PRESENTATION ON SIPAT 660 MW TURBINE " GOVERNING & PROTECTION SYSTEM"
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Transcript of PRESENTATION ON SIPAT 660 MW TURBINE " GOVERNING & PROTECTION SYSTEM"
Topics of Presentation
Overview of Turbine
Concept of Governing System
Functioning of EHC Circuits
Turbine Start Up Procedure
TSI & TSC System
Turbine Protection System
Turbine Block Diagram
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
Turbine Extractions
Turbine Components
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
Overview of Governing Box
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
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
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 < 0.5s Speed Controller Droop is adjustable from 2.5% to 8%
(with dead band of 0.04%)
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
Resetting of Turbine
Operation of Stop Valve
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
Operation of Stop & Control Valves
Components of EHC
EHC comprises of following controllers:
1. Speed Controller
2. Pressure Controller
3. Load Controller
4. Position Controller
Selection of Controls 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
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
Speed Control Circuit
Logic-1
Speed Set Point
R
L
Speed Set Point = 0
Rate Logic
Logic - 2
Actual Speed (Mv3)
+
-Speed Controller O/P
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 CurveSpeed gradients as per Manufacturer’s start up curve are as follows:
Rolling Condition
Target Speed Preset Time Min. Halt Time
Cold Startup ( > 72 H )
3 - 500 rpm 150 sec 300 sec
1200 rpm* 550 sec 300 sec
3000 rpm 630 sec --------
Between 36H – 72H3 - 500 rpm 75 sec 120 sec
3000 rpm 240 sec --------
Between 8H – 36H 3 - 3000 rpm 360 sec --------
Between 2H – 8H3 - 3000 rpm 300 sec --------
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
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
Speed Control Circuit
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 grid3. The grid frequency has gone beyond allowable limits4. Load Measurement faulty (2/3 sensors faulty)5. M.S. Pres. measurement faulty (2V3 sensors faulty)
6. Unit is in Pressure Control mode
Load Control Circuit
Load Ref
R
L Delay Element
Max.Load Lim. Min.Load Lim.
Correction C.K.T
Freq. Corr
Press. Corr
Fast Tracking
Actual Load
+-
O/P
Logic - 4
5
6
STOP3
21
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…
Load Control Circuit
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
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 Open2. The frequency is more than allowable value*3. M.S. pressure transducers failed (2V3)4. Manual Control switched on5. Load control is On6. HPC is out of operation
Pressure Control
• 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
Adder Block
M. S. Pr. Set Point
Actual Pr. Value +
-
PI Controller
MIN
Minimum Pr.Controller
MAX
Control Stage Max Pr. Controller
O/P
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.
MV2
Posn. F/B - 1
Posn. F/B - 2
Control Signal From TC+
- PI
+
+MIN
Limiter
O/P- (0-150mA)
Biasing Current 0.8 to 1A
TO I/HCONVERTOR
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
Operation of I/H Converter
Control Valve Opening Curve
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 > 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
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
START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT
START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT
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)
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
Turbovisory Instruments
Brg. No. Abs. Brg. Vib. Abs.ShelVib.
(2Comp)
Rel.Rotor Vib.
(2 Comp)
Ang. Dis. Brg. Shell
(2 Comp)
Casing Exp.
Rotor Exp.
3 Comp 2 cmp
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
Turbovisory Instruments
The Stress Margin of the Turbine is calculated by measuring the temperatures of following components:
1. HPC Rotor and Outer Casing2. IPC Rotor and Outer Casing3. 2 HP Stop Valves4. 2 IP Stop Valves5. 4 HP Control Valves6. 4 IP Control Valves
TSC System
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 speed3. Over speed Trip #2 at 111% of rated speed4. Governing oil pressure < 20 Ksc
Contd..
Turbine Protection System
Contd…
Axial shift Very High (2V3) [-1.7mm, +1.2mm]
Turbine bearing vibration : Very High (2V10 including X & Y directions)* >11.2mm/sec (Td=2 sec)
Lube oil tank level very Low (2V3)* Td=3sec (Arming with two stop valves open)
Lub oil pressure Very Low (2V3) < 0.3 Ksc; Td =3 sec (Arming with two stop valves open)
Condenser pressure Very High (2V3) > - 0.7ksc (Arming with condenser press < 0.15 ksc Abs)
Contd..
Turbine Protection System
M.S. temp Very Low (2V3) < 470 deg C (arming > 512 deg C)*
M.S. temp Very High (2V3) > 565 deg C*
HRH temp Very Low (2V3) < 500deg C (arming > 535 deg C)*
HRH temp Very High (2V3) > 593deg C*
HPT outlet temperature Very High (2V4) > 420 deg C
Contd…
Turbine Protection System
Gen seal oil level of any seal oil tank Very Low (2V3)* < 0 mm;Td=15 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) < 17.3 m3/hr; Td =120 sec (Arming with any two stop valves open)
Generator hot gas coolers flow Very LOW (2V3)* : <180m3/hr; Td=300sec(Arming with any two stop valves open)
Generator cooler hot gas temp. Very High(2V4) > 85 deg (Td = 300sec
Contd…
Turbine Protection System
MFT operated: (2V3)
Deareator level Very High (2V3) > 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…
Turbine Protection System