07 tur gov _std

April 10, 2023 PMI Revision 00 1

TURBINE GOVERNING


Presentation outline

•Role of turbine governing •Governing Method •Types of Governing systems•Functional division of Governing Ckt•Component of Turbine governing


TURBINE GOVERNING • Role of turbine governing

• Governing Method

• Types of Governing systems

• Functional division of Governing Ckt

• Component of Turbine governing


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.


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


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


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


THE EFFE CT OF CHANGING SPEED SET POINT


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


FREQUENCY VS LOAD CURVE

50 Hz 52.5 Hz51.25 Hz

100%

50%

0% Frequency in Hz

Load in %

Assumption, Droop = 5 %


CHARACTERISTICS OF FREQUENCY INFLUENCE

Droop = 4 %

Droop = 8 %

48 5250

Frequency (in Hz)

+50 %

- 50 %Load

49 51


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


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.


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


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


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


1. MECHANICAL

2. HYDRAULIC

3. ELECTRO-HYDRAULIC

4. Any Combination Of Above Three

Commonly Used System

ELECTRO-HYDRAULIC GOVERNING

(EHG)


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.


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.


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


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.


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.


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)


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


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


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


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


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.


GOVERNING SYSTEM


Block Diagram - HYDRAULIC Controller


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


EHC BLOCK DIAGRAM


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


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


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


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


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


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


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


STARTUP OIL

GETS GENERATED FROM 8 BAR CONTROL FLUID AT STARTUP AND LOAD LIMITING DEVICE.

• HELPS IN OPENING OF STOP VALVE

ORIGIN

FUNCTION


AUXILIARY STARTUP OIL

GETS GENERATED FROM 8 BAR CONTROL FLUID AT STARTUP AND LOAD LIMITING DEVICE.

• RESETS ALL THE HYDRAULIC TRIPPING DEVICES

ORIGIN

FUNCTION


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


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


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


Closing/opening of CV


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


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


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


Startup & Load Limiting Device

8 BAR CONTROL FLUID

STARTUP OIL

AUX. SECONDARY OIL

AUX. STARTUP OIL

PRIMARY OIL

TRIP OIL


Main Trip Valve Operating Mechanism

TRIP OIL

AUX. STARTUP OIL

TESTOIL

CONTROL OIL

AUX. TRIP OIL

CONTROL OIL

CONTROL OIL


HYDRAULIC AMPLIFIER

TRIP OIL

CONTROL OIL

SECONDARY OIL

CONTROL OIL

AUX. SECONDARY OIL


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


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


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 )


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


THANK YOU

07 tur gov _std

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