1. Kurt Uhlir President Standby Power System Consultants, Inc.
Technical Panel Session. Sunday January 11, DC System Failure Modes- Utilities
Kurt Uhlir
President
Standby Power System Consultants, Inc.
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

2. Typical Utility DC Power System Operating Voltages
250 VDC
125 VDC
48 VDC
32 VDC
24 VDC
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

3. Utility DC Power System Applications
Switchgear and control
Communications Microwave SONET
Emergency Lighting
Emergency pumps
UPS
SCADA
Smart Grid Distribution Automation
Instrumentation
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

4. IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA
Substation 125 VDC System
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

5. Typical Utility DC Power Systems
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

6. Typical Utility DC Power Systems
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

7. Typical DC Power System
SPD
Inverter
Eng/Gen
Utility AC
Utility Infrastructure
AC Input
Rectifiers
Batteries
DC Distribution
Protected AC Loads
IEEE PES SBC Winter Meeting. January , New Orleans LA

8. Class 1E Nuclear Plant 125 Volt Battery
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

9. Class 1E Nuclear Plant 125 Volt Battery
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

10. Utility DC Power System Failures
DC System Grounds
Palisades Nuclear – Loss of Class ESF 125 VDC Bus Battery main breaker overcurrent trip Battery charger main breaker overcurrent trip
Overcurrent Protection Coordination of overcurrent devices DC rating vs AC rating Maximum rated voltage
DC Distribution Panel Design
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

11. Utility DC Power System Failures
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

12. Utility DC Power System Failures
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

13. Typical Utility DC Power Systems
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

14. Sources of Battery Grounds
Commercial ground detectors
Water in conduit
Water entering junction boxes or switch/sensor terminations
Wire splices soaking in water
Wildlife
Sharp objects piercing wire insulation
Constant abrasion wearing away wire insulation
Wires that have pulled out of their terminations and touch ground or water
Failed capacitor or semiconductor surge suppressors
Wire insulation cracking
IEEE PES SBC Winter Meeting.
January 11 – 15, 2015 New Orleans, LA

15. Source of Battery Grounds
Grounds can occur on the battery itself
Electrolyte in a cell is conductive
Racks are grounded
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

16. Sources of Battery Grounds
Water is the Number 1 causes of most grounds because it often forms the bond between the exposed conductor and earth ground
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

17. Figure 1 – Single Battery Ground (Normal Operation)
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

18. Figure 2 - Two Battery Grounds (Misoperation)
At a minimum, a floating battery system requires at least two battery grounds before misoperation can occur.
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

19. Typical DC Power System
SPD
Inverter
Eng/Gen
Utility AC
Utility Infrastructure
AC Input
Rectifiers
Batteries
DC Distribution
Protected AC Loads
IEEE PES SBC Winter Meeting. January , New Orleans LA

20. IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA
Poor distribution panel design that attributed to dc power system failure during maintenance activity
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA