Respected sirs,
In our CPP there are 6 gas turbine generators ( frame 9e ) FOR EACH GT WE HAVE TWO BATTERY CHARGER ( 2*100% ) TO FEED EMERGENCY SUPPLY TO GT AUXILIARIES LIKE MARK-6 , EX2100 , PROTECTION PANEL , EMERGENCY LIGHTINGS, MCC INCOMING BREAKER CONTROL CIRCUIT ,VERSAMAX ETC.

My first question is "what will happen if BOTH BATTERY CHARGER FAILS when gas turbine generator running normal?" BATTERIES ( 220 AH,125 VDC ) ARE ALSO CONNECTED TO 125 VDC BUS TO FEED SUPPLY IN THE CASE OF BATTERY CHARGER FAILURE IF THERE IS TURBINE SHUTDOWN IN EVENT OF BOTH BATTERY CHARGER FALURE , THEN WHAT IS THE LOGIC BEHIND GIVING SHUTDOWN COMMAND TO GT. WHAT WILL HAPPEN IF ONLY ONE BATTERY CHARGER FAILS?

MY SECOND QUESTION IS IN THE EVENT OF AC SUPPLY FAILURE TO BATTERY CHARGER ONE OUR GT TRIPPED , DUE TO MEGAWATT TRANSDUCER SIGNAL. I DON'T KNOW WHAT WAS THE SIGNAL BUT I WANT TO WHAT IS CONNECTION BETWEEN BATTERY CHARGER AC SUPPLY FAILURE & MEGAWATT TRANSDUCER ?
IF ANYBODY AWARE OF THIS REPLY ME.

 

Esteemed originator,

I've started writing this response about seven times now, and each time I think of something that hadn't occurred to me before.

The most recent--and I would argue the most important--fact is that were both battery chargers to be lost that the *battery* would continue to supply the loads connected to it. I'm presuming, since you didn't say otherwise, that the battery was still supplying the turbine control panel and exciter regulator. (That's really an important presumption on our part.)

There's just too much we don't and can never know about your installation and the way the plant was designed and what the design criteria were when the plant was designed. Also, we don't know if these are newer units or if they are older units which have retrofitted with Mark VIs and EX2100s.

It's also common for many GE-design heavy duty gas turbines running 50-Hz generators to have alternate source supplies for the turbine control systems (usually called DACAs) that convert AC, usually from a large inverter power supply or UPS (Uninterruptible Power Supply) into 125 VDC for the turbine control panel, so that if the DC *battery* were lost there would still be power for the turbine control panel and other control panels, but *not* for the emergency oil pumps in the event of a loss of AC for Aux. Oil Pump motors during a trip or shutdown. I've even seen two DACAs fed from two different inverters. But, no provision for emergency oil pump power in the event that the main 125 VDC power is lost.

The answer to the question about what happens at *your* site lies in the application code running in the Mark VIs and in the schematic drawings for the generator control panels at your site.

I will tell you that the Speedtronic turbine control panels are designed to run with DC voltage of between approximately 90 and 140 volts. Further, they take draw about 10A or less when running (depending on the number of solenoids powered by the panel). I'm not sure about the current drawn by the EX2100, but it's probably the same or less. So, a properly sized battery being used for a GE-design heavy duty gas turbine and it's auxiliaries, including emergency oil pumps, shouldn't draw the battery down very quickly.

Yes, the battery charger(s) are supplying the current when they are "charging" the battery, but they are connected "through" the battery. If you will, the battery is supplying the current to the loads, and the charger is replenishing the current. Or, the charger is supplying the current, as you wish. But, when the battery is still connected to its loads (the Mark VI and EX2100 in this case) and the charger(s) aren't supplying any current to the battery, then the battery will continue to supply the load until the voltage drops below approximately 90 VDC, at which point the Mark VI power supplies will usually shut themselves off to protect themselves. Which means, the unit will trip.

I don't recall ever seeing a site where the unit tripped or even went into shutdown on loss of the main battery charger(s) (and many sites have 2x100% chargers).

Also, I've personally never seen a load transducer that is powered by DC. Again, some of the 50-Hz units have some "unusual" equipment and it's entirely possible that one was supplied or requested to be supplied. But, most load transducers I've seen recently are either self-powered (meaning they derive their power from the PT (Potential Transformer) and CT (Current Transformer) inputs, or they are powered by "station" AC, meaning some 110/220 VAC source, but I haven't seen many of those recently.

So, I would say that someone (or some people) are associating two things which aren't likely associated. I see this happen all the time when Trip Logs and Historians are properly configured or the proper data isn't accessed and viewed. People see spikes and dips occurring at relatively the same point in time, and associate them without doing much research (which it seems you are attempting to do).

But, we can't easily review the drawings for your site so we can't know. Hopefully, this has given you some food for thought and consideration.

As a relative newcomer to the site, I want to let you know that our community is only as strong as the feedback we get from those who ask questions. I encourage you to learn to use the 'Search' feature here on control.com, because a lot of the questions you might have have probably already been asked and answered. When there is feedback to let others know if the info provided was helpful or useful that lets you know that the info was correct or off the mark completely.

We also like to say that feedback is the most important contribution here at control.com (I'm officially copy-righting that sentiment as of this writing! "Feedback is the most important contribution."(c)) Please let us know if you find the information useful or if we miss the mark completely. It's good for those who post responses as well as for those who use the 'Search' feature to find helpful information or to avoid bad information to hear your feedback.

As others have said before, if you can take the time to write a question you can take the time to write a response to let others know if you found the information helpful or not. So, I note that you have posted at least three questions in very rapid succession. That's okay. We would just like to have three responses in a timely fashion as well.

One last thing, and then I'm through: There have been some sites which used two 125 VDC batteries. One supplied just the turbine control panel and exciter regulator, generator protective relays, etc. The other was used solely for the emergency oil pump motors and emergency DC lighting, etc. We don't know what the situation is at your site, and that's the kind of information which would be helpful in providing a timely and concise response. The more information you can provide, the better the responses. The less questions you will be asked when trying to prepare a proper response.

 

A very good explaination by CSA as always.
Have anyone tried to switch off the 125Vdc breaker which supplies power to Mark V panel from the MCC before?

Thats going to be my next thing to do during the next outage. Wonder whether my 110V AC supply is sufficient to keep everything in order. At least I could make a backup plan should it fails
Lets keep our fingers crossed..

 

Respected originator...
This kind of subject has been discussed in the past but, sometimes amount of information we are been exposed is a bit too much. so asking repeated questions is a way to gather useful information for your inquiry.

Basic information: All the none pirated MKV's and MKVI's all over the world runs on DC power. Regardless how they are feeded double AC lines etc. Somewhere these AC power supplies are converted to 125DC which is used for the panel.

Your first scenario (question1): This scenario is called double jeopardy. What does this mean? Its highly unlikely that both DC supplies (chargers) will fail at the same time. Unless your maintenance crew will do it intentionally. This kind of philosophy is (should be)captured in design philosophy of your company. Some companies follow the so called IPF,IPS,RCM guidelines. These companies’ specified guidelines will finally result in decision whether you want to use one, two or three (unlikely) UPS systems. Usually the use of these redundant UPS systems (2X100%), are used in the nuclear power plant (with its own synchronizing system). To increase the reliability of the plant, small power plants start using this redundant UPS system.

Anyway if you feel to switch of both UPS or in unlikely case of losing both supplies, the GT will remain on its running condition. The MKVI will get his supply from the other AC lines (remember these AC is converted in the MKVI to DC). There will be of course a lot of alarms for under voltage detection etc. If you have this redundant UPS system design in your plant, I assume that the GCP, GPP and the AVR is provided DC from the AC lines (converted to DC).

Note: Some GT's (mechanical drives) used in Oil&Gas plants will trip if the both UPS lines are down and the under voltage is detected from the batteries. The philosophy behind this design is that, this kind of operation might lead to major equipment damage if the redundant AC lines are down/tripped. The emergency lube oil pump will not cut in and the bearings of the GT and the load (f.i centrifugal compressor) will not be sufficient lubricated.

In general, if one of your UPS fails, you will get alarm and NO TRIP.

Answer on Q2: Usually the Megawatt transmitter is single and looped to other redundant MKVI inputs. This transmitter is usually two wire system connected (supply and signal by two wire, internal powered up). It's highly unlikely that this transmitter failed due to power failure (remember internal powered via MKVI). Even do if this transmitter is external powered, still it will not trip the GT due to AC power failure! Remember a single failure in the system should not lead to multiple plant trips. If the MW transmitter will fail, the CPD and or FSR will back up the turbine control (fallback line). You should do some more investigation for the root cause of this trip. Most likely one or more AC/DC lines via the converter is or was in tripped. Check your AC MCB's and the AC/DC converter cards.

Good Luck...Tempus Fugit....feedback please....

 

hello csa ...thanks for that response helped to know some basics ..i am involved in a controls upgrade project for ruston turbine ..thanks once again.

 

Anees,

Thanks for the feedback!