answer EVERY question you will have about what does this symbol mean and why is/isn't that drawn here or there, etc. Just get your own copy and start spending some of the time you seem to have a lot of on familiarizing yourself with the information available there (and there's a LOT of it).
>PT Volts 1</pre>Why here in hardware name column, core name
>is not shown?

Remember that little thing about being consistently inconsistent, and that part about many people having responsibility for many different bits of the total control system, and no one exercising any effort at standardization? Well, add to that the fact that generator terminal voltage inputs were added after the product was initially designed and produced, and, well, it just doesn't follow the typical assignment. BUT, it does tell the reader in the comment after the semicolon that it is connected to <P>, at PTBA I/O terminal board, screw terminal 32 (or, 032).
>Stop/speed ratio valve reg integrator out
>ratio valve reg int convergence ref</pre>
>Above mentioned points are hardware I/O or is any control
>constants in CSP?

Again, this is one of those non-consistent rows in IO.ASG. Personally, I have never seen these used in any CSP, and while I don't believe they are Control Constants, I could be wrong.

>Also, for servo valves of GCV, SRV, IGV how many signals are
>associated? As per my understanding, there is 3mA output to
>three coils of servo valve, then 1 position feedback from
>LVDT, then 1 output to solenoid valve for tripping activated
>from PTR relay 1 to 4.

For a TMR turbine control panel, each electro-hydraulic servo-valve has three coils (two wires per coil), and one of the three coils of each of the servos (as they called for short) is connected to each of <R>, <S> and <T>. Servos ONLY have servo coils that are connected to the Mark*. Under ideal conditions each servo coil of a particular servo, let's say we're talking about the SRV right now, receives approximately -0.267 mA to be able to keep the SRV at some stable position, let's say that's 35.4% of rated travel ("stroke"). Servos have been covered MANY times before in other threads on The only thing I'm going to add at this time is that the servos are bipolar devices--that's important, and it means, positive current causes one action, and negative current causes the opposite action. Some people refer to servos as velocity devices--because the magnitude of the current being applied determines how much hydraulic oil flows to (or from, in some cases) the hydraulic actuator which determines how fast the actuator opens or closes the SRV (in our example). And, lastly, the servos GE uses for their heavy duty gas turbines have fail-safe springs in them which are constantly trying to reduce the flow of fuel or air to the turbine. And, a small amount of what's called "null bias" current is necessary to overcome the spring tension to prevent hydraulic oil from causing the hydraulic actuator to open or close (in other words to hold it a stable position a small amount of current needs to be applied to the servo coils to prevent hydraulic oil from getting to or from the hydraulic actuator which will keep the device (the SRV in our example here) in a stable position. Because the servos are bipolar devices, and because the maximum amount of current (positive or negative) they can receive is 10 mA, GE decided to scale the amount of current (FAGR from above in this thread) in percent, where 1% servo current equals 0.1 mA, and 100% servo current equals 10 mA. Again, servos have been covered MANY times before on, and those threads and responses can be found using's 'Search' feature.

Most devices which have electro-hydraulic servo-valves (servos) also have LVDTs for position feedback. There are usually two LVDTs (for redundancy), and each LVDT requires four connections to the Mark*: two for excitation (approximately 7.0 VAC RMS (Volts AC, Root-Means Square), and two for feedback (approximately 0.70 VAC RMS to approximately 3.5 VAC RMS, when properly set up). The LVDTs are NOT part of the servo; they are part of the device the servo is controlling. A necessary part, in some--but NOT all cases.

In the case of trip solenoid outputs (the PTR (Primary Trip Relay outputs you are referring to), the Stop-Ratio Valve has 20FG-1 which controls whether or not high-pressure hydraulic oil can be ported from the servo to the SRV actuator. It's not a part of the servo, but it IS a part of the hydraulic system. This is where you need the P&IDs (Piping & Instrumentation Diagrams; GE calls them Piping Schematic drawings) to really understand how it all works. AND, you need the Trip- or Control Oil P&ID, the Hydraulic Oil system P&ID, and the Gas Fuel system and you need to be able to follow how they are "mapped" to each other and work together to allow the SRV to be opened or to close the SRV in the event of a trip.

The IGV hydraulic actuator has a servo, and it has one or two LVDTs. Typically it also has a solenoid-operated valve which can control which ports receive high pressure hydraulic oil from the servo, and that is controlled by 20TV-1. (You need the IGV P&ID and the Hydraulic Oil system P&ID, and possibly the Trip- or Control Oil P&ID--and again, you need to become VERY familiar with how all the drawings reference each other and how to follow signals from one to the other--this to see how 20TV-1 and the IGV servo controls the flow of hydraulic oil to and from the double-acting piston of the IGV actuator.)

Usually, there is no solenoid in the hydraulic supply of the GCV.

The solenoids discussed above are NOT part of the servo, but a part of GE's control and protection system for servo-operated devices.

As the Kind, Friendly Moderator said you really need to learn to use the 'Search' feature. It will make you a better person, and you will learn a lot--probably more than you expected. PLEASE, take some time to think through what you read before asking for clarification (we don't like doubts....). We can provide clarification when necessary, but I, for one, am not going to re-hash the same information in a different way just because it didn't answer a specific question in a specific way. Think your question through, re-read the posts you find using 'Search,' and then if you still can't decipher what you're reading we can try to help.

Hope this helps!!!