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Austin Energy Spacer Cable Application

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Presentation on theme: "Austin Energy Spacer Cable Application"— Presentation transcript:

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
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

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