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PRESENTED BY :
BALRAM DEWANGAN
HIMANSHU PANDEY
HEMANTH KUMAR
SHASWAT SAURAV SAHOO
Topic to be covered
MFT
Interlocks and Protection scheme of Turbine
system
ETS
Generator and GT block protection scheme

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INTERLOCKS AND PROTECTION
Interlocks are incorporated in a system to
connect the Equipments with each other
through pre-defined logics. When any
abnormal condition arises or the actual
parameter fluctuates with corresponding set
point then it generates a signal & forwards it
to concerned equipments to stop it in a
controlled manner & it protects the
Equipment. It also acts as permissive for
some equipments.
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MASTER FUEL TRIP (MFT)
MASTER FUEL TRIP(MFT) is a supervisory system used to safely trip
the Boiler in the event of any abnormal conditions act

One PLC system is used for this purpose which receives various
Tripping signals directly from field/DCS, conducts logical processes and
sends out Tripping signals to Trip all means of fuel supply to the boiler

Also generates digital signals for Trip first out and SOE




MFT CONDITIONS
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Furnace pressure HH
Furnace pressure LL
Drum level HHH
Drum level LLL
Both FD,ID fans tripped
Both Air preheaters are stopped
Emergency manual trip push button
Furnace air flow is less than 25 of B-MCR
Scanner air fan has stopped
Loss of fuel




There are three pressure switches in field
The switches will act whenever the pressure goes beyond 3240 Pa.


FURNACE PRESSURE LL

There are three pressure switches in field
The switches will act whenever the pressure falls below -2490 Pa.





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FURNACE PRESSURE HH
FURNACE PRESSURE TRIPPING
DRUM LEVEL HH
Actual Drum level is calculated by the level and pressure signal coming form the
field to DCS
For tripping, the drum level value must go beyond 250 mm with a delay of 3
seconds.

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AND
AND
AND
T_ON
3 sec
Drum lvl1 >250 mm & not BAD
Drum lvl2 >250 mm & not BAD
Drum lvl2 >250 mm & not BAD
Drum lvl3 >250 mm & not BAD
Drum lvl1 >250 mm & not BAD
Drum lvl3 >250 mm & not BAD
TRIP OUTPUT
DRUM LEVEL LL
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Actual Drum level is calculated by the level and pressure signal coming form the
field to DCS
For tripping, the drum level value must fall below -300 mm with a delay of 3
seconds.

AND
AND
AND
T_ON
3 sec
Drum lvl1 <-300mm & not BAD
Drum lvl2 <-300mm & not BAD
Drum lvl2 <-300mm & not BAD
Drum lvl3 <-300mm & not BAD
Drum lvl1 <-300mm & not BAD
Drum lvl3 <-300mm & not BAD
TRIP OUTPUT
FANS TRIPPINGS
BOTH FD FANS TRIPPED

3 independent signals for FD fan A stopped and 3 independent signal comes for
FD fan B stopped comes from electrical switch gear to MFT TMR system
2/3 logic is processed in TMR for FD fan A stopped and FD fan B stopped
MFT is initiated if both FD fan stopped signals are true after 2/3 logic

BOTH ID FANS TRIPPED

3 independent signals for ID fan A stopped and 3 independent signal comes for
ID fan B stopped comes from electrical switch gear to MFT TMR system
2/3 logic is processed in TMR for ID fan A stopped and ID fan B stopped
MFT is initiated if both ID fan stopped signals are true after 2/3 logic






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FLAME TRIPPINGS
LOSS OF FLAME DETECTORS COOLING AIR

Loss of flame detector cooling air occurs whenever at least one of the following
condition acts
Both flame scanner cooling fan stops (AC and DC).This signal is initiated from
DCS
OR
2/3 switches act for cooling air pressure. Set point of the switches are 2.3 Kpa.
These signals directly go to TMR panel from field

LOSS OF FLAME

Loss of flame occurs if any mill comes into service and loss of flame in all coal
layer and all oil layer acts


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TRIPPING FROM FUEL AND APH
LOSS OF FUEL

Loss of fuel acts when all means of fuel to boiler cuts off. The condition is described
below
LDO supply pneumatic valve closed OR all corner LDO valves closed
AND
HFO supply pneumatic valve closed OR all corner HFO valves closed
AND
All mill stopped OR all feeder stopped


BOTH APH TRIPPED

This condition occurs when APH A main an aux motor stopped
AND
APH B main and aux motor stopped
This condition is initiated from DCS to TMR



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MANUAL BOILER TRIPPING


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MANUAL TRIP

Two push buttons are provided on operator desk. Both are to
be pressed at the same time trip the Turbine in any
emergency.


FURNACE AIR FLOW LOW
Total air flow is calculated by adding FD air flow and PA air flow
This condition is initiated when total air flow is less than 550 TPH

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AND
AND
AND
FURNACE AIR FLOW < 550 TPH-1
FURNACE AIR FLOW < 550 TPH-2
FURNACE AIR FLOW < 550 TPH-2
FURNACE AIR FLOW < 550 TPH-3
FURNACE AIR FLOW < 550 TPH-1
FURNACE AIR FLOW < 550 TPH-3
INTERLOCKS AND PROTECTIONS
CONDENSATE EXTRACTION PUMP
MOTOR-DRIVEN BOILER FEED PUMP
TURBO- DRIVEN BOILER FEED PUMP
LUBE OIL AND JACKING OIL SYSTEM
COOLING WATER SYSTEM
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CEP
START PERMISSIVE
Condenser hotwell level > 600 mm
Inlet MOV is opened
Outlet MOV is closed
CEP motor bearing (Up & under) temperature< 70 C
CEP pump thrust bearing temperature < 75 C.
CEP motor winding temperature < 130 C

Protection Trip condition
The outlet is still closed after the pump is running at a period of 30s
Motor-operated valve in condensate pump inlet closed.
Condensate pump is running, condensate water flow <415t/h and recirculation regulating
valve position<50%.
Water level of condensate hot well LL low low

AUTO START CONDITION
When the running pump stop OR outlet header pipe pressure is lower than 2.5MPa,
standby pump puts into operation by interlock.
START PERMISSIVE
Deaerator level normal (-80mm to + 80 mm).
Minimum flow recirculation valve full open.
M-DFBP inlet motor-operated valve fully opened.
Motor-operated valve in M-BFP outlet closed are in interlock
Lube oil pressure normal 0.176 MPa.
MDBFP motor, booster pump and main pump bearing temperatures normal < 90 C
M-BFP electric motor winding temperature not high < 110 C
Hydraulic coupler bearing temperature < 90 C.
No interlock trip condition
PROTECTION TRIP CONDITION
Deaerator level low low (-1500mm )
When M-BFP is running-BFBP outlet feed water flow low low and M-BFP minimum flow recirculation
valve position<60%, delay 8s
M-BFP inlet pressure low low (1.25 Mpa) when M-BFP is running at a period of 30s, delay 5s
Bearing and winding temp. HH (>95 C & > 120 C )
M-BFBP inlet valve closed
hydraulic coupler header lubricating pressure LL (0.22Mpa)
AUTO START CONDITION
When interlock is cut in and any T-BFP trips, interlock will start MD-BFP




MDBFP
TDBFP
START PERMISSIVE
Deareator level > -250mm.
Min. Recirculation Valve opening > 90%
Inlet MOV Open
Outlet MOV closed
Booster should be in running
Booster Pump Motor & bearing temp <75C
Booster Pump motor Phase winding temp <120C

TRIPPING CONDITION OF TDBFP
Inlet MOV closed
EH oil Pr. Low low < 7.8 Mpa
Inlet flow <275 TPH
Recirculation MOV < 75%
Deareator level low (-900 mm)
TBFP revolution High ( Mechanical trip speed: 5530 r/min ,Electrical Trip Speed: 5478 )
Lube oil pressure low low <0.07 Mpa
Vacuum low low -50Kpa
Manual Trip



Lube oil system-

It reduces friction between rotating and fixed elements such as occur
between turbine journal bearing and thrust bearing
Removes heat from the bearings. This heat may be generated by friction
within the bearing.

Jacking oil system-

Used for the Jacking of the turbine shaft.


LUBRICATION SYSTEM mainly composed following equipments

Main oil tank -1 No. Normal capacity 41.6 m 2
Booster oil pump (BOP)
Main Oil Pump (MOP)
Auxiliary oil pump (AOP)
Emergency Oil Pump (EOP)
Main start up pump (MSP)
Oil tank Heaters- 6 nos.







LUBE OIL AND JACKING OIL
START PERMISSIVE
MOT Tank level normal.(+100 mm)
DC EOP should be interlocked With AOP.
Power supply should be available.

AUTO START CONDITION OF MSP
MOP inlet pressure is low (<0.07MPa)
Turbine speed <2900 R.P.M.

AUTO STOP CONDITION OF MSP
At R.P.M. >2900 R.P.M. MSP will be stopped.
Lube oil pressure should not low. 0.115 MPa.

AUTO START CONDITION OF AOP
If MOP Discharge pr. Low < 1.205 Mpa than AOP will start
Turbine speed <2900 R.P.M.
If MOP Suction pr. Low < .007 Mpa than MSP will start

AUTO START CONDITION OF EOP
If AOP is running & Lube oil pressure becomes low< 0.105 Mpa than EOP will start
When AC supply fails EOP will start.

PROTECTION TRIP CONDITION
If Lube oil pressure becomes low< 0.007 Mpa than turbine will trip.
Main oil tank is lower -100mm than LOW alarm acts.


LUBE OIL SYSTEM

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START PERMISSIVE
The oil pump inlet pressure not low.

AUTO START CONDITION OF JOP
Rotor rotate speed <2500rpm
Running pump get tripped (3-second pulse) standby pump will start.
Running pump outlet header pressure Low (7mpa)
When the running pump is tripped, the standby pump interlock start failed, interlock start
jacking oil pump (DC JOP)

AUTO STOP CONDITION OF JOP
Jacking oil pump outlet oil pressure is low and delay 5s.
Turbine rotor speed >2500rpm(3-second pulse)



JACKING OIL SYSTEM
CCCW system
START PERMISSIVE
Expansion Tank Level >1400mm
CCWP Inlet MOV opened
CCWP Outlet MOV closed
Not electrical trip
no interlock trip

PROTECTION TRIP CONDITION
The outlet valve is still closed after the pump is running at a period of 15s.
Closed circulation cooling water expansion tank water level low low

AUTO START CONDITION
If the pump is at standby status and the running pump stops or outlet main pipe pressure
low interlock protection will start the standby pump



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OCCW system
START PERMISSIVE
OCCWP inlet MOV opened
OCCWP outlet MOV closed
OCCWP Motor Bearing temperature<90
OCCWP Winding temperature<120

PROTECTION TRIP CONDITION
Outlet valve is still closed 10 seconds after OCCW pump start-up
OCCW pump motor stator winding temperature HH
OCCW pump motor bearing temperature HH
Motorized filter inlet ,outlet or bypass valves are closed.

AUTO START CONDITION
If the pump is at standby status and the running pump stops or outlet main pipe pressure
low interlock protection will start the standby pump

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EMERGENCY TRIP SYSTEM (ETS)
EMERENCY TRIP SYSTEM (ETS) is a supervisory
system used to safely trip the Turbine in the event of any
abnormal conditions act

One triple redundant PLC system is used for this purpose
which receives various Tripping signals directly from
field/DCS/TSI system (Bentley Nevada),

Also generates digital signals for Trip first out and SOE




ETS CONDITIONS
LUBE OIL PRESSURE LL
EH OIL PRESSURE LL
SHAFT VIBRATION HH
AXIAL SHIFT HH
MAIN STEAM TEMPERATURE
DEH TRIP
HP EXHAUST TEMP & TURBINE OVERSPEED
MANUAL TRIP


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LUBE OIL
The pressure switches will act when the pressure goes below 0.07 Mpa.
To trip the Turbine at least one switch must act from both the lines.
Feedback of the switches directly goes to the ETS panel.




Pressure
Switch 4 (PSC5)
Pressure
Switch 1 (PSC2)
ACTS
Pressure
Switch 2 (PSC3)
Pressure
Switch 3 (PSC4)
ACTS
TRIPPING
LUBE OIL COMMON HEADER
Pressure
Switch 4 (PSC5)
Pressure
Switch 1 (PSC2)
ACTS
Pressure
Switch 2 (PSC3)
Pressure
Switch 3 (PSC4)
ACTS
TRIPPING
The pressure switches will act when the pressure goes below 7.8
Mpa.

EH OIL
EH OIL COMMON HEADER
SHAFT VIBRATION
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If Shaft vibration 1X
or 1Y > 0.25mm
If Shaft Vibration 2X
or 2Y > 0.25mm
If Shaft Vibration 8X
or 8Y > 0.25mm
A
If Shaft vibration 1X or
1Y > 0.125mm
If Shaft Vibration 2X or
2Y > 0.125mm
If Shaft Vibration 8X or
8Y > 0.125mm
B
AND
B
A
TRIP OUTPUT
TO ETS
TURBINE AXIAL SHIFT


AXIAL SHIFT

It is the movement of the Turbine Shaft in Axial direction from its
neutral position when steam is admitted to Turbine
There are three sensors to measure this shift and send the signals
to TSI cabinet
TSI generates digital outputs when the expansion is > 1.2 mm
or < -1.65 mm
These digital outputs from TSI is hardwired to ETS. ETS will trip
the Turbine if any 2 out of 3 signals act.



MAIN STEAM TEMP
This signal is generated through logic from DCS and then one digital output bit goes
to the ETS panel.

This condition arises due to following reasons: If load is greater than certain value
mentioned below and at the same time temperature falls below the corresponding set
point.


Load Temperature set point
>540 MW <480 deg C
>462 MW <468 deg C
>300 MW <428 deg C
>180 MW <390 deg C
>150 MW <385 deg C
HP EXHAUST TEMP & TURBINE OVERSPEED
HP EXHAUST METAL TEMP

There are four numbers of temperature elements mounted on the left and right side(2
on each side) of HP Turbine exhaust.

This condition arises when at least one of the Exhaust temp. from left side and right side
goes above 432 deg C .

This signal is generated through logic from DCS and then one digital output bit goes to
the ETS panel.

TURBINE OVERSPEED
There are three over speed probes mounted on the Turbine shaft inside front pedestal
which gives speed signals to TSI.

TSI generates different digital bits when each speed goes above 3300 RPM

These digital bits pass through a 2/3 logic in ETS and generates a trip output to trip the
Turbine.







MAIN OIL TANK LEVEL
MAIN OIL TANK LEVEL 1( < 800mm)

MAIN OIL TANK LEVEL 2( < 800mm)

TRIP OUTPUT
MAIN OIL TANK LEVEL 2( < 800mm)

MAIN OIL TANK LEVEL 3( < 800mm)

MAIN OIL TANK LEVEL 3( < 800mm)

MAIN OIL TANK LEVEL 1( < 800mm)

There are three nos. of level switches mounted on Main Oil tank which
generate digital inputs when oil level goes below 800 mm.
If more than 2 out of 3 digital inputs from field act, ETS generates a
digital output to trip the turbine




AND
AND
AND
DEH TRIP
Digital Electro Hydraulic Governor (DEH) Trip arises in any of the
following conditions:

Any two out of three speed probes of DEH fail or Speed values are not
matching (400 rpm difference from median value) during turbine in
operation.

If turbine speed reaches 3300 rpm.

Both Power supply to DEH controller fail.



MANUAL TRIP

Two push buttons are provided on operator desk. Both are to be pressed at
the same time to trip the Turbine in any emergency.

MANUAL LEVER TRIP : Tripping Done By Pulling Local Emergency Trip Lever .

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ELECTRICAL INTERLOCK AND PROTECTION SCHEME
The basic requirements of an interlock and protection system for
a unit shall accomplish the followings:

Protect personnel from injury.
Protect equipment from damage.
Protect boiler/turbine/generator operation by limiting action to a
prescribed operating sequence or by initiating trip devices when
approaching an out of range or unstable operating condition.
Safe operation of plant and avoids unnecessary breakdown &
failure of equipment.
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GEN DIFF
CLASS - A
400KV -CB ACQ13-TC-1
O/C WITH U/V SEAL IN 400KV -CBOACQ13-TC-2
90% SEF & GENERATOR INTERTURN
PROTECTION 400KV -CBOACQ12-TC-1
100%SEF 400KV -CBOACQ12-TC-2
ROTOR E/F 400KV -CBOACQ13-CBF START
LOSS OF FIELD 400KV -CBOACQ12-CBF START
U/V AVR DE-EXCITATION COIL1
GEN POLE SLIPPING AVR DE-EXCITATION COIL2
BACK UP IMPEDENCE TRIP TURBINE
GEN OVER VOLTAGE UTA CB
GRN OVER FLUXING STARTING CHANGEOVER UTA SECTION -A
REVERSE POWER(LONG TIME) UTB CB
ET DIFFERENTIAL PROTECTION & OVER
CURRENT PROTECTION AT HV SIDE
STARTING CHANGEOVER UTBSECTION -B
TRIP LOGIC OF GENERATOR PROTECTION
REVERSE POWER(SHORT TIME)
LOW FORWARD POWER PROTECTION
CLASS - B
400KV -CB ACQ13-TC-1
400KV -CBOACQ13-TC-2
400KV -CBOACQ12-TC-1
400KV -CBOACQ12-TC-2
400KV -CBOACQ13-CBF START
400KV -CBOACQ12-CBF START
I & C SIGNAL -TRIP FROM ETS

FREQUENCY F2 47.0 HZ ( TIME DELAY 5
SEC )

AVR DE-EXCITATION COIL1
AVR DE-EXCITATION COIL2
UTA CB1
STARTING CHANGEOVER UTA SECTION -A
UTB CB3
STARTING CHANGEOVER UTA SECTION -B
COOLING WATER LOSS,GEN & ET Thermal
overload
CLASS - D SHUT DOWN TURBINE
TRIP LOGIC OF TRANSFORMER PROTECTION
CLASS I GT & UAT differential protection
GT HV REF & UAT LV REF
GT OVER FLUXING
GT OVER CURRENT PROTECTION AT HV SIDE SAME AS CLASS A
GT E/F IDMT
OVERALL DIFFERENTIAL
CLASS II UT HV SIDE OVER CURRENT - SAME AS CLASS B
CLASS III GT E/F DMT - TRIP SWITCHYAD BKR , STARTING CBF
CLASS IV UT LV SIDE PHASE & EARTH O/C - TRIP UAT BREAKER & BLOCKING SEC CHANGEOVER


IN ADVERTANT ENERGISATION
GEN POLE SLIPPING (CHAR-2)
GENERATOR NEGATIVE SEQUENCE
FREQUENCY F3 < 47.5 HZ
CLASS - C
400KV -CB ACQ13-TC-1
400KV -CBOACQ13-TC-2
400KV -CBOACQ12-TC-1
400KV -CBOACQ12-TC-2
400KV -CBOACQ13-CBF START
400KV -CBOACQ12-CBF START
ELECTRICAL PROTECTION TRIP TO TURBINE TRIP
TRIP SIGNAL FORM ELECTRICAL GRP PANEL TO ETS PANEL & FROM
ETS PANEL TO TURBINE DEH PANEL FOR TURBINE TRIP.
BOILER
TRIP
OPEN HP/LP BYPASS
VALVE
HP/ LP BYPASS
NOT OPENED
MFT
OPERATED
DEH
PANEL
GRP PANEL
CLASS A
OPERATE
TURBINE ETS
PANEL(SHUTDOWN
TURBINE)
TURBINE
TRIP MSV
VALVE
CLOSED
PROTECTION TRIP FROM SWITCHYARD
STUB DIFF
PROTECTION
OPERATED
BUS BAR
PROTECTION
OPERATED
SIDE CB CBF
PROTECTION
OPERATED
TIE CB CBF
PROTECTION
OPERATED
CLASS A
OPERATE
TRIP
GENERATOR
& TURBINE
TURBINE TRIP TO ELECTRICAL TRIP
ETS PANEL SENSED
HIGH VIBRATION
/OVER SPEED/AXIAL
DISPLACEMENT
TURBINE TRIP
(MSV VALVE
CLOSED)
I&C TRIP COMMAND FROM
ETS PANEL TO GRP PANEL
TRIP SWITCHYARD BREAKER
TRIP UAT INCOMER BREAKER
UAT SECTION CHANGEOVER
TRIP FIELD CB
MFT
OPERATED
HP/LP BYPASS NOT
OPENED
GEN LOW
FORWARD
/REVERSE POWER
OPERATED
CLASS B TRIP
CLASS B TRIP
BLR
TRIP
REHEATER PROT
OPERATED
OPEN HP / LP BYPASS VALVE
MOTORING MODE OF GENERATOR
When Generator is connected to grid system and power
input to turbine is insufficient to drive a Generator ,
motoring will occur .
Motoring is harmful to turbine blades if it sustained for a
extended period.
Motoring condition can be detected by the reverse power
relay (32)
Turbine trip result in closing of the main and reheat stop
valve.
The generator should not be tripped immediately until the
turbine generator units reaches a minimum load or negative
load condition.
A reverse power relay (shorter time) is used in the
sequential trip logic scheme where motoring is allowded for
a short time to ensure the prime mover has lost sufficient
energy to prevent over speed flowing a turbine trip.

CONTINUE .


Maximum motoring power for prime movers
Steam turbine 3.0% Water wheel turbine 0.2% Gas turbine 50.0%
Diesel engine 25.0%

STATOR COOLING WATER LOSS PROTECTION


TURBINE ETS
PANEL
GRP PANEL A
& C
TIME DELAY
30 SEC
CLASS D
TRIP
SHUTDOWN
TURBINE
LOW FORWARD
POWER/REVERSE
POWER OPERATED
CLASS B
OPERATE
TRIP SWITCHYARD
BREAKER
TRIP UAT INCOMER
BREAKER
UAT SECTION
CHANGEOVER
TRIP FIELD CB
ACTIVE POWER
STARTS DECREASING
Setting-P forward < supervision pickup 6 MW
P forward > supervision pickup 120 MW
T P forward < time delay 1.5 sec
T setting 120 MW 6 MW - 5 sec
Trip class - B

Reverse power setting - 6 MW
time delay ( long time ) without MSV valve
closed 15 sec trip class- A
time delay ( short time) - with MSV valve closed
1 sec trip class- B
LOW FORWARD POWER & REVERSE POWER
PROTECTION
CONCLUSION
It is Suggested to use of proper Interlocks
systems to identify the abnormal conditions/
any variation in the working parameters and
to protect the equipments, manpower from
injuries by safely tripping the respective
system.
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THANK YOU