Gas Turbine Control 4

(1)

Speedtronic

®

Mark V

Turbine Control System

HPEP,RC Puram

(2)

Gas Turbine

Rotating Blow Torch

Designed to Run

at the

Ragged Edge of

Self Destruction

T

(3)

Control System for Gas Turbine



Gas turbine is controlled Speedtronic control system



Control loops includes

 Start-up

 Acceleration  Speed

 Temperature  Shutdown and

(4)

Speedtronic 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

M

I

N

Display Speed To Turbine Fuel FSR Display Display Acceleration Rate Temperature

(5)

Speedtronic 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.

(6)

Startup/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

(7)

Startup/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)

(8)

Startup/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.

(9)

Start-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 Control

(10)

Start-up Control - FSRSU



Startup control FSR (FSRSU) signal operates

through the MIN value gate to ensure other control

functions can limit FSR as required.

FSRSU

FSRACC

FSRN

FSRT

FSRSYN

FSRMAN

MIN

FSR

FSR = FSRSU

(11)

Start-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

(12)

Acceleration 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

(13)

Acceleration 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% Typical Typical

(14)

Acceleration Control - FSRACC

MIN

FSR

FSRSU

FSRACC

FSRN

FSRT

FSRSYN

FSRMAN

FSR = FSRACC

(15)

Speed 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

(16)

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.

(17)

Speed/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

(18)

Isochronous Speed Control

TNH

TNR

FSRNI

MIN

FSR

FSRSU FSRACC FSRN (or FSRNI) FSRN (or FSRNI) FSRT FSRSYN FSRMAN _{FSR = FSRN}_{FSR = FSRN}

(19)

Droop 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 % S p e ed R e fe re n ce T N R _{100 %}

Low Speed Stop FSNL 100% Setp_oint Droop 104_{% setting} R at ed F S R F u ll S p ee d N o L o ad F S R FSR 95% Min TNR

(20)

Speed/Load Control loop

SPEED CONTROL MANUAL SETPOINT LOG SETPOIINT Speed Target Raise Lower Rate Rate Speed Ref. Command Preset Power Speed Error Speed Load Setpoint Mechanical Os Ememrgency Os Primary Os LOG SET POIINT Load Raise Load Lower Load Rate Rate Load Ref. Cmd Preset MANUAL SET POINT

(21)

Speed Control Schematic

SPEED CONTROL SPEED CONTROL <RST> FSNL TNR SPEED REF. _ERROR SIGNAL + + + FSRNFSRN TNH SPEED DROOP

SPEED CHANGER LOAD SET POINT

TNR SPEED REF. MAX. LIMIT L83SD RATE L70R RAISE L70L LOWER L83PRES PRESET LOGIC PRESET OPERATING START-UP or SHUT DOWN L83TNROP

MIN. SELECT LOGIC

MIN.

MEDIAN SELECT <RST>RST>

(22)

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

(23)

Auto Synchronisation

Speed Speed Matching Matching Speed System Frequency Raise Speed Lower Speed Voltage Voltage Matching Matching Speed System Volts Raise Volts Lower Volts Generator Volts

(24)

Synchronising Scheme

<XYZ>

AUTO SYNCH

AND

Calculated Phase within Limits

Calculated slip within Limits

Calculated Acceleration Calculated Breaker Lead Time

L25 L25 Breaker Breaker Close Close REF REF Gen Volts A A>B B

AND L83AS_{Auto Synch}L83AS

Permissive A A>B B <RST> <RST> AUTO SYNCH PERMISSIVE Line Volts

(25)

Temperature 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

(26)

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

T

C

air

ISO FIRING TEMP T_C

Isothermal Con st F iring Tem p (L inea_rize d)

Compressor Discharge Pressure (CPD)

E xh au st t em p er at u re ( T x)

(27)

Firing 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.

T_A > T_B > T_C T_A T_B T_C Isothermal Con st F iring Tem p (L inea rize_d)

Fuel Stroke Reference (FSR)

E xh au st t em p er at u re ( T x)

(28)

Exhaust 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

(29)

Temperature Control Schematic

TTXDR SORT SORT HIGHEST HIGHEST TO TO LOWEST LOWEST TTXD2 TTXD2 <RST> AVERAGE AVERAGE REMAINING REMAINING REJECT REJECT HIGH HIGH AND AND LOW LOW REJECT REJECT LOW LOW TC’s TC’s TTXDS TTXM To Comb. Monitor TTXDT QUANTITY QUANTITY <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 Used of TC’s Used ISOTHERMAL CORNER CORNER SLOPE SLOPE MIN. MIN. SELECT SELECT + + -+ + -FSRMIN FSRMAX TTRXB TTXM FSR GAIN + - + + MEDIAN MEDIAN SELECT SELECT Temperature Control Temperature Control <RST><RST> CPD FSR FSRT

Temp 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

(30)

Temperature Control Bias program

TTKn_C TTKn_C TTKn_I TTKn_I TT Kn_{_B} TT Kn _B TT_Kn _M TT Kn_{_M} TTKn_K TTKn_K Isothermal Isothermal FS R B_IA S FS R B IA_S CP D B IAS CP D B IAS E xh u a st T em p er atu re CPD FSR

Exhaust Temp Control Setpoints

DIGITAL INPUT DATA COMPUTER MEMORY TEMPERATURE CONTROL BIAS PROGRAM COMPUTER MEMORY CONSTANT STORAGE SELECTED TEMPERATURE REFERANCE TABLE

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)

(31)

Temperature 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

(32)

Temperature 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 are BASE 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 Temperature Reference Select Digital Input Data Selected Temperature Reference Table Temperature Temperature Reference Reference Select Program Select Program

(33)

Fuel 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

(34)

Servo Drive System

(35)

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.

(36)

Liquid 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

(37)

Liquid Fuel System P&ID

<RST> Conn.For Purge When Required Atomizing Air Typical Fuel Nozzles Combustion Chamber FQROUT FQ1 TCQA TCQC 63FL-2 OF Fuel Stop Valve OFV Diff Press Guage FSR1 TNH L4 L20FLX <RST> _<RST> TCQA PR/A To Drain False Start Drain Valve Chamber OFD AD 77FD-1 77FD-2 77FD-3

By-pass Valve Asm

Accessory Gear Drive

Main Fuel Pump

Flow Divider 33FL OLT-Control Oil VR4 65FP

(38)

Fuel 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

(39)

Fuel 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)

(40)

Fuel 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

P

2 P3

(41)

Fuel 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

(42)

Fuel Gas System P&ID

TCQC SPEED RATIO VALVE CONTROL TCQC GAS CONTROL VALVE SERVO TCQC GAS CONTROL VALVE POSITION FEEDBACK TBQB Stop Ratio Valve GAS 63FG-3 FPRG POS2 FPG POS1 FSR2 96FG-2A 96FG-2C 96FG-2B VENT Gas Control Valve COMBUSTION CHAMBER TRANSDUCERS GAS MANIFOLD P2 20 VG 90SR SERVO 90GC SERVO Hydraulic Supply LVDT’S 96GC-1.2 LVDT’S 96SR-1.2 TRIP Vh5-1 Dump Relay

(43)

Gas 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 Servo Valve GCV GAS P2 LVDT’S 96GC -1,-2 Analog I/O HI HI SEL SEL FSROUT TBQC <RST> OFFSET GAIN FSR2 L4 L3GCV <RST> GCV Position Loop Calibration L V D T P o si ti o n

 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

(44)

Speed Ratio/Stop Valve

FPRG <RST> HI SEL _POS2 D A OFFSET GAIN L4 L3GCV <RST> TNH + -TBQB Analog I/O Module 96FG-2B 96FG-2C 96SR-1,2 96FG-2A Op Cyl Posn GAS Dump Relay Trip Oil SRV LVDTs Servo Valve _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

(45)

GCV & SRV schematic

GAS CONTROL VALVE COMMAND

GAS CONTROL

VALVE OUTPUT

GAS FUEL REFERENCE

SERVO 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

(46)

Duel 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

(47)

Fuel splitter - software



FSR is splitter into two signals FSR1 & FSR2 to provide

dual fuel operation.

A=B <RST> <RST> FUEL SPLITTER FUEL SPLITTER _L84TG Total Gas L84TL Total LIQ MAX.LIMIT MIN.LIMIT MEDIAN MEDIAN SELECT SELECT RAMP L83FG Gas Select L83FL Liquid Select L83FZ Permissives Rate FSR LIQ Ref FSR1 FSR1 FSR2 FSR2 GAS Ref A=B

FSR is multiplied by the liquid fuel fraction FX1 to produce FSR1signal FSR1 is then subtracted from the FSR signal to generate FSR2 signal

(48)

Fuel 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 N IT S U N IT S SELECT DISTILLATE PURGE FSR1 TIME TIME U N IT S U N IT S _PURGE FSR2 U N IT S U N IT S _PURGE FSR2 SELECT GAS SELECT GAS FSR1 FSR1 FSR2 TIME TIME TIME TIME SELECT 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.

(49)

Fuel 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

(50)

Modulated 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

(51)

Modulated Inlet Guide Vane Control

HYD. SUPPLY <RST> VH3-1 ORIFICES (2) OLT-1 TRIP OIL C A C2 I N O U T FH6 -1 2 1 OD D R P HM 3-1 CLOSE CLOSE OPEN OPEN 90TV-1 CSRGV <RST> CSRGV _IGV REF D/A CSRGVOUT HIGH SELECT Analog I/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

(52)

Inlet 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

Startup Program Region Of Negative 5th Stage Extraction Pressure Corrected Speed -% (TNCHOR) 0 ₁₀₀ 0 100 FSNL BASE LOAD EXHUAST TEMPERATURE IG V A N G L E D E G ( C S R G 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.

(53)

IGV Control Schematic

Inlet Guide Vane Ref. Servo Output IGV Part Speed Ref. Temp. Control Feedback Temp. Control Reference Manual Command

IGV Part Speed Ref. Compressor Inlet Temp. Speed IGV Position IGV Reference

IGV

Command

(54)

Wet Low NOx Control

Select + _ Injection Flow Steam Flow Injection Flow Gas Flow Dead band Controller Gas dP Gas Press Gas Temp

Gas Fuel Flow

Liq Fuel Flow

Humidity Power Augmentation Flow Basic Injection Flow Lower Injection Flow Required Injection Flow Steam Water Flow Steam Press Steam Temp

(55)

Protection 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

(56)

Protection 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

(57)

Protection 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)

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Protection 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

Master Prot. Circuit <RST> GCV SRV Relay Voting Module 20 FG FUEL PUMP Primary OS Over temp Vibra tion Comb Monitor Sec OS Loss Of Flame Master Prot. Circuit <XYZ> Bypass Valve Servo valve Relay Voting Module 20 FL Gas Fuel Gas Fuel Control Control Valve Valve Gas Fuel Gas Fuel Speed Ratio/ Speed Ratio/ Stop Valve Stop Valve Liquid Liquid Fuel Stop Fuel Stop Valve Valve

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Trip 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.

Master Protection L4 Circuits 20 FG FL20 63HL Gas Fuel Speed Ratio/ Stop Value OH Gas Fuel Dump Relay Valve 63HG Orifice And Check Valve Network Protective Signals RESET Manual Trip OVERSPEED TRIP INLET ORIFICE Manual Trip (When Provided) 12HA Liquid Fuel Stop Valve Gas fuel Liquid Fuel

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Over 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 TNH

High Pressure Over Speed Trip<RST> <XYZ><RST> <XYZ>

HP Speed Trip Setpoint Test Test Premissive TNKHOS LK3HOST

L86MR1 _{Master Reset} Reset

Set And Latch L12H To Master Prot And Alarm Msg A A>B B Manual Reset Manual Trip 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

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Over Temperature Protection

Protects GT against

possible damages

against Over firing.

TTXOT3 TTXOT3 TTXOT1 TTXOT1 TTXOT2 TTXOT2 TTXM TTXM

OVER-TEMP. TRIP & ALARM. OVER-TEMP. TRIP & ALARM.

TTRXB TTRXB L86MR1 L86MR1 L30TXA L30TXA ALARM ALARM To Alarm To Alarm Message Message And And Speed Speed Setpoint Setpoint Lower Lower To To Master Master Prot. Prot. And And Alarm Alarm Msg Msg TRIP TRIP Isothermal Isothermal ALARM

ALARM A _A>BA _A>B

B B A A A>B A>B B B A A A>B A>B B B Set Set And And Latch Latch Reset Reset O O R R TTREF CPD CONTROL 25ºF 25ºF 40ºF 40ºF ALARM TRIP ISO TRIP 1090º F 1030ºF

It is a backup protection system,

operates only after the failure of

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Flame 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

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Flame Detection & Protection

TUEBINE PROTECTION LOGIC TURBINE CONTROL LOGIC FLAME DETECTION LOGIC ANALOG I/O (Flame Detection Channes) 28FD UV SCANNER 28FD UV SCANNER 28FD UV SCANNER 28FD UV SCANNER CRT DISPLAY Speedtronic MK-V Flame Detection

NOTE: Excitation for the sensor and signal processing is performed by SPEEDTRONIC Mk V circuits

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Vibration 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>B B A A<B B L30TEST A A>B B OR AND RESET SET AND LATCH 30V FAULT ALARM TRIP <RST> VF VA VT

Auto Or Manual Reset

TRIP L39VT ALARM L39VA FAULT L39VF

Speedtronic control generates

High Vibration Trip

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Combustion 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> Median Select Calculate Allowable Spread Calculate Actual Spreads A A>B B A A>B B A A>B B A A>B B TTXSPL L60SP2 L60SP3 L60SP4 CTDA Median Select TTKSPL1 TTKSPL2 TTKSPL5 TTKSPL7 Constants TTXC TTXD2

Combustion Monitor Algorithm

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

ALARM - TTXSP1 => TTXSPL

ALARM



TRIP - TTXSP1 > TTXSPL and TTXSP2 > 80% of

TRIP

TTXSPL and Low TC is physically next to the

second to low TC



TRIP - TTXSP2 > 80% of TTXSPL and one TC is

TRIP

failed and 2nd lowest TC next to 3rd to lowest

TC (a failed TC is defined as TTXSP1 > 5 x

TTXSPL)



TRIP - TTXSP3 > 80% of TTXSPL

TRIP

Combustion Monitoring

1

18

18 High

High

Low

Actual Spreads

TTXSP1 = High - Low TTXSP2 = High - 2nd Low

TTXSP3 = High - 3rd Low

Allowable Spread (Spread Limit)

TTXSPL = Based on CTD & TTXM

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Trip 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