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PROJECT
1X40MW CDQ Waste Heat Recovery Co-Generation Power Plant
M/c. TYPE
HNK 63/2.8
GOVERNING SCHEME WRITE-UP HYDERABAD
PROJECT
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Reference scheme
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40MW CDQ WASTE HEAT RECOVERY CO- GENERATION POWER PLANT 1-T1169-00204-S00 (HY-DG-1-30401-16931)
INTRODUCTION: The Turbo-generator set is equipped with Electro-hydraulic governing system. The system offers the advantages of electronics methods for measurement and signal processing and use of hydraulic devices for continuous control of large positioning devises. The advantages of these combinations are better integration capability, high quality steady state and dynamic response and facility for implementation of complicated functions. The signal processing control function and interlocks are incorporated in the electrical control cubicle, which is placed in the control room. An Electro-hydraulic converter provides the link between electronic section and the hydraulic section. The electronic governor is microprocessor based digital governor. The governing system is designed to control the speed corresponding to speed reference signal provided by turbine speed controller at non-synchronized condition & control MW generation corresponding to the MW generation reference signal provided by load controller at synchronized condition. Additionally the system incorporates protective devices like emergency trip device, emergency stop valve, remote trip solenoid valve etc. ELECTRONIC CONTROLLER: The speed transmitters (SE 3500 A, B & C) sense the turbine speed digitally and feed the actual speed signal to speed controller. The speed controller can be programmed for droop mode or isochronous mode depending on requirements. The speed controller gives output signal to Electro-hydraulic converter (1801). The Electro-hydraulic converters convert the electrical signal into hydraulic signal (secondary oil pressure). ELECTRONIC OVER SPEED PROTECTION: A dedicated electronic over speed protection system is provided apart from the protection given in the electronic governor which receives signals from proximity probe transducers or magnetic pickups (SE 3501 A,B & C). REDUNDANT ELECTROHYDRAULIC CONVERTERS (1801): The dual coil redundant Electro-hydraulic converters (1801) consists of two electro-hydraulic converters with a MAX selector for hot changeover between either of these two converters. The Electro-hydraulic converter is connecting link between electronic and hydraulic parts of Electro-hydraulic governing system.
STEAM TURBINE ENGINEERING T & C ENGINEERING FORMAT No REV PREP. BY TER-9235-00
00
APARNA
DEPT CODE CKD. BY SG
TCED 415 APPD. BY KHS
DOCUMENT No 4T116900213.DOC (HY-WU-4-30401-16932) REV 02 SHT. 1 OF 4
PROJECT
1X40MW CDQ Waste Heat Recovery Co-Generation Power Plant
M/c. TYPE
HNK 63/2.8
GOVERNING SCHEME WRITE-UP HYDERABAD
The output signal of electronic governor is fed to the torque motor of Electro-hydraulic converter (I/H). Torque motor positions the control slide, which in turn builds up the secondary oil pressure proportional to the signal. These secondary oil pressures are transmitted to the respective control valve actuators.
EMERGENCY STOP VALVE (2301)) AND SOLENOID VALVES (2221 & 2222): The emergency stop valve (2301) is of quick closing type. The stop valve actuator consists of a spring-loaded piston and piston disc which is connected to the valve cone through a spindle. The closure of the valve is actuated by means loss of trip oil which is done with the help of main trip solenoid valve (2222). The emergency stop valve is opened actuated by means of solenoid valve (2221) and Trip solenoid valve 2222); a control circuit is built in the electronic control cubicle. The logic and inter locking part permits the opening of emergency stop valve only when the control valves (0801) of the turbine is closed. First, the hand trip valve (2250) is engaged either manually or remotely with the help of solenoid valve (1050). On energizing solenoid valve (2221), the start-up oil pressure builds up above the piston by compressing and energizing the spring inside it. This piston forms an oil tight joint with the piston disk connected to the stop valve through a spindle. Pressure Transmitter (PT 3603A, B) initiates the signal and through the logic energizes the main trip solenoid valves (2222) thereby trip oil pressure builds up below the piston disc. As soon as the solenoid valve (2221) is de-energized upon initiation of pressure Transmitter (PT 3602A, B), the oil in the space above the piston of emergency stop valve is allowed to pass to the drain via orifices (5610). The resulting pressure difference across the piston and the piston disk causes the piston with piston disk to be moved to the opening end position with the spring compressed. The full open position is indicated by means of signal lamp (Limit switches ZSH 3601). The opening speeds of emergency stop valves will be factory set with the aid of adjustable orifice (5610) in the oil drain line of the solenoid valves 2221.
TESTER (2309) FOR EMERGENCY STOP VALVE: Testing device (2309) is provided to check the proper functioning of emergency stop valve (2301) during normal operation of turbine. On operating the testing devices, pressure oil is admitted the to the space behind the test piston of emergency stop valves, which will then push against the piston and move the piston and valve spindle towards the closed position (partial closing) up to a mechanical stop inside the actuators. CONTROL VALVE ACTUATOR (SERVOMOTORS) (1910): Control valve actuators (1910) position the control valves (0801) corresponding to the secondary oil pressures generated by the IH converter. Control valve actuators (Servomotors) mainly consists of a pilot valve, a power cylinder and a feedback system. Upon change in secondary oil pressure, pilot valve provides oil passages to and from power cylinder. The movement of power piston is transmitted to the control valves through levers. The feedback lever resets the pilot valve to its neutral position once the power piston occupies new position corresponding to changed secondary oil pressure. The system is such that the increase in STEAM TURBINE ENGINEERING T & C ENGINEERING FORMAT No REV PREP. BY TER-9235-00
00
APARNA
DEPT CODE CKD. BY SG
TCED 415 APPD. BY KHS
DOCUMENT No 4T116900213.DOC (HY-WU-4-30401-16932) REV 02 SHT. 2 OF 4
PROJECT
1X40MW CDQ Waste Heat Recovery Co-Generation Power Plant
M/c. TYPE
HNK 63/2.8
GOVERNING SCHEME WRITE-UP HYDERABAD
secondary oil pressure causes the control valves to open. Hence interruption of secondary oil pressure causes the control valves to close.
DAMPING DEVICE (5620): Damping (5620) damps out the quick oscillations in secondary oil pressures generated by I/H converters. This helps in improving the stability of the governing system.
REMOTE ENGAGEMENT OF HAND TRIP VALVE: Hand trip valve (2250) can be put into operation remotely with the help of a control switch, i.e. a pressure Transmitter (PT3603 A, B) and a solenoid valve (1050). As soon as control switch is pressed, solenoid valve (1050) gets energized and oil flows into hand trip valve (2250) and reset the trip lever. Soon after start-up oil pressure is built up, solenoid valve gets de-energized through the pressure switch (PT3603A, B).
HAND TRIP VALVE (2250) Whenever the turbine is to be tripped, the governing oil pressure (trip oil line after hand operated valve) is drained by hand trip valve. Thus pressure in front of stop valve piston disc and secondary oil pressure falls, resulting in closure of stop valve and control valves. The hand trip valve (2250) is operated either manually or by loss of source oil pressure.
TRIP SOLENOID VALVE (2222): Trip solenoid valves facilitate the tripping of turbine from remote place such as control room through DCS or desk mounted push button. When solenoid valves (2222) are de energized, interrupt the oil supply to trip oil circuit and simultaneously depressurize the trip oil circuit. Solenoid valves are also de energized by any one of the signals initiated by DCS turbine trip logic or upon generator faults.
DUPLEX FILTER (4520): The Duplex filter with 225 lpm 20 micron filtration is consist of filter head with change over valve and two filter bowls which are removable for maintenance. The change over mechanism facilitates redirection of fluid stream from the dirty to clean filter housing without reduction in flow. The arrangement also provided with a maintenance indicator, which monitors the degree of clogging of the filter elements. Arrows indicate which filter bowl is in operation. Closing of both filter bowls simultaneously is not possible.
ACCUMULATOR (4600): Oil accumulators’ supply oil to the system for a short time during changeover of pumps or during quick action of servomotor in transients along with dampening of any system oscillations. The nitrogen pre-charge pressure should be 70% of the control oil header (Whenever the control oil header pressure STEAM TURBINE ENGINEERING T & C ENGINEERING FORMAT No REV PREP. BY TER-9235-00
00
APARNA
DEPT CODE CKD. BY SG
TCED 415 APPD. BY KHS
DOCUMENT No 4T116900213.DOC (HY-WU-4-30401-16932) REV 02 SHT. 3 OF 4
PROJECT
1X40MW CDQ Waste Heat Recovery Co-Generation Power Plant
M/c. TYPE
HNK 63/2.8
GOVERNING SCHEME WRITE-UP HYDERABAD
falls below the nitrogen pre-charge pressure then the oil will be supplied by accumulator to oil circuit to meet the requirement).
STEAM TURBINE ENGINEERING T & C ENGINEERING FORMAT No REV PREP. BY TER-9235-00
00
APARNA
DEPT CODE CKD. BY SG
TCED 415 APPD. BY KHS
DOCUMENT No 4T116900213.DOC (HY-WU-4-30401-16932) REV 02 SHT. 4 OF 4
CONSULTING ENGINEERS LIMITED MUMBAI
TATA STEEL LTD