turbine governing system

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660 MW SUPERCRITICAL TURBINE " GOVERNING
PROTECTION SYSTEM"
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Topics of Presentation

• Overview of Turbine
• Concept of Governing System
• Functioning of EHC Circuits
• Turbine Start Up Procedure
• TSI TSC System
• Turbine Protection System

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OVERVIEW OF TURBINE
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Turbine Block Diagram
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Turbine Extractions
Ext. No Source Of Extraction Destination Equipments
1 13th stage of HPT HPH-8
2 CRH HPH-7
3 3rd stage of IPT HPH-6
3 3rd stage of IPT TDBFP
4 6th stage of IPT DEAERATOR
5 8th stage of IPT LPH-4
6 11th stage of IPT LPH-3
7 2nd stage of LPT LPH-2
8 4th stage of LPT LPH-1
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Turbine Components

• Turbine HPT, IPT, LPT1 and LPT2
• Turbine Bearings 08
• Generator / Exciter Bearings 04
• Turbine Stop Valves 04 (HPSV-12, IPSV-12)
• Turbine Control Valves 08 (4 HPCV 4 IPCV)
• CRH Check Valves 02 ( With Bypass lines for warm
  up)
• Motor driven Shut Off valve in non-stabilized oil
  line to Check Valve
• Motor driven warm up Shut Off valves for HPCV-3
  4
• Governing Box

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Overview of Governing Box
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Governing Box Components

• Motor operated Control Gear to generate resetting
  / protection oil control oil for S.V./
  Summators
• Two Manual trip devices
• Two Over Speed Governor Slide valves (110 111
  )
• Two Remote Trip Solenoids
• Slide Valve for ATT with two solenoids

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CONCEPT OF GOVERNING SYSTEM
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Governing System

• Combination of throttle nozzle governing
• IP Turbine has throttle governing all four
  control valves open simultaneously
• HP Turbine has nozzle governing all four
  control valves open in preset sequence
• Resetting of Turbine is done by Control Gear
  operation
• Operation of Stop Control Valves and CRH Check
  Valves are done by spring type hydraulic
  servomotors
• Servomotors are closed by spring action during
  loss of oil pressure

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Governing System

• HPT control valves open only after achieving
  preset load (12 of 660 MW)
• Opening time of control valve is 1.5 sec
• Closing time of Stop valve in case of operation
  of protection is 0.3 sec
• Turbine maximum speed is restricted to 108 in
  case of generator disconnected from grid
• Over speed protection system stops steam supply
  in HPC in lt 0.5s
• Speed Controller Droop is adjustable from 2.5 to
  8 (with dead band of 0.04)

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Resetting of Turbine
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Resetting of Turbine

• Stabilized oil pressure of 50 Ksc is supplied to
  Control Gear
• The control gear (AE001) is moved from closed
  position (0 degree) to open position (90 deg)
• Oil is first supplied to reset the over speed
  governor slide valves
• Subsequently Protection Oil is generated and
  supplied to protection devices
• Finally, Control Oil for Stop Valves servomotors
  Control Oil for EHC-summators are generated

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Operation of Stop Valve
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Operation of Stop Control Valves

• Control Oil pressure in S.V. servomotor moves up
  slide valve, providing Header Pressure Oil under
  the piston for S.V. opening
• Header Pressure Oil is supplied to C.V. valve
  servomotors via locking pilot valve
  traction/bush arrangements. Opening of C.V. is
  governed by Control Oil from EHC-Summator
• During loss of Header Pressure Oil, the
  servomotors are closed by spring action
• During loss of Control Oil pressure, Bush
  Traction of Pilot valve travels up shutting off
  head pressure oil supply to C.V. servomotors,
  resulting control valve closing
• During S.V. ATT, bush Traction do not travel up
  due to slide valve downward movement by ATT motor

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Components of EHC

• EHC comprises of following controllers
• 1. Speed Controller
• 2. Pressure Controller
• 3. Load Controller
• 4. Position Controller

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Selection of Controls

• EHC can be kept in Manual / Auto Mode as per
  operators choice
• Manual mode can be selected only when Generator
  is connected to grid
• In Manual Mode, operator can directly open /
  close the control valves
• Controllers can be selected in auto mode through
  P.B provided on operators console or through
  interlocks
• Controller output in auto mode depends on set
  point and actual value

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Speed Control Circuit
Logic-1
Logic 1 Turbine protection operated / 2v4 stop
valves closed / 2v3 speed measuring channels
faulty / Deviation between actual speed and set
point during run-up exceeded allowable
value Logic 2 Speed gradient is controlled by
minimum of TSE margin gradient from selected
Start up curve, given by the Turbine
Manufacturer
Contd.
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Rolling Speed Gradient Curve Speed gradients as
per Manufacturers start up curve are as
follows
Rolling Condition Target Speed Preset Time Min. Halt Time
Cold Startup ( gt 72 H ) 3 - 500 rpm 150 sec 300 sec
Cold Startup ( gt 72 H ) 1200 rpm 550 sec 300 sec
Cold Startup ( gt 72 H ) 3000 rpm 630 sec --------
Between 36H 72H 3 - 500 rpm 75 sec 120 sec
Between 36H 72H 3000 rpm 240 sec --------
Between 8H 36H 3 - 3000 rpm 360 sec --------
Between 2H 8H 3 - 3000 rpm 300 sec --------
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Speed Control Circuit

• Speed Controller will be switched on
  automatically in case generator breaker opens
  (with Turbine controller on auto) or Turbine
  trips
• Turbine speed measurement is be done by using 3
  sensors (eddy current type)
• The mean of the three sensors is taken as actual
  speed
• Incase of one sensor fault, maximum of rest two
  sensors will come in service
• Incase of two sensor fault, Turbine trip signal
  is generated to trip the turbine

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Speed Control Circuit

• Speed Ref Tracking
• After Synchronization, with other controller in
  service, the speed controller tracks the actual
  speed between 49HZ to 51HZ (adjustable)
• Islanding Mode
• If actual speed exceeds speed reference by a
  preset limit under Generator Breaker in closed
  condition, Islanding mode occurs Transferring
  Turbine to Speed Control mode

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Load Control Circuit

• Load Control On Load Controller will be switched
  on automatically if Turbine controller is kept on
  auto and connected to the grid under Turbine
  Latched condition.
• Load Control Off Load controller will be
  switched off under following conditions
• 1. Manual control mode is switched on
• 2. The Generator has disconnected from the
  grid
• 3. The grid frequency has gone beyond allowable
  limits
• 4. Load Measurement faulty (2/3 sensors faulty)
• 5. M.S. Pres. measurement faulty (2V3 sensors
  faulty)
• 6. Unit is in Pressure Control mode

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Load Control Circuit
Logic-1 CMC ON, when load ref. will come from
CMC circuit, where TSC Margin
calculation controls the gradient Logic-2 The
Load reference tracks actual load for bump less
transfer once it is connected to
the grid. Contd
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Load Control Circuit
Logic-3 Load Reference will be stopped under
the following Conditions 1. TSC Margin is less
than permissible value 2. The difference
between the actual and reference value is
not in allowable range Logic-4 Maximum and
minimum load set points, set by the Operator
Logic-5 External Frequency Influence ON -
actual frequency will be tracked at a
predefined delayed rate, with an adjustable droop
to help in loading and unloading of the
machine within a band of frequency Contd
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Load Control Circuit
Logic 6 The Pressure correction is divided
into two Parts 1. Before the HPC On is
generated, the pressure correction
will be calculated with R.H. pressure
2.After HPC On is generated, the pressure
correction will be calculated with M.S
pressure HPC On The point at which the
HP Control Valves starts Opening (12 of
full load) Load Measurement Three Transducers
with mean value selection Incase of one of the
transducer failed, maximum of rest two.will be
selected
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Pressure Control Circuit

• Pressure Control is switched ON by the operator
  or automatically through Turbine Control on auto
  when HPC is in operation
• Pressure Controller is automatically deactivated
  under the following conditions
• 1. GCB Open
• 2. The frequency is more than allowable value
• 3. M.S. pressure transducers failed (2V3)
• 4. Manual Control switched on
• 5. Load control is On
• 6. HPC is out of operation

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Pressure Control
Adder Block
PI Controller
MIN
MAX

Actual Pr. Value
O/P
-
M. S. Pr. Set Point
Minimum Pr. Controller
Control Stage Max Pr. Controller

• M.S. pressure set point is dictated by Boiler
  Master
• Limitation of pressure drop to impermissible
  value is ensured by minimum pressure controller
• Limitation of pressure rise to impermissible
  value is ensured by a protective control stage
  maximum steam pressure controller, which comes
  into operation through maximum value selector

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Position Control Circuit

• A PI controller is used to generate the signal
  to the current amplifiers through
  Limiter
• Command to HP control valves extends under HPC
  ON condition
• Loss of current signal to I/H Converter results
  in closing of the C.V.

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Operation of I/H Converter
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Operation of I/H Converter

• I/H Converters control the opening and closing of
  the corresponding control valves
• Individual I/H converters get command from
  Turbine controller
• 50 Ksc Header Pressure Oil holds the piston (2)
  up against spring action
• As the slide valve (1) moves as per I/H
  converter, 35 Ksc control oil output is regulated
  for C.V. servomotor operation
• When 50 KSC Governing oil pressure collapses,
  piston (2) travels down due to spring action
  thus draining the oil line of C.V. servomotor

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Control Valve Opening Curve
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Turbine Start Up Sequence

• Start Turbine rolling with Speed Control on from
  barring speed to 500 rpm
• After achieving desired criteria, raise speed set
  point to 1200 rpm and subsequently to 3000 rpm
• After synchronization Load Controller gets
  switched On raise load gt 80MW when HPC ON
  signal is generated
• Turbine Pressure Control will be automatically
  switched On
• After HPCV demand crosses 80, switch ON Position
  controller to hold 80 as the o/p to control
  valves for raising pressure to rated value
• Switch ON Pres. Controller to raise load to rated
  value
• Switch ON Load Control after load reaches the
  rated value

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START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE
UNIT
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Start Up Curves Nomenclature

• To S.H Live steam temperature.
• Trh R.H steam temperature
• Po S.H outlet steam pressure
• Prh R.H. steam pressure
• Go Electrical Load of TG
• Ne Live steam flow from boiler
• N Turbine rotor speed
• A Steam Admission
• B Synchronization
• C HPC switch on
• D HPCV open with 20 Throttle reserve Loading
  with constant HPCV position HP heaters charged
• E HPCV no-3 opening. Throttle pressure reduced
• F Full Load

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START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE
UNIT
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START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE
UNIT
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TSI TSC SYSTEM
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Turbovisory Instruments

• Turbo Generator consists of 12 bearings 8 for
  Turbine 2 for Generator 2 for Exciter
• For Bearing no. 1-10, abs. brg. vibration is
  measured in 3 components (Horizontal, Vertical
  Horizontal axial)
• For Bearing no. 11 12, abs. brg. vibration is
  measured in 2 components (Horizontal Vertical)
• Absolute shell vibration is measured for all the
  bearings in 2 components (Horizontal Vertical)

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Turbovisory Instruments

• Rotor Relative Vibration is measured in all the
  bearings in 2 components
• Absolute Rotor Vibration is derived from Absolute
  Bearing Shell Vibration and Rotor Relative
  Vibration for all the bearings
• Axial Shift measurement is done in Bearing no. 3
• Eccentricity measurement is done in Bearing no. 1
• Turbine Speed sensors and Key phasor are
  Installed in Bearing no. 1

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Turbovisory Instruments
Brg. No. Abs. Brg. Vib. Abs. Brg. Vib. Abs.ShelVib. (2Comp) Rel.Rotor Vib. (2 Comp) Ang. Dis. Brg. Shell (2 Comp) Casing Exp. Rotor Exp.
Brg. No. 3 Comp 2 cmp Abs.ShelVib. (2Comp) Rel.Rotor Vib. (2 Comp) Ang. Dis. Brg. Shell (2 Comp) Casing Exp. Rotor Exp.
1 Y N Y Y N Y (HPC) Y
2 Y N Y Y N
3 Y N Y Y N
4 Y N Y Y Y Y (IPC) Y
5 Y N Y Y Y
6 Y N Y Y Y Y (LPC-1) Y
7 Y N Y Y Y
8 Y N Y Y Y Y (LPC-2) Y
9 Y N Y Y Y
10 Y N Y Y N
11 N Y Y Y N
12 N Y Y Y N
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TSC System

• The Stress Margin of the Turbine is calculated by
  measuring the temperatures of following
  components
• 1. HPC Rotor and Outer Casing
• 2. IPC Rotor and Outer Casing
• 3. 2 HP Stop Valves
• 4. 2 IP Stop Valves
• 5. 4 HP Control Valves
• 6. 4 IP Control Valves

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PROTECTION SYSTEM
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Turbine Protection System

• Turbine protection system consists of Two
  Independent channels, each operating the
  corresponding solenoid (220V DC) to trip the
  Turbine in case of actuation of remote protection
• Hydraulic Protection Apart from the
  Electrical Trip, Turbine is equipped with the
  following Hydraulic Protections
• 1. Local Manual Trip (1V2)
• 2. Over speed Trip 1 at 110 of rated speed
• 3. Over speed Trip 2 at 111 of rated speed
• 4. Governing oil pressure lt 20 Ksc
• Contd..

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Turbine Protection System
Contd
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Turbine Protection System

• Axial shift Very High (2V3) -1.7mm, 1.2mm
• Turbine bearing vibration Very High (2V10
  including X Y directions) gt11.2mm/sec (Td2
  sec)
• Lube oil tank level very Low (2V3) Td3sec
  (Arming with two stop valves open)
• Lub oil pressure Very Low (2V3) lt 0.3 Ksc Td 3
  sec (Arming with two stop valves open)
• Condenser pressure Very High (2V3) gt - 0.7ksc
• (Arming with condenser press lt 0.15 ksc Abs)
• Contd..

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Turbine Protection System

• M.S. temp Very Low (2V3) lt 470 deg C (arming gt
  512 deg C)
• M.S. temp Very High (2V3) gt 565 deg C
• HRH temp Very Low (2V3) lt 500deg C (arming gt 535
  deg C)
• HRH temp Very High (2V3) gt 593deg C
• HPT outlet temperature Very High (2V4) gt 420 deg
  C
• Contd

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Turbine Protection System

• Gen seal oil level of any seal oil tank Very Low
  (2V3) lt 0 mmTd15 sec (Arming with any two stop
  valves open)
• All Generator seal oil pumps OFF (3V3) Td 9 sec
  (Arming with any two stop valves open)
• Generator Stator winding flow Very Low (2v3) lt
  17.3 m3/hr Td 120 sec (Arming with any two stop
  valves open)
• Generator hot gas coolers flow Very LOW (2V3)
  lt180m3/hr Td300sec(Arming with any two stop
  valves open)
• Generator cooler hot gas temp. Very High(2V4) gt
  85 deg (Td 300sec
• Contd

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Turbine Protection System

• MFT operated (2V3)
• Deareator level Very High (2V3) gt 3400 mm
• HP heater level protection operated (2V3)
• Generator Electrical protection operated (2V3)
• Turbine over speed protection operated (114)
• Turbine Controller failure protection operated
  (2V3)
• Contd

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