dc supply system_stdm

7/28/2019 DC Supply System_Stdm

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20 July 2013 PMI Revision 00 1

DC Supply

System




•Duties

•DC Loads

•DC system

•Types of Batteries

Presentation outline




DC SYSTEM IS

DESIGNED• TO SUPPLY HIGH STANDARD OF RELIABLE &

SECURE DC POWER

• TO PROVIDE CONTINUOUS & QUALITY POWER 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




DUTIES

• TO SUPPLY EQUIPMENT WHICH REQUIRES DCDURING NORMAL CONDITIONS

• TO SUPPLY STANDBY EQUIPMENT/DC DRIVES

• TO SUPPLY STARTERS OF VARIOUSEQUIPMENT

• TO SUPPLY EQUIPMENT WHEN AC SUPPLIESHAVE BEEN LOST




Types of Power Supplies

In a Power Plant

• 11KV/3.3KV/415V AC Power Supply

• 415V AC Emergency Supply(DG)

• DC Power Supply

• UPS Supply




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




DC Supplies……………Why?

• Emergency Lube Oil Pump

• Emergency Jacking Oil Pump

• Emergency Scanner Air Fan

• Emergency Seal Oil Pump

• Breaker/Unit Protections

• Emergency Lighting




The Ultimate Backup

In 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.




Selection of voltage -DC

POWER SUPPLY

• In power plant D.C. pumps, lighting require comparativelyhigh 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.




DC POWER SUPPLY

SCHEME

1. Earlier concept;

• 1X100% battery bank along with its chargers for each unit with inter-unit interconnection through high capacity DC bus bar.

• In view of large size of above DC loads of each unit and the large unitpitch it is necessary to provide a separate DC system (battery

+chargers) to enhance the plant’s overall reliability. • NTPC earlier plants –Kahalgaon-I, Vindhchachal-I and some other also

have above DC scheme.

2) Present concept;

• In view of the reasons explained above 2x100% capacity DC system isprovided for each unit and switchyard separately.

• Minor DC loads of offsite areas in the plant i.e. WTP, Ash handling arefed from plant DC system as it is now restricted to limited areaswitchgear rooms, as control now no longer relay based.




DC System

• Battery

• Battery Charger




DC SYSTEM

• BATTERY CHARGERS [TWO/THREE]

• BATTERY BANKS [ONE/TWO]

• DC DISTRIBUTION BOARDS [ONE/TWO]

•

DC FUSE BOARDS• UN EARTHED SYSTEM

• CHARGER TROUBLE, DC EARTH FAULT ANDDC VOLTAGE ABNORMAL ALARMS IN UCB




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




Typical UPS System

Module

Power supply

440 V

AC

220 V

DC Battery 220 V DC

220 V

AC UPS

All Unit Controls

&

Protection

48 V, 15V, 24 V, DC

Converter

Inverter

ACDB




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




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’




220 V DC

• FSSS

• HT Breakers• Vacuum Breakers

• HOTV/HORV

• Deaerator Overflow Valve

• GRP• HP Heater Protections

• DC Fans & Pumps

• Extraction FCNRV V/V’s

• SADC

• Trim Device

• Load Shedding Relay

• Scanner Air Fan Outlet & Emergency Damper

• All DC Lights




220 V Supplies

EMCC USS

MAIN CHARGER RESERVE CHARGER

UPS CHARGER-1 UPS CHARGER -2

DAS UPS CHARGER – 1 DAS UPS CHARGER-2

+/- 24 VA DC CHARGER +/- 24 VB DC

CHARGER

DG SET BATTERY

SYSTEM



20 July 2013 19

+/- 24 V DC System

+/-24 V

CHARGER-

A

+/-24 V

CHARGER-B

Batteries

350AH

Batteries3

50AH

EMCC

USS



20 July 2013 20

+/- 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



20 July 2013 21

Battery




Types of Batteries

Lead Acid Nickel - Cadmium

Plante

Tubular

VRLA

Pasted Plate

Pocket Plate

Tubular Plate

Sintered Plate




Applicable Standards

• Lead Acid Plante Batteries – IS:1652

• Vented Ni-Cd Batteries – IS:10918, IEC:60623




Manufacturers In India

Lead Acid Plante

Batteries

• Exide Industries

Ni-Cd Pocket Plate

Batteries

• AMCO Batteries

• HBL NIFE Batteries




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




SELECTION OF BATTERY

TYPE 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.




THANK YOU

dc supply system_stdm

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