Presentation on theme: "Austin Energy Spacer Cable Application"— Presentation transcript:
1 Austin Energy Spacer Cable Application SWEDE - April 27th, GalvestonTommy Nylec
2 Overview Introduction to Austin Energy Spacer Cable Description ApplicationsOperational ConcernsFuture Work and Conclusions
3 Austin Energy Statistics >400,000 Customers>2,800 MW Generation> 50 Distribution Substations> 10,000 miles of Distribution>1,600 EmployeesServe 437 square miles including Austin city limits and neighboring areasStarted in 1887
4 Austin Energy’s Operational View City Council is Board of DirectorsCitizens equivalent to Investors/MembersPublic Opinion drives utility directionAlternative Energy InitiativeIntegrate nature into cityGoal to become compact cityCity 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 spacingMessenger supports the spacers and conductors and may be used as system neutral.Messengers up to 4/0 AWG equivalent conductivity are availableShields system from lightning strikesSpecial messengers available for long spansConductorAvailable in various voltages & sizesHigh density polyethylene (gray or black)UV resistantTrack resistantLong leakage distance, self-washing design allows operation with contamination
7 Spacer DetailsVoltageDimensions (in)Conductor Spacing (in)Messenger Range (in)Cable Range (in)Max System Voltage (kV)Short Circuit Rating (kA)Weight (lbs)DEANACBC15 kV16.523.58.5810.7513.52.5
9 Spacer Cable Application Heavily wooded or trimming limitationsROW or property line boundariesClearance concernsUnder built facilitiesMultiple circuitsCritical reliabilitySensitive environmental areasLong span distancesPublic request for fewer poles
10 Designing with Spacer Cable Pole loading can be reducedConceptually similar to overhead fiber designRequires unique sag and tension tablesTechnical design guides availablePLS-CADD data for modeling purposesTurnkey 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.
20 Tree Trimming ImpactReduces vegetation management costs due to extending cycles through smaller footprints
21 Spacer Cable Operational Observations Prevents faults caused by incidental contactRequires special tools and techniquesVery difficult to remove coveringAllows taps without additional hazards sometimes created by vertical constructionTreat as uninsulated when being worked
22 Spacer Cable Technical Benefits Designed to prevent storm related outagesCompact designHigh mechanical strengthLightning shield wireLess voltage drop
23 Initial Cost versus O&M Savings Material more expensive than standard constructionCan be more labor intensive until familiar with equipmentReduction of tree trimming expensesROW acquisition costs reducedMessenger use requires less structurally significant poles
24 Spacer Cable at Austin Energy Initially used for long spans for river crossings and long highway crossingsStill primary useBeginning to investigate use for zero lot line & tree trimming reduction795 only option w/ 4/0 equivalent neutral4/0 Aluminum electrical equivalent has RBS of 32,670. Weighs ~.7 lbs/ft.
25 Summary Advantages Disadvantages Great for long spans Can reduce tree trimmingCan use shorter polesGreat for multiple circuits or existing ROWVery reliableDisadvantagesHigher initial costs versus standard overhead linesPole breaks before messengerDifficulty during install or reinstallNot 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 SubcomitteePresentation provided by James Bouford of Transmission and Distribution Conference and Exposition, T&D. IEEE/PESAdditional technical information can be found at