Gas Turbine Control 4

HPEP,RC Puram

Speedtronic® Mark V Turbine Control System

Gas Turbine Rotating Blow Torch Designed to Run at the Ragged Edge of Self Destruction

C

T

G

Control 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 loops 

Major Control loops   



Secondary control loops

Start-up Speed and Temperature

Acceleration Manual FSR and Shutdown

Output of these control loopsDisplay is fed to a minimum value gate Fuel circuit Temperature Display Speed

Acceleration Rate Display Start Up Shut Down Manual

M I N

FSR

To Turbine

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.

Startup/Shutdown Sequence and Control  Startup 

Zero speed up to Operating speed.

 Allows 

control brings the gas turbine

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 

Command signals to Turbine Accessories, Starting device and Fuel control system

 Safe 



Sequencing involves

and successful start-up

depends on proper functioning of GT equipment.

Software Sequencing ensures safe operation of Turbine

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 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)

M/s

Startup/Shutdown Sequence and Control  Actual

settings of speed relays are listed in Control

specification.  The

control constants are programmed in

processors EEPROM.  Always

ensure correct site specific, machine

specific control specification.  Consult

your system designer for any queries.

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

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

FSR MIN

FSRSYN FSRMAN

FSR = FSRSU

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



Shuts down the hydraulic ratchet motor (88HR)

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

state.

control takes over after Warm-up

Acceleration Control - FSRACC  Acceleration

reference is a Control constant programmed in EEPROMS Typical

0.35 %/sec

0.10 %/sec 0%

40% 50% 75% 95% 100%

TNH

Acceleration Control - FSRACC FSRSU FSRACC FSRN FSRT

FSR MIN

FSRSYN FSRMAN

FSR = FSRACC

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

FSRN

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 

95% (min) to 107% (max) for a generator drive turbine

 Start-up 

Speed (TNR) range

speed reference is 100.3%.

This is preset when START signal is initiated.

 Turbine

follows 100.3% TNH for synchronization

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

Speed control becomes Load control loop

Control:



Isochronous Speed control



Droop Speed Control

Isochronous Speed Control

TNH

FSRNI

TNR FSRSU FSRACC FSRN (or FSRNI) FSRT

MIN

FSR

FSRSYN FSRMAN

FSR = FSRN

Droop Speed Control  Droop



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’ Droop 104% settin g

FSNL

100 %

95% Min TNR

Full Speed No Load FSR

Speed Reference TNR

104 %

100% Setpo int

Low Speed Stop

FSR

Rated FSR



Control is a proportional control.

Speed/Load Control loop Raise

Rate

Lower

Speed Ref. Command

LOG SETPOIINT

Rate

Speed Target MANUAL SETPOINT

Power

Primary Os

Speed Error

Preset Ememrgency Os

Mechanical Os Load Raise Load Lower

Load Rate

Rate

LOG SET POIINT

Speed

Load Ref. Cmd MANUAL SET POINT

Preset

Load Setpoint

SPEED CONTROL

Speed Control Schematic SPEED CONTROL



FSNL TNR SPEED REF.

+

+

ERROR +

-

FSRN

SIGNAL

TNH SPEED DROOP

RST>

SPEED CHANGER LOAD SET POINT MAX. LIMIT

L83SD RATE L70R RAISE

L83PRES PRESET LOGIC

L70L LOWER

MEDIAN SELECT

PRESET OPERATING

START-UP or SHUT DOWN

L83TNROP MIN. SELECT LOGIC

MIN.

TNR SPEED REF.

Synchronising - FSRSYN  Automatic 

synchronization software

Algorithms programmed into controller and software.

 Bus

and Generator voltage are input signals to Protective core . 

Isolation transformers are built into core



software drives the synch check and system permissive relays. 

Sequencing and algorithms are programmed into EEPROM



hardware and software sends voted command to actual breaker closure.

Auto Synchronisation Speed

System Frequency

Raise Speed Speed Matching Lower Speed Speed Raise Volts Generator Volts

System Volts

Voltage Matching Lower Volts

Synchronising Scheme AUTO SYNCH PERMISSIVE Gen Volts

A A>B

REF

B AND

Line Volts REF

L83AS Auto Synch Permissive

AUTO SYNCH

A A>B B

Calculated Phase within Limits Calculated slip within Limits Calculated Acceleration Calculated Breaker Lead Time

AND

L25 Breaker Close

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

FSRT

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

air

C

T

ISO FIRING TEMP TC

Exhaust temperature (Tx)



Co Isothermal ns tF irin gT em p( Lin ea riz ed )

Compressor Discharge Pressure (CPD)

Firing Temperature  Firing

 



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 > TC

Exhaust temperature (Tx)



temperature can also be approximated as

Co Isothermal ns tF irin gT em p( Lin ea riz ed )

Fuel Stroke Reference (FSR)

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



Temperature reference selection.

Temperature Control Schematic



If ONE Controller should fail, this rogram ignore the readings from the ailed Controller. TTXM is based on emaining controllers thermocouples. Alarm will be generated Temp Control Ref

TTXDR TTXDS TTXDT

QUANTITY of TC’s Used

CORNER

+

-

REJECT HIGH AND LOW

AVERAGE REMAINING

TTRXB

SLOPE

MIN. SELECT

-

+ -

CORNER ISOTHERMAL 

REJECT LOW TC’s

TTXM

FSRMIN FSRMAX

+

SLOPE

FSR

SORT HIGHEST TO LOWEST

Temperature Control -

CPD

To Comb. Monitor

TTXD2

TTXM

+

+ -

MEDIAN SELECT

+

FSRT

+

GAIN

FSR

The temp-control-command program in compares the exhaust temp control setpoint (calculated in the temp-control-bias program and stored in computer memory) TTRXB to the value to determine temp error. The software program converts the temp error to a FSRT

TTX

Temperature Control Bias program

SELECTED TEMPERATURE REFERANCE TABLE

TT Kn _B

COMPUTER MEMORY

TEMPERATURE CONTROL BIAS PROGRAM

Exhuast Temperature

DIGITAL INPUT DATA

COMPUTER MEMORY

CONSTANT STORAGE

TTKn_K

TTKn_I

Isothermal

TTKn_C CP D

FS R BI AS

BI AS

CPD FSR

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 temperaturereference table.

TT Kn _M

Exhaust Temp Control Setpoints 





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)

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 which is stored in the computer memory.

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

Temperature Reference Select

Digital Input Data

• When appropriate set of constants are selected they are stored in the selected-temperature-reference memory.

Constant Storage

Selected Temperature Reference Table

Temperature Reference Select Program

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 with Liquid fuel and/or gas fuel.

Servo 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 , 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 System  Liquid 

Fuel handling components – – – – – –



Fuel system consists of

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&ID FQ1



FSR1



FQROUT

TCQA

TCQA TCQC

TNH L4 L20FLX

Flow Divider

By-pass Valve Asm 65FP

77FD-1

Fuel Stop Valve

Typical Fuel Nozzles Combustion Chamber

Diff Press Guage

63FL-2

PR/A

Conn.For Purge When Required

OFV

AD

VR4

OF Main Fuel Pump Accessory Gear Drive

33FL OLTControl Oil

77FD-2 77FD-3

Atomizing Air To Drain

False Start Drain Valve Chamber OFD

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

Therefore FQROUT ~~ FSR

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)

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 springloaded 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

P1

Fuel Supply

SRV

P 2

P3

GCV

To Turbine

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

–

Speedtronic control cards TBQB and TCQC

Fuel Gas System P&ID TCQC

FPRG POS2 FPG

POS1 FSR2

SPEED RATIO VALVE CONTROL

TBQB

GAS CONTROL VALVE SERVO

96FG-2A 96FG-2B 96FG-2C TRANSDUCERS

63FG-3

20 VG

GAS CONTROL VALVE POSITION FEEDBACK

VENT

COMBUSTION CHAMBER

Gas Control Valve

Stop Ratio Valve

GAS

TCQC

TCQC

P2 LVDT’S 96SR-1.2 TRIP Vh5-1 Dump Relay 90SR SERVO Hydraulic Supply

LVDT’S 96GC-1.2 90GC SERVO

GAS MANIFOLD

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 OFFSET GAIN



FSR2



L4

HI SEL

L3GCV

TBQC

Analog I/O

FSROUT

FSR2 goes through Fuel splitter algorithm. TCQC converts FSROUT to an analog signal. GAS P2 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.

GCV GCV Position Loop Calibration

Servo Valve

LVDT’S 96GC -1,-2

LVDT Position



FSR

Speed Ratio/Stop Valve 

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







GAIN OFFSET

FPRG

+

D

-

FPG

L4 L3GCV

During a trip or no-run condition, a posive voltage bias is placed on servo coils holding them in the “valve closed” position

SRV GAS

Op Cyl Posn Trip Oil

Servo Valve

A HI SEL

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

–

TNH

POS2

96FG-2A 96FG-2B 96FG-2C

96SR-1,2 LVDTs

Analog I/O Module

TBQB

Dump Relay

Hydraulic Oil

SRV Pres Calibration

P2 TNH

P2 = (FPKGNG x TNH) + FPKGNO

GCV & SRV schematic GAS FUEL CONTROL VALVE

GAS FUEL REFERENCE

GAS CONTROL FQROUT SERVO GAS CONTROL VALVE VALVE OUTPUT COMMAND OUTPUT

GAS CONTROL VALVE POSITION

GAS RATIO VALVE CONTROL GAS REQUIRED PRESSURE SPEED CONTROL VALVE` OUTPUT SPEED RATIO VALVE SERVO COMMAND MIDVALVE GAS FUEL PRESSURE OUTPUT SPEED RATIO VALVE POSITION

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 Mixed fuel operation logics and algorithms

Fuel splitter - software  FSR

is splitter into two signals FSR1 & FSR2 to provide dual fuel operation. FUEL SPLITTER

FSR is multiplied by the liquid fuel fraction FX1 to produce FSR1signal

MAX.LIMIT

A=B

L84TG Total Gas

A=B

L84TL Total LIQ

MIN.LIMIT

FSR1 is then subtracted from the FSR signal to generate FSR2 signal

L83FZ Permissives

MEDIAN SELECT

RAMP

Rate

L83FG Gas Select

FSR = FSR1 + FSR2

L83FL Liquid Select FSR

LIQ Ref FSR1 FSR2 GAS Ref

Fuel Transfer - Liquid to Gas, Gas to Liquid

Fuel transfer from Liquid to Gas STI NU

FSR2

FSR1 PURGE SELECT DISTILLATE

TIME

Transfer from Full Liquid to Full Gas.

STI NU

FSR1

FSR2 PURGE SELECT GAS

TIME

Transfer from Full Liquid to Mixture. FSR1

STI NU

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.

Transfer from Full Gas to Full Liquid

FSR2 PURGE SELECT GAS

SELECT MIX

TIME

Fuel Control System  Liquid 

To prevent the coking of the liquid fuel nozzles

 Mixed 





fuel Purge 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 System  IGV  



Bang-Bang type (2 position) Modulated

IGV modulates during   



system

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 Control

IGV Operation:



CSRGV CSRGV

IGV REF

During start-up IGV is fully closed (34º) from 0% to 83% of corrected speed.

CSRGVOUT

D/A HIGH SELECT

Analog I/O

Turbine speed is corrected to reflect the air conditions at 80ºF, this compensates for changes in air density as ambient conditions change. HYD.

CLOSE

SUPPLY

At Amb.Temp >80ºF TNHCOR < TNH At Amb.Temp TNH

I FH6 O N -1 U T

R

OPEN

P

90TV-1 2

1

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

A

OLT-1

C

TRIP OIL

VH3-1 D

C2 OD

ORIFICES (2)

HM 3-1

Inlet Guide Vane Operation 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. Fuel Open Max. Angle IGV ANGLE - DEG (CSRGV))

For Simple Cycle operation IGV move to full open position at preselected exhaust temperature, usually 700ºF. For Combined Cycle operation, IGV begins to move to full open pos. as exh.temp approaches Temp. Control ref. temperature

Simple Cycle (CSKGVSSR)

Combined Cycle (TTRX)

MIN Full Speed Angle Startup Program

(Normally IGVs begin open when Tx is within

Region Of Negative 5th Stage Extraction Pressure

30ºF of temp control Ref.) 0

100 100

Corrected Speed -% 0 (TNCHOR) FSNL

BASE LOAD EXHUAST TEMPERATURE

IGV Control Schematic Temp. Control Feedback Temp. Control Reference

Compressor Inlet Temp.

Speed

Manual Command

IGV Part IGV Part Speed Ref. Speed Ref.

IGV Position

Inlet Guide Vane Ref.

Servo IGV Output Command IGV Reference

Wet Low NOx Control Gas dP Gas Press Gas Gas Temp

Flow

Gas Fuel Flow Liq Fuel Flow Humidity

Injection Flow

Required Injection Flow

Select

Injection Flow

Power Augmentation Flow

Water Flow

Steam Steam Press Steam Temp

Steam Flow

Basic Injection Flow + _

Dead band Controller Lower

Injection Flow

Protection Systems  Turbine

protection system consists of number of subsystems  

which operate during each normal start-up and shutdown Few operate strictly during emergency and abnormal operating conditions.

 Protection  

Detect and alarm the failure. If the failure is of serious nature, protection system will trip the turbine.

 Protection 

systems are set up to

system responds to:

Simple trip signals like – –

low lube oil press switch high gas compressor discharge pressure etc….

Protection Systems 

More Complex parameters like

 To

–

Over speed

–

Over temperature

–

High Vibration,

–

Combustion monitor

–

Loss of flame etc…..

ensure the safety and safe operation of turbine

Speedtronic system is equipped with master control and protection circuit

Protection Systems  Turbine 

Trip Oil – – –

 Over  



Inlet orifice, Check Valves & Orifice network Pressure switches Dump valves

speed Protection

Electronic Over speed trip Mechanical Over speed bolt

Over temperature Protection  



Protection systems includes:

Over temperature alarm (L30TXA) Over temperature Trip (L86TXT)

Flame Detection and Protection System

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

Primary OS

Master Prot. Circuit

Over temp

GCV

Gas Fuel Control Valve

SRV

Gas Fuel Speed Ratio/ Stop Valve

Vibra tion Comb Monitor

Sec OS Loss Of Flame

Relay Voting Module

Master Prot. Circuit

20 FG

Bypass Valve Servo valve

Relay Voting Module

FUEL PUMP

20 FL

Liquid Fuel Stop Valve

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. 

Protective Signals

Manual Trip (When Provided)

Master Protection L4 Circuits

20 FG

Orifice And Check Valve Network

Gas Fuel Speed Ratio/ Stop Value

Gas fuel 12HA

Liquid Fuel Stop Valve

63HL

INLET ORIFICE OVERSPEED TRIP

20 FL

Liquid Fuel

63HG RESET Manual Trip

Gas Fuel Dump Relay Valve

OH

Over Speed Protection 

Electronic Over speed function is performed in and .  



TNH is compared with TNKHOS. When TNH>TNKHOS, turbine is tripped and latched till Reset. “ELECTRICAL OVERSPEED TRIP” is displayed in CRT.

TNH TNKHOS

12HP Manual Reset

Test

LK3HOST

Test Premissive

L86MR1



Manual Trip 

Overspeed Bolt

Master Reset

A>B

B

L12H To Master Set Prot And And Latch Alarm Msg

Reset

Mechanical Over speed system Consists of



OD

Trip Setpoint

TNKHOST



OLT

High Pressure Over Speed Trip HP Speed A

 

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 Protection Protects GT against possible damages against Over firing. ISO TRIP

1090º F

40ºF 40ºF

TTREF 1030ºF

OVER-TEMP. TRIP & ALARM. TTXM TTXOT3

TTRXB

25ºF 25ºF

ALARM CONTROL

CPD

A A>B B

TTXOT2

TTXOT1 L86MR1

TRIP

ALARM

A A>B B

TRIP Isothermal

A A>B B

L30TXA ALARM

O R Set And Latch

To Alarm Message And Speed Setpoint Lower

To Master Prot. And Alarm Msg

Reset

It is a backup protection system, operates only after the failure of temperature control system.

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

present.

300 pulses/sec when strong UV signal is

Flame Detection & Protection Speedtronic MK-V Flame Detection 28FD UV SCANNER

28FD UV SCANNER

28FD UV SCANNER

28FD UV SCANNER

ANALOG I/O (Flame Detection Channes)

TUEBINE PROTECTION LOGIC

FLAME DETECTION LOGIC

TURBINE CONTROL LOGIC

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

CRT DISPLAY

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.



L30TEST

30V

FAULT L39VF

OR FAULT

ALARM TRIP

A VF AB B A VT A>B B

ALARM L39VA SET AND L39VT LATCH

AND TRIP

RESET

Auto Or Manual Reset

Speedtronic control generates High Vibration Trip Vibration Transducer Fault

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

Combustion Monitor Algorithm

CTDA TTKSPL1 TTKSPL2

TTXC

Median Select Calculate Allowable Spread

TTXSPL Median Select

TTKSPL5 TTKSPL7 Constants

TTXD2 Calculate Actual Spreads

A A>B B

L60SP1

A A>B B

L60SP2

A A>B B

L60SP3

A A>B B

L60SP4

Speedtronic Control Software performs

Combustion Monitoring 1 High

18 Low

Actual Spreads TTXSP1 = High - Low TTXSP2 = High - 2nd Low TTXSP3 = High - 3rd Low Allowable Spread (Spread Limit) TTXSPL = Based on CTD & TTXM

 ALARM

- TTXSP1 => TTXSPL  TRIP - TTXSP1 > TTXSPL and TTXSP2 > 80% of TTXSPL and Low TC is physically next to the second to low TC  TRIP - 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 - TTXSP3 > 80% of TTXSPL

Trip Functions Primary Over speed Detected Emergency Over speed Detected Loss Of Speed Signal Vibration Trip Exhaust Over temp 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

OR

TRIP TURBINE