steam turbine control
TRANSCRIPT
Steam Turbine Control System
Basic of Steam TurbineBasic of Steam Turbine
TurbineTurbine
• The turbine converts the high-pressuredriving force created by steam, water,combustion gas into rotation energy(mechanical energy) that turns the generator rotor.
• The generator rotor is connected to theturbine via a shaft.
Fossil Fired Steam UnitFossil Fired Steam Unit
– The moving blade “Buckets”
– A set of stationary blade“Nozzle Partition”
Turbine StageTurbine Stage
HP/IP turbine blading
HP & IP Rotor
TYPE OF STEAM TURBINE
Straight Condensing TurbineStraight Condensing Turbine
INITIAL PRESSURE
CONTROL VALVE
TO CONDENSER EXHAUST PRESSURE LESS THAN
ATMOSPHERIC
Straight NonStraight Non--condensing Turbinecondensing Turbine
INITIAL PRESSURE
CONTROL VALVE
EXHAUST PRESSURE GREATER THAN ATMOSPHERIC
Non automatic Extraction TurbineNon automatic Extraction Turbine(Condensing or Non condensing)(Condensing or Non condensing)
INITIAL PRESSURE
EXCTRACTION ONE OR MORE
EXHAUST PRESSURE
CONTROL VALVE
Automatic Extraction TurbineAutomatic Extraction Turbine(Condensing or Non condensing)(Condensing or Non condensing)
CONTROL VALVE
INITIAL PRESSURE
CONTROLLED EXTRACTION PRESSURE
EXUAST PRESSURE
Mixed Press TurbineMixed Press Turbine(Condensing or Non(Condensing or Non-- condensing)condensing)
P1 ≠ P2
P2 = INITIAL PRESSURE
P1 = INITIAL PRESSURE
EXHAUST PRESSURE
Reheat TurbineReheat Turbine(Condensing or Non(Condensing or Non--condensing)condensing)
CONTROL VALVE
INITIAL PRESSURE
CONTROL VALVE
CONDENSERREHEATER
FROM REHEAT
– Single cylinder
– Multi-cylinder• Tandem-compound• Cross-compound
Turbine Sections (Cylinders)Turbine Sections (Cylinders)
• Tandem compound turbine-generator
– High press (HP), intermediate pressure (IP), Low pressure (LP) and generator on a common shaft
Non-reheat tandem compound steam turbine
HP LP LP GEN
Cross over
Condenser
From boiler
MSV
CV
MSV Main Stop Valve
CV Control Valve
shaft
Single reheat tandem compound steam turbine
HP LP LP GEN
Cross over
Condenser
From boilerMSV
CV
RH Reheater
RSV Reheat Stop Valve
IV Intercept Valve
IP
RH
RSV
IV
shaft
Single reheat tandem compound steam turbine
Cross overFrom boiler
RH Reheater
RSV Reheat Stop Valve
IV Intercept Valve
HP LP LP GEN
Condenser
MSVCV
RH
RSVIV
LP LPIP IP
Steam turbine rotorSteam turbine rotor
• Cross compound turbine- generator– Commonly with HP, IP and one generator on
one shaft , LP and another generator on a second shaft
• Greater capacity• Improved efficiency• More expensive
HE seriesHE series
100 MW – 700 MW
• H turbine- Single flow HP turbine module- one stop and control valve
• E turbine- Single flow IP / LP section combined in one cylinder
Modular Design of the E-Turbine
KN seriesKN series
250 MW – 700 MW
• K turbine- combined HP/IP
• N turbine- Double flow LP section
Modular Design of the K-Turbine
Stop and Control valve
Generator HP stage
svcv
svcv
LEFT
RIGHT
LP stage
LP H
EA
DE
R
HP
HE
AD
ER
Process parameter control
• MW output.• Main steam• Fuel / Air• Feed water
Steam Turbine Controller
The tasks of steam turbine controller
• Starting up and shutting down the turbine• Synchronizing with grid* • Loading the turbine• Influencing the grid regulator• Pressure stabilization• Limitation of load• Control of Isolated operation• Turbine interception during load rejection• Monitoring function
Steam turbine controller ( Conventional Hydraulic Governor)
Steam turbine control (DEH Governor)
Comparison between DEH governor andconventional hydraulic governor
Speed and Load Control
2 out of 3Voting Logic
Speedsummer
Speed setpoint
Load Setpoint
1/S HoldIntgrl
SummerSpeedGain Speed
/Loadsummer
Speed signal
TNE
TNH
PWR
-
+
+
++
+
TNR
Hard ware of turbine controller• Very fast response digital system
- Microprocessor-based controller• Redundant structure
– Dual, TMR• Man machine interface with CRT• Standardize interface technique with other
systems• Control panel*
– Hard wired push buttons comply with minimum requirements for backup operation
SPEEDTRONIC TM Mark V Steam Turbine Controls
Mark V Control Simplex Configuration
Mark V Control TMR Configuration
Mark VI
Siemens AG, Power GenerationModern Automation Concepts
Alstom P400 Turbine Control
GE Fanuc
PACSystem RX7i
TMR SYSTEM
Mark V TMR Control Sequence
Hardware voting for analog Outputs
Hardware voting of logic outputs
Servo Position Controller (SPC)
Block diagram of SPC
Single coil wiring - Integrating Servo Application
Over Speed Protection Device
Over views diagram of TurboSentry Application
Steam Turbine Operation Steam Turbine Operation
STARTING AND LOADING
• Successful operation• Maintenance• Long life a turbine-generator
Main factors involved during starting and loading
• 1) Thermal Stress • 2) Vibration• 3) Shell and Rotor differential expansion• 4) HP exhaust temperature
Thermal Stress
• Operating Transients can be produce high thermal stresses in stem turbine rotor and shell– Start-ups– Load changes– Shutdowns
Turbine Stress Evaluation (TSE)Turbine Stress Evaluation (TSE)
• Limiting the acceleration during start-up • Load ramp gradients under normal loading
operation
Differential expansion
• Rotor temperature change faster than outer shells.
• Lead to differential expansion large enough to cause internal rubbing
Oil and Hydraulic Fluid SystemCheck lube oil temp. >
50 F°/ 70 F°
Starting AC lube oil pump
Check lube oil pressure &
flow to bearing
Check lube oil protection sequence
Return to normal
configuration
Recheck lube oil
pressure
ALube oil ready
Oil and Hydraulic Fluid SystemCheck EH fluid reservoir level
Check EH fluid temp.
Open pump suction valve
(if used)
Adjust cooling water flow
Place backup fluid pump on auto.
Check auto. Start of
backup pump
B
Start number 1 fluid pump
EH fluid ready
Oil and Hydraulic Fluid System
B
ALube oil and
hydraulic systems ready
AND
Turbine rotor prewarming• rotor warming (prewarm) prior to roll-off
after the vacuum system is in operation.
• rotor warming (heatsoak) be performed during turbine acceleration and involves a “part speed hold”
• In either case the manufacturer ‘s specific recommendations should be followed
Valve trip testing• the main turbine valves should be tested
to verify that the testable functions of thetrip system are working properly.- verifying that all valves involved are in
the proper position.- manually tripping the turbine from thecontrol-room panel and observing that allvalves return to the tripped status.
Turbine preroll• Energize the supervisory instruments.• Energize the EH (electro-hydraulic) electronic
governor at least 2 h before admitting steaminto the turbine.
• If an electrical-trip system shall be energizedprior to turbine roll-off.
• Control & Stop valves are closed• resetting the turbine trip system and the
status of the various valves when reset varywith manufacturers.
Energize supervisory instrument
Energize electronic governor
Energize electric trip system
Check main stop valve closed
Check control valve closed
Check intercept valve closed
Check generator ok
AND
Unit onturning gear
Lube oil system ok
Unit on turning gear
Hydraulic fluid system ok
Vacuum ok
Steam seal ok
Drain valve open
Eccentricity ok
AND
Turbine rotorprewarmed(if required)
Eccentricity ok
1
Reset turbine
All trip lockouts reset
Deactivate initial pressure reg.
Check main stream press. & Temp ok
Water induction preroll checks
ANDReady to roll
1
DDigital igital EElectrolectro--HHydraulic ydraulic CControl Systemontrol System(DEHC)(DEHC)
RATCHABURI THERMAL POWER PLANTRATCHABURI THERMAL POWER PLANT
Turbine Specification
• Rated output 735,000 KW• Revolution 3000 r.p.m.• Steam condition
– Main steam pressure 24.22 MPa– Main steam temp. 538 °C– Reheat steam temp. 566 °C– Condenser vacuum 700 mm Hg– Number of Extraction 8
UnitUnit CapabilityCapability andand MinimumMinimum LoadLoad
• Unit capability refers to the maximumpossible megawatt output that thegenerating unit can safely produce.
• Minimum load is the smallest amount ofgeneration that a unit cansustain for an extended period.
HP LP LP GENIP
Reheater
Boiler
ICV
MSV
MSV
RSV
RSV ICV
GV
GV
LP LP
DEHC
• MSV : Main Stop Valve• GV : Governing Valve• ICV : Interceptor Valve• RSV : Reheat Stop Valve
Servo drive
Solenoid valve
Stop Valves / Throttle Valves- Normally provide fast interruption of the
main energy input to the turbine.
A stop valve is defined as an open or closed valve
A throttle valve have some portion of its opening through which it can modulate flow ( used for turbine control during start-up)
DEHC Function
• Control function– Speed up control– Valve transfer control– Close all valves– Load / Frequency control– Load limiter– IMP control (Impulse chamber pressure)– Valve management
DEHC Function
• Protection function– EOST (Electrical Over Speed Trip)– OPC (Over Speed Protection Control)– IPR (Initial Pressure Regulator)
DEHC Function
• Test function– Valve closing test– OPC test– MOST test (Mechanic Over Speed Trip)
Start-up curve
T/B reset
400
2200
3000
rpm
Heat soak
Rub check
Startup
Valve transfer
41E on
Synchronizing
Speed control
• Turbine speed is controlled by MSV from starting to rated speed.
• GV full open
Speed control
T/B reset
EH AUTO
GV (full open)RSV
Target speed select 400 rpm
MSV
Program GO
position
Speed Control
> H
Speedreference
KMSV
control+
-Speed A
Speed B
3000 Hz
• What is 3000 r.p.m. ?
r.p.m. round / minute ( r/min )
• Frequency of network = 50 Hz (Thailand)
Hz round / second (r/sec)
50 HZ = 50 round / secondIn one minute = 60 Second
Rotation in one minute = 50 x 60 = 3,000 round or 3000 round / minute = 3000 r.p.m.
• Turbine speed = 3000 rpm.• No. of gear teeth = 60• Pulse / min = 60 x 3000 • Pulse / sec. = 60 x 3000 = 3000 Hz
60
Taget speed & Speed change rate
• Taget Speed– 400 rpm– 2,200 rpm– 3,000 rpm
• Speed Change Rate– 75 rpm/min– 150 rpm/min– 300 rpm/min
Valve transfer
• After turbine has reached the rated speed.• Speed control change from MSV to GV
Valve transfer
Full open BiasGV
MSV
GV position demand
Valve transfer
complete
Valve transfer
Full open
0%
(No load valve position)
41E permit
Start-up
Transfer
Synchronize
Full open
Speed Control
Load Control
Speed control
Full open
Full open
GV MSV
Close all valves
• For turbine stop and rub check• MSV, GV and ICV are fully Closed by the
sevo valve.• RSV still open.
Load control
• Load frequency control• Load limiter
– limit steam flow
Load control
Loadsetter
droop
<LDCS
3000rpm
Actual speed
GV control
Loadlimiter
Comparator
+-
+
+
Response RateResponse Rate
• Response rate is the rate of load changethat a generating unit can achieve fornormal operating purposes in MW/min.
Position Controller
K E/H+20 mA
LVDT
Position demand +
-
Electrohydraulic Servovalve
Voltage vs Range of Travel Curve
Partial Arc Admission( a nozzle governing system)
• Lower throttling Loss• Better heat rate
• Two or more regulation valve are opened one after another
• The Load being control by varying a nozzle area and a constant rated pressure
Partial Arc Admission
Full Arc Admission( a throttling governing system)
• Preferred during start-up turbine• Lower stress
• Two or more regulating valve are opened and closed at a time
• The Load being control by varying a pressure at a constant nozzle area
100%
100%LOAD
STEAM FLOW
100%
100%STEAM FLOW
VALVE AREA
100%
100%VALVE LIFT
VALVE AREA
100%
100%VALVE LIFT
STEAM DEMAND
IMP (Impulse chamber pressure) control
• For valve closing test• Keep the power of turbine
IMP (Impulse chamber pressure) control
HP LP LP GENIP
Boiler GV
GV
MSV
MSV
LP LP
Px HP turbine 1 st steam pressure
EOST (Electrical Overspeed Trip)
>111%
3300 rpm
speed
>111%speed
>111%speed
2/3 Turbine Trip
MOST (Mechanical Overspeed Trip) test
• To confirm mechanical overspeedprotection device (before synchronization)
• EOST setting 111% 115%• OPC is blocked
MOST setting
MOST 110%
- 15 rpm
+ 15 rpm
(+ 0.5%)
OPC (Overspeed Protection Control)
• Power-load imbalance• To avoid overspeed trip when load
rejection• Speed up to 107.5% OPC valve solenoid
are energized.
• Power output IP Turbine inlet pressure(Mechanical)
• Power output CT (current transformer)(Electrical)
HP LP LP GENIP
Boiler GV
GV
MSV
MSV
LP LP
Px IP turbine inlet pressure
Gen.Current
OPC (Overspeed Protection Control)
IPR (Initial Pressure Regulator)
• Protect against excessive decrease of the initial (main) steam pressure
• Main steam deviate from main steam pressure reference > 25 bar
• Turbine water damage prevention• Load reference runback rate 200%/min.
100%
GV = 25%
200% / min
Load setter
IPR (Initial Pressure Regulator)
Time (sec)
Valve Closing Test
• Confirm the safety function– GV & MSV valve test (RH, LH)– RSV & ICV valve test (RH, LH)
GV – MSV Valve test
GV
Test
MSV
IMP IN
ICV – RSV Valve test
ICV
Close
RSV energized
De-energized
OPC Test
GV
ICV
energized
De-energized
1 Sec.
Overall unit control
• Boiler following mode (Turbine leading)
• Turbine following mode (Boiler leading)
• The integrated or coordinated boiler turbine control
• Sliding pressure mode
Boiler following mode (Turbine leading)
• Change in generation are initiated by turbine control valves.
• The boiler controls respond to the resulting changes in steam flow and pressure by changing steam productions.
Turbine following mode (Boiler leading)
• Change in generation are initiated by change input to the boiler.
• The MW demand signal is applied to the combustion control.
• The turbine control valves regulate the boiler pressure.
The integrated or coordinated boiler- turbine control
• Provides an adjustable blend of both boiler-following and turbine-following mode of control.
• The improvement in unit response achieved through integrated control.
• The integrated control strikes a compromise between fast response a boiler safety.
The sliding pressure mode
• The control valves are left wide open.
• The turbine power output is controlled by controlling the throttling pressure through manipulation of the boiler control.
