Hello Friends,

Good Day

I am working on GE Mark V Simplex panel. I have a alarm persisting and could not be resetted.Iit prevents turbine from start up.

Please guide me proper process of eliminating this alarm

TCEA 4 relay circuit FDBK (external Trip) L4_FB_ALM

Thanks

 

Hello Friend,

Good Day.

You haven't told what kind of turbine you are working on, and which Trip Card (TCTG; TCTS; or TCTL) is installed in Loc. 4 of the <P> core.

You need to look at Appendix D, Signal Flow Diagrams, in GEH-6195, and find the drawing titled: "Emergency Trip Pushbutton Connections on PTBA." I believe this alarm is referring to the 4-1, 4-2, 4-3 and 4-4 relays shown on the drawing--I believe, but I'm not 100% certain, only 98.749%. If that's true, then there's something amiss with:

1) the E-Stop Pushbutton wiring connected to the PTBA card (you could try jumpering (remembering it's powered by 125 VDC!!!) from PTBA, terminal 43, to PTBA, terminal 58--effectively jumpering out all E-Stop Pushbuttons. If the alarm clears then there's some problem with the E-stop Pushbutton wiring connected to the panel.

2) The JN ribbon cable between the PTBA and the TCTG or TCTS or TCTL. I DO NOT recommend trying to remove/re-connect this cable with power on the <P> core. The JN ribbon cable is carrying 125 VDC, albeit at low currents, but it's still not a good idea to try unplugging or re-inserting either end of this cable with power on the <P> core.

I say this ALL the time, and it's becoming more and more true as the Mark V product ages: It's very important to use a small amount of conductive grease on EVERY ribbon cable/connector in the entire panel about once every one or two years. The pins and receptacles of the ribbon cables are KNOWN to develop corrosion. Sometimes just unplugging them and plugging them back in two or three times (carefully!) is enough to get them to work again, for a short while, without conductive grease. (Heatsink grease works just fine). Just put a SMALL amount of grease on the female connectors and spread the grease across the entire face of the connector. Too much grease is worse than no grease!

3) A problem with the TCTG or TCTS or TCTL card. The small yellow plastic thingies are the 4-1, 4-2, 4-3 & 4-4 relays. You could try tapping on them with something like the handle of a small screwdriver (while the jumper from 1) above is in place) to see if the alarm clears. That would indicate a problem with the relays, which has been known to happen, but it's rare.

It could just be a problem with something else on the TCTG, TCTS or TCTL card. And, even if it's the little yellow relay thingies, they can't be removed or replaced; they're permanently soldered to the card.

Hope this helps!!!

In the future, it would be REALLY helpful if you posted ALL active alarms, BOTH Process AND Diagnostic, even if you think one or three are not directly relevant.

 

Dear CSA,

Thanks for your valuable info. Turbine is GE, frame 5, Mark V HMI Simplex, It has TCTG card on <P> core loc 4

I followed your advice to loop 43-56 on PTBA, alarm got resetted. Later on, individual trip circuit removed and looped to see which one got problem. Then it was found on <p> PTBA 45/46, contact was open. This contact should be closed from modification done earlier by plant personal. They brought out signal L86TXT TO <CD> core, CO 57, 97/98 - DTBD,which for some reason was not working and gave open contact to give alarm P 243 TCEA 4 Relay Circuit FDBK (external trip).

Earlier the plant personal observed turbine tripped through Exhaust over temp at 2.5 MW, when it was only 272 Deg C on TTXM. The TCQA card was also replaced on <R> core. Now the unit is running fine on load

Thanks for all your instruction

 

Powerisland,

Thank you for the feedback!

Glad to hear all is running well now.