Transcript Slide 1


Overview of Turbine

Concept of Governing System

Functioning of EHC Circuits

Turbine Start Up Procedure

TSI & TSC System
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Turbine Protection System
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: HPT, IPT, LPT1 and LPT2
Turbine Bearings: 08
Generator / Exciter Bearings: 04
Turbine Stop Valves: 04 (HPSV-1&2, IPSV-1&2)
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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Motor operated Control Gear to generate resetting /
protection oil & control oil for S.V./ Summators
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Two Manual trip devices
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Two Over Speed Governor Slide valves (110 % & 111 %)
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Two Remote Trip Solenoids
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Slide Valve for ATT with two solenoids
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Combination of throttle & nozzle governing
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IP Turbine has throttle governing – all four control
valves open simultaneously
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HP Turbine has nozzle governing – all four control
valves open in preset sequence
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Resetting of Turbine is done by Control Gear operation
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Operation of Stop & Control Valves and CRH Check
Valves are done by spring type hydraulic servomotors
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Servomotors are closed by spring action during loss of
oil pressure
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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 < 0.5s
Speed Controller Droop is adjustable from 2.5% to 8%
(with dead band of 0.04%)
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Stabilized oil pressure of 50 Ksc is supplied to Control
Gear
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The control gear (AE001) is moved from closed position
(0 degree) to open position (90 deg)
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Oil is first supplied to reset the over speed governor slide
valves
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Subsequently Protection Oil is generated and supplied
to protection devices
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Finally, Control Oil for Stop Valves servomotors &
Control Oil for EHC-summators are generated
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Control Oil pressure in S.V. servomotor moves up slide valve,
providing Header Pressure Oil under the piston for S.V. opening
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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
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During loss of Header Pressure Oil, the servomotors are closed by
spring action
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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
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During S.V. ATT, bush & Traction do not travel up due to slide valve
downward movement by ATT motor
EHC comprises of following controllers:
1. Speed Controller
2. Pressure Controller
3. Load Controller
4. Position Controller
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EHC can be kept in Manual / Auto Mode as per
operator’s choice
Manual mode can be selected only when Generator is
connected to grid
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In Manual Mode, operator can directly open / close the
control valves
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Controllers can be selected in auto mode through P.B
provided on operators console or through interlocks
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Controller output in auto mode depends on set point and
actual value
R
L
+
Speed
Set Point
Rate Logic
-
Speed
Controller
O/P
Logic - 2
Logic-1
Speed Set
Point = 0
Actual Speed
(Mv3)
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….
Rolling Speed Gradient Curve
Speed gradients as per Manufacturer’s start up curve are as follows:
Rolling Condition
Cold Startup
( > 72 H )
Between 36H – 72H
Between 8H – 36H
Between 2H – 8H
Target Speed
Preset Time
Min. Halt Time
3 - 500 rpm
150 sec
300 sec
1200 rpm*
550 sec
300 sec
3000 rpm
630 sec
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3 - 500 rpm
75 sec
120 sec
3000 rpm
240 sec
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3 - 3000 rpm
360 sec
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3 - 3000 rpm
300 sec
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Speed Controller will be switched on automatically in
case generator breaker opens (with Turbine controller
on auto) or Turbine trips
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Turbine speed measurement is be done by using 3
sensors (eddy current type)
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The mean* of the three sensors is taken as actual
speed
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Incase of one sensor fault, maximum of rest two
sensors will come in service
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Incase of two sensor fault, Turbine trip signal is
generated to trip the turbine
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Speed Ref Tracking:
After Synchronization, with other controller in service,
the speed controller tracks the actual speed between
49HZ to 51HZ (adjustable)
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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 On: Load Controller will be switched on
automatically if Turbine controller is kept on auto and
connected to the grid under “Turbine Latched” condition.
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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
R
L
3
STOP
Correction
C.K.T
Delay Element
Load Ref
+
Fast
Tracking
Freq. Corr
2
1
5
Max.Load Lim. Min.Load Lim.
O/P
-
Actual Load
Press. Corr
6
Logic - 4
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…
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…
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 is switched ON by the operator or
automatically through Turbine Control on auto when HPC
is in operation
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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
Actual Pr. Value
+
Adder Block
-
PI
Controller
MIN
MAX
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
+
O/P- (0-150mA)
Control Signal From TC
+
Posn. F/B - 1
-
PI
+
MIN
TO I/H
CONVERTOR
Posn. F/B - 2 MV2
Limiter
Biasing Current 0.8 to 1A
• 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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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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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 > 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
START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT
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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
START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT
START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT
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Turbo Generator consists of 12 bearings – 8 for Turbine
& 2 for Generator & 2 for Exciter
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For Bearing no. 1-10, abs. brg. vibration is measured in
3 components (Horizontal, Vertical & Horizontal axial)
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For Bearing no. 11 & 12, abs. brg. vibration is measured
in 2 components (Horizontal & Vertical)
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Absolute shell vibration is measured for all the bearings
in 2 components (Horizontal & Vertical)
Turbovisory Instruments
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Rotor Relative Vibration is measured in all the bearings in
2 components
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Absolute Rotor Vibration is derived from Absolute Bearing
Shell Vibration and Rotor Relative Vibration for all the
bearings
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Axial Shift measurement is done in Bearing no. 3
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Eccentricity measurement is done in Bearing no. 1
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Turbine Speed sensors and Key phasor are Installed in
Bearing no. 1
Turbovisory Instruments
Brg. No.
Abs. Brg. Vib.
3 Comp
2 cmp
Abs.Shel
Vib.
(2Comp)
Rel.Rotor
Vib.
(2 Comp)
Ang. Dis.
Brg.
Shell
(2 Comp)
1
Y
N
Y
Y
N
2
Y
N
Y
Y
N
3
Y
N
Y
Y
N
4
Y
N
Y
Y
Y
5
Y
N
Y
Y
Y
6
Y
N
Y
Y
Y
7
Y
N
Y
Y
Y
8
Y
N
Y
Y
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
Casing
Exp.
Rotor
Exp.
Y (HPC)
Y
Y (IPC)
Y
Y (LPC-1)
Y
Y (LPC-2)
Y
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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
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 < 20 Ksc
Contd..
Contd…
Turbine Protection System
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Axial shift Very High (2V3) [-1.7mm, +1.2mm]
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Turbine bearing vibration : Very High (2V10 including X &
Y directions)* >11.2mm/sec (Td=2 sec)
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Lube oil tank level very Low (2V3)* Td=3sec (Arming with
two stop valves open)
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Lub oil pressure Very Low (2V3) < 0.3 Ksc; Td =3 sec
(Arming with two stop valves open)
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Condenser pressure Very High (2V3) > - 0.7ksc
(Arming with condenser press < 0.15 ksc Abs)
Contd..
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M.S. temp Very Low (2V3) < 470 deg C (arming > 512
deg C)*
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M.S. temp Very High (2V3) > 565 deg C*
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HRH temp Very Low (2V3) < 500deg C (arming > 535
deg C)*
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HRH temp Very High (2V3) > 593deg C*
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HPT outlet temperature Very High (2V4) > 420 deg C
Contd…
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Gen seal oil level of any seal oil tank Very Low (2V3)* <
0 mm;Td=15 sec (Arming with any two stop valves
open)
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All Generator seal oil pumps OFF (3V3)* Td: 9 sec
(Arming with any two stop valves open)
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Generator Stator winding flow Very Low (2v3) < 17.3
m3/hr; Td =120 sec (Arming with any two stop valves
open)
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Generator hot gas coolers flow Very LOW (2V3)* :
<180m3/hr; Td=300sec(Arming with any two stop
valves open)
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Generator cooler hot gas temp. Very High(2V4) > 85
deg (Td = 300sec
Contd…
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MFT operated: (2V3)
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Deareator level Very High (2V3) > 3400 mm*
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HP heater level protection operated (2V3)*
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Generator Electrical protection operated (2V3)
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Turbine over speed protection operated (114%)
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Turbine Controller failure protection operated (2V3)
Contd…