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April 10, 2023 PMI Revision 00 1
TURBINE GOVERNING
April 10, 2023 PMI Revision 00 2
Presentation outline
•Role of turbine governing •Governing Method •Types of Governing systems•Functional division of Governing Ckt•Component of Turbine governing
April 10, 2023 PMI Revision 00 3
TURBINE GOVERNING • Role of turbine governing
• Governing Method
• Types of Governing systems
• Functional division of Governing Ckt
• Component of Turbine governing
April 10, 2023 PMI Revision 00 4
Functions of Governing System
• To control the initial run up and synchronization of the machine• To control the turbine load when running in parallel with other
generating sets.• To contain the speed rise within acceptable limits in case of the unit
getting disconnected from the load• To provide protective gears to ensure the safe operation of the
turbine
Thus the individual TG governing system imply a need to withstand a full load rejection safely provide appropriate contributions to system frequency control.
April 10, 2023 PMI Revision 00 5
FUNCTIONS OF GOVERNING SYSTEM
Safe Rolling, Synchronising, Loading And Unloading Of The Turbine. Maintaining Load/Throttle Steam Pr. / Speed as per requirement
SAFE ISLANDING OPERATION In Case Of Grid Disturbance
PROTECTING THE TURBINE In Case Of Emergency
April 10, 2023 PMI Revision 00 6
Governor characteristics
The main characteristics of a governing system is therefore the relationship between the generated load of the machine and its speed which is the prime governor input. This is known as the speed-loop droop or frequency regulation characteristics of the governor.
Considering NR: Rated speed,
NPR : Speed at full load
NO: Speed at No load
The steady state overall frequency regulation is defined as
1000
NNNR
PR
April 10, 2023 PMI Revision 00 7
THE EFFECT OF REGULATIONThis regulation permits a machine to
share load with other machines in a stable manner. Generally the droop of a turbine used for electric power generation varies between 4-7%.
Typical governor frequency regulation characteristics is shown here as
April 10, 2023 PMI Revision 00 8
THE EFFE CT OF CHANGING SPEED SET POINT
April 10, 2023 PMI Revision 00 9
Closed loop control of turbine electrical load by use of proportional and integral load controllers is added to the basic governing system to facilitate the provision of variable droop settings. The frequency range over which the load loop is operative is limited so that even when the load loop droop is set to high or infinite values the unit response any large frequency errors in a manner matched to the characteristics of the normal droop of the basic speed governor.
USE OF VARIABLE DROOP SETTINGS FOR CLOSED LOOP LOAD CONTROL
April 10, 2023 PMI Revision 00 10
FREQUENCY VS LOAD CURVE
50 Hz 52.5 Hz51.25 Hz
100%
50%
0% Frequency in Hz
Load in %
Assumption, Droop = 5 %
April 10, 2023 PMI Revision 00 11
CHARACTERISTICS OF FREQUENCY INFLUENCE
Droop = 4 %
Droop = 8 %
48 5250
Frequency (in Hz)
+50 %
- 50 %Load
49 51
April 10, 2023 PMI Revision 00 12
VARIATION IN LOAD IN A GRID
DROOP
3 % 4 % 5 %
100 % 1.5 Hz 2 Hz 2.5 Hz
50 % .75 Hz 1 Hz 1.25 Hz
25 % .375 Hz 0.5 Hz 0.625 Hz
10 % 0.15 Hz 0.2 Hz .25 Hz
5 % 0.075Hz 0.1 Hz 0.125 Hz
EFFECT OF DROOP SETTING ON GRID REQUENCY
April 10, 2023 PMI Revision 00 13
Governing Of Large Reheat Machines
On reheat machines it is necessary to control not only the hp valves but also the interceptor (IP) valves because on a full load rejection the stored steam in the reheater and the associated pipe lines could be sufficient to overspeed the machine to destruction. The characterstics of the IP valves are such that they usually remain fully open over the normal low range of the machine and the governing action is achieved by throttling of the HP valves. This operating regime is known as HP governing & is achieved by giving a fixed bias to the IP valves.
However, the reheater control valves comes into action during certain abnormal conditions like fast load rejection or low load conditions with excessively high reheater pressure, with the help of over riding controls provided by features like load sheding relay, IP trimming device etc.
April 10, 2023 PMI Revision 00 14
Governing Methods
• To control load, the turbine can be either
NOZZLE CONTROLLED
or
THROTTLE CONTROLLED
with the unit in both cases operating at constant steam pressure or variable pressure or a combination of two
April 10, 2023 PMI Revision 00 15
THROTTLE GOVERNING
In throttle controlled turbines, steam flow is controlled by opening and closing of all the control valves simultaneously to the extent required by load and admitting the steam to the group of nozzles located on the entire periphery
April 10, 2023 PMI Revision 00 16
NOZZLE GOVERNING
In nozzle controlled turbines, steam flow is controlled by sequential opening or closing of control valves allowing steam to flow to associated nozzle groups
April 10, 2023 PMI Revision 00 17
1. MECHANICAL
2. HYDRAULIC
3. ELECTRO-HYDRAULIC
4. Any Combination Of Above Three
Commonly Used System
ELECTRO-HYDRAULIC GOVERNING
(EHG)
April 10, 2023 PMI Revision 00 18
MECHANICAL
• In mechanical governing system, speed transducer is mechanical centrifugal type speed governor, which actuates control valves through mechanical linkages.
Now-a-days purely mechanical governing systems are not used for utility turbines.
April 10, 2023 PMI Revision 00 19
April 10, 2023 PMI Revision 00 20
Hydraulic Governor• A hydraulic Governor for a turbine consists of a
centrifugal pump driven from the main shaft which supplies oil to a cylinder containing a spring loaded piston or bellows. The pressure is proportional to the square of the speed, so the position of the piston or bellows is a function of speed.
April 10, 2023 PMI Revision 00 21
HYDRAULIC
In hydraulic governing system , speed transducer is a centrifugal pump , whose discharge pressure is proportional to square of speed.
This signal is sent to hydraulic converter / transformer which generates signal proportional to valve opening / closure required.
Before applying the signal to control valve servomotors, the same is suitably amplified
April 10, 2023 PMI Revision 00 22
ELECTRO-HYDRAULIC
This system provides very good combination of electrical measuring & signal processing and hydraulic controls.
It offers many advantages over other three types of governing systems and is popular in large steam turbine units due to growing automation of turbine and generator sets.
April 10, 2023 PMI Revision 00 23
Electrical governor• Common design incorporates a permanent type shaft driven
permanent magnet generator producing an a.c. wave having frequency of shaft speed. This wave is fed into an electric filter that resonates at a frequency corresponding to rated speed and the output is rectified to produce a d.c signal proportional to difference between rated and actual speed. This signal is amplified to form required speed correction signal.
• Another design utilizes digital signals from a shaft driven square wave generator, the output is compared with a reference square wave signal generated by an oscillator. The output of the comparator is rectified and amplified to form required control signal.
April 10, 2023 PMI Revision 00 24
Type Of Governing System ( KWU Turbine )
ELECTRO-HYDRAULIC GOVERNER ( EHG )
Main Controller
MECHANICAL-HYDRAULIC GOVERNER ( HG )
Backup
FEATURES
• Automatic Controller With All Integrated Functions
• Can Work With CMC
• Safety And Protection
FEATURES
• Manual Controller
• Safety And Protection
• Tracks To Main Controller (CAN TAKE OVER IN CASE OF FAILURE OF MAIN CONTROLLER)
April 10, 2023 PMI Revision 00 25
Hydraulic Governing
1. Output signal ( Aux. Secondary Fluid Pr.) is a function of
i) Speed Signal ( Primary Oil Pressure )
ii) Remote / Local Command
2. It can never be isolated from the system
3. Normally it acts as back-up of EHG.
4. Must be resorted to for Resetting of
Governing System
April 10, 2023 PMI Revision 00 26
HYDRAULIC GOVERNING
HYD. AMPLIFIERwith F.U.Piston
HPCV SERVO. IPCV SERVO.
HPCV IPCV
HYD. SPEED GOV.
HYD. SPEED TRANS.
HYD. PRESS. SIGNAL
HYD. PRESS. SIGNAL
HP SEC. OIL IP SEC OIL
MECHANICAL COUPLING MECHANICAL COUPLING
April 10, 2023 PMI Revision 00 27
Electro Hydraulic Governing (EHG)
Load Controller ( PI Controller ) Pressure Controller ( PI Controller ) Speed Controller ( PD Controller )
Any one of the three controllers becomes
operative based on minimum selection
April 10, 2023 PMI Revision 00 28
ELECTRO-HYD. GOVERNING
EHCwith F.U.Piston
HPCV SERVO. IPCV SERVO.
HPCV IPCV
ELEC. SPEED SENSOR
ELECTRICAL SIGNAL
HP SEC. OIL IP SEC OIL
MECHANICAL COUPLING MECHANICAL COUPLING
April 10, 2023 PMI Revision 00 29
Advantages Of Electro Hydraulic Governing
1. Accurate control of the load gradient while loading the machine
2. Provision of load controller : Proportional + Integral control action Proportional + Integral control action as against pure proportional actionas against pure proportional action of Mechanical/Hydraulic governors.
3. Accurate control of the desired acceleration & speed of the machine during rolling
4.4. Provision of taking aspects of thermal stressesProvision of taking aspects of thermal stresses of different parts of the turbine during startup, shutdown and normal load operation. This is valuable for enhancing life of the Turbine.
5. House load operation is possible within acceptable range of frequency.
April 10, 2023 PMI Revision 00 30
GOVERNING SYSTEM
April 10, 2023 PMI Revision 00 31
Block Diagram - HYDRAULIC Controller
April 10, 2023 PMI Revision 00 32
Features of Governing System
• EHC backed-up by Mechanical Hydraulic Controller (MHC)• Tracking device for bumpless transfer from EHC to MHC• Electrical processing ensures high sensitivity, quick response
and dynamic stability• Hydraulic actuation of valves provides continuous control of
large forces• Provision for frequency support• Interfacing with Unit Coordinated Control• Dependable control during load rejection• Can accept control inputs from Auto Load Dispatch Station
April 10, 2023 PMI Revision 00 33
EHC BLOCK DIAGRAM
April 10, 2023 PMI Revision 00 34
Features of Electrohydraulic Controller
• Speed, Load and Pressure controllers act as leading controller• Selection circuit to select output of one of the three controllers
as the final one• Valve Position Controller acts as the subordinate controller• Output of valve position controller acts on Electro-hydraulic
controller which converts the electrical positioning signal to hydraulic one
• Signal from mechanical and electro-hydraulic controllers are linked together though a hydraulic minimum gate
• Tracking device keeps the mechanical controller signal approx. 10% higher
April 10, 2023 PMI Revision 00 35
FUNCTIONAL DIVISIONS OF GOVERNING SYSTEM
COMPONENTS• Resetting Circuit
a) Resetting the Protective Devices
b) Resetting of HP & IP Stop Valves
• CONTROLLER
Regulating Opening of control valves
• Testing Circuit ( ATT Automatic Turbine Testing )
• SAFETY CIRCUIT a)Closure of Stop Valves b) Temporary Closure of Control Valves
April 10, 2023 PMI Revision 00 36
COMPONENTS OF SAFETY CIRCUIT• MAIN TRIP VALVE
• OVERSPEED TRIP DEVICE
• LOW VACUUM TRIP DEVICE
• THRUST BEARING TRIP DEVICE
• HAND TRIP DEVICE
• REMOTE SOLENOID TRIP
HP & IP Stop Valve Servo Motors
Actuators of CRH NRV & Extraction
lines FCNRV
April 10, 2023 PMI Revision 00 37
COMPONENTS OF CONTROLLER
• PRIMARY OIL PUMP
• STARTUP AND LOAD LIMITING DEVICE
• HYDRAULIC AMPLIFIER
• ELECTRO HYDRAULIC CONVERTER
• CONTROL VALVE SERVO MOTOR
• PILOT VALVES AND FOLLOWUP PISTONS
April 10, 2023 PMI Revision 00 38
COMPONENTS OF ATT
• MAIN TRIP VALVE
• CHANGE OVER VALVE
• OVERSPEED TRIP TEST DEVICE
• LOW VACUUM TRIP TEST
• STOP VALVE TEST VALVE
• TEST SOLENOIDS
• RESET SOLENOIDS
April 10, 2023 PMI Revision 00 39
OIL SUPPLY TO GOVERNING SYSTEM
HIGH PRESSURE CONTROL OIL (32 BAR)
POWER OIL TO CONTROL VALVE SERVO MOTOR
LOW PRESSURE CONTROL OIL (8 BAR)
FEEDS TO SAFETY CIRCUIT, ATT AND CONTROL CIRCUIT
LUBE OIL
FEEDS TO PRIMARY OIL PUMP FOR HYDRAULIC SPEED SENSING
April 10, 2023 PMI Revision 00 40
GENERATED FLUIDS AND THEIR FUNCTIONS
• START UP OIL• AUXILIARY STARTUP OIL
•TRIP OIL
• AUXILIARY TRIP OIL
SECONDARY OIL
• AUXILIARY SECONDARY OIL
• TEST OIL
• PRIMARY OIL
April 10, 2023 PMI Revision 00 41
STARTUP OIL
GETS GENERATED FROM 8 BAR CONTROL FLUID AT STARTUP AND LOAD LIMITING DEVICE.
• HELPS IN OPENING OF STOP VALVE
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 42
April 10, 2023 PMI Revision 00 43
AUXILIARY STARTUP OIL
GETS GENERATED FROM 8 BAR CONTROL FLUID AT STARTUP AND LOAD LIMITING DEVICE.
• RESETS ALL THE HYDRAULIC TRIPPING DEVICES
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 44
April 10, 2023 PMI Revision 00 45
TRIP OIL
GETS GENERATED FROM 8 BAR CONTROL FLUID AT MAIN TRIP VALVE.
• FEEDS THE AUXILIARY TRIP OIL CIRCUIT (SAFETY DEVICES)
• FEEDS CONTROL CIRCUIT (SIGNAL OIL)
• OPERATES STOP VALES
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 46
AUXILIARY TRIP OIL
GETS GENERATED FROM TRIP OIL AT MAIN TRIP VALVE.
• KEEPS MAIN TRIP VALVE IN OPERATING POSITION
• ALL THE HYDRAULIC SAFETY DEVICES ARE CONNECTED TO THIS CIRCUIT
• DRAINING OF THIS OIL TRIPS THE TURBINE
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 47
SECONDARY OIL
GETS GENERATED FROM TRIP OIL AT HYDRAULIC AMPLIFIER OR ELECTRO HYDRULIC CONVERTER
• IT IS THE SIGNAL OIL FOR THE CONTROL VALES OPENING
• PRESSURE OF THIS OIL DECIDES THE OPENING OF CONTROL VALVES.
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 48
Closing/opening of CV
April 10, 2023 PMI Revision 00 49
April 10, 2023 PMI Revision 00 50
AUXILIARY SECONDARY OIL
GETS GENERATED FROM TRIP OIL AT SPEEDER GEAR
• IT IS THE SIGNAL OIL FOR GENERATION OF SECONDARY OIL PRESSURE AT HYDRAULIC AMPLIFIER
• PRESSURE OF THIS OIL DECIDES THE OPENING OF CONTROL VALVES WHILE IN HYDRAULIC GOVERNER.
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 51
PRIMARY OIL
GETS GENERATED FROM LUBE OIL BY PRIMARY OIL PUMP
• IT IS THE SPEED SENSING SIGNAL FOR THE HYDRAULIC GOVERNER
• PRESSURE OF THIS OIL VARIES WITH SPEED OF THE TURBINE.
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 52
TEST OIL
GETS GENERATED FROM LUBE OIL AT OVER SPEED TRIP TEST VALVE.
• IT IS THE INJECTION OIL FOR OPERATING THE FLY BALL OF MECHANICAL OVER SPEED TRIP DEVICE.
ORIGIN
FUNCTION
April 10, 2023 PMI Revision 00 53
Startup & Load Limiting Device
8 BAR CONTROL FLUID
STARTUP OIL
AUX. SECONDARY OIL
AUX. STARTUP OIL
PRIMARY OIL
TRIP OIL
April 10, 2023 PMI Revision 00 54
Main Trip Valve Operating Mechanism
TRIP OIL
AUX. STARTUP OIL
TESTOIL
CONTROL OIL
AUX. TRIP OIL
CONTROL OIL
CONTROL OIL
April 10, 2023 PMI Revision 00 55
HYDRAULIC AMPLIFIER
TRIP OIL
CONTROL OIL
SECONDARY OIL
CONTROL OIL
AUX. SECONDARY OIL
April 10, 2023 PMI Revision 00 56
Governing Oil • Name of oil pipeline colour source • Control oil yellow MOP/AOP• Aux Start up oil Orange white Filtered oil• Start up oil Orange do• Aux trip oil Red white do• Trip oil Red do• Primary oil green • Aux
April 10, 2023 PMI Revision 00 57
Features of Load Controller• Changes Turbine Load as per a) Load Set point and Gradient b) TSE Margin• Reduces unit load at High Frequency Operation• Comes in operation when Unit is running on Boiler Follow Boiler Follow
Mode Mode ( i.e any change in throttle steam pressure is taken care of
by Boiler Control )• Enables House Load Operation subsequent to a full load throw-off
April 10, 2023 PMI Revision 00 58
Features of Speed Controller• Changes Turbine Speed
( only when M/C is not Synchronised )
a) Speed Set point
b) TSE Margin deciding the gradient
c) Ensures dN/dt monitoring
for speed Exclusion range• Changes Turbine Load as per controller deviation
( i.e speed set point – actual speed )
April 10, 2023 PMI Revision 00 59
Features of Pressure Controller• Maintains Throttle Steam Pressure
as per Throttle Steam Pressure Set point
a PI Controller
comes in action on Turbine Follow Mode
April 10, 2023 PMI Revision 00 60GOVERNING RACK
April 10, 2023 PMI Revision 00 61
April 10, 2023 PMI Revision 00 62
THANK YOU
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