GE frame 7FA, runback and trip


Thread Starter

khalil gaser

i work for plant 3 machines, 7FA one of the machines was run at 130 MW preselect load. and for 1 second, i loss the power in the MCC1e due to electrical trip.

after the power become normal i observed that the unit run-back to 6 MW in less than 3 secs, and these alarm appears:

01:17 Smoke detect - PEECC &PEECC battery compt alarms.
01:17 DWATT sensor failure - 01 remaining.
01:17 Lube oil pressure low
01:17 Emergency seal oil pump running,.
01:17 Emergency lube oil pump motor running.
01:17 startup control lockout alarm and unit and unit got run back from 130 MW
01:17 ARES fault - step to spinning reserve
01:17 PCC Bus #1E undervoltage .
01:17 PCC panel board undervoltage.
01:17 Aux hudrailic oil lag pump motor running.
01:17 Standby lube oil pump motor running.


after that i master rest the machine, check the motors, confirm that all the motors running on lead and the standby motors are normal, then start to increase the load gradually. but approximate @71, GT trip due to high exhaust temperature spread trip.

## and these is the alarms appear:
01:31 DLN high spread runback (QUAT disable) alarm.
01:31 Combustion trouble alarm
01:31 Unit tripped due to high exhaust temperature spread trip.


i want to know what is the reason that make the unit 1ST run-back? and also what is reason for the trip?

^^ hint:: the unit is running under MARK VIe, toolbox ST, the tuning system MBC is used also, unit already tuned and the performance test already succeeded.

for any details plz all send me email with the points you ask about::
my email is (([email protected]))
It sounds like the machines are relatively new (MBC (Model-Based Control, I presume) is pretty new to GE's machines). And, many F-class machines are monitored by one or more of GE's Remote Monitoring and Diagnostics Centers. Have you spoken with GE about this?

Without being able to see the application code running in the Mark VIe, it would be very difficult to say for certain what caused the runback. Just from looking at the information provided, I would say the cause of the runback was the "ARES fault - step to spinning reserve" condition.

The trip was the result of an excessive exhaust temperature spread, which was preceded by the "Combustion Trouble" alarm and the QUAT high spread alarm.