GEK106899 April 1998 Replaces SUSFSS01
GE Power Systems Gas Turbine
Starting/Shutdown Sequence and Control
I. GENERAL Starting the gas turbine involves proper sequencing of command signals to the accessories, starting device and fuel control system. Since a safe and successful startup depends on proper functioning of almost all of the gas turbine equipment, it is important to verify the state of selected devices in sequence. Much of the control logic circuitry is associated not only with actuating control devices, but enabling protective circuits, and obtaining permissive conditions before proceeding. Reference to the SPEEDTRONIC documentation is necessary for complete understanding of all the logic functions included for the particular equipment provided with a gas turbine. The operating sequences of the Control Specifications are written to explain significant functions which pertain to a specific gas turbine. A block diagram of all SPEEDTRONIC circuits which can interplay to control startup, is shown in Figure 1. Detailed descriptions are found in the SPEEDTRONIC panel information included in this manual and in the SPEEDTRONIC documentation. Utilize Figure 2, a plot of a typical startup, to aid in understanding the sequences described here. Startup and shutdown cycle improvements have been included to reduce low cycle fatigue of hot gas path parts. II. SPEED DETECTORS An important part of the startup/shut- down sequence control of the turbine is proper speed sensing. This is necessary for the logic sequences in startup and shutdown of the gas turbine. The following speed detectors and speed relays are used: L14HR Zero-Speed Detector (approximately 0% speed), L14HM Minimum Firing Speed Relay Detector (approximately 15% speed), L14HA Accelerating Relay Speed Detector (approximately 50% speed), and L14HS High-Speed Relay (approximately 95% speed), L14HP Purge Speed Relay detector (approximately 25% speed), and L14HT Turning Gear Operation Speed Relay (approximately 0.5% speed). The zero-speed detector, L14HR, provides the signal when the turbine shaft starts rotating. The Purge Speed Relay Detector indicates that the shaft has achieved purge speed. This speed is held until the Purge Timer times out. Speed relay L14HT indicates that the turning gear is running which permits static starter operation. The minimum speed detector L14HM indicates that the turbine has reached the minimum firing speed and initiates the purge prior to ignition. The dropout of the L14HM minimum-speed relay provides several permissive functions in the restarting of the gas turbine after shutdown.
These instructions do not purport to cover all details or variations in equipment nor to provide for every possible contingency to be met in connection with installation, operation or maintenance. Should further information be desired or should particular problems arise which are not covered sufficiently for the purchaser’s purposes the matter should be referred to the GE Company. 1998 GENERAL ELECTRIC COMPANY
GEK106899
Starting/Shutdown Sequence and Control
The acceleration speed relay L14HA pickup indicates that the turbine has reached approximately 50 percent in the acceleration cycle. The high-speed sensor L14HS pickup indicates that the turbine is at operating speed, and that the accelerating sequence is complete. Should the turbine and generator bog down, L14HS will drop out at the under frequency speed setting. The compressor bleed valves will open and inlet guide vanes will close as a function of corrected speed. Approximately 1.5 seconds after 14HS drops out the generator breaker will trip open and the digital setpoint will be reset to 100.3%. As the turbine accelerates, 14HS will pick up, and the inlet guide vanes will open. The turbine will then require a start signal before the generator breaker is permitted to close again. The actual settings of the speed relays are programmed in the controllers as constants and are listed in the Control Specifications. III. STARTUP CONTROL The startup control operates as an open loop control in the use of preset levels of the fuel command signal, FSR. The levels set are “FIRE”, “WARM-UP”, and “ACCELERATE LIMIT”. The Control Specifications provide proper settings calculated for the fuel anticipated. The FSR levels must be set in the SPEEDTRONIC startup control. Startup control FSR signals operate through the minimum value gate to insure that speed control and temperature control can limit FSR if required. During the starting sequence, rates of increase in speed and exhaust temperature are restricted to protect the turbine parts from excessive mechanical and thermal stresses. The rates of acceleration and temperature rise are controlled independently by the closed loops of the speed and temperature control systems. The rate limits operate through the SPEEDTRONIC control circuits discussed in those control systems. The fuel command signals are generated by the SPEEDTRONIC startup software. See the Control Sequence Program. In addition to the three startup levels, the software sets maximum and minimum FSR and provides for manual control of FSR. Pressing the switches for “MANUAL CONTROL” and “FSR GAG RAISE OR LOWER” allows manual adjustment of FSR setting between FSRMIN and FSRMAX. While the turbine is at rest, electronic checks are made of the stop/speed ratio valve, the gas control valve, the accessories, and the voltage supplies. At this time, the operator display will be normal and the “SHUTDOWN STATUS” will be displayed on the CRT. Activating the Master Operation Switch L43 from “OFF” to an operating mode will activate the ready circuit. If all protective circuits and trip latches are permissive the “STARTUP STATUS” and “READY TO START” messages will be displayed and indicates the turbine will accept a start signal. Depressing the “START” Master Control Switch (L1. START) will introduce the start signal to the panel. The start signal energizes the Master Control and Protection circuits (the L4 circuit), and starts the necessary auxiliary equipment. The turning gear is started. The start-up status message “STARTING” is displayed. See point A on Figure 2. The turbine rotor breaks-away, and the turning gear breaks away the turbine rotor to approximately 6 RPM. The purge timer is started once the static starter has brought the unit to Purge Speed. The purge cycle purges the turbine of any combustible mixture by forcing about four changes of air through the exhaust. At the end of the purge cycle, the torque converter is drained if applicable and the turbine speed is allowed to decay below firing speed (14HM drop-out speed). At this point the SPEEDTRONIC will require the static starter to maintain the turbine at the minimum firing speed.
2
Starting/Shutdown Sequence and Control
GEK106899
When turbine speed reaches the firing level (14HM pickup), startup control FSR is set at the “FIRING” level, the firing timer, L2F, is started, and fuel flow is enabled. See Point B on Figure 2. When flame detector output signals indicate flame is established in the combustion chambers, the warmup timer, L2W, starts and the startup fuel command FSR is set at the “WARM UP” FSR level. The warmup time is provided to minimize thermal stresses during the initial part of the startup. During warmup the starting device is set at the maximum acceleration torque position. At the completion of the warmup period, the startup control FSR command is ramped to the maximum allowable startup value. This setting is called the “ACCELERATE LIMIT”. The static starter begins to roll off once the unit reaches 85% speed and begins its reset sequence upon reaching 95% speed. During startup the startup control establishes the maximum FSR fuel command. Other controls may reduce FSR to perform their control functions. It is possible to reach the temperature control limit, speed control, or acceleration rate limit. The lowest FSR command is always selected to control fuel. The control parameter which is limiting or controlling is displayed on the control panel. IV. CONTROL MODE DISPLAY AND OPERATING CONDITION Display
Condition
STARTUP
Startup Program
ACCEL
Acceleration Control
DROOP SPEED
Speed Control
TEMP
Temperature Control
The startup cycle has been designed to moderate the highest firing temperature produced during acceleration. This is done by programming a low acceleration rate control setting during startup. It also aids smooth transition to speed control at the end of the startup sequence. The startup sequence time is extended to an optimum time to minimize strains produced on the hot gas path parts in mid-acceleration cycle. The minimum FSR limit is incorporated into temperature, acceleration and speed control circuits. This prevents these controllers from driving FSR below the value which would cause flameout during a transient condition. When the generator breaker closes, the startup control FSR command is quickly ramped to “MAX” FSR. Refer to Figures 1, 2, and 3 for starting sequence and control descriptions. V. FIRED SHUTDOWN A normal shut-down is initiated by selecting STOP from the control panel followed by execute. This activates the L94X signal. If the generator breaker is closed when the stop signal is initiated, FSR and load are reduced until the reverse power relay operates to open the generator breaker. When this occurs, FSR is ramped down as a function of corrected speed until the turbine reaches L14HM. Fuel to the turbine is shut off when the flame detectors indicate a loss of flame. Fuel is shut off by clamping FSR to zero and tripping the stop valve closed. In the event flame detection is maintained, fuel is turned off 60 seconds after turbine speed falls below the run-back speed setpoint (K60RB approximately 20% TNH). Cooldown sequence circuits ensure slow roll on turning gear until the cooldown timer expires.
3
GEK106899
Starting/Shutdown Sequence and Control
Operation Sel. Switch, L43
(Start-up Status) Message on CRT (Starting) Start/ Stop Circuits
Master Control Switch, L1
(Stop)
Protective Circuits
L4 TNH
Speed Level Detectors
(Ready to Start) (Seq. in Progress)
Master Protection “L4” Circuits
L14HM L14HA L14HS L14HR L14HP L14HT
Starting Device Logic
Purge L2TV, Fire L2F Logic (L14HM)
Speed Logic and Aux. Speed Relays
Flame Det.
(Cranking) To Start Device 20TU–1, –2, 20FG, 20FL (Firing) Spark Plugs
Ignition Circuit
Flame Det. Warm-up L2W L28FD
Complete Sequence L2TVX (Fire) L28FDZ (Warm-up) I2WX (Accel) L52GX (Max) L4
Four (4) Flame Detectors
Run Status Full Speed No.
(Warming Up)
Startup
(Accelerating) TNH
Speed Min. Gate
TTXD
Temperature Control System
Figure 1. Startup Sequence Flow Diagram.
4
FSR
Starting/Shutdown Sequence and Control
°
(Modulating IGV with HRSG Application)
%FSR, %TNH, 10X F, MW
120 °
Tx F
110 %TNH
100
Turbine Speed (TNH) Exhaust Temperature (TTXD) Fuel FSR (FSR) MW
90 MW
80 70
Tx %FSR
60 50 40 %TNH
30 20
%FSR
Standard Automatic Loading Rate of 12 Min. from No Load to Full Load as Shown. (4%/12 Min.)
10 0 0
5
10
15
20
25
30
35
40
Time (in Minutes)
B
5
Figure 2. Typical Startup/Loading (@ISO).
GEK106899
A
GEK106899
6 Ready to Start: Select Operation:
Energized if Power to Panel Servo Valve Checks and Voltage Checks Are Satisfied and No Trip Signal.
Master selector switch in Crank, Fire, Auto, Remote or Manual.
If “Check” Circuit Is Energized, Protective Status and Start Checks Are Satisfied.
Start Signal: Master Control Switch.
The Master Control/Protective Relays Are Energized, Which Results in Energizing Relays To: 1. Start Auxiliary Oil Pump 2. Pressurize the Control Oil System with Solenoid 20FL or 20FG 3. Engage the Starting Clutch
The Starting Means Is Started.
Turbine Is Accelerated to purge speed. Speed Relay L14HP is Energized & Turbine Timer (L2TV) Started When Turbine Reaches Minimum Fire Speed. Turbine Will Hold This Purge Speed Until L2TV Has Completed its Cycle. Fuel Is Held Shut off. FSR Is Zero.
No Flame Detected: Before L2F Timer Times out, Turbine Master Control/ Protective Circuit Trips the Turbine.
1
Turbine Speed Is Reduced Firing Speed. 2. Firing Timer Initiated. 3. Firing FSR Set. 4. Spark Plugs Are Energized.
FSR Reduced to Warm-up and Warm-up Timer Initiated.
Warm-up Time Complete: Startup Control Permits FSR to Ramp to FSR “Accelerate Limit” Acceleration Rate of Turbine Held Below Low-Cycle Fatigue Schedule Which Is a Function of TNH.
Speed Relays L14HA Indicates the Turbine Is in the Acceleration Phase of Start-up. L14HS Indicates the HP Turbine Has Reached the Min Governing Speed.
Figure 3. Starting Sequence.
Full Speed No Load: Indicated When L14HS Is Satisfied. The Turbine Will Trip if Complete Sequence Is Not Reached Before Incomplete Sequence Timer Times out.
Starting/Shutdown Sequence and Control
Flame Detected
Turbine Vent Timer Complete:
PAGE LEFT INTENTIONALLY BLANK.
GE Power Systems General Electric Company One River Road, Schenectady, NY 12345 518 • 385 • 2211 TX: 145354
GEK 106866A Revised, August 1999 Replaces LCGD03
GE Power Systems Gas Turbine
Loading Characteristics – General
I. GENERAL Once the unit has been synchronized either manually or automatically it can be loaded by several loading sequences. For instance, a unit can be loaded manually or automatically up to a temperature control limit, or a (KW) output load limit. More details on the actual control panel features are described in the Operation section of this manual. II. SYNCHRONIZING Automatic synchronizing is accomplished using a microprocessor synchronizing circuit. The circuit inputs are transmitted through an interface module. The interface module contains an isolation transformer for the generator and line input signals and the breaker closing relay. The synchronizing software is part of the SPEEDTRONIC computer. For synchronizing, the unit is brought to 100.3% of rated speed. If the system frequency has varied enough to cause an unacceptably high slip frequency a speed matching circuit in the synchronizer will adjust the turbine governor to reduce the slip frequency and permit synchronizing. For added protection a synchronism check relay is provided. It is used in series with both the auto synchronizing relay and the manual breaker close switch to prevent large out-of-phase breaker closures. III. FULL-SPEED, NO-LOAD The reason that the “Full-Speed, No-Load” adjustment is important is that it actually calibrates speed with the called-for speed using the digital setpoint. The 100.3% setpoint will cause an increase in fuel command necessary to raise the speed 0.3% above synchronous grid frequency. It is essential that the generator and system frequency be matched within 0.33 Hz to synchronize quickly with the synchronizing relay. “FullSpeed-No-Load” therefore is an important setting to assure proper speed for synchronizing. IV. LOAD CONTROL Speed load control increases fuel through the digital setpoint to maintain output value. Most units have three values of output control; reference to the Control Specifications for settings is required.
These instructions do not purport to cover all details or variations in equipment nor to provide for every possible contingency to be met in connection with installation, operation or maintenance. Should further information be desired or should particular problems arise which are not covered sufficiently for the purchaser’s purposes the matter should be referred to the GE Company. 1999 GENERAL ELECTRIC COMPANY
GEK 106866A
Loading Characteristics – General
1. Spinning Reserve — Once the generator breaker is closed, the turbine will load to this setting. 2. Preselected Load — This load is selected by giving the unit a second start signal after it is at spinning reserve. 3. Load Limit — The load is not selectable but is an output protection beyond which the unit is not permitted to operate. It is normally the material limit for the generator. V. MANUAL LOAD The operator may increase or decrease load between no-load and base temperature control line. The loading is accomplished by raising or lowering the digital setpoint. VI. TEMPERATURE CONTROL Temperature control is initiated by the switch 43BP. In this mode of control load is increased automatically until a temperature control limit is reached. Load is then held at a constant firing temperature as more fully described in the Temperature Control text. Turbine output in this mode of control is a function of ambient temperature. VII. LOAD RATE Load may be increased from FSNL to base load according to the following table for 4% droop: Non-DLN
DLN
Model Series
Manual
Normal
Fast Load
Manual
Normal
Fast Load
MS5001P
30 sec
4 min
30 sec
30 sec
4 min
2 min
MS6001B
30 sec
4 min
30 sec
30 sec
4 min
2 min
MS7001EA
6 min
12 min
90 sec
6 min
12 min
3 min
MS7001FA
6 min
12 min
90 sec
6 min
12 min
4 min
MS9001E
6 min
12 min
90 sec
6 min
12 min
3 min
MS9001EC
6 min
12 min
90 sec
6 min
12 min
3 min
MS9001FA
6 min
12 min
90 sec
6 min
12 min
4 min
MS6001FA
6 min
12 min
N/A
6 min
12 min
N/A
NOTE Manual load control is provided for full convenient rapid adjustment of load. It is not intended to be used to raise load to rated output without interruption. Frequent use of manual setpoint control to reach rated load rapidly can reduce hot gas path parts life. Similarly excessive use of “Fast Start” can also reduce hot gas path parts life.
GE Power Systems General Electric Company One River Road, Schenectady, NY 12345 518 • 385 • 2211 TX: 145354
