gas turbine control 4
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Speedtronic® Mark V Turbine Control System
HPEP,RC PuramHPEP,RC Puram
Gas Turbine
Rotating Blow Torch
Designed to Run at the
Ragged Edge of
Self Destruction
TC G
Control System for Gas TurbineControl System for Gas Turbine
Gas turbine is controlled Speedtronic control system Control loops includes
Start-up Acceleration Speed Temperature Shutdown and Manual Control functions
Speedtronic Control loopsSpeedtronic Control loops Major Control loops Secondary control loops
Start-up Acceleration Speed and Manual FSR and Temperature Shutdown
Output of these control loops is fed to a minimum value gate circuit
Start Up
Shut Down
Manual
MIN
Display
Speed
To Turbine
Fuel
FSR
Display
Display
AccelerationRate
Temperature
Speedtronic Control loopsSpeedtronic Control loops
Fuel Stroke Reference (FSR) Command signal for fuel flow
Controlling FSR Lowest of the six control loops Establishes the fuel input to turbine @ rate required by system
which is in control
Only ONE control loop will be in control at anytime. The control loop which controls FSR is displayed in operator
friendly CRT.
Startup/Shutdown Sequence and ControlStartup/Shutdown Sequence and Control Startup control brings the gas turbine
Zero speed up to Operating speed. Allows proper fuel to establish
Flame & Accelerate the turbine in such a manner as to minimize the Low cycle Fatigue of the hot gas path parts during the sequence
Software Sequencing involves Command signals to Turbine Accessories, Starting device
and Fuel control system Safe and successful start-up
depends on proper functioning of GT equipment. Software Sequencing ensures safe operation of
Turbine
Startup/Shutdown Sequence and ControlStartup/Shutdown Sequence and Control Control logic circuitry is associated not only with
actuating control devices, but enables protective circuits and obtains permissive conditions before proceeding.
Control settings play a vital role in determining the proper sequencing.
Actual site specific control settings are generated by M/s GEICS,USA.
Speed detection - by magnetic pickups L14HR Zero-Speed (Approx. 0% TNH) L14HM Min Speed (Approx.. 16% TNH) L14HA Accelerating Speed (Approx. 50% TNH) L14HS Operating speed (Approx..95% TNH)
Startup/Shutdown Sequence and ControlStartup/Shutdown Sequence and Control
Actual settings of speed relays are listed in Control
specification.
The control constants are programmed in <RST>
processors EEPROM.
Always ensure correct site specific, machine specific
control specification.
Consult your system designer for any queries.
Start-up Control - FSRSUStart-up Control - FSRSU Open loop control
Uses preset levels of fuel command
Various Fuel levels Zero, Fire, Warm-up, Accelerate and Max.
Typical values for Frame-6
Fire 15.62% Warm-up 11.62% Accelerate 19.82% Maximum 100%
Open Loop ControlOpen Loop Control
Start-up Control - FSRSUStart-up Control - FSRSU
Startup control FSR (FSRSU) signal operates through the MIN value gate to ensure other control functions can limit FSR as required.
FSRSUFSRSU
FSRACC
FSRN
FSRT
FSRSYN
FSRMAN
MINFSRFSR
FSR = FSRSUFSR = FSRSU
Start-up Control - FSRSUStart-up Control - FSRSU Speedtronic Control Start-up software
generates Fuel command signal (FSR).
Speedtronic Control Software also sets the
MAX and MIN limits for FSR for Manual
Control FSR
[ FSRMIN < FSRMAN < FSRMAX ]
When Turbine Breaks away (starts to rotate) L14HR pick-up
Starting clutch solenoid 20CS de-energizes
Shuts down the hydraulic ratchet motor (88HR)
Acceleration Control - FSRACCAcceleration Control - FSRACC
Acceleration control software compares the present value of Speed signal with the value at the
last sample time. Difference between these two numbers is a measure of
acceleration.
When actual acceleration is greater acceleration reference, FSRACC is reduced, which reduces FSR, thus reduction in fuel supply to turbine.
During startup-acceleration reference is a function of turbine speed.
Acceleration control takes over after Warm-up state.
Acceleration Control - FSRACCAcceleration Control - FSRACC
Acceleration reference is a Control constant programmed in <RST> EEPROMS
TNH
0.35 %/sec
100%0%
0.10 %/sec
40% 50% 75% 95%
TypicalTypical
Acceleration Control - FSRACCAcceleration Control - FSRACC
MINFSRFSR
FSRSU
FSRACCFSRACC
FSRN
FSRT
FSRSYN
FSRMAN
FSR = FSRACCFSR = FSRACC
Speed Control - FSRNSpeed Control - FSRN Speed Control System software
controls the speed and load of the gas turbine generator
in response to the actual turbine speed signal (TNH) and the called-for speed reference(TNR)
TNH
TNR
FSRN
Speed/Load Control Speed/Load Control
Speed/Load Reference:
Speed control software will change FSR in proportion to the
difference the actual turbine generator speed (TNH) and the
called-for reference (TNR)
Reference Speed (TNR) range
95% (min) to 107% (max) for a generator drive turbine
Start-up speed reference is 100.3%.
This is preset when START signal is initiated.
Turbine follows 100.3% TNH for synchronization
Speed/Load ControlSpeed/Load Control
Turbine Speed is held constant when Generator Breaker is
closed onto Power grid
Fuel flow in excess of the necessary to maintain FSNL will
result in increased power produced by the generator.
Thereby Speed control becomes Load control loop
Speed Control:
Isochronous Speed control
Droop Speed Control
Isochronous Speed ControlIsochronous Speed Control
TNH
TNR
FSRNI
MINFSRFSR
FSRSU
FSRACC
FSRN (or FSRNI)FSRN (or FSRNI)
FSRT
FSRSYN
FSRMAN FSR = FSRNFSR = FSRN
Droop Speed ControlDroop Speed Control Droop Control is a proportional control.
Any change in actual speed (grid frequency) will cause a proportional change in unit load.
This proportionality is adjustable to the desired regulation or ‘Droop’
104 %
Sp
eed
R
efe
ren
ce
TN
R 100 %
Low Speed Stop
FSNL
100% Setpoint
Droop 104% setting
Ra
ted
FS
R
Fu
ll S
pe
ed
No
Lo
ad
FS
R
FSR95%
Min TNR
Speed/Load Control loopSpeed/Load Control loop
SPEED CONTROL
MANUALSETPOINT
LOGSETPOIINT
Speed Target
Raise
Lower
Rate
Rate
Speed Ref.Command
Preset
Power
Speed Error
Speed
Load Setpoint
MechanicalOs
Ememrgency Os
Primary Os
LOGSET
POIINT
Load Raise
Load Lower
Load Rate
Rate
Load Ref.Cmd
Preset
MANUALSET
POINT
Speed Control SchematicSpeed Control SchematicSPEED CONTROLSPEED CONTROL <RST>
FSNL
TNRSPEED REF. ERROR
SIGNAL
+
-
+ +
FSRNFSRN
TNHSPEED
DROOP
SPEED CHANGER LOAD SET POINTSPEED CHANGER LOAD SET POINT
TNRSPEED REF.
MAX. LIMITL83SDRATE
L70RRAISE
L70LLOWER
L83PRESPRESET LOGIC
PRESET
OPERATING
START-UP
or SHUT DOWN
L83TNROPMIN. SELECT LOGIC
MIN.
MEDIANSELECT
<RST>RST>
Synchronising - FSRSYN Automatic synchronization software
Algorithms programmed into <RST> controller and <P> software.
Bus and Generator voltage are input signals to Protective core <P>.
Isolation transformers are built into <P> core
<RST> software drives the synch check and system permissive relays.
Sequencing and algorithms are programmed into <RST> EEPROM
<P> hardware and software sends voted command to actual breaker closure.
Auto SynchronisationAuto Synchronisation
SpeedSpeedMatchingMatching
Speed
System
Frequency
Raise Speed
Lower Speed
VoltageVoltageMatchingMatching
Speed
System Volts
Raise Volts
Lower Volts
Generator Volts
Synchronising Scheme
<XYZ><XYZ>AUTO SYNCH
AND
Calculated Phase within Limits
Calculated slip within Limits
Calculated Acceleration
Calculated Breaker Lead Time
L25L25BreakerBreakerCloseClose
REF
REF
Gen VoltsA A>BB
ANDL83ASL83ASAuto SynchPermissive
A A>BB
<RST><RST>AUTO SYNCHPERMISSIVE
Line Volts
Temperature Control - FSRTTemperature Control - FSRT Temp.Control software/algorithms
limit fuel flow to the turbine to maintain internal operating
temperatures within design parameters of turbine hot gas
path parts.
Highest temperature is in the flame zone of
combustion chambers.
TTXM
TTREF
FSRT
Firing Temperature Firing Temperature Firing temperature - temperature of gas as it exits the
first stage nozzle. Speedtronic limits this firing temperature. Firing temperature is calculated by
thermodynamic relation ships GT performance calculations, and site conditions as a function of Exhaust Temp(Tx) and CPD
fuel
TCair
ISO FIRING TEMP TC
IsothermalConst Firing Temp (Linearized)
Compressor Discharge Pressure (CPD)
Exh
aust
tem
per
atu
re (
Tx)
Firing TemperatureFiring Temperature Firing temperature can also be approximated as
a function of Tx and Fuel flow (FSR) and as a function of Tx and Generator MW output Line of constant firing temperature are used in control
software to limit the gas turbine operating temp whereas the constant exhaust temperature limit protects the
exhaust system during start-up.
TA > TB > TC
TA TB TCIsothermalConst Firing Temp (Linearized)
Fuel Stroke Reference (FSR)
Exh
aust
tem
per
atu
re (
Tx)
Exhaust Temp control softwareExhaust Temp control software
Series of application programs written to
perform critical exhaust temperature control and monitoring.
Major function is
– Exhaust temperature control.
Software is Programmed for
Temperature control command
Temperature control bias calculations
Temperature reference selection.
Temperature Control SchematicTemperature Control SchematicTTXDR
SORT SORT HIGHESTHIGHEST
TO TO LOWESTLOWEST
TTXD2TTXD2
<RST>
AVERAGEAVERAGEREMAININGREMAINING
REJECTREJECTHIGHHIGHAND AND LOWLOW
REJECTREJECTLOWLOWTC’sTC’s
TTXDS
TTXM
To Comb.Monitor
TTXDT
QUANTITYQUANTITY<RST><RST>
If ONE Controller should fail, this
program ignore the readings from the
failed Controller. TTXM is based on
remaining controllers thermocouples. Alarm will be generated
of TC’s Usedof TC’s Used
ISOTHERMAL
CORNER
CORNER
SLOPE
SLOPEMIN.MIN.
SELECTSELECT
- +
- +
-+
+ -
FSRMINFSRMAX
TTRXB
TTXM
FSR
GAIN
+- +
+
MEDIANMEDIANSELECTSELECT
Temperature Control Temperature Control <RST><RST>
CPD
FSR
FSRT
Temp Control RefTemp Control Ref
The temp-control-command program in <RST> compares the exhaust temp control setpoint (calculated in the temp-control-bias program and stored in computer memory) TTRXB to the TTXM value to determine temp error. The software program converts the temp error to a FSRT
Temperature Control Bias programTemperature Control Bias program
TTKn_CTTKn_C
TTKn_ITTKn_I
TTKn_B
TTKn_BTTKn_M
TTKn_M
TTKn_KTTKn_KIsothermalIsothermal
FSR BIAS
FSR BIAS
CPD BIAS
CPD BIAS
Exh
uas
t T
emp
erat
ure
CPD FSR
Exhaust Temp Control Setpoints
DIGITALINPUTDATA
COMPUTERMEMORY
TEMPERATURECONTROL
BIASPROGRAM
COMPUTER MEMORY
CONSTANT STORAGE
SELECTED TEMPERATURE
REFERANCETABLE
Temperature Control Bias Temp control Bias program calculates the Exhaust
temp control setpoint TTRXB based on CPD data
stored in computer memory and constants from the
selected temp-reference table. This Program also calculates another setpoint based
on FSR and constants from another temperature-
reference table.
TTKn_C (CPD bias corner) and TTKn_S (CPD bias slope)
are used with the CPD data to determine the CPD
bias exhaust temperature setpoint. TTKn_K (FSR bias corner) and TTKn_M (FSR bias slope)
are used with the FSR data to determine the FSR
bias exhaust temperature setpoint. Program also selects isothermal setpoint
Final temp control Ref=MIN(FSR bias, CPD bias, Isothermal setpoint (TTKn_I)Final temp control Ref=MIN(FSR bias, CPD bias, Isothermal setpoint (TTKn_I)
Temperature Control Bias ProgramTemperature Control Bias Program This Program selects the minimum of the three set points, CPD bias, FSR bias, or
isothermal setpoint for the final exhaust temperature control reference. During normal operation with Gas or light Distillate fuels, this selection results in a CPD
bias control with an isothermal limit. CPD bias setpoint is compared with the FSR bias setpoint by the program and an
alarm occurs when the CPD setpoint exceeds the FSR bias setpoint. During normal operation with Heavy fuels, FSR bias setpoint will be selected to minimize
the turbine nozzle plugging on firing temperature. FSR bias setpoint is compared with CPD bias setpoint and an alarm occurs when the
FSR bias setpoint exceeds the CPD bias setpoint. A ramp function is provided in the program to limit the rate of setpoint change. Both Max
(TTKRXR1) and Min (TTKRXR2) change in ramp rates (slopes) are programmed.Typical rate change limit is 1.5deg F.
The output of this ramp function is the Exhaust temp.control setpoint which is stored in the computer memory.
Temperature Reference Select ProgramTemperature Reference Select Program Exhaust temperature control function selects control set points to
allow GT operation at firing temperatures. Temperature-control-select program determines the operational
level for control set points based on Digital input information representing temperature control requirements.
Three digital input signals are decoded to select one set of constants which defines the control set points necessary to meet the demand.
Typical digital signals areBASE SELECT, PEAK SELECT and HEAVY FUEL SELECT
• When appropriate set of constants are selected they are stored in the selected-temperature-reference memory.
Constant Storage
TemperatureReference
Select
Digital Input Data
SelectedTemperature
ReferenceTable
TemperatureTemperatureReferenceReferenceSelect ProgramSelect Program
Fuel Control systemFuel Control system
Turbine fuel control system will change fuel flow to the
combustors in response to the fuel stroke reference signal(FSR).
FSR actually consists of two separate signals added
together.
FSR = FSR1 + FSR2
FSR1 = Called-for liquid fuel flow
FSR2 = Called-for gas fuel flow
Standard fuel systems are designed for operation with
Liquid fuel and/or gas fuel.
Servo Drive SystemServo Drive System
Servo drive System The heart of Fuel Control System
3 coil Electro Hydraulic Servo Valve Servo valve is the interface between the electrical and
mechanical systems Servo valve controls the direction and rate of motion of
a hydraulic actuator based on the input current to the servo.
Servo valve contains three electrically isolated coils on the torque motor.
Each coil is connected to one of the three controllers <RST>, thereby redundancy is ensured if one of the controller fails.
A null-bias spring positions the servo so that actuator goes to the fail safe position when ALL power and/or control signal is lost.
Liquid Fuel SystemLiquid Fuel System Liquid Fuel system consists of
Fuel handling components– Primary fuel oil filter (low pressure)– Fuel oil stop valve - Fuel pump– Fuel bypass valve - Fuel oil pressure relief valve– Secondary fuel oil filter (High pressure)– Flow dividers - Combined Selector valve– False start drain valve - Fuel lines & fuel nozzles
Electrical Control components– Liquid fuel press sw (upstream) 63FL-2– Fuel oil stop valve limit sw 33FL– Fuel pump clutch solenoid 20CF– Liquid fuel pump bypass valve Servo valve 65FP– Flow divider magnetic pickups 77FD-1,2,3 and– Speedtronic Control cards TCQC and TCQA
Liquid Fuel System P&IDLiquid Fuel System P&ID
<RST>
Conn.For PurgeWhen Required
AtomizingAir
TypicalFuel Nozzles
CombustionChamber
FQROUT
FQ1
TCQATCQC
63FL-2
OF
Fuel StopValve
OFV
Diff PressGuage
FSR1
TNHL4L20FLX
<RST> <RST>
TCQA
PR/A
To Drain
False StartDrain Valve
Chamber OFD
AD
77FD-1
77FD-2
77FD-3
By-pass Valve Asm
AccessoryGearDrive
Main Fuel Pump
FlowDivider
33FL
OLT-Control
Oil
VR4
65FP
Fuel oil Control - SoftwareFuel oil Control - Software Control system checks the permissive L4 and L20FLX to allow FSR1
for closing the Bypass valve (closing bypass valve sends fuel to the combustors)
These signals control the opening and closing of the fuel oil stop valve. Fuel pump clutch solenoid (20CF) is energised to drive the pump when
the Stop valve opens. Fuel splitter algorithm ensures requisite FSR when FSR1 is active FSR1 is multiplied by TNH - to make it a function of speed (an
important parameter of Turbine) to ensure better resolution at the lower, more critical speeds where air
flow will be low. Net result is FQROUT- a digital liquid fuel flow command At Full speed, TNH does not change
Therefore FQROUT ~~ FSR
Fuel oil Control - SoftwareFuel oil Control - Software Analog signal is converted to digital counts and is used in the
controllers’ software to compare to certain limits as well as for display in CRT.
The checks performed by software program L60FFLH - Excessive fuel flow on start-up L3LFLT - Loss of LVDT position feedback L3LFBSQ - Bypass valve is not fully open when the stop
valve is closed L3LFBSC - Servo Current is detected when stop valve is
closed L3LFT - Loss of flow divider feedback
(L60FFLH persists for 2 sec and this fault initiates trip, L3LFT also initiates trip during start-up)
Fuel Gas SystemFuel Gas System Fuel gas is controlled by
Gas Speed ratio/stop valve (SRV) Gas Control Valve (GCV)(Both are servo controlled by signals from Speedtronic control panel and
actuated by spring acting hydraulic cylinders moving against spring-loaded valve plugs)
GCV controls the desired gas fuel flow in response to the FSR command signal.
SRV is designed to maintain a predetermined pressure (P2) at the inlet of the GCV as a function of turbine speed
SRV GCV
P1 P2 P3
Fuel Supply To Turbine
Fuel Gas SystemFuel Gas System
Gas Fuel System consists of Fuel handling components
– Gas Strainer - Speed Ratio/Stop Vlv assembly
– Control valve assembly - Dump valves
– Three pressure gauges -
– Gas manifold with ’pigtails’ to respective fuel nozzles
Electrical control components
– Gas supply press sw 63FG - Fuel gas press xducer(s) 96FG
– Gas fuel vent sol valve 20VG -LVDTs 96GC-1,2 & 96SR-1,2
– Electro hydraulic servo vlv 90SR & 65GC
– Speedtronic control cards TBQB and TCQC
Fuel Gas System P&IDFuel Gas System P&ID TCQC
SPEED RATIOVALVE CONTROL
TCQC
GAS CONTROL
VALVE SERVO
TCQC
GAS CONTROLVALVE POSITION
FEEDBACK
TBQB
StopRatioValve
GAS
63FG-3
FPRG
POS2
FPG
POS1
FSR2
96FG-2A
96FG-2C
96FG-2B
VENT
GasControlValve
COMBUSTIONCHAMBER
TRANSDUCERS
GAS MANIFOLD
P2
20VG
90SR SERVO 90GC SERVO
Hydraulic Supply
LVDT’S96GC-1.2
LVDT’S96SR-1.2 TRIP
Vh5-1 Dump Relay
Gas Control ValveGas Control Valve Gas Control Valve
GCV position is proportional to FSR2(Actuation of spring-loaded GCV is by a hydraulic cylinder controlled
by an Electro-hydraulic servo valve) GCV will open only when permissive L4, L20FGX and
L2TVX (purge complete) are true. – Stroke of the valve is proportional to FSR
FSR
ServoValve
GCVGASP2
LVDT’S96GC -1,-2
AnalogI/O
HIHISELSEL
FSROUT
TBQC<RST>
OFFSET
GAIN
FSR2
L4
L3GCV
<RST>
GCV Position LoopCalibration
LV
DT
Po
sit
ion
FSR2 goes through Fuel splitter algorithm. TCQC converts FSROUT to an analog signal. GCV stem position is sensed by LVDTs and
fed back to an op-amp on TCQC card to compare
with FSROUT input signal at summing junction. Op-amp on TCQC converts error signal and sends
to servo valve to drive GCV accordingly.
Speed Ratio/Stop ValveSpeed Ratio/Stop Valve
FPRG
<RST>
HISEL POS2
D A
OFFSET
GAIN
L4
L3GCV
<RST>TNH
+-
TBQB
AnalogI/O
Module
96FG-2B96FG-2C
96SR-1,2
96FG-2A
Op Cyl Posn
GAS
DumpRelayTrip Oil
SRV
LVDTs
ServoValve Hydraulic
Oil
FPG
P2
TNH
SRV Pres Calibration
It is dual function valve (It serves as a pressure regulating valve to hold a desired fuel gas pressure ahead of GCV) As a Stop Valve
- integral part of protection system Speed Ratio/Stop Vlv has Two control loops
Position loop similar to GCV Pressure control loop• Fuel gas pressure P2 at the inlet of GCV is
controlled by the pressure loop as a function of turbine speed (in proportion to the turbine speed TNH) to become Gas fuel press Ref FPRG
• TCQC card converts FPRG to analog signalP2 (FPG) is compared to the FPRG and the error signal is in turn compared with the 96SR LVDT feedback to reposition the valve as in GCV loop
– During a trip or no-run condition, a posive voltage bias is placed on servo coils holding them in the “valve closed” position
P2 = (FPKGNG x TNH) + FPKGNO
GCV & SRV schematicGCV & SRV schematic
GAS CONTROL VALVE COMMAND
GAS CONTROL
VALVEOUTPUT
GAS FUEL REFERENCESERVO OUTPUT
FQROUT
GAS CONTROL VALVE POSITION
GAS FUEL CONTROL VALVE
SPEED RATIO VALVE COMMAND
GAS CONTROL
VALVE`OUTPUT
SPEED
SERVO OUTPUT
REQUIRED PRESSURE
MIDVALVE GAS FUEL PRESSURE
SPEED RATIO VALVE POSITION
GAS RATIO VALVE CONTROL
Duel Fuel ControlDuel Fuel Control Turbines designed to operate on both liquid and gaseous
fuel systems are equipped with Control software accordingly. Control software performs the following:
– Transfer of one fuel to other on command– Allow time for filling lines with the type of fuel to which turbine operation is
being transferred.– Mixed fuel operation– Operation of liquid fuel nozzle purge when operating totally on gas fuel.
Software programming involves: Fuel splitter Fuel transfer- Liquid to Gas Liquid fuel purge Fuel transfer-Gas to Liquid Mixed fuel operation logics and algorithms
Fuel splitter - softwareFuel splitter - software
FSR is splitter into two signals FSR1 & FSR2 to provide dual fuel operation.
A=B
<RST><RST>
FUEL SPLITTERFUEL SPLITTER L84TGTotal Gas
L84TLTotal LIQMAX.LIMIT
MIN.LIMIT
MEDIANMEDIANSELECTSELECT
RAMP
L83FGGas Select
L83FLLiquid Select
L83FZPermissives
Rate
FSR
LIQ Ref FSR1FSR1
FSR2FSR2GAS Ref
A=BFSR is multiplied by the liquid fuel
fraction FX1 to produce FSR1signal
FSR1 is then subtracted from the
FSR signal to generate FSR2 signal
FSR = FSR1 + FSR2FSR = FSR1 + FSR2
Fuel Transfer - Liquid to Gas, Gas to LiquidFuel Transfer - Liquid to Gas, Gas to Liquid
Transfer from Full Gas to Full Liquid
Transfer from Full Liquid to Full Gas.
Transfer from Full Liquid to Mixture.U
NIT
SU
NIT
S
SELECT DISTILLATE
PURGE
FSR1
TIMETIME
UN
ITS
UN
ITS
PURGE
FSR2
UN
ITS
UN
ITS
PURGE
FSR2
SELECT GAS
SELECT GAS
FSR1
FSR1
FSR2
TIMETIME
TIMETIMESELECT MIX
– Fuel transfer from Liquid to Gas GT running on Liquid (FSR1) and GAS transfer
selected.
FSR1 will remain at its initial value,
FSR2 will step-up to slightly greater than
Zero value (0.5%). This opens the GCV
slightly to bleed down the inter valve volume.
The presence of a high pressure than that
required by the SRV would cause slow
response in initiating gas flow.
After delay of 30 sec to bleed down the P2
pressure and fill the gas supply line, the
software program ramps the fuel commands
FSR2 to increase and FSR1 to decrease at
a programmed rate through median select
gate. Fuel transfer completes in 30 sec.
Fuel Control SystemFuel Control System
Liquid fuel Purge To prevent the coking of the liquid fuel nozzles
Mixed fuel Operation Gas Turbine can be operated on both GAS & LIQ in any
proportion when operator choses to be on MIX mode.
Limits of fuel mixture are required to ensure proper combustion, gas fuel distribution and gas nozzle flow velocities.
% of gas flow must be increased as load is decreased to maintain the minimum pressure ratio across the fuel nozzle.
Modulated Inlet Guide Vane SystemModulated Inlet Guide Vane System IGV system
Bang-Bang type (2 position) Modulated
IGV modulates during acceleration of turbine at rated speed., loading and unloading of the generator deceleration of gas turbine
IGV modulation maintains proper flows and pressures, and thus the stresses in the compressor. Maintains minimum pressure drop across fuel nozzles in Combined cycle operations maintains high exhaust temperatures at
low loads.
Modulated Inlet Guide Vane ControlModulated Inlet Guide Vane Control
HYD. SUPPLY
<RST>
VH3-1
ORIFICES (2)
OLT-1
TRIP OILC
A
C2
IN
OUT
FH6-1
2 1
OD
D
R P
HM 3-1CLOSECLOSE
OPENOPEN
90TV-1
CSRGV
<RST>CSRGV IGV
REFD/A
CSRGVOUT
HIGH SELECT
AnalogI/O
IGV Operation:
During start-up IGV is fully closed (34º)
from 0% to 83% of corrected speed.
Turbine speed is corrected to reflect the air
conditions at 80ºF, this compensates
for changes in air density as ambient conditions
change.
At Amb.Temp >80ºF TNHCOR < TNH
At Amb.Temp <80ºF TNHCOR > TNH
Above 83% IGV open at 6.7º per % increase in
TNHCOR.
IGV open to minimum full speed angle 57º and
stop opening at 91% TNH
Inlet Guide Vane OperationInlet Guide Vane Operation
For Simple Cycle operation
IGV move to full open position at pre-selected exhaust temperature,
usually 700ºF.
For Combined Cycle operation,
IGV begins to move to full open pos.
as exh.temp approaches Temp.
Control ref. temperature
(Normally IGVs begin open when Tx is within
30ºF of temp control Ref.)
Fuel Open Max. Angle
Simple Cycle(CSKGVSSR)
Combined Cycle
(TTRX)
MIN Full Speed Angle
StartupProgram
Region Of Negative5th Stage ExtractionPressure
Corrected Speed -%(TNCHOR)
0 100
0 100
FSNL BASE LOAD
EXHUAST TEMPERATURE
IGV
AN
GL
E -
DE
G (
CS
RG
V))
By not allowing the guide vanes to close to an angle less than than the min full speed angle at 100%TNH, a min press drop is maintained across the fuel nozzles, thereby lessening combustion system resonance.
IGV Control SchematicIGV Control Schematic
Inlet GuideVaneRef.
Servo Output
IGVPart
Speed Ref.
Temp. ControlFeedback
Temp. Control Reference
ManualCommand
IGV Part Speed Ref.
Compressor Inlet Temp.
Speed
IGV Position
IGV Reference
IGV Command
Wet Low NOx ControlWet Low NOx Control
Select
+ _
InjectionFlow
SteamFlow
InjectionFlow
GasFlow
Dead bandController
Gas dP
Gas Press
Gas Temp
Gas Fuel Flow
Liq Fuel Flow
Humidity
Power Augmentation Flow
BasicInjection Flow
Lower Injection Flow
RequiredInjectionFlow
Steam
Water Flow
Steam Press
Steam Temp
Protection SystemsProtection Systems Turbine protection system consists of number of sub-systems
which operate during each normal start-up and shutdown Few operate strictly during emergency and abnormal operating
conditions.
Protection systems are set up to Detect and alarm the failure. If the failure is of serious nature, protection system will trip the turbine.
Protection system responds to: Simple trip signals like
– low lube oil press switch– high gas compressor discharge pressure etc….
Protection SystemsProtection Systems
More Complex parameters like
– Over speed
– Over temperature
– High Vibration,
– Combustion monitor
– Loss of flame etc…..
To ensure the safety and safe operation of turbine
Speedtronic system is equipped with master control and
protection circuit
Protection SystemsProtection Systems Turbine Protection systems includes:
Trip Oil – Inlet orifice, Check Valves & Orifice network– Pressure switches– Dump valves
Over speed Protection Electronic Over speed trip Mechanical Over speed bolt
Over temperature Protection Over temperature alarm (L30TXA) Over temperature Trip (L86TXT)
Flame Detection and Protection System
Protection SystemsProtection Systems
Vibration Protection High Vibration Alarm & Trip Vibration transducer fault Alarm
Combustion monitoring Spread calculations Exhaust Thermocouple Trouble
Alarm Combustion Trouble Alarm High Exhaust Temperature
Spread Trip Spread monitor enable
MasterProt.
Circuit<RST>
GCV
SRV
RelayVoting
Module
20FG
FUELPUMP
PrimaryOS
Overtemp
Vibration
CombMonitor
SecOS
LossOf
Flame
MasterProt.
Circuit<XYZ>
BypassValveServovalve
RelayVotingModule
20FL
Gas FuelGas FuelControlControl ValveValve
Gas FuelGas FuelSpeed Ratio/Speed Ratio/Stop ValveStop Valve
LiquidLiquidFuel StopFuel StopValveValve
Trip Oil SystemTrip Oil System It is a primary protection interface between the turbine control and
protection system and the components of the turbine which admit or shut-off, fuel.
System devices are electrically operated by Speedtronic control system as well as some totally mechanical devices.
MasterProtection
L4Circuits
20FG
20FL
63HL
Gas FuelSpeed Ratio/Stop Value
OH
Gas Fuel Dump Relay
Valve
63HG
Orifice AndCheck Valve
Network
Protective Signals
RESETManual
Trip
OVERSPEEDTRIP
INLET ORIFICE
Manual Trip(When Provided)
12HA
Liquid Fuel Stop Valve
Gas fuel
LiquidFuel
Over Speed ProtectionOver Speed Protection Electronic Over speed function is
performed in <RST> and <XYZ>. TNH is compared with TNKHOS. When TNH>TNKHOS, turbine is
tripped and latched till Reset. “ELECTRICAL OVERSPEED TRIP”
is displayed in CRT.
TNKHOST
TNHHigh Pressure Over Speed Trip
<RST> <XYZ><RST> <XYZ>
HP Speed
Trip Setpoint
Test
Test Premissive
TNKHOS
LK3HOST
L86MR1 Master ResetReset
SetAnd
Latch
L12H To Master
ProtAnd
AlarmMsg
A A>BB
ManualReset
ManualTrip
12HP
OD
Overspeed Bolt
OLT Mechanical Over speed system
Consists of Over speed bolt assembly in accessory
gear box. Over speed trip mechanism in the
assessory gear. Position limit switch 12 HA. Acts as a back-up control Trip setting > Electronic Setting
Over Temperature ProtectionOver Temperature Protection
Protects GT against possible damages against Over firing.
TTXOT3TTXOT3
TTXOT1TTXOT1
TTXOT2TTXOT2
TTXMTTXMOVER-TEMP. TRIP & ALARM.OVER-TEMP. TRIP & ALARM.
TTRXBTTRXB
L86MR1L86MR1
L30TXAL30TXAALARMALARM
To AlarmTo AlarmMessageMessage
And And SpeedSpeed
SetpointSetpointLowerLower
To To Master Master
Prot.Prot.And And
AlarmAlarmMsgMsg
TRIPTRIP IsothermalIsothermal
ALARMALARMA A A>BA>BBB
AA A>BA>BBB
A A A>BA>BBB
SetSetAndAnd
LatchLatch
ResetReset
OORR
TTREF
CPD
CONTROL
25ºF25ºF
40ºF40ºF
ALARM
TRIP
ISO TRIP1090º F
1030ºF
It is a backup protection system, operates only after the failure of temperature control system.
Flame Detection & ProtectionFlame Detection & Protection Speedtronic Mark-V flame detectors perform two functions
One in the Sequencing system other in Protective system
Flame detected by UV radiation. Speedtronic control furnish +350VDC to drive the UV detector
tube. In the presence of UV radiation, the gas in the detector tube ionizes and conducts current.
Speedtronic counts the no.of current pulses/sec through UV sensor.
Typically 300 pulses/sec when strong UV signal is present.
Flame Detection & ProtectionFlame Detection & Protection
TUEBINEPROTECTION
LOGIC
TURBINECONTROL
LOGIC
FLAMEDETECTION
LOGIC
ANALOGI/O
(FlameDetectionChannes)
28FDUV SCANNER
28FDUV SCANNER
28FDUV SCANNER
28FDUV SCANNER
CRTDISPLAY
Speedtronic MK-V Flame Detection
NOTE: Excitation for the sensor and signal processing is performed by SPEEDTRONIC Mk V circuits
<P>
Vibration ProtectionVibration Protection Gas Turbine unit comprises
Several independent vibration channels
Each channel detects excessive vibration by a seismic pickup
Each channel includes one vibration pickup (velocity type) and a Speedtronic Mark-V amplifier circuit.
Vibration detectors generate a relatively low voltage by the relative motion of a permanent magnet suspended in a coil and therefore no excitation is required.
Vibration protection system trips the turbine when vibration level exceeds predetermined level.
A A>BB
A A<BB
L30TEST
A A>BB
OR
AND
RESET
SETAND
LATCH
30V
FAULT
ALARM
TRIP
<RST>
VF
VA
VT
Auto Or Manual Reset
TRIPL39VT
ALARML39VA
FAULTL39VF
Speedtronic control generatesHigh Vibration Trip
Vibration Transducer Fault
Combustion MonitoringCombustion Monitoring Primary function
to reduce the likelihood of extensive damage to the gas turbine if the combustion system deteriorates.
Continuously examines the exhaust temperature and compressor discharge temperature thermocouples
Reliability of combustion monitor depends on condition of exhaust thermocouples.
Several software programs are written to achieve this
<RST><RST>
MedianSelect
CalculateAllowable
Spread
CalculateActual
Spreads
A A>BB
A A>BB
A A>BB
A A>BB
TTXSPL
L60SP2
L60SP3
L60SP4
CTDA
MedianSelect
TTKSPL1
TTKSPL2
TTKSPL5
TTKSPL7
Constants
TTXC
TTXD2
Combustion Monitor Algorithm
L60SP1
ALARMALARM - TTXSP1 => TTXSPL TRIPTRIP - TTXSP1 > TTXSPL and TTXSP2 > 80%
of TTXSPL and Low TC is physically next to the second to low TC
TRIPTRIP - TTXSP2 > 80% of TTXSPL and one TC is failed and 2nd lowest TC next to 3rd to lowest TC (a failed TC is defined as TTXSP1 > 5 x TTXSPL)
TRIP TRIP - TTXSP3 > 80% of TTXSPL
Combustion MonitoringCombustion Monitoring11 1818
HighHigh LowLowActual Spreads
TTXSP1 = High - Low TTXSP2 = High - 2nd LowTTXSP3 = High - 3rd Low
Allowable Spread (Spread Limit)TTXSPL = Based on CTD & TTXM
Sp
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dtr
on
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ftw
are
p
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orm
s
Trip FunctionsTrip Functions
OR
Primary Over speed Detected
Emergency Over speed Detected
Loss Of Speed Signal
Vibration Trip
Differential Expansion Trip
Low Lube Oil Level Trip
Low Lube Oil Pressure Trip
Low Servo Pressure Trip
Axial Position Trip
Generator Differential Fault
Manual Trip
Customer Trip
Exhaust Over temp Trip
TRIP TURBINE
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