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Mark V Diagnostic Alarm
May 16, 2008 2:30 am, by Neptune
Subject : Process Control
 from the Automation List dept.
Text :
We are using a Mark-V simplex system installed on GE Frame 5 turbine. During the startup phase, at the time of synchronization with bus bar, we normally get the following diagnostic alarms every time.
U SA P DROP Description
T2 1 R 1597 TCE2 25P Trouble
T2 1 R 1469 TCE3 25P Trouble
T2 1 R 1725 TCE1 25P Trouble
These alarms persist even after the synchronization has been completed.
Any pointers...?
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Re: Mark V Diagnostic Alarm
May 16, 2008 9:56 pm, by CSA
Mark V SIMPLEX panels were used to retrofit or replace or upgrade older control systems. Unfortunately, there are *many* configurations of the generator breaker closure circuit, so unless we could see the one in use at your site we can't be much help.
The following is from one of the Diag. Alarm Help files that floated around (no; I can't send anyone an electronic copy; and, obviously, the EFFECT listed below doesn't affect all units which have these alarms!):
1469 ;TCE3 25P trouble 1597 ;TCE2 25P trouble 1725 ;TCE1 25P trouble
CAUSE This is a loop back test on relay 25P, k1 on TCT_; it means the feedback of 25P (synch permissive relay) contact disagrees with the required or intended position of this particular relay; the (TCE3) board only checks the 25P relay; it is driven by TCQA, <RST>, the relay is on TCT_ and the voting is done at the logic level.
EFFECT . Will inhibit the closing of the gen breaker.
ACTION If reported by all three processors, and diag 1353 is not showing, suspect the "CSP" sequencing; the relay is driven from TCQA and checked by TCEA; the CSP must write the relay status to an appropriate coil (L25PX) to inform TCEA what TCQA is doing; also, since there is only one relay, suspect trip board TCT_; Make sure the k1 relay is not loose. If still a problem suspect TCQA's. If it is on one TCEA board only then suspect the TCEA board or the cable JL.
The above is for a TMR panel, but it's mostly applicable to SIMPLEX applications, as well (there are three TCEAs in a SIMPLEX panel, but there's only one TCQA).
I suspect that something in the CSP is not writing to the 25P relay on the TCTG (which is the card used for heavy duty gas turbine applications), which is causing the problem. That's a guess, based partly on the information above. Sometimes the 25P relay was driven by or in conjunction with 52Z relay, which is the Diag Alarm they are referring to in the ACTION section (1353, 'TCQA 52Z relay driver RD1 failure). In the synchronizing schemes of many older GE-designed and -packages units there was usually a 52Z relay for auto-synchronization enable/permissive. If that was left in place and was not removed or duplicated in the CSP, then this alarm could be the result. Also, many of the Business Associates of GE (packagers of GE-design heavy duty gas turbines) also sold and configured Mark V SIMPLEX panels, so that adds yet another layer or two of possibility into the mix.
Unfortunately, there are too many Mark IVs, Mark Vs, and Mark VIs around the world with too many nuisance Diagnostic Alarms; this is obviously one of the nuisance ones since the unit is able to synchronize. I would imagine the only way to get rid of the alarms would be to re-boot the TCEA cards, but the first time the unit was synchronized again they would likely come back, until you get at the root cause, which is probably the lack of sequencing.
Hope this helps in some small way.
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Re: Mark V Diagnostic Alarm
May 16, 2008 9:35 pm, by Sandy
This looks like a feedback problem. It means that the feedback from the P (synch permissive relay) contact disagrees with the required condition. You need to check the relay and/or connections.
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