Industrial Design Application for Industrial Design Application for Power Distribution Power Distribution over Extra-Long Distances over Extra-Long Distances Or Or Lots of Lots of Wire Wire Little Vd Little Vd Robert A Durham, Robert A Durham, PE PE New Dominion, LLC New Dominion, LLC Tulsa, OK Tulsa, OK Marcus O Durham, Marcus O Durham, PhD, PE PhD, PE THEWAY Corp THEWAY Corp Tulsa, OK Tulsa, OK
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Industrial Design Application for Power Distribution over Extra-Long Distances Or Lots of Wire Little Vd Robert A Durham, PE New Dominion, LLC Tulsa,
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Industrial Design Application Industrial Design Application for Power Distribution for Power Distribution
over Extra-Long Distancesover Extra-Long Distances
Large loads over large distance Large loads over large distance cause unique problemscause unique problems
• Downtime eliminatedDowntime eliminated• Protection system isolates faultsProtection system isolates faults• Total system voltage > 95%Total system voltage > 95%• Contingency is bi-directional feedContingency is bi-directional feed• Adequate Ampacity to prevent sagsAdequate Ampacity to prevent sags
• Primary Loads (150 – 400 Hp)Primary Loads (150 – 400 Hp)– Generally started across the lineGenerally started across the line– Some use VFDSome use VFD– Inherent robustness of system adequateInherent robustness of system adequate
• System spread: over 900 square milesSystem spread: over 900 square miles• Main trunk line: 25 miles in lengthMain trunk line: 25 miles in length• Radial lines: 1 – 12 miles longRadial lines: 1 – 12 miles long• Each radial: 1 – 5 MWEach radial: 1 – 5 MW
Design PhilosophyDesign Philosophy
• Difference between utility & industrialDifference between utility & industrial- purely a matter of economics- purely a matter of economics
• Utility: Downtime = loss of electric salesUtility: Downtime = loss of electric sales
• Industrial: Downtime = loss of production Industrial: Downtime = loss of production sales sales
• Damage to production may be unrecoverableDamage to production may be unrecoverable
• Industrial has much larger riskIndustrial has much larger risk
Construction ManagementConstruction Management
• Emphasis on elimination of maintenanceEmphasis on elimination of maintenance• Contractors used on day work basisContractors used on day work basis
Environmental ControlsEnvironmental Controls
• ROW clearingROW clearing– 60’ - 100’ wide60’ - 100’ wide– leave root balls for erosion controlleave root balls for erosion control– treat with herbicidetreat with herbicide
• 95% of recovered product is waste95% of recovered product is waste
• Extensive load shedding and motor controlExtensive load shedding and motor control
used to ensure responsible disposalused to ensure responsible disposal
477 kcmil 64 m (210 ft) 76 m (250 ft)477 kcmil 64 m (210 ft) 76 m (250 ft)
#4/0 69 m (225 ft) 76 m (250 ft)#4/0 69 m (225 ft) 76 m (250 ft)
#1/0 69 m (225 ft) 90 m (295 ft)#1/0 69 m (225 ft) 90 m (295 ft)
#2 76 m (250 ft) 90 m (295 ft)#2 76 m (250 ft) 90 m (295 ft)
Add 4 poles / mile (1.63 km)Add 4 poles / mile (1.63 km)
Results of PhilosophyResults of Philosophy
• Recent winter stormRecent winter storm• Severe icing in regionSevere icing in region• Some areas w/o utility for 30 daysSome areas w/o utility for 30 days• The system discussed hereThe system discussed here
– single incidence of blown fusessingle incidence of blown fuses– no line on groundno line on ground
SupplySupply
• Most loads this size served from transmissionMost loads this size served from transmission• Limited number of 69 /138 kV lines in areaLimited number of 69 /138 kV lines in area• Supply taken at distribution levelsSupply taken at distribution levels
SupplySupply
• Supply taken at distribution levelsSupply taken at distribution levels– Many areas served from REC linesMany areas served from REC lines– Some dedicated 138/25kV subsSome dedicated 138/25kV subs– At dedicated subs, voltage as high as At dedicated subs, voltage as high as
120% assists with voltage conditions120% assists with voltage conditions
Electrical ConstraintsElectrical Constraints
Wire size based on ampacity- SagWire size based on ampacity- Sag
Here, voltage drop is main concernHere, voltage drop is main concern
Low power factor contributesLow power factor contributes
Main trunk line : 477 ACSRMain trunk line : 477 ACSR
Main branch feeders: 4/0 ACSRMain branch feeders: 4/0 ACSR
• Nearest to loadNearest to load• Can downsizeCan downsize
transformerstransformersand fusesand fuses
• Cost less than Cost less than oil switchesoil switches
Overcurrent ProtectionOvercurrent Protection
• Two unique systemsTwo unique systems– Protect motor & transformer (load point)Protect motor & transformer (load point)– Protect system from cascading faultsProtect system from cascading faults
Overcurrent ProtectionOvercurrent Protection
• Load points protected with fused cutoutsLoad points protected with fused cutouts– Fuse links sized tightly to avoid extra tripsFuse links sized tightly to avoid extra trips– Use high speed (X speed) fuse linksUse high speed (X speed) fuse links
Overcurrent ProtectionOvercurrent ProtectionMain Line CutoutsMain Line Cutouts
• High risk of single phasing motorsHigh risk of single phasing motors• High rating of fuses makes coordinationHigh rating of fuses makes coordination
with utility difficult with utility difficult• Electric storms cause unacceptable # of Electric storms cause unacceptable # of
outages due to arrestor operation outages due to arrestor operation
• Outages require electrician to restore powerOutages require electrician to restore power
= excessive downtime= excessive downtime
Overcurrent ProtectionOvercurrent ProtectionMain Line ReclosersMain Line Reclosers
• Oil reclosers placed at utility supply pointOil reclosers placed at utility supply point
and each main branch feederand each main branch feeder
(2MW or greater load)(2MW or greater load)• Oil reclosers placed along trunk every 10 MWOil reclosers placed along trunk every 10 MW
Overcurrent ProtectionOvercurrent ProtectionMain Line ReclosersMain Line Reclosers
• Main line reclosers use Main line reclosers use processor relaysprocessor relays
• Branch reclosers can use Branch reclosers can use – plug-setting type relays plug-setting type relays processor when availableprocessor when available
LightningLightning
• Lightning is a major concern in this areaLightning is a major concern in this area• 55 isoceraunic days per year 55 isoceraunic days per year
– odds of induced or direct strike highodds of induced or direct strike high
• Lightning arrestors Lightning arrestors – placed every 1500 – 1700 feetplaced every 1500 – 1700 feet
• Excellent ground system is imperativeExcellent ground system is imperative
Length of system #1 factorLength of system #1 factorL of ground wire L of ground wire length lengthLong distance = high ZLong distance = high ZSingle point groundSingle point ground
• Build single motor model for each service pointBuild single motor model for each service point• Create motor subsystem consisting of Create motor subsystem consisting of
motor, transformer, switches, etcmotor, transformer, switches, etc• Combine several subsystemsCombine several subsystems
• Tie sub-trunk feeders to main trunk lineTie sub-trunk feeders to main trunk line• Add detail for protection devices, fuses, Add detail for protection devices, fuses,
• Used model during construction forUsed model during construction for communication with crews communication with crews
Computer ModelingComputer ModelingUsesUses
• Refined model for operations – Refined model for operations –
voltage drop, current, power factor voltage drop, current, power factor • Updated model for system upgradesUpdated model for system upgrades• Recent upgrade netted 8% reductionRecent upgrade netted 8% reduction
in electric bill – 6 month payoutin electric bill – 6 month payout
• Downtime eliminatedDowntime eliminated• Protection system isolates faultsProtection system isolates faults• Total system voltage > 95%Total system voltage > 95%• Contingency is bi-directional feedContingency is bi-directional feed• Adequate Ampacity to prevent sagsAdequate Ampacity to prevent sags
• Under normal conditions voltage drop is 8%Under normal conditions voltage drop is 8%
• Supply voltages at 115% allow forSupply voltages at 115% allow for continuous operation under contingency continuous operation under contingency
• Advanced coordination of protection allowedAdvanced coordination of protection allowed advanced devices with little on-site prep advanced devices with little on-site prep
• Enhanced specs, > cost, more reliableEnhanced specs, > cost, more reliable• w/o computer, complex system impossiblew/o computer, complex system impossible• Design, construction, operations, mgt.Design, construction, operations, mgt.• One engineerOne engineer
ConclusionsConclusions
ConclusionConclusion
• ConclusivelyConclusivelyWith the aid of modern tools, With the aid of modern tools, a system can be designed thata system can be designed that
* can meet industrial needs * can meet industrial needs * in a utility environment * in a utility environment * with environmental astuteness* with environmental astuteness* by a single engineer* by a single engineer