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25 December 2013 PMI Revision 00 1
DC SupplySystem
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25 December 2013 PMI Revision 00 2
Duties
DC Loads
DC system
Types of Batteries
Presentation outline
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25 December 2013 PMI Revision 00 3
DC SYSTEM ISDESIGNED TO SUPPLY HIGH STANDARD OF RELIABLE &
SECURE DC POWER
TO PROVIDE CONTINUOUS & QUALITYPOWER AS AND WHEN REQUIRED
UNDER NORMAL & ABNORMAL OPERATINGCONDITIONS
ULTIMATE & FINAL DC BACK-UP POWER TOEQUIPMENT AND DC DRIVES WHEN TOTAL ACSUPPLY FAILS
HENCE THEY ARE BATTERY BACKED
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25 December 2013 PMI Revision 00 4
DUTIES TO SUPPLY EQUIPMENT WHICH REQUIRES DC
DURING NORMAL CONDITIONS
TO SUPPLY STANDBY EQUIPMENT/DC DRIVES
TO SUPPLY STARTERS OF VARIOUSEQUIPMENT
TO SUPPLY EQUIPMENT WHEN AC SUPPLIESHAVE BEEN LOST
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Types of Power SuppliesIn a Power Plant 11KV/3.3KV/415V AC Power Supply
415V AC Emergency Supply(DG)
DC Power Supply
UPS Supply
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25 December 2013 PMI Revision 00 6
DC Power Supply Various Critical Drives
Emergency DC Lighting
Switchgear Control Supply for closing & tripping
Control, Protection And Interlocks
Indication, Annunciation & Alarm System
Public Address System
DAS And Communication System
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DC SuppliesWhy Emergency Lube Oil Pump
Emergency Jacking Oil Pump
Emergency Scanner Air Fan
Emergency Seal Oil Pump
Breaker/Unit Protections
Emergency Lighting
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25 December 2013 PMI Revision 00 8
The Ultimate BackupIn case of unit tripping / grid failure, either station
changeover takes place / DG would start.
Normally, grid supply would be restored in minimum
possible time and DG would shut down.
In case of DG failure, the DC backup comes in to
service to facilitate safe shut down.
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25 December 2013 PMI Revision 00 9
Selection of voltage -DCPOWER SUPPLY In power plant D.C. pumps, lighting require comparatively
high voltage due to their high power requirement. Hence asa standard these applications are designed with 220V level.
It is desirable to have comparatively lower voltage-24V/48V/110V for control/indications/annunciation due tosafety reasons. However to avoid multiplicity of DC supplies(particularly we require two control supplies), we haveadopted uniform 220V DC voltage for plant electricalsystems for switchgear control, protection and interlockoperation.
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25 December 2013 PMI Revision 00 11
DC System Battery
Battery Charger
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25 December 2013 PMI Revision 00 13
220 V DC SYSTEM
Charger I
440 V
220 V DC
Charger II
Battery
Bank
Battery
Bank
Feeders
440 V
220 V DC
Feeders
DCDB
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25 December 2013 PMI Revision 00 15
X X
X X
X XX X
DG-1DG-3
DG-2
DG SWGR-1DG SWGR-2
UNIT EMER
SWGR-1UNIT EMER
SWGR-2
UNIT EMER
SWGR-3
UNIT EMER
SWGR-4
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25 December 2013 PMI Revision 00 16
EMCC(1) AOP-1 (2) Em. Lighting Trf.
(3) TVDC Reserve Supply (4) UPS Ch.
(5) Scanner Air Fan (6) BVDC Reserve Supply
(7) AC Seal Oil Pump (8) Air Heater Lub Oil Panel
(9) Jacking Oil Pump (10) Stator Water Pump-B
(11) Barring Gear (12) +26 V DC ATRS Ch. B(13) -26V DC ATRS Ch.B(14) 26V DC FSSS Ch. B
(15) 26V DC DDC Ch. A
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25 December 2013 PMI Revision 00 17
220 V DC FSSS
HT Breakers Vacuum Breakers
HOTV/HORV
Deaerator Overflow Valve
GRP HP Heater Protections
DC Fans & Pumps
Extraction FCNRV V/Vs
SADC
Trim Device
Load Shedding Relay
Scanner Air Fan Outlet & Emergency Damper
All DC Lights
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/- 24 V DC System
+/-24 V
CHARGER-
A
+/-24 V
CHARGER-B
Batteries
350AH
Batteries3
50AH
EMCC
USS
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/- 24 V DC System+24 V DC - 24 VDC
EHC LPBP
ATRS PANNEL SPEEDER GEAR/STARTING DEVICE
ALL TURBINE PROTECTIONS EHC
LPBP ATT
TSE ACS CABIN
STARTING DEVICE TSE
LUB OIL TEMP/CONTROL FLUID TEMP/MAL
TEMP/COLD GAS TEMP
LUB OIL TEMP/CONTROL FLUID
TEMP/MAL TEMP/COLD GAS TEMP
EXCITATION SYSTEM CARDS AVR
JOP-3 GRP
LOAD SHEDDING SOLENOID
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Battery
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25 December 2013 PMI Revision 00 23
Applicable Standards Lead Acid Plante BatteriesIS:1652
Vented Ni-Cd BatteriesIS:10918, IEC:60623
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25 December 2013 PMI Revision 00 24
Manufacturers In IndiaLead Acid Plante
Batteries
Exide Industries
Ni-Cd Pocket Plate
Batteries
AMCO Batteries
HBL NIFE Batteries
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Battery Capacity Expressed in ampere hour(AH)
Duration of discharge-10 hr for Plante/5 hr for Ni-
Cd
End cell voltage-1.85 volt for Lead acid plante/1.0
volt for Ni-Cd
Ambient temperature-27 deg cent.
Electrolyte specific gravity-1.2+-.005 lead acidplante cells
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25 December 2013 PMI Revision 00 26
SELECTION OF BATTERYTYPE IN POWER PLANT Power plant batteries standby duty require high discharge
performance with continuously connected on float mode operation.
Expected Life of lead acid tubular is of the order of 8-10 years so in
a power plant life of 25 years minimum two replacement would be
required.
Lead acid PLANTE and Ni-Cd (alkaline) have expected life of 15-20years hence only one replacement would be required in whole plant
life.
In addition lead acid plante have much better discharge
performance than tubular type for the specified emergency duration.
In view of above plante type lead acid or Ni-Cd high dischargebatteries are specified for power plant applications.
Wherever there is space constraints VRLA batteries may be an
option however this has also expected life of 8-10 years.
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