2. Safe operation of plant
Lowest cost of generation
Long equipment life
Minimum environmental effects
3. The basic requirements of an interlock
system for a unit shall accomplish the following:
(1) Protect personnel from injury.
(2) Protect equipment from damage.
(3) Protect boiler/turbine/generator operation by
limiting actions to a prescribed operating
sequence or by initiating trip devices when
approaching an out-of-range or unstable operating
condition.
5. Operating safety ,
To prevent uncontrolled fire ,
To prevent implosions and explosions in the
boiler.
6. Less than fireball and loss of 240 V AC any elevation in service.
Drum level very low
Drum level very high
Both ID fan off
Both FD fan off
Air flow is less than 30%
Furnace press VLO
Furnace press VHI
Loss of all fuel trip
Unit flame failure trip
Both emergency PB trip
Reheater protection trip
Loss of 220 V DC more than 2 sec
7. Shut/close main fuel valve (LDO)
Shut/close main fuel valve (HFO)
Trip all running mills
Trip all running P A fans
Trip all running SA fans
Close HPLP bypass( if open)
Turbine trip
Shut/close SH attemp block valve
Shut/close RH attemp block valve
Trip Electrostatic Precipitators (ESP)
Boiler
Fuel
trip
15. Turbine vacuum breaker will open to reduce coasting down
time of turbine :
If Turbine tripped on
1. axial shift tripped,
2. Lube oil press VLO,
3. Fire protection operated,
17. Class A tripping• This trip will operate
when the fault needs to isolate the generator
immediately. • This gives the command to trip
turbine and generator.
Class B tripping – • This trip will operate when
the fault is not serious view of generator or it is
not directly harmful to generator • This gives the
command to trip turbine.
21. Differential protection-87
UT LV side ref protection -64UAT
Overcurrent protection-50/51UAT
Earth fault protection-51NUAT
UAT buchholz relay
UAT PRV trip
UAT oil temp HI
UAT winding temp HI
22. Liquid main leads top max
Cold gas cooler temp A+B more than 55 c deg
Cold gas cooler temp C+D more than 55 c deg
Hot air main exciter more than 85 c deg
23. When generator is connected to the grid system and
power input to turbine is insufficient to drive
generator ,motoring will occur.
Motoring is harmfull to turbine blades if it sustained
for extended period.
This is due to loss of the cooling effect of steam flow
which can result in overheating the last stage blading.
Anti motoring detection include exhaust hood
temperature monitoring and reverse power relay(32G)
with long timer.
24. 1. Reverse power relay ( long timer eg 30 sec ) logic for
anti motoring
( it is a protection of turbine )
2.Reverse power relay (short timer eg 3 sec ) logic for turbine trip to
Generator trip to prevent overspeed of Turbine
Reverse
power relay
32-1
Long
Timer
30 sec
Trip generator and
Field breaker
26. 1. NFPA 85 -Boiler and Combustion Systems
Hazards.
2. IEEE Guide for Protective relay applications to
Power Transformer (IEEE Std C37.91) .
3. IEEE Guide for AC Generator Protection (IEEE Std
C37.102).
27. BOILER TRIP Conditions ,FSSS, master fuel
relay( MFR)
BHEL (T) Boiler ,500 MW
1• Less than fire ball and loss of +24V DC(N) at any elevation in service.
2• Drum level very low for more than 5 seconds.
3• Drum level very high for more than 10 seconds.
4• Both FD Fans off.
5• Both ID Fans off.
6• Air flow is less than 30%
7• Furnace pressure very low.
8• Furnace pressure very high.
9• Loss of all fuel trip
10• Unit flame failure trip
11• Both emergency trip Push Buttons pressed (Operator initiated boiler trip)
12• Loss of reheater protection.
13• Loss of +24V DC(T) for more than 2 seconds
14• All Secondary Air Heaters off.
15• Water wall circulation not correct for more than 5 seconds
16• Boiler feed pumps tripped for more than 10 seconds
28. Turbine Trip
KWU Steam Turbine – 500 MW
1. Turbine overspeed ( hyraulic)
2. Manual trip device (hydrualic)
3. Turbine overspeed (electronic)
4. Axial shift
5. Trip switch optd (Desk)
6. HP exh temp high
7. TG brg temp high
8. Condenser press trip
9. Fire protection trip
10. MOT Level VLO
11. Low MS temp trip
12. Trip command from ATRS
13. Gen electrical protection
14. Gen protection (mech)
15. MFT Relay optd
16. HP casing top-bot diff HI
17. IP Casing top-bot diff HI
18. LP casing top bot diff HI
30. BOILER TRIP Conditions ,FSSS, master fuel relay( MFR)
Doosan Boiler ,660 MW ,Supercritical boiler
1.Both ID Fans Off
2.Both FD Fans Off
3.Unit Air Flow < 30 % TMCR
4.All Feed Water Pumps Are Off For More Than 40 Sec
5. the furnace pressure High / Low for more than 8 sec ( 150 mmwc / -180
mmwc))
6. the furnace pressure High – High / Low - Low ( 250 mmwc / - 250 mmwc)
7.Loss Of Re-heater Protection
8.EPB Pressed
9.All SAPH Off
10.Economizer Inlet Flow Low For More Than 10 Sec
11.Furnace Vertical Wall Temperature High For more than 3 Sec (479 C)
12.SH Pressure High On Both Side
13.SH Temperature High For More Than 20 Sec ( 590 C)
14.RH O/L Temperature High For More Than 20 Sec ( 590 C)
15.Separator Level Low-Low During Wet Mode
16.Separator Level High-High During Wet Mode
17. MFT Relay Tripped
18.Loss Of Fuel Trip
19.Unit Flame Failure Trip
31. Boiler trip -FSSS MFR conditions
-Shanghai electric co ,China- boiler 600 MW
(1) Manually operate MFR
(2) IDF trip
(3) FDF trip
(4) All preheater trip
(5) MCS power loss
(6) Drum water over max.
(7) Boiler light-up failed
(8) Drum water below min.
(9) Boiler pressure excess max limitation (choose two from the three)
(10) Boiler pressure below min limitation (choose two from the three)
(11) Whole furnace loses fuel
(12) Whole furnace loses flame
(13) Loss flame test cooling air (delayed) (choose two from the three)
(14) Air flow below min. value (choose two from the three)
（ 15 ） All boiler water recycle pump trip
（ 16 ） Reheater loses protection.
（ 17 ） All water feed pump trip
（ 18 ） Air flow of economizer inlet is lower than min set value (choose two from the three)
32. Steam Turbine emergency trip conditions ( electric)
Harbin Power Engg Co Ltd –China ;turbine- 600 MW
1. When turbine is over speeding to 3300rpm.
2 .When condenser pressure VHIGH
3 .When axial displacement is more than +1.0mm or less than -1.0mm.
4. When lube oil pressure is as Vlow
5 .HP /LP casing expansion difference reachs to +11.1mm or -5.1mm.
6 .LP casing expansion difference reachs to +27.8mm or -4.3mm.
7. When generator trips.
8. When boiler MFT.
9 .When EH oil pressure is as low
10. DEH is in fault (power off).
11. ETS is in fault (power off).
12 .X or Y bearing vibration of any bearing of #1 ～ 8 is HIGH
13. Stop unit manually by button on standby manual operation panel.
14 .Stop turbine remotely.
15. Local STOP button in turbine hall.
