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