Gas Turbine Control Philosophy

Gas Turbine

Rotating Blow Torch

Designed to Run at the

Ragged Edge of

Self Destruction

TC G

Speedtronic Control SystemSpeedtronic Control System

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