TCCA Status S page xmit failure


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TCCA Status S page xmit failure
can any body explain me in detail about this alarm, its cause and action to be taken.
we are having MARK-V control system with TMR configuration for gas turbine 9FA.

There have been other posts on before about this alarm. The 'Search' feature here at is very fast and very good, though not as user-friendly as before or as a generic Internet search engine. You can click on ' - help - ' next to the 'search' button for details.

You haven't told us if this alarm has been active for some time, just became active, or has been intermittent for some brief period of time or has been intermittently being annunciated for a long time.

This alarm is trying to tell you that there has been a problem with the communication between the Mark V and the EX2000 exciter regulator control system. Status S is the communication protocol that the Mark V and the EX2000 use to communicate with each other over the StageLink (ARCnet-style LAN) used to connect the Mark V to the operator interface(s) and to the EX2000.

This alarm is sometimes falsely annunciated for units *without* EX2000 exciter regulators. This is sometimes referred to as a software "feature" instead of the software "bug" that it is. I believe that there is a PROMset upgrade available from GE that could eliminate that Diag. Alarm for units without EX2000 exciter regulators, but I'm not certain about that.

Likely causes are poor BNC connector terminations on the coaxial cable used for StageLink connections, and/or if a fiber optic link is used anywhere in the StageLink, it might be a problem with the MODHUBs or the fiber optic connections in that portion of the link(s).

The StageLink also uses BNC tee connectors at most of the nodes, and termination resistors at the ends of the link. These components have been known to deteriorate over time and simply replacing them have proven effective at eliminating these alarms.

StageLink cables have also been found to be damaged either during construction or maintenance and replacing them has eliminated the alarms. Also, sharp bends and "kinks" in the cables can cause problems. It was also a poor practice to use the wrong coaxial cable during construction, and it would seem to work fine for a while and then develop intermittent problems or just fail altogether. Refer to the Mark V manuals for information about the proper type of cables, and then ensure the proper type of cable was used for each segment.

The BNC connectors used for ARCnet coaxial installations are slightly different than those used for Ethernet 10-Base2 coaxial installations (or so I've been told). Many times non-ARCnet connectors were used (BNC cable ends and BNC tee connectors) in construction of the StageLink segments.

Finally, if the unit is equipped with an EX2000 exciter regulator that is present on the StageLink with the Mark V and the operator interfaces, this Diag. Alarm means that there is some communication loss between the Mark V and EX2000, which could prove problematic if not resolved.
thanks CSA for help,
we are facing the problem with 4 units (2 gas turbines and 2 steam turbines) that suddenly the DWATT fluctuates abnormally almost to full range (0-200MW). the units are running at 200MW. i ran a view file putting parameters like SRV command and feedback, gas Pressure FPG2 &FPG3, gas flow FQG, frequency and during the fluctuation all these were found normal. this fluctuation is coming in any unit at any time and the common alarm in all the unit is

TCCA Status S page xmit failure

can this problem be related with this alarm.
there are no other diagnostics during this fluctuation.
our units are equipped with EX2K and in one of the unit following EX2K alarms are found:

416 LARCMSGF This arcnet node did not receive an
ack after a transmitted message.
417 LARCTAFL The destination node doesnot have
any free receive buffers.
423 LARCRBFL This arcnet node's receive buffer
has overflowed.

i ran a view file to observe the situation and included the parameters SRV command and opening, gas control valve command and opening, FPG2 and FPG3 gas pressures, FQG gas flow, frequency.
during the MWATT i/p fluctuation all these parameters were found normal so it should not be actual MWATT hunting.
kindly help me.
You still haven't told us if these alarms just started occurring or if they have been ongoing for some time (like since original commissioning).

I don't know what else to tell you to try. Have you tried any of the things listed as possible problems?

As for the DWATT signal, I'm only accustomed to seeing transducers used to supply the signals; transducers with PT and CT sensing circuits to generate a 4-20 mA output proportional to load. Usually, for the gas turbines, there are multiple transducers, and there's some kind of high-select block or median select block if there are three transducers (which sometimes there was).

DWATT is a very important signal to the Mark V, and I don't think the designers of the control system would use a single feedback over the StageLink from the EX2000 for that signal.

I have to wonder if you're confusing DWATT with a separate signal that's coming in from the EX2000 over the StageLink. I would think it would have a slightly different signal name, but that's just a guess. I'm also guessing it might be something like GN_WATTS; you should be able to find the signal name in the EX2000 section of IO.ASG.

It was common for the GN_WATTS signal name to be used as the value for load on display screens, but not in the CSP for any control function. Are you assuming the value of load on a display screen is DWATT?

In your VIEW2 file, did you put DWATT and DWATT1 and DWATT2 and FSG and GN_WATTS? You're right that if the load were really swinging you would be seeing some change in Gas Control Valve position and fuel flow, but you aren't seeing that.

But, as for the communication problem, you need to systematically go though the suggested possible causes, eliminating them one at a time. That's what a GE field engineer would do.

I would also wonder about the StageLink configuration, if something was changed from the original configuration as left after commissioning, and if so, did these alarms start occurring after the change?

Lastly, since communication between the Mark V and its associated EX2000 is over the StageLink, one has to wonder if the StageLink traffic is really high, or if something was done that caused it to increase recently? Like a change to MODBUS or GSM lists, or some field modifications to CIMPLICITY projects.

There's not much else to recommend.