1. IEEE PES SBC Winter Meeting. January 11 – 15, 2014. New Orleans, LA
Technical Panel Session. Sunday January 11, DC System Failure Modes
Part 2
IEEE PES SBC Winter Meeting.
January 11 – 15, New Orleans, LA

2. Typical DC Power System
Batteries
Discussion:
Types of Battery
Battery Disconnects
Low Voltage Disconnects
Battery Disconnect
Batteries
Low Volts Disconnect
IEEE PES SBC Winter Meeting. January , New Orleans LA

3. Typical DC Power System
Battery Disconnect.
A provision for disconnecting an
entire battery plant and/or Individual
battery strings from the system for:
Maintenance
Over current protection.
Battery Cell Replacement.
Two basic types of battery protection.
Not to be confused with a battery
low-voltage disconnect.
Can be stand alone or integrated.
Can be a switch with a fuse in-line or a circuit breaker
IEEE PES SBC Winter Meeting. January , New Orleans LA

4. Typical DC Power System
Low-Voltage Disconnect
Provides a means to
disconnect the battery
from the load to prevent
over discharge.
Either the load or the
batteries can be disconnected.
Multiple LVD’s in the load line
allow sequenced load shedding –
keep revenue earning loads powered
longer.
Non-essential load
Essential load
LVD in battery line
LVD’s in load lines
IEEE PES SBC Winter Meeting. January , New Orleans LA

5. DC System Failure Modes Somewhat Unique to Telecom?
Curtis Ashton
IEEE PES StaBatt
Winter 2015 (Jan 11) mtg
Sunday Technical Panel Sessions
IEEE PES SBC Winter Meeting. January , New Orleans LA

6. IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Overview
Things the Telecom Industry Does Differently Thanks to the FCC
FCC Best Practices
No Battery Disconnects in COs
What this means for Grounding Cable Sizing
No LVDs in COs
What This Does to Batteries on OverDischarge
IEEE PES SBC Winter Meeting. January , New Orleans LA

7. A Couple of Relevant FCC Best Practices
Network Operators Should Not Use Battery Disconnects at CO Battery Plants
Network Operators Should Not Use LVDs at CO Battery Plants
IEEE PES SBC Winter Meeting. January , New Orleans LA

8. Battery Disconnects Required by NEC Outside COs
Commonly Used Where NEC “Not Covered” Exemptions for Telecom/Utility Don’t Apply
e.g. Business Customer Premises, or Collocation Hotels
IEEE PES SBC Winter Meeting. January , New Orleans LA

9. Frame Grounding of Trays/ Racks/Stands w/Brkr Disconnect
Per NEC
Max Ampacities Per B17 (Single Conductor) or A (30-min Multi-Wire)
Typical Disconnect Brkr Size
Typical Ah
Typical Short Ckt Amps
Ground AWG
Typical Ampacity 40
100
4,000 10 30
300
12,000 8 70
400
1200
18,000 2
173
600
1680
24,000
1/0
259
1000
3000
30,000
2/0
294
4000
40,000
4/0
399
IEEE PES SBC Winter Meeting. January , New Orleans LA

10. Typical Breaker I-t Curve
IEEE PES SBC Winter Meeting. January , New Orleans LA

11. CO #6 AWG Rack Ground Wire
IEEE PES SBC Winter Meeting. January , New Orleans LA

12. Burnt Up on Short Circuit
IEEE PES SBC Winter Meeting. January , New Orleans LA

13. IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
LVDs
LVD Contactors Keep Batteries from Damage Due to OverDischarge
Typically Keep Telecom Batteries Above 1.75 V/cell
At Least One Battery Manufacturer Has LVDs as a Requirement for Honoring Standard Warranty
LVLDs vs LVBDs
False Operations In Telecom Led to More Adoption of LVBDs After Electronics Changed to Prevent Burnup
More False Operations (even of LVBDs) Led to FCC Best Practice for COs
We’d Rather Sacrifice the Batteries, But Keep Loads Working
LVBDs Still Sometimes Used Outside the CO Depending on Company Practice and Priorities
IEEE PES SBC Winter Meeting. January , New Orleans LA

14. IEEE PES SBC Winter Meeting. January 11 - 15, 2014. New Orleans LA
Damage w/o LVDs
While Most Telecom Equipment Shuts Itself Off Before Battery Max Discharge Avg of 1.67 V/Cell, Some will allow Draining Batteries Below 1.0 V/Cell
IEEE PES SBC Winter Meeting. January , New Orleans LA

15. Typical DC Power System
Batteries
Two Main Chemistries:
Lead-Acid
Nickel - Cadmium
IEEE PES SBC Winter Meeting. January , New Orleans LA

16. Typical DC Power System
Batteries
Two Main Types:
Valve-regulated. (Out gassing is limited by a pressure relief valve).
Vented. The gasses are allowed to vent from the battery.
They are available in both lead-acid and nickel cadmium
IEEE PES SBC Winter Meeting. January , New Orleans LA

17. Typical DC Power System
Batteries
Three main types of Vented Lead-Acid Batteries:
Vented Planté (Pure Lead) Plate
Vented Flat (Pasted) Plate Calcium, Selenium, and Antimony
Tubular Plate
IEEE PES SBC Winter Meeting. January , New Orleans LA

18. Typical DC Power System
Typical VLA (Flooded) Battery Systems
Note Spill Containment
IEEE PES SBC Winter Meeting. January , New Orleans LA

19. Typical DC Power System
Batteries
Two Main Types of Valve-Regulated
Lead-Acid (VRLA) Batteries:
Absorbed (starved) Electrolyte
Gelled Electrolyte
These are mostly Lead-Calcium
but some contain other alloys.
IEEE PES SBC Winter Meeting. January , New Orleans LA

20. Typical DC Power System
Typical VRLA 20 Year Batteries.
Large 48 Volt Plant
Small 24 Volt Plant
IEEE PES SBC Winter Meeting. January , New Orleans LA

21. Typical DC Power System
Typical 10 Year Front Terminal Batteries
IEEE PES SBC Winter Meeting. January , New Orleans LA