Dear CSA/PV and all..
Ours is a GE Fr5 Mk6 controller GT. While the turbine was running under 10 MW load,the following alarms appeared:

1. L86TCI_ALM Compressor inlet TC disagree
2. L3VTCC_ALM Exhaust TC card fault from "S" core. "R" and "T" core OK.

On going thro the fault findings,[these diagnostic alarm come and goes] the CIF-2 value goes on and off whereas CIF-1 value is steady. This attributes to the cause of this alarm. Apart from these alarms, core<R><S>and<T> also have VSVO diagnosis alarms for "LVDT#4 RMS voltage out of limits" which is originating from <T> core. Under these existing alarms, while the operator tried to carry out "Master Reset", the turbine load started reducing and BKR got opened due to Reverse power.

How the "master Reset"could affect the load reduction in this case?Turbine started again and instructed NOT to carry out "Master Reset" unless it is most essential. We also have slot#1"VCMI"fault Diag. alarm for<S>core. (Bit error5 and VME error bit 4 being logic "1") NOT getting RESET.

Kindly advise/suggest..
Thanx...

 

GE makes a distinct difference between <b>turbine tripping</b> and generator breaker opening (sometimes called breaker tripping). A turbine trip (which is the title of this thread) means an immediate shut-off of fuel, followed by a breaker opening. As you have described the situation, the turbine did not experience a trip, but the generator breaker was opened (tripped).

You didn't tell us if the unit remained at FSNL after the breaker opening or if it went into a normal, fired shutdown to Cooldown (ratchet). That's a pretty important piece of information. You did say the turbine was re-started, so from that one can presume a STOP was active at the time the MASTER RESET when initiated and some existing alarm was unblocked and the STOP was allowed to unload the unit, open the breaker on reverse power, and the unit went into a fired shutdown and decelerated/coasted down to Cooldown (ratchet).

So, that kind of reinforces the presumption that some STOP was active at the time the MASTER RESET was issued and was unblocked and allowed to shut the machine down in an orderly fashion (again: not a turbine trip).

The typical cause for a T/C reading to go "...on and off..." is a loose termination somewhere along the circuit. That's a pretty simple fix.

We would need to be able to see the application code running in the Speedtronic at your site to be able to understand what might have happened. We would also need to know all of the other Process- and Diagnostic Alarms that were active at the time of the event.

There are some Process Alarm conditions that block a RAISE or LOWER when they are active, and some of them are latched through the MASTER RESET function (meaning that when they are unlatched when a MASTER RESET is initiated by the operator) that any pending RAISE or LOWER commands would then be unblocked.

<b>From the information provided,</b> the alarms listed should not have resulted in the condition you described in a typically configured Speedtronic turbine control system. But, we don't have enough information about what happened before this event, how the turbine was being operated (Preselect Load Control; External Load Control; etc.). We don't know if a STOP was active for some reason (which would explain the unloading and breaker opening you said occurred).

There's just too much we don't know, and, again without being able to see the application code running in the Speedtronic at your site--and the Alarm Log from the HMI at your site--we can't probably add much more to this thread.

You are correct in that under normal circumstances a MASTER RESET should not cause the turbine to shut down or trip. But, we don't know what the existing alarms were prior to the event and we don't know how the Speedtronic at your site is configured to operate.

When one issues a MASTER RESET from the HMI, it's not selective. It works on every instance of MASTER RESET in the application code, and in firmware. So, while the Comp. Inlet T/C Disagreement alarm required the MASTER RESET to unlatch it, when initiated the MASTER RESET must have unblocked an existing STOP and it was allowed to shut the unit down in an orderly fashion, just as you have described.

 

Master reset trip

Hi Eskay , well i agree with CSA the master reset seems to have initiated a fired shutdown. did the machine sustain in FSNL or did it go for a full shutdown. this problem might be unique to your application code. If possible can be you send the historian data during the time of the indecent as a .trn file or as a .csv file for us to analyze. the SOE list from TCI will also be a great bonus.

this is the first time i am hearing that such a innocuous signal like the master trip initiating a trip. but without the historian there is just too much to guess and plenty to go wrong as the master reset is used in many many places. upload the files or send us a private mail , hopefully we will be able to fill in the pieces.