Technical Panel Session. Sunday January 11, 2015. DC System Failure Modes- Utilities

1. Technical Panel Session. Sunday January 11, 2015.DC System Failure Modes- Utilities Kurt Uhlir President Standby Power System Consultants, Inc. IEEE PES SBC Winter Meeting. January 11 – 15, 2015. 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, 2015. 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, 2015. New Orleans, LA

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

5. Typical Utility DC Power Systems IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA

6. Typical Utility DC Power Systems IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA

7. Typical DC Power System SPD Inverter Eng/Gen Utility AC Utility Infrastructure AC Input Protected AC Loads Rectifiers Batteries DC Distribution IEEE PES SBC Winter Meeting. January 11 - 15, 2015. New Orleans LA

8. Class 1E Nuclear Plant 125 Volt Battery IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA

9. Class 1E Nuclear Plant 125 Volt Battery IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA

10. Utility DC Power System Failures • DC System Grounds • Palisades Nuclear – Loss of Class ESF 125 VDC BusBattery main breaker overcurrent trip Battery charger main breaker overcurrent trip • Overcurrent ProtectionCoordination of overcurrent devices DC rating vs AC rating Maximum rated voltage • DC Distribution Panel Design IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA

11. Utility DC Power System Failures IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA

12. Utility DC Power System Failures IEEE PES SBC Winter Meeting. January 11 – 15, 2015. New Orleans, LA

13. Typical Utility DC Power Systems IEEE PES SBC Winter Meeting. January 11 – 15, 2015. 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, 2015. 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, 2015. New Orleans, LA

17. Figure 1 – Single Battery Ground (Normal Operation) IEEE PES SBC Winter Meeting. January 11 – 15, 2015. 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, 2015. New Orleans, LA

19. Typical DC Power System SPD Inverter Eng/Gen Utility AC Utility Infrastructure AC Input Protected AC Loads Rectifiers Batteries DC Distribution IEEE PES SBC Winter Meeting. January 11 - 15, 2015. New Orleans LA

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