110 vac power supply loss in gas turbine running

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WE HAVE GAS TURBINE FRAME-V WITH MARK-VIE CONTROL SYSTEM. Turbine is in running condition. Input control power supply of turbine is 125VDC provided from its separate battery bank. 110AC is supplied to its UDH/PDH and HMI and spark plug through UPS.

Now we want to stop our system 110VAC power supply due to replacement of UPS.

We want to know, what will effect on running turbine or its control system if 110VAC power loss. Turbine will trip or running in normal condition?
 
If you remove the 110VAC UPS the turbine will trip. The UPS powers the Ethernet network switches for the UDH/PDH and the IONET, along with the HMI's. The spark plug is not needed once the turbine is running.

What you will need to do to replace the UPS with the turbine running:

1. Get out the Network Diagram (4108 drawing). The network switches are shown. You will need to have an alternate 110VAC (shop AC?) source available for each switch. Ideally, you should have 2 separate power sources. The network switches are set up as 2 separate, redundant systems, I think called "A" and "B". Keep the "A" switches on one feeder and the "B" switches on a second feeder, so a single breaker trip won't kill both networks.

2. Assuming all the switches are operating properly (no network diagnostic alarms), ONE AT A TIME, unplug a network switch from the UPS and connect it to the alternate AC supply. You will get diagnostic alarms each time you unplug a network switch. You should clear these alarms before moving on to the next switch.

3. Then, ONE AT A TIME, power down each HMI and switch it over to an alternate AC Source. Power it back up, and when on line, do the next one. The HMIs are all connected to both "A" and "B" networks, so just make sure you connect half of them to 1 AC feeder and the other half to a second feeder.

4. If you have a Historian, you should connect that to an alternate source, although you could shut it down without tripping the unit - you just lose data collection while it is down.

5. You can also connect the spark plug to an alternate AC source in case you do have a shutdown while the UPS is being replaced and you need to re-start while the UPS is down, but I think with proper planning it should be possible to change out the UPS fairly quickly.
 
IF your control system is typical of most GE-provided systems, the only interruption you will experience is loss of communications between the HMI(s) and the Mark VIe due to loss of power to the network switches.

Not a small interruption, unfortunately, but as long as the process is relatively stable and is anticipated to remain stable during the UPS outage, then the turbine should continue to run with no ill effects due to the UPS power interruption.

Can you temporarily supply the network switches and HMIs with station AC while the UPS is being worked on? You will temporarily lose communications when switching from and then back to UPS power, but that's better than being without communications for the entire procedure.

It is highly recommended you power down the HMI(s) normally before "killing" the power to them and/or the network switches to prevent nuisance problems with re-establishing communications which would likely require a re-start of the HMI(s) anyway.

Write back to let us know how you fared.
 
otised,

I respectfully disagree that the 110 VAC UPS powers the IONET network switches. They are <b>usually</b> powered by the 125 VDC-28 VDC power supplies in the Mark VIe panel, not by an external power source, UPS or not.

The Mark VIe should continue to operate even if the HMI(s) are incapable of communicating with the Mark VIe. That's kind of a scary way to operate the turbine, since there is no "back-up" operator interface as there was with the Mark IV and the Mark V. (Though most people didn't ever learn or know how to use the Auxiliary Display (Mark IV) or the <BOI> (Mark V) to operate the turbine; a real shame, as the Auxiliary Display was an excellent troubleshooting tool. GE has really left owners/operators without a good back-up operator interface solution in the event the HMIs or the network switches used for connecting the HMIs to the Mark* control are unavailable, failed, or lose power. The only good thing is that the Mark* will continue to control and protect the turbine even without an operator interface (HMI).... Which is both good and bad at most sites.)

Sorry; but in my experience, the IONET network switches are NOT powered by an external source, but rather are powered by the same power supply(s) as the main control processors are powered, which if I understand the original question correctly would be 125 VDC (converted to 28 VDC).

Now, things may have changed in the last few years, but this would represent a major departure from the reliability philosophy that GE has maintained so faithfully over decades--powering the Mark VIe IONET switches by an external power supply, even if that power supply was from a UPS. I would be extremely surprised to learn of such a change in philosophy.

Personally, I have ALWAYS felt that at least ONE UDH network switch should be powered by the 125 VDC battery that (usually) powers the Mark*, as well as least one HMI, in order to have at least one operator interface capable of communicating with the Mark VIe in the event of loss of AC (UPS or station). But, GE "deems" otherwise, and a lot of sites have been unpleasantly surprised to learn of this failure to have a back-up operator interface when AC to the UDH network switches, and/or the HMI(s) is lost. C'est la vie.

Or maybe more appropriately, caveat emptor.
 
F
I will agree with CSA when he says that the UPS outage will NOT trip the gas turbine. That is because the critical IONET (N-TRON) switches inside the cabinet are powered through the 28V power Supplies and those are fed off the 125VDC bus DIRECTLY.

The UPS is there to power devices that really must have AC power. These are usually the A) Allied Telesis switches which form the UDH/PDH/ADH network B) the Local HMI (which is an off the shelf windows based PC with a 220VAC power supply) C) auxiliary panel devices such as Hazardous Gas Detection, Vibration monitoring etc D) some other lighting and non-critical loads.

Before I delve deeper, let me just ask the OP: Are you sure that the spark plug ignitor is powered by the UPS? (Read: Have you referred to your site specific MCC drawings to be sure?) In my experience ignitors are NOT powered from the UPS. I believe the UPS is not sized to handle that kind of load. It makes sense since it wouldn't make much sense sizing a UPS to accommodate a load that is only usually required during startup (exceptions being some DLN machines that require a primary zone re-ignition in certain combustion modes). There are some contingencies which could be better covered if ignitors are also powered via UPS, but then that's a question of cost vs benefit for the packager/GE and maybe they do have it at your site. Only way to be sure would be the drawings.

Back on the topic of UPS outage impacts, Please note that NOTHING inside the MarkVIe panel is powered by the UPS power supply (check the elementary). Nothing critical out in the field is powered by the UPS. If you take out the UPS, sure you lose operator visibility of the GT, but that's just about it. The turbine will continue running and will be protected by the markvie. Do not expect the operator to be happy, though.

I have seen this happening first hand. An electrical cable got pinched in the the HMI cabinet door, and this caused a short circuit in the UPS power supply. The breaker tripped. The local HMI turned off, and since the power supply to the PDH/UDH/ADH switches was also cut, the remote HMI also lost that GT. The turbine DID NOT trip.

Having safely identified & removed the short circuit, the breaker was again set and all communications and HMI functionality was restored.

Having said all that, if I were you I would wait for a planned shutdown to do the activity. The rule is, don't fix it if ain't broke, bro! :) Occam's razor is a good principle in Plant Maintenance roles. But if you absolutely have to, go ahead, I wouldn't be too worried doing this online IF I absolutely had to. Or you can arrange an alternate AC power supply and use that to mitigate any real or imaginary risk.

Good luck.

P.S: PLEASE refer to your site specific drawings to be sure of what the UPS is powering on site.
 
CSA - you are probably correct that the N-TRON IONET switches for the gas turbine are powered by 125 VDC, although I am not sure that is the case on combined cycle projects for the HRSG and BOP equipment. I don't recall running 125 VDC power out to those locations on any of the combined cycle projects I worked on.

Ignitors are powered by a UPS if the unit has black start capability. Sometimes there is a small dedicated UPS in the local control compartment for this purpose.

I also agree you can run without the UDH/PDH and HMI's, but I wouldn't want to. And I haven't met any operators that would.
 
V
Thanks a lot sir,

I have checked in drawing and found UPS power supply given to HMI/UDH/PDH/SPAR PLUG. 125VDC is powered to IONET switch.

Please also suggest on:

If shut down 110VAC power and after UPS replacement it to be ON then any possibility of gas turbine trip or any abnormalities?

any procedure of 110VAC power off to prevent any abnormalities.

220VAC power shall be available during UPS replacement, then can we provide 110VAC from step down transformer to gas turbine system UDH/PDH/HMI/SPARK PLUG?
 
>If shut down 110VAC power and after UPS
>replacement it to be ON then any
>possibility of gas turbine trip or any
>abnormalities?

No. "The HMI does not perform any control or protection of the turbine--that's all done by the Mark VIe. '

> any procedure of 110VAC power off to prevent any abnormalities.

Please reread the previous messages on this topic.

The spark plugs are only used during starting on a GE-design heavy duty gas turbine. It's not a two-stroke or four-stroke reciprocating engine. The only time power is required for the spark plugs is when the turbine is being started, and then only for 30-60 seconds. Once flame is established it doesn't need spark plugs to keep it burning.

Just power down the HMIs as you normally would shut down any PC, shut down the UPS. And once 110 VAC power is available (temporary and/or permanent) power the HMIs up just as you would any PC--just power one up at a time and wait five minutes after the PC is fuy operational (at the desktop) to let the communications get re-established for each PC and network before powering up any other HMI.

If you can't do this, get someone knowledgeable to do it for you. The turbine isn't going to trip when you power down any or all HMI(s). Or when you power them back up. The biggest problem you will have is re-establishing communications without problems.

But the turbine ain't gonna trip--even if you remove the power to the spark plug circuit.
 
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