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,
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.
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.
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by Seth Price
by Seth Price