Presentation on Gas Turbine Instrumentation List of contents

Presentation on Gas Turbine Instrumentation

List of contents 1. GT introduction 2. Why Instrumentation system 3. Speedtronic system 4. Control schemes 5. Protection system 6. Startup & shutdown sequence 7. MARK-IV Hardware configuration 8. Introduction to MARK-V 9. Difference between MARK-IV &MARK-V

GAS TURBINE A machine which transfers fuel energy into mechanical energy AIR FUEL TO EXHAUST SD LOAD Starting device COMPRESSION HEAT ADDITION EXPANSION WORK DONE By heating up compressed air expanding it in nozzles mechanical/rotational energy is obtained

GAS TURBINE CYCLES (JOULE/BRAYTON) 3 2 3 P T 2 4 4 1 V 1 S 1 -2 COMPRESSION (COMPRESSOR) 2 - 3 HEAT ADDITION (COMBUSTION CHAMBER) 3 - 4 EXPANSION (TURBINE) 4 - 1 HEAT REJECTION

WHY GT GT is a mechanical driver can be used for driving, Compressor Generator Ships Air crafts Pumps

Single shaft machines Compressor & turbine are coupled to common single shaft Normally used in process where less speed variation is required Extremely suitable for generator drives Due to large rotor mass the speed can easily be kept constant

Two shaft machines Nozzle High pressure (HP) turbine & compressor are attached to one shaft Low pressure (LP) turbine are attached to another These machines provide wide speed range with sufficient power & efficiency By varying nozzle angle speed control is achieved considerably Well suited for mechanical drive (compressors & pumps ) More complex than single shaft machines (Ex. More no. of bearings)

GT should be protected from, *Over temperature *Over speed *Loss of flame *Vibration *High pressure *Fire Hence control system plays vital role for safe running of GT Any control system should be designed # To crank the turbine # Bring it to purging speed # Fire it (Heat addition ) # Bring the unit to operating speed # Synchronize the GT to line These sequences must occur automatically

> A dedicated control system designed by General Electric (G. E ), U. S. A > First Speedtronic system introduced in 1968 > The latest version of GE control system is Speedtronic Mark-V Speedtronic system takes care of, * Startup control * Speed control * Temperature control * GT protection * Control sequencing * Smooth shutdown & * power supply

Objective of Speedtronic system * Improved application flexiblity * Enhanced operator interface *A substantial decrease in GT outage rate * Softening of the startup cycle * High availability & reliability This is achieved by distributing control functions among powerful microcomputers. These computers continuously monitor GT performance round the clock

Control concepts Speedtronic system uses triple redundant configuration There are 3 identical sections to carryout diagnostics If one section fails the turbine continuous to run under control of remaining sections The failed section can be serviced and put back into service The fourth section is for communication purpose The 3 identical sections are named as <R>, <S>, & <T> which are powerful microcomputers The fourth section is named as <C> as communicator

MARK-IV Functional description Analog inputs Logic inputs (contacts) Analog outputs Memory Input hardware unit Processor Output hardware unit Software Logic outputs CRT Turbine mounted sensors monitors turbine operating conditions. The input hardware unit converts the analog & logic signals from these sensors into digital data for computation by the processor. The processor(CPU) calculates the analog & logic signals, required control, protection & sequencing of Gas turbine. The software (I. e. compute program)defines this computation. The output hardware unit then converts the digital results of these computations to physical analog & logic signals to activate devices like solenoids In general analog signals position servo valves and logic signals energize relays.

SPEEDTRONIC SCHEMATICS F I E L D S I G N A L S *Each computers <R>, <S> & <T> are connected independently. <R> <S> <T> Relay module Contact output Servos <C> OP. X-FACE Valve control * These computers are generally mentioned as <RST> signifying that they are identical. * All the critical sensors are distri-buted among <RST> such that each section has an independent assessment of turbine conditions. * Sensors that are not critical to operations are brought directly into <C> , to avoid extra I/O and processing in <RST>. *GT will continuous to run even if <C> computer fails.

Voting function *Output from 3 computers must be voted ordinarily 2 out of 3 are required * Critical outputs (like trip command )will be issued only if 2 or all 3 of <RST> computers indicates trip status. <R> 1 1 AND 0 1 <S> 0 1 Trip command 00 <S> 0 1 10 AND OR 00 <T> 0 0 <R> 1 1 AND # If only one computer (Ex. <R>= 1 ) gives trip command output will be ‘ 0’ It will not do any trip function. # If 2 computers ( Ex. <R>= 1, <S>= 1) give trip command output will be ‘ 1’ which will trip the GT. * This configuration is called 2 out of 3 voting

Logic voting CIM 1 -2 Field contact RDM OI <R> 2/3 OI <S> RD OI <T> 1/ 1 OI <C> CIM 3 -6 CIM - Contact Input Module. RDM - Relay Driver Module. RELAY NO NC COM. RD NO NC COM. After logic execution output from <RST> computers going to relay driver module Where it is getting hardware voted. If 2/3 voting is true, trip command goes to de-energize the relay coil. Contacts from this relay is used for final trip in the field. There is no 2/3 voting for contacts from <C> computer.

Sequential control Switch CIM : Contact Input Module <RST> RDM : Relay Driver Module * The sequential control is achieved by ladder logic (like PLC system ) * Contact input module (CIM ) receives close or open status from GT * Relay driver module ( RDM ) receives command signal from <RST> computers and sends it to the final control element (like solenoid valves, pumps etc.

Sequential control CIM 1 -2 Field contact RDM OI <R> 2/3 OI <S> RD OI <T> 1/ 1 OI <C> CIM 3 -6 CIM - Contact Input Module. RDM - Relay Driver Module. OI - Optical isolator. RELAY NO NC COM. RD NO NC COM. Totally there are 6 contact input modules (CIM). CIM 1 -2 are used for <RST> computers. Remaining CIM 3 -6 are used for <C> computer. All digital signals are isolated from the field by optical isolators, Where the signals also triplicate.

Analog control <RST> D/A SERVO VALVE * Analog / continuous control is achieved by servo valves which has 3 coils * Each computer drives one coil of 3 coil servo valve * Digital signals from <RST> computers are converted into analog signals by A/D converters before going to servo valves # TWO coils are enough to operate the servo valves

Analog control LVDT Vibration Pressure Speed Analog I/O module <R> Servo valve <S> TCM<R> <T> T/C’s TCM<S> TCM<T> TCM C 1 -C 3 med <C> Analog I/O module All analog & Thermocouple (T/C) signals are connected to <RST> & <C> computers via analog I/O & thermocouple cards. Analog control takes place in <RST> computers. <C> computer gives corrective or bias value for analog computation.

1. Maximum selector gate A B A>B C Analog input signals A & B are compared with one another. The logic output C becomes ‘ 1’ if A is greater than B, else C becomes ‘ 0’. 2. Minimum selector gate A B A<B C Here C becomes ‘ 1’ if A is less than B else it becomes ‘ 0’

3. multiplier A AXB B C Analog signals A & B are multiplied , the result equals C 4. Divider A B A/B C The output C equals the division of the inputs A & B

5 Clamper Minimum Maximum a(t) CLAMP The analog output C (t) equals a(t) unless C(t) is limited by either the constants specified as ‘Minimum’ or ‘Maximum’. 6. Median gate A B C Median selector gate Y This gate outputs intermediate value of inputs , I. e. it neglects minimum and maximum value. In median gate minimum and maximum value is defined by user.

Control system SPEEDTONIC system consists of 4 major controls, Fuel affecting control Special control (Nozzle control, IGV control etc. ) Protection system ( speed, temperature, pressure, etc. ) Startup &shutdown sequence

Protection system Trip algorithm. Protections : Flame, temp, pressure etc. DW FSR algorithm Tx TNH CPD GCV control SRV control TNH P 2 Fuel SRV P 2 GCV Inter valve pressure T N H

SRV control Fuel affecting control GCV control Fuel To combustion chamber SRV GCV SRV - Speed / Stop Ratio Valve GCV - Gas Control Valve Both SRV & GCV are SERVO VALVES which are operated by high pressure hydraulic oil. GCV is responsible for maintaining desired fuel flow. Basically it is a fuel control valve SRV does two functions, 1. It acts as a pressure regulating valve. Basically it is a pressure control valve 2. During emergency / normal shutdown it will be in full tight off position in order to to stop any further flow.

Principle of SRV control software Fuel SRV TNH P 2 Inter valve pressure To combustion chamber GCV SRV maintains downstream pressure P 2, (called as inter - valve pressure) constant ‘SRV control software’ receives ‘TNH’ signal and maintains P 2 according to control algorithm. If any trip occurs (TNH becomes zero) SRV becomes full tight shut off position and does not allow any further fuel flow.

SRV control Error amplifier <RST> TNH + + - Position feedback P 2 Fuel in SRV P 2 LVDT Cylinder Dump relay Servo valve Analog I/O module

SRV Characteristics P 2 inter valve pressure LVDT Characteristics LVDT output TNH SRV control is designed such that inter valve pressure is linearly related with TNH signal. LVDT is Linear Variable Differential Transformer, which gives linear output voltage Valve lift position (intern proportional to TNH signal ).

SRV control scheme * TNH (HP shaft speed )signal is linearly related with inter valve pressure, P 2. * TNH signal is fed to <RST> computers. * <RST> receives inter valve pressure, P 2 signal from 3 pressure transmitters. It also receives position feedback of servo valve from LVDT. *As TNH and P 2 are linearly related, depends upon TNH, <RST> computers maintains desired P 2 by issuing proper command. * The inter valve pressure signal P 2 is compared with TNH signal and the error signal (if any )is again compared with LVDT position feedback signal to reposition the valve. *In this way SRV maintains constant inter valve pressure, P 2 depending upon TNH signal.

During trip condition Gas fuel SRV No further fuel Cylinder Trip oil Dump relay Drain Servo valve Hydraulic oil in * Whenever trip condition exist trip logic actuates the trip oil *Trip oil intern actuates dump relay, which will drain all the high pressure hydraulic oil to drain line. * As there is no hydraulic oil SRV will suddenly come to shut off position.

Principle of GCV control GCV - Gas Control Valve Purpose : To maintain desired gas fuel flow. Start up control Speed control Acceleration control Temperature control Shut down control Minimum value selector gate Fuel in FSR GCV signal Manual control There are six independent fuel flow control algorithms , continuously monitor their own GCV opening ( generally called Fuel Stroke Reference - FSR ). These six results are fed to a minimum selector gate, which selects lowest among them. In this way the lowest value is assigned to FSR (fuel Stroke Reference) signal which determines Exact fuel flow to the gas turbine.

Brief over view The fuel flow to the GT is always determined by the lowest value of the following six FSR signal algorithms. 1. Start up control : (FSRSU) This control comprises the ignition, warm up, and the gradual rise of fuel flow to the acceleration. The algorithm output is ‘FSRSU’. 2. Speed / load control ; (FSRN) Fuel flow is adjusted by the speed control loop in such a way that the load demand is maintained. The controller algorithm is ‘FSRN’. 3. Acceleration control : (FSRACC ) This reduces the fuel flow in case of a too high acceleration of the rotor, Ex. Caused by loss of full load. This prevents excessive vibration. The algorithm output is ‘FSRACC’.

4. Temperature control : (FSRT) * This control reduces the fuel flow to prevent overheating of the GT The control algorithm output is ‘FSRT’. 5. Shut down control : (FSRSD) * This control reduces the fuel flow during a normal stop (I. e. from the moment that the generator breaker has opened until flame has extinguished ). * The control algorithm output is ‘FSRSD’. 6. Manual control : (FSRMAN ) The operator can enter a value of FSRMAN in this mode. *In this way an upper limit for FSR is established. *If this mode is not used that means FSRMAN = 100 % is the default value.

Startup control This control comprises the ignition, warm-up and the gradual raise of fuel flow for acceleration. Startup control is a open loop control which increases FSR signal as the GT startup sequence progresses to pre assigned plateaus. When the master protection signal (called as L 4 signal ) is healthy FSRSU becomes FSR during startup. First GT should be purged for blowing out present explosive fuel mixture Once the purging is over startup control initiates firing command, wait for sometime warm-up the engine and then gradually raise the fuel flow to accelerate the GT.

100% Gradual raise of fuel takes place to Warm-up period accelerate the GT to avoid thermal shock fuel level slightly decreased Firing starts. Flame detected FSRSU 35. 6 23. 8 18. 8 0% Purging period time FSRSU signal before reaching this point FSRN signal I. e. speed control loop will take over FSR control. So FSRSU will no longer comes into picture until next cycle starts Once the flame is detected by the flame detectors transition takes place from firing state warm-up state. After warm-up period is over gradual raise of fuel takes place until the control changeover to speed control loop.

Speed control Objective Fuel flow is adjusted by the speed control loop in such a way that the load demand is maintained Principle TNH TNR Speed control S/W Minimum select gate TNH - HP turbine shaft speed TNR - Speed reference corresponding to load The speed control S/W will change FSR in proportion to the difference between TNH and TNR

Droop mode Speed control Isochronoues mode Droop mode : This mode is generally used where the GT is coupled on a large grid system. As the generator is electrically locked to the grid, speed control of one GT is not possible but the speed reference will be used for load control. Load sharing is the main advantage of droop mode.

Droop mode configuration 100 % FSR min TNR + _ TNH + _ Droop correction factor + Clamper gate FSRN _ FSNL Full speed no load Speed controller on droop is a proportional controller It changes FSRN signal in proportion to the difference between turbine speed and speed reference. The error signal between TNR and TNH is corrected by droop correction factor and full speed no load level and then it is limited between 100 % and FSRMIN.

104 103 102 101 100 4% Droop % Speed TNR 0% Load 100% The speed control loop is used as load control loop The proportional setting is normally 4% droop. This means that the speed reference signal (TNR) range of 100% to 104% corresponds to a load range of 0% to 100%. So depends upon the load changes (0 - 100% ), speed reference signal (TNR) will vary and control software takes corrective action. As TNR is directly related with load it is also called load reference. In general TNR is called as speed/load reference.

FSR max FSRN % FSNL 0% 100% 0% Load TNR Droop 100% 104% 4% In droop mode depends upon the load conditions speed reference signal (TNH) is adjusted automatically. The controller algorithm position the FSRN signal according to speed reference change , which is a function of load.

Isochronous mode This mode is generally used for the purpose of stand alone operation of turbine - generator unit. FSNL Control software TNR T N H GCV valve GT Generator Speed sensor TNH In this mode the speed set point TNR is always 100% Here the generator load cannot be set by operator, the load is set by the consumer. As the load increases TNH signal will come down. the error between TNR&TNH will increase As long as the error exist control S/W keep on increasing the output until it reaches zero.

Temperature control Objective *Is to reduce the fuel flow to prevent overheating of the *To maintain constant firing temperature. NOTE Highest temperature point takes place in the combustion chamber (around 1200 ) It is practically not possible to measure the temperature at this point Combustion chamber temperature (called as firing temperature) is computed as a function of exhaust temperature and compressor discharge pressure according to thermodynamic laws. Firing temperature can also be computed as a function of exhaust temperature and amount of fuel flow (FSR signal). This can be used as back up, if CPD signal fails.

1. Firing temperature as a function of CPD Isothermal line Exhaust temperature TTRX Constant firing temperature (Tf) Tf = TTRX * (CPD)k CPD 2. Firing temperature as a function of FSR/LOAD Isothermal line Exhaust Constant firing temperature (Tf) As Tf is constant just by measuring CPD or FSR we can compute temperature exhaust temperature TTRX. This signal can be used as the TTRX Tf = TTRX * (FSR)k temperature control reference value. FSR

Temperature control algorithm receives actual exhaust temperature , TTXM from thermocouples. It computes corresponding exhaust temperature reference set point (TTRX) from compressor discharge pressure (CPD) and constant firing temperature. The difference between set point & measured value (TTRX - TTXM) goes as command signal to limit the exhaust temperature. Thermocouples Exhaust plenum The exhaust temperature is measured by 13 thermocouples, located around the exhaust plenum. This signal is called as TTXM.

How TTXM is measured ? 1 2 13 Receive all 13 T/C values Quantity 13 Sort high to low Reject all T/C less than constant Reject high & low T/C Average remaining TTXM constant <RST> computers receives 13 T/C readings and then it sorts out highest value to lowest value. Next it rejects all T/C’s less than some constant value. This step is to avoid bad T/C values Again it rejects highest & lowest values and then it calculates average of the remaining T/C’s. The final output is called as actual exhaust temperature TTXM

Acceleration control To prevent the over speed of the turbine if the load is rejected suddenly. To limit the rate of change of turbine speed to reduce thermal shock constant TNH Z-1 + + controller + + Mini select gate FSRACC FSR This control compares the present value of the speed signal with the value at last sample time(0. 25 second) The difference between these two values is the measure of acceleration. If the acceleration is greater FSRACC is reduced which will reduce FSR & consequently fuel to the GT.

Manual control (FSRMAN) In this mode the operator can enter the value for FSR manually. This mode is not often used , which means that FSRMAN = 100% will be the default value Hence FSRMAN acts as the upper limit (100%) for the FSR signal. FSRMAN is an open loop FSR usually set at 100%. It will stay at this position until manually lowered to override other control loops. When FSRMAN becomes lesser than FSRMAX alarm will be generated to alert the operator.

Manual control contd. Raise constant 1 constant 2 FSR max FSR min Median select gate FSRMAN Lower Z -1 By pressing raise / lower buttons FSRMAN signal value can be changed manually.

Shutdown control GT shutdown (called as fired shutdown) when the stop command is issued. This results in unloading the turbine I. e. lowering TNR until the generator breaker opens on reverse power protection or it reaches full speed no load (FSNL). From this moment the shutdown control algorithm lowers the value of FSR value until flame is extinguished. When all the flame detectors sees no flame FSRSD becomes zero. After FSRSD becomes zero , cool down sequence starts. This is achieved by hydraulic mechanism. This ratchet mechanism rotates the rotor approximately 47 degrees every 3 minutes. This provides uniform cooling of rotor. This cool down sequence continuous until cool down off is manually selected.

Shutdown curve Stop execute Lowering of TNR Lowering Breaker open of FSR First can out % FSR Intercept FSRMIN Flame out Start ramp to blow out Fuel shutoff time

How final FSR is calculated FSRSU FSRSD FSRT FSRN FSRACC FSRMAN Mini select gate <RST> FSRS 1 min FSRC max Final FSR to servo valve Median select gate <C> FSRS 1<R> FSRS 1<S> FSRS 1<T> Median select gate FSRC Each individual computers <R> <S> & <T> generates their own FSR signal from minimum selector gate. <C> computer provides corrective bias to <RST> computer. Hence even if <C> fails GT will continue to run.

Nozzle angle control Why do we need nozzle angle control ? In single shaft machines depends upon the load condition turbine shaft speed can be adjusted by modulating fuel flow & air flow. But in 2 shaft machines HP & LP turbines are isolated. output hot gasses from HP turbine enters into LP turbine through nozzles. Hence by varying nozzle angle the amount pressure drop across each turbine can be varied. FSRT algorithm takes care of maintaining constant firing temperature and FSRN algorithm takes care of load variation. But nozzle angle control associates with these 2 algorithms to control exhaust temperature. This is achieved by controlling pressure drop across HP & LP turbines.

Nozzle angle function Nozzle angle can be varied from +15 Full open -5 Full close Full open condition *There will be less back pressure and hence more pressure drop across HP *HP turbine speed will increase *LP turbine speed will decrease Full close condition *Back pressure will be more consequently less pressure drop across HP *HP turbine speed will decrease *LP turbine speed will obviously decrease Hence by varying nozzle angle HP & LP turbine speed can be varied.

Reference set point calculation(TNRH) Max Min TTRX TTXM + Median select gate TNRH Gain TTRX is calculated from fixed firing temperature and CPD or FSR signal as in the case of FSRT algorithm. It acts as reference exhaust temperature. TTXM is the actual measured exhaust temperature obtained from thermocouples. TNRH is determined by the difference between TTRX & TTXM and it is limited between minimum and maximum values. TNRH acts as reference signal for HP turbine. It also acts as reference signal for maintaining exhaust temperature.

Nozzle angle control contd. Full open angle TNRH TNH OFFSET Full close angle - + Median select gate TSRNZ + Gain TNRH is the reference signal for nozzle angle control depends upon exhaust temperature reference value. TNH is the measured HP turbine speed obtained from speed sensors. Deviation between TNH & TNRH determines exact opening of nozzle. Nozzle angle open/close command , TSRNZ is limited between max. open angle & full close angle. So the ultimate aim of nozzle angle control is to maintain exhaust temperature constant.

Protection system takes care of safe running of gas turbine It continuously monitors various GT parameters, if any parameter reaches near danger limit it will give alarm to alert the operator. When it reaches a predefined danger limit it will trip the GT. Protection system takes care of * flame detection * over speed protection * over temperature protection * vibration protection * combustion monitoring

Protection system schematics Over speed Over temp. Vibration Master protection S/W <R> <S> Flame out <T> GCV Servo valve 2/3 Servo SRV valve 2/3 SV Master protection system for <R>, <S> & <T> computers receives all the critical parameters from the field. If the master protection system found any abnormalities it will give trip command individually. This trip command from all 3 computers voted 2 out of 3.

Overspeed protection Overspeed system is designed to protect the GT against possible damage caused by overspeed of the turbine shaft. Under normal operating conditions the speed of the shaft is the under the control loop. Overspeed protection electronic overspeed protection (primary) mechanical overspeed protection(secondary)

Electronic overspeed system LATCH TNH A Overspeed setpoint A>B set Overspeed trip command B Master reset Electronic overspeed is achieved by computer software turbine shaft is measured by three magnetic pick up speed sensors connected to <R> , <S>&<T>, individually. When the turbine speed (TNH) exceeds overspeed setpoint it will trip command through latch circuit. Output will remain in trip status until master reset is done

Mechanical overspeed (secondary) system It acts as a back up for electronic overspeed system Since it is a back up system overspeed setpoint will be greater than electronic overspeed setpoint The mechanical overspeed trip system consists of * overspeed bolt assembly * overspeed trip mechanism Overspeed bolt assembly acts as a sensing and feed back mechanism Centrifugal force is used as a measure of force. Set point is adjusted by spring force adjustment. When the overspeed occurs centrifugal force will overcome spring force. The resultant force will activate trip mechanism This trip mechanism drains all the hydraulic oil from the servo valve circuit to stop further fuel flow.

How tripping takes place? The ultimate aim of trip circuit to shut off the fuel control valve to stop further fuel flow Trip command from <RST>computers activates trip oil circuit which finally closes fuel shutoff valve Trip oil is controlled by dump solenoid valves which are operated by trip circuits this dump solenoidvalves are normally enerzised to run Whenever trip condition exists dump solenoid valve get de energised to trip This causes all the trip oil get drained. This in term will cause all the high pressure hydraulic oil in the servo valve will get drained As there is no hydraulic oil, the servo valve will go to shutoff position. During running conditions, dump solenoid valves will be energized , trip oil will alllowes high pressure hydraulic oil to actuate servo valves.

Trip oil schematics Normal condition Trip condition Protection signals Master protection circuit Trip Fuel solenoid trip valve 20 FG Mechanical Overspeed trip Fuel in Reset latch Overspeed trip Manual trip SRV To GCV From <RST> Servo valve High pressure hydraulic oil Drain

Overtemperature protection * this system protects GT against possible damage caused overfiring. * it is backup system which operate only after failure of the temperature control loop. Under normal operating conditions temperature control loop controls fuel flow when the firing temperature limit is reached. In certain failure modes however exhaust temperature and fuel flow can exceed control limits. Under such circumstances the over temperarture protection system provides an overtemperature alarm. If the temperature raises further GT will be tripped. The actual exhaust temperature TTXM is compared with alarm and trip set points. Alarm will be generated if TTXM exceeds the temp control reference TTRX plus the alarm margin(constant 3).

TTXM Constant-3 TTRX Constant-2 Constant-1 A B A>B A A>B B Alarm OR gate Trip Isothermal trip TTXM Trip Alarm TTRX. Over temperature trip will occur if the exhaust temperature(TTXM) exceeds temperature control reference plus the trip margin(constant-2) It also trips if TTXM exceeds isothermal trip value(constant-1)

Flame detection Fuel should not be allowed without flame existence. Other wise GT should be tripped. Flame detectors (Ultra violet scanners) monitor on the turbine and generate logic signals depends upon flame condition Flame detectors are utilized both in start up sequence and running Totally there are 4 flame detectors mounted on the GT If one flame detector detects flame the stressing sequence is allowed to proceed. Conversely if one flame detector fails it allow the unit continue to run but will alarm. If both detectors detecting loss of flame the unit is immediately shut down

Flame detection <RST> Flame detector-1 Flame detector-2 Flame detector-3 Flame detector-4 FIELD Honey well flame detector Flame detector software Honey well flame detector Analog input/output module To start up and protection

Vibration protection The vibration protection system of a GT composed of several independent vibration measuring channel. Each channel detects excessive vibration by means of vibration pick up mounted on the bearing houses. If a predetermined vibration level is exceeded the vibration protection system trips the GT. Totally there are 7 vibration probes, Two probes for HP shaft Two probes for LP shaft Two probes for generator One probe for gear box

Vibration pickup A/D Analog I/O <RST> Fault A A<B B Alarm A A<B B Trip Master reset A A<B B Transducer fault alarm Alarm Latch Trip Millivolt signal from vibration pickup <RST> computers via A/D converter. This vibration signals are compares with predefined constants to generate trip and alarm signals. Trip command is issued through latch circuit. Master reset command is used to reset the system.

Startup sequence Ready to start Start command & execute AOP starts , Diesel engine starts Turbine is accelerated to cranking speed Purging takes place, FSR=0 N Purge completed ? Y Firing timer is initiated, Firing FSR is set, Spark plugs are energized N No flame is detected Trip Flame detected Y A

A FSR level is reduced to warm-up level N Warm-up time over Y FSR is increased exponentially to accelerate limit Turbine accelerate until 14 HA picks up which indicates turbine has reached minimum governing speed AOP & AHOP are stopped Full speed no load displayed Complete sequence displayed

Startup curves FSNL TNH Tx FSR TNR MW 104% Sequence complete 14 HS AOP stops Generator breaker opens 70% 14 HA Ignition 14 HM 0 1 Boiler Start purge command Cranking Flame 5 10 15 Loading Base load 20

Shutdown sequence Stop & execute command TNR gradually reduced resulting in generator unloading from full load to no load Generator breaker opens on reverse power Fired shutdown displayed, AOP stops FSR level is decreased at 0. 05%/sec. Till minimum FSR is reached Speed reduction takes place without loosing flame B

B When TNH reaches below operating speed (14 HS) AOP stops Turbine decelerates below the Accelerate speed (14 HA) FSR level is decreased till the FD sees no flame If all FD’s see no flame FSR is set to zero level Turbine coasts to zero speed (14 HR)

104% 100% TNH Tx FSR TNR MW 70% Generator breaker opens 0 Base load 1 Unloading 5 10 15 Coasting down 20

What is Hardware ? Hardware is an electronic circuit arranged in a specific fashion called a module or a card This card performs specific functions as directed by the software The required software (I. e. our requirement) can be stored in any memory unit. Why should I know about Hardware ? The hardware rather than software is the most likely cause of a problem in the Mark-IV control system. The hardware must be functioning correctly for the software to function properly. The hardware must be correctly assembled to function properly.

Hardware of Mark-IV <R> Critical signals I/O module <S> I/O module To field I/O module To alarm unit <T> Non Critical signals I/O module <C> All the critical inputs which are needed to keep the turbine running are connected to <RST> computers. All the non-critical inputs (just for monitoring purpose) are connected to <C> Even if <C> fails turbine will keep running.

Major hardware components in mark-IV <R>, <S>, and <T> computers <C> computer Analog I/O module Contact input module Relay driver module Relay modules CRT - Video display module Power distribution module All these individual units are arranged in the turbine control panel compartment to carryout specific tasks.

<C> communicator The major functions of the <C> communicator is to, * Perform the non-critical turbine control , protection and sequencing functions. * Monitor the health of the controllers <RST> * Drive the primary display unit (CRT) and printer. * Perform diagnostic tests. All this functions are achieved by specific electronic cards (Hardware module) which are residing in <C> communicator contains 16 card slots. Out of which 14 are used in normal practice , remaining 2 are optional.

Hardware of <C> communicator contains 2 rows of 12 card slots(positions). These card slots are arranged in the form of matrix. Numbers 1 & 2 designate the top row and bottom row Letters A through M (except I ) designate the 12 columns from right to left. A typical arrangement will be M A 1 M 1 A 1 2 M 2 A 2

<C> communicator cards SLOT CARD NA, ME 1 A HVDB VIDEO DRIVER 1 B 1 C 1 D 1 E HCVA ANALOG INPUT 1 F 1 G HCMA HRMB MASTER HIGHWAY BRAM 1 H 1 J 1 K HUMA UNIVERSAL MEMORY 1 L 1 M 2 A HXPD HMPF HCMA EXPANDER MICROPROCESSOR COMMUNICATOR 2 B 2 C 2 D 2 E NTCF HAIC THERMOCOUPLE ANALOG INPUT 2 F 2 G HAFA HMHA AUXILIARY FUNCTION MASTER HIGHWAY 2 H 2 J 2 K 2 L HIOD HCMA DIGITAL I / O COMMUNICATION 2 M HIOD DIGITAL I / O FUNCTION DRIVES CRT DISPLAY OPTIONAL 2 ANALOG OUTPUT OPTIONAL COMMUNICATION BRAM - MEMORY STORAGE MEMORY, INTERRUPT & LOGIC I / O PROCESSOR FUNCTIONS & LOGIC OUTPUT OPTONAL - ADDITIONAL RS 232 LINK OPTIONAL 16 T / C INPUTS 16 ANALOG INPUTS 14 ANALOG INPUTS & 32 LOGIC OUTPUTS COMMUNICATION 32 DIGITAL INPUT & 32 DIGITAL OUTPUT RS 232 SERIAL DATA LINK TO <R> & <S> 32 DIGITAL INPUT & 32 DIGITAL OUTPUT RS 232 SERIAL DATA LINK TO <T> & PRINTER 32 DIGITAL INPUT & 32 DIGITAL OUTPUT

<C> Interface diagram L-BUS HMPF HUMA HRMB CRT HXPD RDM HIOD Digital RELAY output 3 -6 HAIC HVDV CIM OPM Digital input <R> HCMA <S> <T> NTCF HAFA HCMA PRINT TCM HMHA HCVA AIO Analog input Analog output

<RST> computers Each controller <R>, <S>, and <T> Performs the critical turbine control, protection and sequencing functions. Performs diagnostic tests. Exchanges data with <C> communicator. <RST> controller contains required software and hardware that will keep the turbine running and perform a normal shutdown even if <C> fails. The hardware and software identical in each controller.

<RST> controller hardware All the critical inputs are fed into each controllers. All these critical outputs are hardware voted on 2 out of 3 basis. All the non-critical outputs from <RST> controllers fed to <C> where they are software voted. Totally there are 12 cards arranged in matrix form. F 1 F 2 F E D C B A 1 A 2 A 1 2

<RST> controller cards SLOT 1 A 1 B 1 C 1 D 1 E 1 F 2 A 2 B CARD HPRB Pulse rate HAFA Auxiliary function NTCD Thermocouple HXPD Expander HCVA Vibration / pressure 2 E HMPF NVCB HAIC HSAA 2 F HSAA 2 C 2 D NAME FUNCTION 4 pulse rate/Digital inputs 14 Analog & 32 Logic inputs 16 Thermocouple inputs Memory, Interrupt & Logic I/O Optional 2 Analog input Microprocessor Processor fn. , memory & 8 logic O/P’s Vibration /pressure Optional 6 vibration & 4 analog I/P Vibration / pressure Analog input 16 analog inputs Servo amplifier Optional 2 LVDT I/P’s & Servo O/P’s

<RST> controller interface diagram L-BUS HMPF Thermocouple input TCM NTCF Flame signal HAFA Vibration NVCB LVDT Analog output Speed AIO <C> HCMA HAIC RDM Relay Logic outputs HXPD HSAA NVCA HPRB CIM Logic input

SPEEDTRONIC MAK - V It is an advanced version of Mark-IV, introduced by general Electric in 1991. The Speedtronic Mark-IV control & protection system is based on microcomputers. This system can be used for both single shaft & double shaft machines. Triple redundancy I. e. 3 redundant computers (<R>, <S> &<T> )is applied for the essential control & protections. A fourth non-redundant computer <C>, is used for the communication with the operator interface <I>.

MARK V - AN OVERVIEW • 3 Redundant computers <R> , <S> & <T> denoted by <Q>. • <C> for communication. • <P> for protection. • <I> for operator interface. • <BOI> for backup operation. (communication via backup net) • Data exchange between <R> , <S> , <T> & <C> is done by DE net. • Digital inputs &outputs are transferred to the respective locations via IO net. • Only one computer votes and if it fails another computer takes over immediately.

Functional description of Mark-V Arithmetic unit From field A/D Control unit D/A To field Memory All the field signals are converted into digital form and then stored in the memory. The memory also contains the program for Gas turbine control & instructions of the system software. The control unit executes all the programs with the help of Arithmetic unit. The result of this digital operation is stored in the memory and then converted into analog signals.

Principle of Mark-V system Logic inputs Mark-V system uses Software Implemented Fault Tolerance(SIFT) technique. This means all the 3 computers individually vote all 3 corresponding logic inputs. Logic output value is software voted by one redundant computer (the voter). Only for the master protection system a hardware 2 out of 3 voting with relays is executed in the protection module <P>. The voted master protection signal (=trip signal) controls the power of trip relays and solenoids. Analog values Analog inputs are converted into digital form , processed by the processor and then converted back into analog form to actuate servos.

Principle of Mark-V Analog I/P A/D Digital I/P 2/3 , , A/D 2/3 Digital O/P D/A <S> A/D , , Analog O/P <R> 2/3 , , D/A 2/3 D/A <T> 2/3 A/D <C> 1/1 DE net , , 2/3 D/A 1/1 , ,

Mark-V system configuration The major component of mark-V are, <I> Computer It is the operator interface, just like personal computer (PC) with color screen. <BOI> Module The backup operator interface communicates via a backup net with the redundant computers <RST>. The malfunctioning of <C> or a unpowered <C> does not affect this communication. <C> Communicator It is a common non-redundant computer. Mainly dedicated for communication with <I> computer. Though if <C> fails the turbine can still be operated from the <BOI>and is controlled by <RST> computers These are 3 identical redundant computers.

<P>Module This module is called protective module which acts as interface between <RST> computers and field solenoids. This module receives trip command from <RST> computers and performs 2 out of 3 voting. Then it issues trip command to field solenoids. <CD> module It is a digital I/O module of which digital input & output signals are routed to/from <C> communicator. This module provides 96 contact inputs and 60 contact outputs. <QD 1> Module The digital I/O module of which the digital inputs & output signals are routed to/from <RST> computers. This module provides 96 contact inputs & 60 contact outputs. * Analog inputs & outputs for <RST> are connected to terminal boards of <RST>computers

MARK-V System configuration <CD> Logic Input/ output <QD> <P> <I> Analog I/O <C> Analog I/O <R> Analog I/O <S> Analog I/O <T> DE net

MARK - IV MARK - V <R> <S> <C> <T>

Difference between Mark-IV & Mark-V MARK - IV MARK - V There is no direct <R>, <S>, & <T> inter communication <R> , <S> <T> talk to each other Protection functions done by <RST> computers. There is a special <P> computer for protection functions. There is a mechanical over speed bolt trip in addition to electrical over speed trip No mechanical over speed trip. Instead an additional electronic trip has been provided <R>, <S> & <T> can talk to <C> independently <R, <S> < T> & <C> can talk via DE net

MARK - IV Startup of GT cannot be performed if <C> has failed. During normal operation, however failure of <C> does not affect the GT operation. (The auxiliary display cannot be used for startup. On failure of <C> triple redundant of Mark-IV is lost All cards are plugged into their respective mother boards. MARK - V All control operations of the GT can be performed through the <BOI>. Hence even if <C> fails the GT can be started using <BOI>. Triple redundancy is not affected by the failure of <C>. Mother board concept is not there. All cards are interconnected via ribbon cables.