Starting a GE Gas Turbine


A former colleague of mine used to use a little rhyme to help operators remember the basic steps for starting a GE-design heavy duty gas turbine with a PC-based operator interface:


Once the unit is started, and possibly a load selection is made (see below), it will be necessary to close the generator breaker to produce electric power (I am presuming the Frame 5 is a generator drive; you didn't indicate otherwise).

Fuel Selection
If the unit is capable of operation on more than one fuel, it is important to select the fuel to be burned during starting BEFORE initiating a START. (That's because once the shaft reaches minimum firing speed during the start sequence the fuel can't be changed until the unit reaches approximately 95% speed, and it would be necessary to STOP the unit to change fuel if the desired fuel wasn't selected BEFORE initiating the START.) When you click on the appropriate fuel there should be a confirmation dialog box that opens and you have to decide how to respond to continue.

Mode Selection
The usual operating mode for GE-design heavy duty gas turbines is AUTO mode, sometimes it's REMOTE mode. But, to get a 'READY TO START' indication it's necessary for the Master Control Select Function (the "MODE" selector) to be in some mode OTHER THAN OFF. When you click on the appropriate mode selection there should be a confirmation dialog box that opens and you have to decide how to respond to continue.

At this point, the Status Field of the Main Display (where the "buttons" are located) should display either 'READY TO START' or 'NOT READY TO START.' If the Status Field displays 'READY TO START' move to the next step. If the Status Field displays 'NOT READY TO START,' then you have to check the Alarm Display and/or the Start-Check Display (and possibly the Trip Display) to find out what condition(s) is(are) preventing the unit from starting (called "start-check" conditions, or permissives). The standard is that ANY condition that prevents the unit from being STARTed will have a Process Alarm associated with it. And, units with Start-Check Displays can make the process of reading through the Process Alarms to find out which one (or ones) is (or are) preventing a 'READY TO START.' Once the start-check conditions have all been satisfied, the Status Field will switch from 'NOT READY TO START' to 'READY TO START' and then the operator can initiate a START.

START Initiation
Click on START (and answer the dialog box that opens appropriately), and the unit will go into the starting sequence (purging; firing; and acceleration to rated speed (FSNL; Full Speed-No Load). Other than Alarm Management, the operator doesn't need to do anything else--the Mark* will handle all of the sequencing and control and protection.

Load Selection
If desired, it is possible after initiating a START to select the load you want the unit to go to after synchronization. There should be some buttons under the "Load Control" section, such as PRE-SELECT LOAD and BASE LOAD, and sometimes PEAK LOAD. PRE-SELECT LOAD allows the operator to designate (set) a particular load the unit is to go to and maintain after synchronization. You should see a button to click on to enter the desired load. Once the desired Pre-Selected Load reference is entered, then you can click on PRE-SELECT LOAD and after synchronization the unit will go to and maintain the load setpoint. Or, if you want the unit to go to full load, you can click on BASE LOAD and after synchronization the unit will automatically increase load to full load. (PEAK LOAD is a kind of "emergency" load capability to produce approximately 10% more power--but it's hard on the unit and not intended for continuous operation.)

Generator Synchronization
Once the unit reaches rated speed (FSNL, or Full Speed-No Load), it is most often necessary to initiate the synchronization process if the unit is in AUTO mode. (If the unit is in REMOTE mode, usually, the unit will go straight into synchronization and close the generator breaker.) Usually, if the unit is in AUTO mode there is a switch somewhere in the control enclosure to select either AUTOmatic or MANual synchronization. Just select AUTOmatic synchronization (it's well beyond the ability of this forum to teach anyone to manually synchronize the unit).

You should know that there are a couple of conditions that will prevent automatic synchronization (either in AUTO mode or REMOTE mode). One is that all of the auxiliary pumps (the Aux. L.O. Pump and the Aux. Hyd. Pump (if so equipped), as well as the Emer. (D.C.) L.O. Pump all have to be stopped in order for AUTOmatic synchronization to occur. There will be Process Alarms if the pumps are running when they should not be.

Hope this helps!