GT Control

Gas turbine control system   

   

Control of gas turbine is done by Startup control Acceleration control Speed control Temperature control Shut down control Manual control

How to determine operating condition



The sensors ,( detected turbine speed, exhaust thermocouple ,compressor discharge pressure,and other parameter)are used to determine the operating condition of the gas turbine

Fuel stroke reference (FSR)  



FSR is the command signal for fuel flow Control of gas turbine is done by the lowest FSR(FSR SU, FSR ACC ,FSRN, FSRT,FSR SD,FSR MAN) The lowest FSR value of the six control loop is allowed to fuel control system

Simplify control schematic

Control shem. block diagram

Start up/Shut down sequence and control 





Start up function objective Bring the gas turbine from zero speed to full speed safely by providing proper fuel to established flame and accelerate the turbine safely

Minimize the low cycle fatigue of the hot gas parts during the sequence

Speed detector 





Speed is the important parameter during start up because the sequence of start up is the relation of speed

Turbine speed is measured by magnetic pick up Speed detector sent signal to Mark V to convert electrical signal to be the turbine speed in percent or rpm.

Speed converter

Speed relay 

   

The speed relay that are used to control the sequence of start up L14HR Zero speed L14HM Minimum speed L14HA Acceleration speed L14HS Full speed

0.06 %

L14HR Zero Speed

0.31% 18% 19%

L14HP Spare speed signal

95% 90%

L14HF At field flashing speed

18% 15%

L14HM Minimum Firing Speed

50% 46%

L14HA Accelerating speed

96.4% 94.8% 60% 50% 8.4% 3.2%

L14HS Min operating speed

L14HC Auxiliary Cranking Speed Relay

L14HT Cool down Slow Roll Start Speed Relay

Start up control 



Operate as an open loop control using preset level of the fuel command signal FSR(Zero , Fire ,Warm up,Accelerate,) FSR level are set as control constant and calculation in the Mark V

17.5%

14.4% 30.6%

0.05%/s 5%/s

1 sec

Start up FSR

Start up curve

Fire shut down 

Fire shut down is an improvement over the former fuel shut off at L14HS drop out by maintaining flame down to lower speed to reduction the strain develop on hot gas path part

100 % FSRMAX -- Max Fuel Reference L83SDSET-- Preset FSRSD to Existing FSR L83SDMIN-- Set FSRSD to FSRMIN

FSRSD -- Shut down FSR Signal %

FSR -- Fuel Stroke Reference % FSRMIN -- FSR: Minimum % FSKSDn -- Shutdown FSR Ramp n L83JSDn -- Set FSRSD Ramp Rate to FSK SDn L83SDL-- FSRSD Lower Logic

L83SDR -- FSRSD Raise Logic FSRMIN-- FSR: Minimum % FSKSDB -- Shutdown FSR Ramp Dead band 0.1%

L60SDM -- FSRSD at Min FSR

L83SDSET

0.25 s

L94SDY

-- T.D. L94SD

L94SD

-- Shutdown with Breaker Open

L83SDSET

-- Preset FSRSD to Existing FSR

L83SDMIN

L60SDM

-- FSRSD at Min FSR

L83SDMIN

-- Set FSRSD to FSRMIN

L28CAN

-- Any Can Flamed Out

L83RB

-- Ramp to Blowout Selected

L94SD

-- Shutdown with Breaker Open

L4

-- Master protective signal

FSR Shut down ramp rate 0.1 %/sec 5 %/sec 0.05 %/sec 0.1 %/sec 1 %/sec 0.1 %/sec

0.1 %

L83JSD1

L94X

-- Turbine Shutdown

L83SDR

-- FSRSD Raise Logic

L4

-- Master protective signal

L83JSD1

-- Set FSRSD Ramp Rate to FSK SD1

L83SDL FSR Lower logic

L83 SDL will be logic true in the case of below - L60SDM logic false when FSRSD-FSRMIN >0.1 % - L83RB logic true when Flame out >1 sec or Flame ON but TNH 0.1 %

Flame ON TNHFSR bias Alarm will show GT.Operate by heavy oil(monitor nozzle plugging) if FSR bias >CPD bias alarm will show

CPD & FSR bias temp control

Temperature reference select program 

  

For temperature reference select,three digital input signal are decode (L83JTN) to select one set of constant i.e. Base load open cycle select Base load combined cycle select Peak load select

Temperature reference select program

Fuel control system 

Fuel control system will change fuel flow to the combustion in response to the fuel stroke reference signal(FSR) FSR1 call for liquid fuel flow FSR2 call for gas fuel flow FSR =

FSR1 + FSR2

Liquid fuel control system

Liquid fuel bypass servo valve

Liquid fuel control system 



When liquid fuel is selected and start. The control system will check L4 logic(1). At minimum speed L20FLX(FO. trip valve) and L20CF(fuel oil clutch) will energized. When GT. Firing FSRSU will go to control turbine through fuel splitter and liquid fuel flow command FQROUT will demand to fuel oil by pass valve to control liquid fuel flow to combustion chamber.

Liquid fuel flow diagram FSRSU FSRSD FSRT FSRN FSRMAN

Min sel

FSR

Fuel Splitter

FSR1

Fuel flow Command

FQROUT Bypass Servo Command

DC mA

Servo valve

Liquid fuel flow control

FSR1V1 Fuel splitter Mixed Fuel Operation Completely on Liquid Fuel

Completely on Gas Fuel Fuel change permissive

3.3 %SP/s

Fuel Split Transfer Rate

Fraction of Liquid Fuel

Fraction of Liq Fuel Set point Command Increase Liquid Fuel Increase Gas Fuel Fuel Stroke Reference Fuel Splitter Liquid Fuel Purge Level

Fuel Splitter Gas Fuel Purge Level

Liquid Fuel Stroke Ref from Fuel Splitter 0.5 %

Gas Fuel Stroke Ref from Fuel Splitter 0.5 %

Liq Fuel Flow Reference Angle %

Liquid Fuel Stroke Ref from Fuel Splitter %

Liquid fuel bypass valve servo command[65FP-1]

Turbine Speed % Liquid Fuel Stop Valve Control Signal Master protective signal Calibration position reference % Calib selection command pass code Flow divider mag pickup speed Excessive Liq Fuel Startup Liq Fuel Bypass Valve Flow Detection Trouble Set point Liq fuel bypass valve servo current 30 % 10 sec

Liquid Fuel Flow High (trip ) 8.5 %

3%

Liq Fuel Bypass Valve Flow Detected Trouble Alarm

LF. Byp. Vlv. Servo Current Trouble Alarm

Master reset ALM171:'LIQUID FUEL CONTROL FAULT'

System check from flow divider and servo valve 

 



Excessive flow on start up (trip GT. If excessive flow exist during warm up period) L60FFLH LVDT. Position feed back Bypass valve is not fully open when stop valve is close Loss of flow divider feed back

Fuel gas control system 





Fuel gas flow is controlled by the gas speed ratio stop valve (SRV) and Gas control valve (GCV) SRV is designed to maintain a predetermined pressure(P2)at the inlet of gas control valve as a function of gas turbine speed GCV plug is intended to be proportional to FSR2 for fuel gas flow

GVC & SRV control block diagram FSRSU FSRSD FSRT FSRN

Min sel

FSR

Fuel Splitter

FSR2

GCV. Command

FSROUT

Gas Servo Command

DC mA

Servo valve 96GC

FG. Flow Control

Servo valve 90SR

FG. Press Control

FSRMAN

SRV. SRV. FPRGOUT Servo ComCommand mand

DC mA

GCV. Schematic diagram

Gas control valve out put

Gas Fuel Stroke Ref from Fuel Splitter

Gas Fuel Stop Valve Open Master protective signal Calibration selection command pass code

Calibration position reference %

GCV servo command [65GC-1] %

SRV. Schematic Turbine Speed

Master protective Gas Ratio Valve Open

SRV. Out put signal Stop/Speed Ratio Valve Shutdown Command Set point

-40 psi

Gas Ratio Valve Control Press Ref (psi) Fuel Gas Press Ratio Control Gain 3.5146 psi/% Fuel Gas Press Ratio Control Offset

Gas Ratio Valve Control Press Ref psi

-17.88 psi

Stop/speed ratio valve servo command [90SR-1] psi

Fuel gas control and monitor alarm  







Excessive fuel flow during start up Loss of LVDT feed back on SRV and GCV

Servo current to SRV. detected prior to permissive to open Servo current to GCV. detected prior to permissive to open Inter valve pressure low

Gas Fuel Stroke Ref from Fuel Splitter % Position fdbck gas controlvalve [96GC-1] %

Gas control valve not following reference 3% 3 sec

5%

Gas control valve not following reference trip

5 sec

Position fdbck gas controlvalve [96GC-1] %

Gas control valve servo current %

-5 %

Gas Control Valve Position Feedback Fault

5%

Gas Control Valve Open Trouble Alarm

37.5 %

Gas Control Valve Servo Current Fault

Gas Fuel Stop Valve Open

3 sec

COMMAND PB Master reset

ALM133:'GAS CONTROL VALVE SERVO TROUBLE'

Position fdbck srv [96SR-1] % 33.3 %

-6.67 %

6.67 %

Startup Gas Fuel Stroke High

Stop/Ratio Valve Position FeedbackTrouble Alarm Lo

Stop/Ratio Valve Open Trouble Alarm

Speed ratio valve

servo current % 15 %

Gas Ratio Valve Open

Stop/Ratio Valve Servo Current Trouble Alarm

Interstage fuel gas press xmitter [96FG-2A] psi -5 psi

ALM134:'GAS FUEL INTERVALVE PRESSURE TROUBLE'

2 sec

COMMAND PB Master reset

ALM132:'GAS RATIO VALVE POSITION SERVO TROUBLE'

Dual fuel control 

  



Gas turbine are designed to operate by both FG & FO. The control has provide the following feature Transfer from one fuel to another Allow time for filling the line Mix fuel operation

operation of liquid fuel nozzle purge when operating totally on Gas fuel.

Fuel splitter schematic

Fuel transfer

Mix Fuel operation 

   

Limit on the fuel mixture are required to ensure Proper combustion Liquid fuel distribution Liquid fuel flow velocity Combustion ratio

Fuel transfer limit (For GE.9E)   

Transfer(select one fuel)prior to startup Do not transfer fuel below 30 MW. Do not operate mix below 30% rated gas flow or 60% gas at 30MW.(to avoid nozzle pressure ratio dropping below 1.25 and possibly causing combustion chamber pulsation.)

Fuel transfer limit (For GE.9E) 

Do not mixed below 10% rated liquid flow(to avoid excessive liquid fuel recalculation flow resulting in fuel over heating and possibly causing fuel oil pump damage.)

Mix fuel Allowable range curve Rated

MW NO

LOAD

MIXED OK

MIXED

No MIX

30 MW NO MIXED

0 100

30 70

60 40

90 10

100 % GAS % LIQ 0

Modulate Inlet Guide Vane 





Protect compressor pulsation by modulate during the acceleration of gas turbine to rated speed.

IGV modulation maintain proper flow and pressure to combustion. Maintain high exhaust temperature at low load when combined cycle application.

Modulate IGV control scheme.

IGV. Control control reference (CSRGV) L83GVMAX

CSRGV

86 DGA

CPD.

(IGV CONTROL REFERENCE) IGV part Speed

TNH.

MIN SEL

57 DGA MAX SEL

CLOSE OPEN

IGV MAN

L83GVMAN TTRX L83GVSS 371 c 1120 c TTXM

MIN SEL

IGV TEMP CON TROL

X

+

CSRGVX

IGV. Control Algorithm from Mark V Temp Control and Manual Control Ref Airflow Control Reference %

IGV on Temperature Control

1 DGA/%

Stator 17 IGV Gain VIGV Temp Control Airflow Ref Offset

0 DGA

IGV Manual Control Permissive 57 DGA 57 DGA

IGV at Minimum Position

Permissive Inlet Guide Vane Ref IGV Part speed control 86 DGA

VIGV. Reference Angle (DGA)

CPRS. OFF Line washing IGV at Maximum Position

Calibration position reference % Calibration selection command pass code

Turb inlet guide vane servo vlv command [90TV-1] DGA

IGV. Part speed reference 519 o F

Compressor Temperature Ratio

Speed Correction Factor

Max Comp Inlet Flange Temp

oF

HP Turbine Speed % VIGV Part Speed HP Corr Speed Offset % VIGV Part Speed HP Corr Speed Gain Open IGV Position VIGV Part Speed Ref Min Setpoint

Turbine Speed HP, Iso Corrected 77.320 %

6.786 86 DGA

34 DGA

DGA/% Part Speed VIGV Reference

IGV. Control control reference (CSRGV) L83GVMAX

CSRGV

86 DGA

CPD.

(IGV CONTROL REFERENCE) IGV part Speed

TNH.

MIN SEL

57 DGA MAX SEL

CLOSE OPEN

IGV MAN

L83GVMAN TTRX L83GVSS 371 c 1120 c TTXM

MIN SEL

IGV TEMP CON TROL

X

+

CSRGVX

From Where ?

CSRGVX TTXM TTRX CSKGVDB

2 deg F

X Min SEL

L83GVDB TTRXGVB

X

700 F 2048 F

CSRGVX

L83GVSS

X

TNGV CSKGVTPG CSKGVTC CSRGV L83GVMAN_CMD

2 deg F 4 sec

X

X

T

V = OUT 1+TS V

RESET OUT =V

IGV MAN

TTRX L83REC TTRXC TTRXR1 1.5 F/sec TTRXR2

-1 F/sec

TTRMINSEL

MED SEL

TTRX

X

X Z-1

IGV Temperature control (CSRGVX) Bias by FSR. , CPD. +X

FSR

X

42.707 %

Conner

+

X

L60TRF A A