OPERATING SEQUENCE The following flow chart pertains to typical operation of a Frame 6 gas turbine unit designed for generator drive application. The differences from unit to unit (which are based on the specific requirements of each unit) are not discussed here. Refer to the project or unit specific documentation for more details. Operational information includes startup and shutdown sequencing in the auto mode of operation. This is intended to cover normal operation and assumes that initial startup, calibration and checkouts have been completed and that the turbine is in the stand by mode ready for operation with ac and dc power available for all equipment, and all annunciators are cleared. The following flow chart lists operator control system and machine actions or events in the starting sequence of the gas turbine.
BHEL-GE Gas Turbine Services Ltd GTSTAR01-1001
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Gas Turbine Training Manual
NORMAL START
Operator Selects ‘ Normal ‘ Display “SHUTDOWN STATUS” } “ Not Ready to Start” } Displays “Off Cool Down” } “ Off Select” } Operator presses “ Auto” and then “ Execute” LED next to “AUTO” Comes on Steady
Protection System Checks Ready to Start Permissive 1. Generator Lockout relay is reset 2. Turbine is at zero speed 3. Lube oil tank temperature is normal 4. Over speed bolt is not tripped 5. Flame is not detected in all the scanners 6. OFF is not selected 7. Fuel valve is closed an lockout reset 8. Compressor or bleed valves are open 9. IGV’s are closed 10. Master Protective “4” logic is reset 11. , and Master Protective Agree 12. Emergency Lube oil Pump voltage is normal 13. Diesel Test is not in progress 14. Off line diagnostics are not in progress 15. , and communication links healthy 16. Generator breaker is open 17. Diesel warm up timer reset 18. Multiple starts counter reset
All Trip functions are checked to be in the “ Not Tripped” and reset
BHEL-GE Gas Turbine Services Ltd GTSTAR01-1001
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Gas Turbine Training Manual “Ready to Start” displayed “Not Ready to Start” goes off Operator presses “ Start” and then “ Execute” LED next to “ Start” is blinking
Base, Peak or Pre-selected load is not selected Communication link is healthy and reset Auxiliary checks are good Starting Device trip is reset Multiple start counter is reset Emergency Push button is reset Stop sequence is not in progress Generator breaker closing timer is reset Control is not in “OFF” mode
LED next to “ Start” is steady ON “Start Select” “ Sequence in Progress” displayed “ Off Cool Down” goes off “ Manual Initiated Starts” counter incremented Auto Synch permissive is latched Turbine speed reference TNR is preset to start value Multiple start timer is started Fast start system is disabled AC lube oil pump is started Hydraulic ratchet Pump is started (88HR) – if not done already Starting clutch solenoid energized (20CS) Jaw clutch is engaged and feedback is obtained through 33CSE Master Protective System Energizes ( L4) “Starting “ displayed “Ready to Start” goes off
BHEL-GE Gas Turbine Services Ltd GTSTAR01-1001
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Gas Turbine Training Manual
Auxiliary Hydraulic Pump is started (88HQ) Diesel stop valve is energized (20 DV) Diesel engine cranking motor starts for 5 seconds (88DC) Diesel engine starts and Diesel lube oil pressure pickups (63QD) Total starts counter is incremented by 1 Distillate Fuel forwarding pump is started: 5 sec later distillate fuel stop valve (20FD) is energized Liquid Fuel Purge solenoid valve (20PL) is de-energized
On Liquid? No
Gas Fuel Trip servo solenoid is energized (20FG) Liquid Fuel purge solenoid is energized (20PL)
Diesel engine reaches minimum speed (idle speed) Diesel engine goes on 2 minute warm up Warm up completes. Diesel engine accelerating Diesel engine accelerating Solenoid is energized (20DA-2)
Hydraulic ratchet starts continuous ratchet Turbine breaks away (L14HR becomes zero) “ Cranking” displayed “ Starting” goes off Starting clutch solenoid de-energized (20CS) Hydraulic ratchet pump shutdown NOTE: Jaw clutch is held engaged by the torque of diesel engine Diesel engine reaches its cranking speed (14DC) Diesel engine accelerating solenoid valve de-energized (20DA-2) Diesel engine cranking speed drops out (14DC) Diesel cranking speed locking solenoid energized (20DA-1) and speed stays constant
BHEL-GE Gas Turbine Services Ltd GTSTAR01-1001
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Gas Turbine Training Manual
On Gas?
Gas Fuel vent solenoid is energized (20VG)
No Turbine Air Inlet separator Motor (88TA) started (if used) Turbine accelerates to minimum firing speed (14HM)
Crank Select?
End of Sequence
No Auxiliary Turbine Vent timer energized (2TV) Ignition relay is energized after time out (2TVX) Spark plugs are energized (95SP) 60 second Firing timer is started (2TF)
No
On Liquid ?
Yes
Permissive for SRV to open is enabled Permissive for GCV to open is enabled Energizes Liquid fuel trip solenoid (20FL) Energizes fuel pump clutch solenoid (20CF) Permissive for Fuel Pump Bypass valve to operate is enabled
Fuel Stroke Reference (FSR) is set to Firing Value, which in turn is FSR OUT for Gas and FQROUT for liquid
BHEL-GE Gas Turbine Services Ltd GTSTAR01-1001
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Gas Turbine Training Manual “ Firing” displayed “Startup Control” displayed “ Cranking” goes off
Flame is detected in 2 out of 4 scanned
Yes
Flame is steady for 2 sec before firing timer Times out
Yes
FSR cuts back to warm up value “ Firing” goes off “Warming up” displayed
Fire Select?
End of Sequence
No
No
“ Failure to Fire” alarm appears • Operator presses “Crank” and then “Execute” • “Crank” LED comes steady ON • Operator presses “ Fire” or “ Auto” and then “Execute” • LED comes steady ON • Turbine vent timer is started for air purge
Warm up timer starts (60 sec) (2W) Turbine compartment vent fans are started (88BT) Fired hours timer is energized Fired starts counter is incremented by 1 After warm up timer times out, FSR is increased at a predetermined rate to the accelerate limit FSR Diesel engine locking solenoid is de-energized (20DA-1) Diesel accelerating solenoid is energized (20DA-2)
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Gas Turbine Training Manual
Turbine accelerates Turbine reaches acceleration set point (14HA) at approximately 50% speed Between 55 to 60% speed, diesel engine torque into turbine becomes low and the jaw clutch disengages as detected by the limit switch (33CS) and the diesel engine cool down timer starts. Diesel engine accelerating solenoid de-energizes and the diesel engine will idle until the cool down timer times out (5 minutes) Turbine accelerates further
At about 97% speed, 14HS speed relay picks up. Inlet Guide vanes solenoid energizes (20TV) to open IGV’s to 57 deg Compressor Bleed valves are closed Generator Field Flashing relay (41FX) picks up.
Turbine Exhaust Frame cooling fans are started (88TK-1 and 2) Auxiliary Lube Oil Pump is stopped Auxiliary Hydraulic Pump is stopped
Yes On Gas?
Energize Atomizing Air Bypass valve Solenoid (20AA)
Enables Operator to transfer From one fuel to the other Control system goes through complete sequence checks • Above operating speed (14HS) • AC Lube oil pump is off • DC lube oil pump is off • AC Hydraulic Pump is off • Jaw clutch is disengaged
BHEL-GE Gas Turbine Services Ltd GTSTAR01-1001
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Gas Turbine Training Manual “Complete Sequence” displayed “Sequence in Progress” goes off “Start Select” goes off Enables manual raise / lower of the turbine speed reference TNR. Closes compressor bleed valves (20CB), if not already closed Note : Shuts of black start inverter on black start “Run Status” displayed “Full Speed No Load” displayed “ Start up Status” goes off “ Cranking” goes off
Is Generator Synchronizing Selector in AUTO
End of Sequence
Synchronizing Control takes over to synchronize the unit
“Synh. Control” displayed “Speed Control” goes off. Synchronize Status” displayed “ Full Speed No Load” goes off. If Auto Synch permissives are OK, generator and lin are present an dabove the minimums, the control system will modultae FSR to bring the speed TNH to 100.3% of the station line frequency ande close the generator breaker when the phase angle is OK “ Synch Control” goes off “Startup Control” displayed
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Gas Turbine Training Manual
“Loading” displayed “Speed control” displayed
Pre-selected load is selected?
Turbine speed reference increase until the pre-selected load is reached “Pre-Selected” displayed “Loading” goes off “ Cranking” goes off
Base Select
End of Sequence
Unit goes to spinning reserve ; end of sequence “ Loading” displayed “Synchronizing” goes off
“ Spinning Reserve” displayed
Turbine speed difference increases until temperature control limit is reached. “ Temperature Control” displayed “Speed Control” goes off “ Base Load” is displayed “ Loading goes off”
End of Sequence
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Normal Shutdown
Operator presses “ Stop” then “ Execute” LED comes steady ON
“Stop Select” displayed “ Unloading” displayed “ Base Load” goes off “Temperature Control” goes off “ Sequence in Progress” displayed
Turbine Speed Reference TNR is reduced at a predetermined rate to unload the unit When the load is low enough to trip the reverse power relay, the generator breaker opens “ Unloading” goes off “ Fired Shutdown” displayed FSR is reduced at a predetermined rate to reduce speed of turbine Auxiliary Lube oil Pump is started when speed falls below 14HS Auxiliary Hydraulic pump is started when speed falls below 14HS Compressor bleed valves are open IFV is closed
On Liquid
Atomizing Air bypass solenoid de-energizes
Yes Turbine decelerates below the acceleration speed set point (14HA). At about 20% speed shutdown command is given to close fuel valves
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Gas Turbine Training Manual
No
On Liquid
Distillate Fuel forwarding pump shuts down Liquid Fuel Stop valve solenoid is de-energized and stop valve is closed Liquid Fuel Pump Clutch is disengaged
Liquid Fuel Air Purge Solenoid de-energized (20PL)
“Coasting Down” Displayed “ Stop Select” goes off “ Speed Control” goes off Turbine coasts down to zero speed (14HR) Turbine Inlet air dirt separator fan motor (88TA) is stopped if used Gas Fuel vent solenoid is deenergized (20VG) Starting clutch solenoid is energized (20CS) Jaw clutch engages Hydraulic ratchet starts “Sequence in Progress” displayed “ On Cool down” displayed
