A Presentation on DC System

NTPC Anta

Presentation Outline

1. Purpose of DC System at Power Plants- Typical Applications

2. Building Blocks of DC and UPS System- Standby Supply

3. Typical Single Line Diagrams

4. Details of Battery Bank Installations at NTPC Anta

5. Charger/Rectifier Protections/Interlocks

6. Maintenance Practices of DC System

7. Advantage Ni-Cd

Purpose- Typical Applications

220 V

48 V

+/- 24 V

Signaling

Controlling

Indication

Protection

Communication

Building Blocks

• Battery Banks

• Rectifier/ Charges

• Inverters

• AC/DC Distribution Buses

• Measuring/Protections/Monitoring

220 V DC System Single Line Diagram

+/- 24/48 V DC System Single Line Diagram

Details of Battery Installations Type Make AH

CapacityNo. of Cells

Bank Voltage

Area

KBH127P HBL 127 169 220 GTG

KBH471P HBL 471 19 +/-24 GTG

KBH79P HBL 79 19 +/-24 GTG

KBH471P HBL 471 169 220 STG

KBH805P HBL 805 20 +/-24 STG

KBH245P HBL 245 20 +/-24 STG

172KBH471P HBL NIFE

471 169 220 S YARD

YKP25 Exide 300 24 48 PLCC

RECTIFIER/CHARGER PROTECTIONS

• AC UNDERVOLTAGE

• DC OVERVOLTAGE

• DC UNDERVOLTAGE

• DC OVERCURRENT

• THYRISTOR FUSE FAILURE

Advantage Ni Cd

Lead Acid batteries are rated for C10 discharge rate where as Ni Cd batteries are rated for C5 discharge rate therefore they can provide longer backup duration when needed.

Ni Cd batteries are not prone to sudden failure as they are not prone to corrosion phenomenon due to superior electrochemistry.

Highly resistant to abuse and harsh environment.

Expected life in stationary applications in 20 years.

Highly reliable and long service life.

MAINTENANCE PRACTICES

• ROUTINE MAINTENANCE

• ANNUAL CAPACITY TEST

• ANNUAL CHARGER TESTING

• BREAKDOWN MAINTENANCE

• ANNUAL UPS TESTING

• IMPEDANCE MEASUREMENT