1. Austin Energy Spacer Cable Application
SWEDE - April 27th, Galveston
Tommy Nylec

2. Overview Introduction to Austin Energy Spacer Cable Description
Applications
Operational Concerns
Future Work and Conclusions

3. Austin Energy Statistics
>400,000 Customers
>2,800 MW Generation
> 50 Distribution Substations
> 10,000 miles of Distribution
>1,600 Employees
Serve 437 square miles including Austin city limits and neighboring areas
Started in 1887

4. Austin Energy’s Operational View
City Council is Board of Directors
Citizens equivalent to Investors/Members
Public Opinion drives utility direction
Alternative Energy Initiative
Integrate nature into city
Goal to become compact city
City ordinances

5. Spacer Cable Introduction
Spacer cable is a messenger supported primary distribution system using covered conductors in a close triangular configuration. The system has the mechanical strength to weather severe storms and the electrical strength to prevent faults due to phase to ground or phase to phase contact, tree contact or animal contact.

6. Cable Details Messenger Conductor
Supports conductors and maintains phase spacing
Messenger supports the spacers and conductors and may be used as system neutral.
Messengers up to 4/0 AWG equivalent conductivity are available
Shields system from lightning strikes
Special messengers available for long spans
Conductor
Available in various voltages & sizes
High density polyethylene (gray or black)
UV resistant
Track resistant
Long leakage distance, self-washing design allows operation with contamination

7. Spacer Details
Voltage
Dimensions (in)
Conductor Spacing (in)
Messenger Range (in)
Cable Range (in)
Max System Voltage (kV)
Short Circuit Rating (kA)
Weight (lbs) D E AN AC BC
15 kV
16.5
23.5
8.5 8
10.75
13.5
2.5

8. Minimum Ultimate Load (lbs) V1 (vertical)
Bracket Details
Voltage
Dimensions (in)
Minimum Ultimate Load (lbs) V1 (vertical)
Weight (lbs) A B
15 kV 8 14
3200
8.6

9. Spacer Cable Application
Heavily wooded or trimming limitations
ROW or property line boundaries
Clearance concerns
Under built facilities
Multiple circuits
Critical reliability
Sensitive environmental areas
Long span distances
Public request for fewer poles

10. Designing with Spacer Cable
Pole loading can be reduced
Conceptually similar to overhead fiber design
Requires unique sag and tension tables
Technical design guides available
PLS-CADD data for modeling purposes
Turnkey services available from vendors
• Spacer cable provides a more compact and more reliable overhead distribution line than conventional “open wire” armless or crossarm designs.
• Spacer cable allows for more circuits on a pole line than conventional construction.

11. Spacer Cable Installation

12. Tangent Framing

13. Dead End Framing

14. Angle Framing

15. Tap Connections Clean up images that are vendor specific Tap
1. Distribution Transformer
2. Hotline Clamp
3. Protective Guard

16. Installation Examples

17. River Crossing Example

18. River Crossing Example

19. Dead End Framing Example

20. Tree Trimming Impact
Reduces vegetation management costs due to extending cycles through smaller footprints

21. Spacer Cable Operational Observations
Prevents faults caused by incidental contact
Requires special tools and techniques
Very difficult to remove covering
Allows taps without additional hazards sometimes created by vertical construction
Treat as uninsulated when being worked

22. Spacer Cable Technical Benefits
Designed to prevent storm related outages
Compact design
High mechanical strength
Lightning shield wire
Less voltage drop

23. Initial Cost versus O&M Savings
Material more expensive than standard construction
Can be more labor intensive until familiar with equipment
Reduction of tree trimming expenses
ROW acquisition costs reduced
Messenger use requires less structurally significant poles

24. Spacer Cable at Austin Energy
Initially used for long spans for river crossings and long highway crossings
Still primary use
Beginning to investigate use for zero lot line & tree trimming reduction
795 only option w/ 4/0 equivalent neutral
4/0 Aluminum electrical equivalent has RBS of 32,670. Weighs ~.7 lbs/ft.

25. Summary Advantages Disadvantages Great for long spans
Can reduce tree trimming
Can use shorter poles
Great for multiple circuits or existing ROW
Very reliable
Disadvantages
Higher initial costs versus standard overhead lines
Pole breaks before messenger
Difficulty during install or reinstall
Not always supported by line workers

26. Additional technical information can be found at http://www.pesicc.org
Questions?
Sources:
Papers provided at A19 Fall 2006 PES ICC Subcomittee
Presentation provided by James Bouford of Transmission and Distribution Conference and Exposition, T&D. IEEE/PES
Additional technical information can be found at