Frame-9E GT tripping because of composite trip while attempt is made to start the unit.

All field cables to TTUR TPRO TREG TRPG have been inspected for integrity and tightness.

No change in the settings in m6b has been done and the Unit was running normal till the last shutdown.

Kindly guide us for further troubleshooting.

Thanks and Regards
sdbarman

 

sdbarman,

There is, or should be, a "description" of what constitutes a composite trip in the Mark VI System Guide, GEH-6421. I think you will find it in the section on the VPRO and TREG cards. I have heard that newer Mark VI System Guides have a new volume (II or III ???) that lists all the Diagnostic Alarms and explanations. You may also be able to find some (maybe the same?) information in the Toolbox Help file.

My recollection of composite trips means they are a "group" of trips that are associated with inputs to the <P> core and are usually connected to the TPRO and/or TREG cards. There are usually several discrete inputs to the TREG card (I believe--I don't have access to GEH-6421 as I write this) which can be used as permissives or trips for the emergency tripping function. Also, I believe the E-Stop Pushbutton circuit(s) are part of the composite trip function. Some of the trips which are commonly connected to the <P> core via the TPRO/TREG cards include boiler drum level hi-hi/lo-lo; DCS trips; etc.

While the terminations on the field wiring to the cards may be tight, the integrity of intermediate terminations on the circuits may not be tight. And, there may be some mechanical vibrations or intermittent operation of these discrete inputs to the TREG.

I have also seen serious 125 VDC battery grounds cause problems like this. Is the Mark VI annunciating a 125 VDC battery ground alarm?

Also, unshielded wiring, or wiring with improperly terminated shield ground wires have been known to cause problems like this. The emergency overspeed speed pick-ups are connected

Hope this helps!

Please write back to let us know what you find!!!

 

sdbarman,

One more thing, the terminal boards on the TRPG, TPRO, TTUR and TREG are all removable. (There are two screws at each end of a 12 terminal section; loosen the screws and the top portion of the terminal board can be pulled off (with some effort) with the field wiring attached.) It happens very often that when the removable portion of the terminal board is re-attached that it's not sufficiently seated and the terminal contacts don't make good contact. The screws should be used to make sure the removable portion of the terminal board is fully seated by making sure that they are tight (the screws) and inspecting the outer edges of the removable portions of the terminal boards to make sure they are fully engaged with the stationary terminal board bases.

Failure to ensure the removable terminal boards are properly inserted into the stationary bases have caused intermittent problems such as you are describing.

 

Dear CSA

The composite trip got resolved after replacing the TREG TB and forcing and unforcing L4_XTP signal.
The unit was subsequently started and loaded.

Thanks a lot for your kind guidance.