Dear All..

GE Fr5-Mk5 control protection system Diag.alarm. The following diagnostic alarms appears in the screen since 2 days with turbine running in Gas fuel mode.

1.TCE1 TMR check trouble,ETR1 {Diag Drop#1696}
for R-S-T controller.

2.TCE1 TMR check trouble,ETR2 {Diag.Drop#1697}for R-S-T controller

3.Voting mismatch,"S" 4ETR1 {C 2278}

4.Voting mismatch,"S" 4ETR2 {C 2279}

5.Voting mismatch ,"S"L12_ACC{C2282}

6.TCE1 HP reading,Hardware trouble for "S"{1680}

By going thro these alarms, I understand that one of the voting {input} from "S" processor has failed and turbine continue running with available 2/3 voting from R and T. I think,that these alarms could be due to failure of NHP speed sensor signal going to TCEA "y" in "P" core OR failure of RD in TCTG trip card OR TCEA "Y" card at Loc3 of "P" core. Am I corect? I need to shut down the turbine in order to diagnose the fault. Could you PLs some one suggest/help solve the problem. Thanx

 

you need check de TCEA "Y" and confirm de ok relay K4 in TCTG only with de TG of-line

 

The <P> (Protective) core requires three speed signals, and for most new unit Mark V applications that was done with three separate speed pick-ups, 77HT-1, -2, & -3 (separate from the "primary" shaft speed pick-ups, 77NH-1, -2 & -3 which are connected to <R>, <S>, and <T>, respectively).

You can see the three <P> core speed signals using the Pre-vote Data Display, looking at signal TNH_OS. So, if one of them is not reading the same as the others, it should be obvious there.

You can also use a frequency meter or a voltmeter capable of reading frequency to measure the frequency at the terminals without tripping the unit. It's an AC frequency, usually about 6-50 VAC, and 1 Hz equals 1 RPM. So, 5100 Hz equals 5100 RPM.

If one of the three "emergency" (Protective) speed pick-ups is not working, it will cause the alarms you have listed for the reason you have described.

You can not replace the speed pick-up while the unit is running, unless you want to risk damaging the new speed pick-up while installing it. You'll need to shut the unit down, remove the failed/failing pick-up, and install the new one and set the gap to the proper setting, and then connect it to the Mark V.

Some people have successfully disconnected speed pick-up wires from the failed input (it looks like PTBA-5 & -6 in your case), and then jumpered the speed signal from PTBA-1 & -2 or PTBA-9 & -10) over to PTBA-5 & -6. However, if you're not careful when connecting the jumpers to the other input, you can definitely trip the unit.

So, best to shut down, even if you're just going to jumper the speed pick-up. And if you're going to shut down to jumper a working speed pick-up to this failed one, best to jumper the respective primary speed pick-up to the <P> core inputs. In your case, that would be the <S> speed pick-up input, which is usually at <S> QTBA-51 & -52.

 

Dar CSA,

I have checked the TNH_OS signal values in Pre-vote display. Core R-S-T-readings are almost same. ie: <pre>
R - 100.19%
S - 100.21%
T - 100.16%
Voted-100.19</pre>
It means that there is NO NHP signal problem in Protection core. Then probably, it will be either TCTG OR TCTA "y" card.

Is there anything I can check with turbine running now? Pls guide me...

 

ESKAY,

If the alarm indicating a problem with the <Y> speed pick-up was annunciated (TCE1 HP reading,Hardware trouble for "S"{1680}) that means there was a problem with the speed feedback. That problem may be intermittent and that's why when you look at it now it doesn't appear to be a problem.

Have you performed a 'Master Reset' to try to clear the alarms? When this kind of condition is annunciated, the condition is "latched" and requires a Master Reset to unlatch once the condition is resolved in order to clear the alarms. The latching is done to prevent an intermittent problem from excessively toggling and also to allow the problem to be troubleshot (if the condition was only briefly intermittent and didn't latch, it might be very difficult to understand what caused the alarm, hence the latching function).

Have you used the Pre-Vote Data Display to look at the primary speed feedback signals, TNH, to see if there is a problem with those signals?

Something is amiss, and it may or may not be a permanently bad signal; it may be an intermittently bad signal.