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PRESENTATION ON SIPAT 660 MW TURBINE " GOVERNING & PROTECTION SYSTEM"

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. OVERVIEW OF TURBINE.

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PRESENTATION ON SIPAT 660 MW TURBINE " GOVERNING & PROTECTION SYSTEM"

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  1. PRESENTATION ON SIPAT 660 MW TURBINE " GOVERNING & PROTECTION SYSTEM"

  2. Topics of Presentation • Overview of Turbine • Concept of Governing System • Functioning of EHC Circuits • Turbine Start Up Procedure • TSI & TSC System • Turbine Protection System

  3. OVERVIEW OF TURBINE

  4. Turbine Block Diagram

  5. Turbine Extractions

  6. 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

  7. Overview of Governing Box

  8. 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

  9. CONCEPT OF GOVERNING SYSTEM

  10. 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

  11. 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%)

  12. Resetting of Turbine

  13. 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

  14. Operationof Stop Valve

  15. 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

  16. Components of EHC EHC comprises of following controllers: 1. Speed Controller 2. Pressure Controller 3. Load Controller 4. Position Controller

  17. 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

  18. + R Speed Set Point Speed Controller O/P Rate Logic - L Logic - 2 Actual Speed (Mv3) Speed Set Point = 0 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….

  19. Rolling Speed Gradient Curve Speed gradients as per Manufacturer’s start up curve are as follows:

  20. 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

  21. 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

  22. 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

  23. R 3 STOP L Correction C.K.T Delay Element O/P + Load Ref - Fast Tracking Freq. Corr Actual Load 2 5 Press. Corr 1 Min.Load Lim. 6 Max.Load Lim. Logic - 4 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…

  24. 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…

  25. 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

  26. 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

  27. 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

  28. O/P- (0-150mA) + Control Signal From TC MIN + TO I/H CONVERTOR PI + Posn. F/B - 1 MV2 - Posn. F/B - 2 Limiter Biasing Current 0.8 to 1A 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.

  29. Operation of I/H Converter

  30. 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

  31. Control Valve Opening Curve

  32. 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

  33. START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT

  34. 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

  35. START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT

  36. START UP CURVES OF TURBINE AFTER SHUTDOWN OF THE UNIT

  37. TSI & TSC SYSTEM

  38. 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)

  39. 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

  40. Turbovisory Instruments

  41. 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

  42. PROTECTION SYSTEM

  43. 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 < 20 Ksc Contd..

  44. Turbine Protection System Contd…

  45. Turbine Protection System • 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..

  46. 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…

  47. 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…

  48. 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…

  49. THANK YOU

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