Austin Energy
Spacer Cable Application
SWEDE - April 27th, 2012 - Galveston
Tommy Nylec
Overview
 Introduction to Austin
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Energy
 Spacer Cable
Description
 Applications
Operational Concerns
 Future Work and
Conclusions
Austin Energy Statistics
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>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
Austin Energy’s Operational View
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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
Spacer Cable Introduction
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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.
Cable Details
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Messenger
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
Spacer Details
Voltage
15 kV
77
Dimensions
(in)
Conductor Spacing
(in)
D
E
AN
AC
BC
16.5
23.5
8.5
8
8
Messenger Range
(in)
Cable Range (in)
10.75
.375-.750
Max System
Voltage
(kV)
.438-2.00
Short Circuit
Rating
(kA)
Weight (lbs)
13.5
2.5
Bracket Details
Voltage
15 kV
88
Dimensions (in)
A
B
8
14
Minimum Ultimate Load (lbs) V1 (vertical)
Weight
(lbs)
3200
8.6
Spacer Cable Application
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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
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
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Spacer Cable Installation
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Tangent Framing
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Dead End Framing
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Angle Framing
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Tap Connections
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Installation Examples
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River Crossing Example
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River Crossing Example
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Dead End Framing Example
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Tree Trimming Impact
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Reduces vegetation management costs due to
extending cycles through smaller footprints
Spacer Cable Operational Observations
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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
Spacer Cable Technical Benefits
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Designed to prevent
storm related outages
Compact design
High mechanical strength
Lightning shield wire
Less voltage drop
Initial Cost versus O&M Savings
+ Material more expensive than standard construction
+ Can be more labor intensive until familiar with
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equipment
Reduction of tree trimming expenses
ROW acquisition costs reduced
Messenger use requires less structurally significant
poles
Spacer Cable at Austin Energy
 Initially used for long spans for river crossings
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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
Summary
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Advantages
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Great for long spans
Can reduce tree trimming
Can use shorter poles
Great for multiple circuits or existing ROW
Very reliable
Disadvantages
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Higher initial costs versus standard overhead lines
Pole breaks before messenger
Difficulty during install or reinstall
Not always supported by line workers
Questions?
Additional technical information can be found at http://www.pesicc.org
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