GE Mark VIe control panel

Dipti prakasha Bhanja,

SERIOUSLY.

SERIOUSLY???!!!?!?!

AC or DC voltage?

STRAY VOLTAGE MEASURED WHERE?

STRAY VOLTAGE MEASURED WHEN?


HOW DID YOU NOTICE THIS STRAY VOLTAGE?

WHAT EFFECT IS IT HAVING (IF ANY) ON THE UNIT OPERATION?

IS THE MARK VIe POWERED BY A 125 VDC BATTERY?

DOES THE MARK VIe PANEL USE A DACA MODULE (AC-to-125 vdc converter)? IF SO, WHAT IS THE SOURCE VOLTAGE FOR THE DACA (UPS; LARGE INVERTER; STATION AC)?

WHAT KIND OF TURBINE IS THE MARK VIe CONTROLLING (STEAM; GAS)? OR IS IT A DCS APPLICATION (BALANCE OF PLANT CONTROL)?

If I told you, in a World Wide Web forum my watch wasn't working, and nothing more, what would you say? How many questions would you ask to determine what kind of watch it is (analog or digital; electric or spring-driven), when it quit working, what I've done to try to get it working, etc.)?

Come on, man. Help us to help you as quickly and concisely as possible by telling us as much about the situation as possible. EVERY MARK VIe IS NOT LIKE EVERY OTHER MARK VIe There are SIMPLEX and DUAL redundant and TMR Mark VIe's. Just because it's called Mark VIe doesn't mean we know specifically how your Mark VIe is built, configured and powered. Why do so many people think they can just say something is wrong with their equipment without providing ANY details and someone is going to know exactly what to tell them to do to resolve the problem?

And, most importantly, if you've done any troubleshooting--tell us what you've done AND WHAT THE RESULTS WERE?

Answer the questions above (all of them--not just the ones you deem relevant!) and we can probably help you. Provide any other information you think would help us understand the problem.

I'm betting you're not going to write back because I "insulted" you. Well, I am flattered you think we can read your mind and just know intuitively what the problem is. But, we can't. We aren't that advanced as creatures. I'm not intending to insult you--just to get you to think about your original post. We are getting WAY TOO MANY similar posts. We're good, but we're not that good.
 
Dipti prakasha Bhanja,

SERIOUSLY.

SERIOUSLY???!!!?!?!

AC or DC voltage?

STRAY VOLTAGE MEASURED WHERE?

STRAY VOLTAGE MEASURED WHEN?


HOW DID YOU NOTICE THIS STRAY VOLTAGE?

WHAT EFFECT IS IT HAVING (IF ANY) ON THE UNIT OPERATION?

IS THE MARK VI POWERED BY A 125 VDC BATTERY?

DOES THE MARK VI PANEL USE A DACA MODULE (AC-to-125 vdc converter)? IF SO, WHAT IS THE SOURCE VOLTAGE FOR THE DACA (UPS; LARGE INVERTER; STATION AC)?

WHAT KIND OF TURBINE IS THE MARK VI CONTROLLING (STEAM; GAS)? OR IS IT A DCS APPLICATION (BALANCE OF PLANT CONTROL)?

If I told you, in a World Wide Web forum my watch wasn't working, and nothing more, what would you say? How many questions would you ask to determine what kind of watch it is (analog or digital; electric or spring-driven), when it quit working, what I've done to try to get it working, etc.)?

Come on, man. Help us to help you as quickly and concisely as possible by telling us as much about the situation as possible. EVERY MARK VI IS NOT LIKE EVERY OTHER MARK VI. There are SIMPLEX and TMR Mark VI's; there are "skeleton" Mark VI's. Just because it's called Mark VI doesn't mean we know specifically how your Mark VI is built, configured and powered. Why does so many people think they can just say something is wrong with their equipment without providing ANY details and someone is going to know exactly what to tell them to do to resolve the problem?

And, most importantly, if you've done any troubleshooting--tell us what you've done AND WHAT THE RESULTS WERE?

Answer the questions above (all of them--not just the ones you deem relevant!) and we can probably help you. Provide any other information you think would help us understand the problem.

I'm betting you're not going to write back because I "insulted" you. Well, I am flattered you think we can read your mind and just know intuitively what the problem is. But, we can't. We aren't that advanced as creatures. I'm not intending to insult you--just to get you to think about your original post. We are getting WAY TOO MANY similar posts. We're good, but we're not that good.
It is TMR , mark vie for GT control, supplied by BHEL, it is under commissioning. Already GT run twice. Stay voltage observed at DO side, those which are hooked up with MCC for drive operation. BHEL told it will not affect the healthiness of the control system.
 
Dipti prakasha Bhanja,

Still not enough information. USUALLY, the DOs of the Mark VIe connected to the MCC for starting and stopping motors are "dry contacts"--meaning they just switch power which comes from an external source, in this case from the control power circuit of the motor starters.

Many motor starters have status contacts (running status; thermal overload status; etc.) that are connected to DIs of the Mark VIe. AND they are often run in the same conduit/cables as the DOs for starting and stopping the motors, and even in the same wire troughs of the MCC as the high-voltage motor leads (440 VAC). So, it's often likely that induced AC voltages make their way back to the Mark VIe on these status contact wires connected to the Mark VIe DI input terminals.

30 VAC isn't bad, but it's NOT great, either. However, because this is a construction problem (mixing voltages in the same cables/conduits/troughs) it's difficult to correct. You should monitor the situation, periodically, and take action when the voltage levels exceed 40 VAC (as measured using an oscilloscope). The Mark VIe is a little more robust in resisting these induced voltages, but, it can still be damaged if the levels get too high. When we're talking about MCC DO and DI circuits, some mixing of voltages is unavoidable, but it should be avoided as much as possible.

Another all-too-common construction practice is to run Mark VIe DI wires in the same conduit or cable tray/trench as high voltage motor leads (440 VAC). THAT is a no-no, and if construction personnel are still on site they should be "persuaded" to correct that--and the sooner the better. Allowed to remain this practice will definitely get worse with time, and cause intermittent problems (up to and including units trips/shutdowns, and/or nuisance alarms (Process and Diagnostic) and even printed circuit card and I/O Pack failures. So, this should not be allowed to remain--especially if construction personnel are still on site and can be held responsible for correcting the situation, and correcting the situation.

Again, still not enough information. I have presumed what you are poorly describing is what I have alluded to--no guarantee this is correct. The Mark* is a technical piece of equipment, and it needs to be talked about and discussed as such with actionable data not anecdotal data. (Actionable data is values and terminal board points. Anecdotal data is "word of mouth" with no values or locations.)

30 VAC isn't bad, but as was written it's not great either. It's approaching values that can cause intermittent problems (the worst to try to solve!) and even lead to unit shutdowns/trips and Mark VIe component failures (terminal boards and I/O Packs, or worse).

Hope this helps!





AC or DC fluctuations?

WHERE is the stray voltage being measured in the Mark VIe? Exactly. Terminal board and screws.
 
Thanks a lot , I joined 1 month before , this is my first experience with mark vie . I have worked with other control systems previous , those are steam turbine control like SPPA 3000. But such problem I am facing for the first time, we measured at DO terminals , we always get some voltage around 30. I thought this may cause other problems including spurious tripping. You are absolutely correct , this is due to wrong cabling practice only. At this stage BHEL came with resolution that this voltage will noway create any problem. But you know this is a big problem. Cable rerouting is now not at all possible . The earthing of our system is also not good, its around 2.5 Ohm . We will try to improve the same bring back to at least below 1 ohm. Will it help us. Because what I understand all shield are connected with earthing . It may reduce some voltage. If I am wrong please correct. Thanks a lot for your reply

Dipti prakasha Bhanja,

Still not enough information. USUALLY, the DOs of the Mark VIe connected to the MCC for starting and stopping motors are "dry contacts"--meaning they just switch power which comes from an external source, in this case from the control power circuit of the motor starters.

Many motor starters have status contacts (running status; thermal overload status; etc.) that are connected to DIs of the Mark VIe. AND they are often run in the same conduit/cables as the DOs for starting and stopping the motors, and even in the same wire troughs of the MCC as the high-voltage motor leads (440 VAC). So, it's often likely that induced AC voltages make their way back to the Mark VIe on these status contact wires connected to the Mark VIe DI input terminals.

30 VAC isn't bad, but it's NOT great, either. However, because this is a construction problem (mixing voltages in the same cables/conduits/troughs) it's difficult to correct. You should monitor the situation, periodically, and take action when the voltage levels exceed 40 VAC (as measured using an oscilloscope). The Mark VIe is a little more robust in resisting these induced voltages, but, it can still be damaged if the levels get too high. When we're talking about MCC DO and DI circuits, some mixing of voltages is unavoidable, but it should be avoided as much as possible.

Another all-too-common construction practice is to run Mark VIe DI wires in the same conduit or cable tray/trench as high voltage motor leads (440 VAC). THAT is a no-no, and if construction personnel are still on site they should be "persuaded" to correct that--and the sooner the better. Allowed to remain this practice will definitely get worse with time, and cause intermittent problems (up to and including units trips/shutdowns, and/or nuisance alarms (Process and Diagnostic) and even printed circuit card and I/O Pack failures. So, this should not be allowed to remain--especially if construction personnel are still on site and can be held responsible for correcting the situation, and correcting the situation.

Again, still not enough information. I have presumed what you are poorly describing is what I have alluded to--no guarantee this is correct. The Mark* is a technical piece of equipment, and it needs to be talked about and discussed as such with actionable data not anecdotal data. (Actionable data is values and terminal board points. Anecdotal data is "word of mouth" with no values or locations.)

30 VAC isn't bad, but as was written it's not great either. It's approaching values that can cause intermittent problems (the worst to try to solve!) and even lead to unit shutdowns/trips and Mark VIe component failures (terminal boards and I/O Packs, or worse).

Hope this helps!





AC or DC fluctuations?

WHERE is the stray voltage being measured in the Mark VIe? Exactly. Terminal board and screws.
 
Well, if you are measuring this voltage when the Mark VIe DO contacts are open, but it disappears when the contacts close then it's probably not a problem at all. It's just induced voltage that has "nowhere" to go--until the contacts close and then the neutral connection in the motor starter control power circuit connects one side of the circuit to ground and the induced voltage "disappears."

If you are seeing this voltage (and it's NOT clear how you are measuring this voltage) when the Mark VIe DO contacts are closed (meaning the DO output for a particular circuit is closed and you are measuring the voltage from each of the contact terminals to ground and you are seeing this stray voltage) then it's probably a problem.

The Mark VIe has a unique system for grounding/earthing that many installers--and even field service people--are not aware of. The panel is usually built for two earthing circuits--one referred to as Protective earth and one referred to as Functional earth. Protective earth is intended to be to protect personnel from shocks. Functional earth is intended to earth control-related circuits--and in many cases shield drain wires for low-voltage twisted cables. The two earths are usually connected together in the Mark VIe panel by a braided cable or a large, thick cable. If the site has the two earthing systems, the cable connecting the two in the Mark VIe should be removed, and then connected to the proper site earth. If the site has only ONE earth, the cable/connector between the two Mark VIe earths should NOT be removed, and the Mark VIe should be adequately connected to the one site earth.

You can usually find the Mark VIe earthing system very well described in Vol. I of the 'Mark VIe System Guide, GEH-6721.' And, if you haven't done so already, you should start familiarizing yourself with these two manuals--they information contained in each is different, and the "organization" of the information really confuses most people (even field service people). I prefer to make paper copies of the two volumes so I can make notes in the margins (they margins are purposely wide just for this reason!). And, I strongly suggest you obtain some adhesive "flags" and take some "quiet time" and go through the manuals one page at a time (this can take a few hours) and place an adhesive "flag" on sections you want to return to later. You are really just "skimming" through the manual, getting to see the layout and organization and seeing the information contained it the manual WITHOUT reading the entire manual--and placing "flags" for areas you want to read and study in more detail. There's a LOT of good information in the manuals--not everything you need to know, but a very good start.

If a site has the two earthing systems, it's very important for the electricians/installers to know that and NOT mix the two--because that can and quite often does lead to weird problems and intermittent problems. To them, "earth is earth" and that's just not true and can and will most likely lead to problems now or in the future.

So, please tell us when and where you're seeing these voltages, the nature of the voltages (all things asked in my first response, by the way!) and we can probably tell you if it's a problem or not. AND you should also check out the earthing system(s) in the panel and how they're connected to the site earthing system(s). I have been to a lot of sites that used very small wires to connect the Mark VIe earthing bar(s) to site earthing system(s) and that also caused a lot of problem. Follow the recomendations in GEH-6721, Vol. II.

Best of luck! If you want more help, we need actionable data--terminal boards/screws; contact condition when you are seeing these stray voltages; AC or DC voltage; etc.
 
Dipti prakasha Bhanja,

I forgot to mention that if the stray voltages you are reporting are ONLY at DO terminal screws they are probably NOT going to harm the Mark VIe. And won't probably cause intermittent problems or worse. It's the wires used for DI circuits which can be greatly affected by induced voltages because of improper construction. These voltages are often harder to spot (need good voltmeters, True AC RMS voltmeters are best; or an oscilloscope). But these are the input circuits that are most affected by "stray" induced voltages. And, a lot of that happens when poor construction practices are used. You really need to be careful when using this argument to try to force changes to existing wiring; you need to be SURE of what you're alleging and exactly which wires/circuits are affected because of known poor construction practices. And, there are very few technical regulations or standards you can rely on for help in pursuing your goal. GE used to publish a drawing which was supplied with every GT called Cable Specifications, and it detailed many very important practices they have come to know over decades that result in the most reliable and trouble-free operation. I don't know if they still issue that drawing, or if their licensed packagers do (they used to--because they used GE turbine control systems and GE wouldn't warrant the control systems if their practices weren't followed).

Shields (shield drain wires, to be specific), are typically only used on low-voltage circuits (24 VDC; 10 VDC; 5 VDC; mA circuits; etc.) on twisted, shielded pair cable or twisted, shielded three-conductor cables. The shield should be terminated at one end only. (This topic has been covered MANY times before on Control.com and can be found using the 'Search' feature.)

Some multi-conductor cables used for high-voltage circuits (125 VDC; 120 VAC; 220 VAC) have an over-all cable shield, but that doesn't really do much to prevent induced voltages from occurring on the conductors inside the shield. It helps reduce the magnitude, but not really the existence.

I think the two replies above cover most of your concerns--without actionable data.
 
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