TURBINE_GOVERNING KWU.pdf

Team turbine BHEL Governing system

1. TURBINE GOVERNING SYSTEM
PRESENTATION BY
M DEENADAYALAN
C M NIKHIL
B VASANTH KUMAR

2. TOPICS OF DISCUSSION
INTRODUCTION
CONCEPT OF GOVERNING SYSTEM
FEATURES OF KWU GOVERNING SYSTEM
GOVERNING SYSTEM DEVICES
WORKING OF GOVERNING SYSTEM
HYDRAULIC AND ELECTROHYDRAULIC SYSTEM
PROTECTIVE DEVICES IN GOVERNING SYSTEM
QUERIES

3. WHAT IS GOVERNING SYSTEM ?
Turbine Governing systemismeant for regulationofturbine
speedundernoloadandvaryingloadcondition.
Toregulate the steam control valve position and hence load
generated.
Tocontrol the initial runupand synchronizationofthe
machine
Toassistinmatching the power generatedtothat demanded
byrespondingtothenetworkfrequencychanges.

4. SALENT FEATURES OF 200 MW KWU TURBINE
GOVERNING SYSTEM
KWU200MWturbineisathrottlegovernedmachine.
Two governors, electro-hydraulic and hydraulic are
incorporated. Both the governors are connectedin
parallel.
Only one governorcanbeselectedata time through the
processofhydraulicminimumselection.
Thecontrol valve opening dependsonsecondaryoil
pressure and thereisa definite relationship between the
openingofHPcontrolvalveandIPcontrolvalve.
Between40to200MWthe turbine loadisvariedby
changingtheHPcontrolvalvethrottlingalone.

5. HYDRAULIC GOVERNOR SALIENTFEATURES
Hydraulic governorishaving only one control
loopcalledspeedcontroller.
Machine speedismeasured and indicatedas
primaryoilpressure.
Rangeofspeedcontrolis2800-3210rpm.
Speedregulationrange(droop)ofHGis7%.
HGactsasaback-uptotheEHG.
HGcannotbeisolatedmechanicallylikeEHG
andHGisconsideredtobethe primary
governoroftheKWUturbine

6. ELECTRO-HYDRAULICGOVERNOR SALIENT
FEATURES
EHG consistsofthree control loops for speed, load and
pressure.
EHGoptimizestheturbinelifebyconservativeoperationwith
theaidofTSE.
Fasterresponseandprecisefrequencycontrol.
Actualspeedoftheturbineismeasuredbyusinghallprobes
Rangeofspeedcontroliswider(0-3210)rpm.
Speedregulation(Droop)canbechangedfrom2.5%to8%in
astepof0.5%evenwhenthemachinerunsonload.Theusual
settingofdroopinEHGis5%.
EHGcanbemechanicallyisolatedbyclosingthesecondaryoil
linefromthelocal.

7. GOVERNING SYSTEM DEVICES
Remote trip solenoids
Turbine trip gear
(Main trip valve)
Starting and load limiting
device
Speeder gear
Auxiliary follow-up piston
Follow-up piston
Hydraulic amplifier
Electro-hydraulic
convertor
Sequence trimming device
Solenoid for load shedding
relay

8. DIFFERENT OILS USED IN KWU TURBINE
Control oil (source oil)
Auxiliary start-up oil
Start-up oil
Auxiliary trip oil
Trip oil
Auxiliary secondary oil
secondary oil
Test oil
Primary oil
Lube oil
Jacking oil

9. REMOTE TRIP SOLENOIDS

10. TURBINE TRIP GEAR

11. Trip gearisthe main protection mechanism of the turbine.Itdiverts
the control oil coming from the RTSin toTRIPOILand AUX.TRIP
OIL. Aux.trip oil keeps the trip gear spool valveinopen conditionso
that uninterrupted trip oil pressureisensured. Aux.trip oilisalso
connectedtothree hydraulic safety devices namely Over speed , Low
vacuum&ThrustbearingTripDevices.

12. STARTING AND LOAD LIMITING DEVICE
USED FOR RESETTING THE TURBINE AFTER TRIPPING
FOR OPENING THE STOP VALVES AND RELEASING THE CONTROL
VALVES FOR OPENING
STARTING DEVICE AT 0% POSITION
BELLOWS COMPRESSED (CONTROL VALVE CLOSED POSITION)
AUX STARTUP OIL RESETS TRIP DEVICES
STARTUP OIL RESETS STOP VALVES (ESVs AND Ivs)
PILOT VALVE(STARTING DEVICE) POSITION RAISED
START-UP OIL AND AUXILIARY START-UP OIL CIRCUITS ARE DRAINED
ESVS OPEN AT 42% AND IVS OPEN AT 56% POSITIONS OF THE STARTING
DEVICE

15. SPEEDER GEAR
ASSEMBLY OF A BELLOW AND A SPRING
BELLOW COMPRESSION CONTROLLED BY
STARTING DEVICE POSITOIN
SPEEDER GEAR POSITION (ALTERS SPRING TENSION)
PRIMARY OIL PRESSURE
OPERATED FROM UCB OR LOCAL
PRIMARY OIL PRESSURE (SPEED FEEDBACK)

17. AUXILIARY FOLLOW UP-PISTONS

18. TEST VALVES
HP/IP STOP VALVES RECEIVE TRIP OIL THROUGH
THEIR RESPECTIVE TEST VALVES
PORT OPENINGS FOR BOTH TRIP OIL AND
START-UP OIL
USED IN RESETTING OF STOP VALVES AFTER
TURBINE TRIP
VALVE CAN BE OPERATED WITH HANDWHEEL

19. WORKING OF GOVERNING SYSTEM
SPEEDER
GEAR
STARTING
DEVICE
AFUP
HYRAULIC
CONVERTER
FUP
TRIP VALVE
AUX START UP OIL
TO RESET TRIP V/V
EHC
FUP
EHC INPUT
IP SECONDARY OIL
HP SECONDAY OIL
TRIP OIL
TRIP OIL
CONTROL
OIL
AUX TRIP OIL
LOW VACUUM
TRIP DEVICE
OVER SPEED
DEVICE
THRUST
BEARING DEVICE
HP/IP
STOP VALVE
RESET
CONTROL
OIL
TRIP OIL
AUX
TRIP OIL
CONTROL OIL
FROM RTS

23. SELECTION BETWEEN HYDRAULIC AND
ELECTRO HYDRAULIC GOVERNING
MINIMUM PRESSURE BETWEEN HP AND IP
SECONDARY OIL
TURBINE STARTUP USING EHC WITH HC
SYSTEM FOR BACK UP
SECONDARY OIL PRESSURE SET HIGHER THAN
THE EHC SYSTEM AND MAINTAINED USING A
TRACKING SYSTEM

24. ESV OPENING

48. PROTECTIVE DEVICES IN GOVERNING
SYSTEM

49. TURBINE PROTECTON
Two type of protection
a)Electrical protection
b)Mechanical tripping
Electrical protection(through RTS)
Turbine UCB manual trip
Stator water conductivity >21 mho/sec
Stator water flow <13 cubic m/s
Boiler to turbine through UTR
Gen to turbine through UTR
Lube oil pressure low -low <1.2 ksc(2/3)
Fire protection(channel 1&2)
UTR manual trip
ATRS shut down programme
Mechanical devices
TG over speed trip (bolt-1 –3300 rpm,2-3330 rpm)
Condenser vacuum low
Axial shift high

50. GOVERNING CONTROL SYSTEM
Governor control systems consist of three basic elements:
These elements are
Sensing elements –fly ball weight etc.
Transmitting elements -mechanical linkage, hydraulic or
pneumatic pressure, electrical signals or, as is most common, a
combination.
and Correctingelements -the valve or valves that control the
flow of steam to the turbine.

51. MECHANICAL PROTECTION DEVICES-
OVER SPEED TRIP DEVICE OR EMERGENCY GOVERNORS
•The function is to stop turbine when permissible speed is
exceeded.
•Two over speed bolts, one acts when speed reaches 110%
(3300rpm) of the rated speed and others comes in action at
111% of the rated speed (3330 rpm)
•It is situated in the front end bearing pedestal & consists of
eccentric bolt, adjusting screw, spring, pawl and screw plug. .
•The speed is measured with the help of hall probe.
•When the over speed occurs & goes beyond the preset value(s)
the bolts fly out due to centrifugal force & strike against the
respective pawls. This will lead to the opening of the Drain port
through which Auxiliary trip oil will be drained, resulting in the
draining of the trip oil & thereby tripping the turbine.

52. •Below the tripping speed the bolt is held in position by spring and
bears against the plug.
•At speed higher than over speed limit, the centrifugal force overcomes
the spring force and forces bolt out of turbine rotor. This activates the
turbine trip mechanism.
•Before over speed device comes into action, an another term called
DROOP should come in action to reduce the speed of the turbine.
•Speed regulation of the turbine is called Droop

53. DROOP OR PROPORTIONAL BAND
Droop= amount of speed change from no load to full load divided by
rated speed
In KWU turbines Droop is in the range from 2.5 to 8%.
Usually it is taken as 5% of the rated speed. This maximum speed is
called ‘Dead band’ beyond which Droop comes in action to increase or
decrease the speed of the turbine by opening or closing the control
valve .
It is necessary in the control system to sense a change in speed & thus
to reposition the valves
If droop =5%, it means +2.5% from 3000 rpm.

57. LOW VACUUM TRIP DEVICE
The function of the device is to trip the turbine on dropping of
condenser vacuum below a limit.
Condenser vacuum permissible is -0.9 ksc.
It consists of twin chamber arrangement with a separating diaphragm.
Upper side is connected to the condenser vacuum and lower side to
atmosphere. Upper side is also subjected to the primary oil pressure
through the piston.
Under poor vacuum with sufficiently high machine speed(>600rpm),
the net force acting on the upper side is more than the lower side . This
causes the opening of the drain port through which the Aux.trip oil will
drain.
This protection is not effective during low speed because of the non
availability of the primary oil pressure.
For resetting it doesn’t require Auxiliary start up oil.

59. THRUST BEARING DEVICE
It is used to protect the turbine against high axial shift and high
thrust pad wear.
It consists of a two pair of small cams, one set before and
another after a pawl are fitted on the turbine shaft 180⁰
opposite.
The pawl is so arranged that whenever the shaft moves
horizontally too much (>0.6mm)either in left side or right side,
one sets of cam comes in contact with the pawl and thereby
thrust bearing trip device’s latch will be released. This will cause
the opening of the drain port through which auxiliary trip will
be drained.

62. THANK YOU