1 Sagging Line Mitigator (SLiM) Status & Future IEEE Winter Technical Meeting TPC/ESMOL Joint Meeting Las Vegas, NV January 28, 2003 Material Integrity Solutions, Inc. Problem Statement b More than 50% of lines in WSCC region are 230kV ACSR lines: ~37,500 miles. b These lines are typically thermally limited. b Survey results: • Sag problems are of most concern on 115-230kV lines. • Most sag problems are due to high load demand on hot days. • The majority of sag problems are under 5 feet of excessive sag.
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b More than 50% of lines in WSCC region are230kV ACSR lines: ~37,500 miles.
b These lines are typically thermally limited.b Survey results:
• Sag problems are of most concern on 115-230kVlines.
• Most sag problems are due to high load demand onhot days.
• The majority of sag problems are under 5 feet ofexcessive sag.
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Alternative Solutions
Current Methods:• Limit Line Ampacity• Raise Tower Height• Reduce Tower Spacing• Re-conductor• Construct new/parallel lines
or... Sagging Line Mitigator (SLiM)!
SLiM Philosophy
A small decrease in conductor length equals alarge decrease in sag.
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Our Goal
To design, construct, demonstrate, andcommercialize a device which keeps thesag in power transmission lines almost
constant by automatically compensatingfor temperature and loading changes.
Criteria, Targets, Standards
b Meets Codes & Standardsb Uses common rules & practicesb Performance Criteria
– Mitigate additional sag that occurs in conductorsheated from 110°F to 212°F
– Voltage range 230kV– Up to 6” range of motion– Up to 5000 lbs. working line tension– Mechanical failure > 35,000 lbs.
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Criteria, Targets, Standards
b Functionality Criteria– Corrosion resistant– Low E-field for corona– Negligible impact on stability– Negligible impact on line vibration– Emergency Constraints
b Cost Targets - less expensive than otheralternatives, e.g. raising towers
Current Designs & Prototype
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General Specifications
How SLiM Works
b A portion of line currentpasses through SMAactuator.
b Actuator shortens whenheated.
b Lever arm magnifies actuatormotion.
b Line tension extendsactuator when cool.
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Modeling
Corona Behavior Stress-Strain
Modeling
36.6mH
50k
close at t=5ms
100 close at t=0
SLiM
1.6H
100kv
104.5kmSRCA SWA
SRA
ENDASENDA SENDB
104.5km ENDB
Electromagnetic Transients
750'
Case #2
Case #3
Effect on Line Vibration
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Modeling
Percentage Sag Reduced vs Number of Slim Devices in Rail 10 600'-Spans Transmission Line
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
100.00%
0 1 2 3 4 5 6 7 8 9 10
Number of Slim Devices
Cap
acity
for
Sag
Red
uctio
n
Effect on SLiM on continuous lines
SmartConductor - SLiM’s Partner
b Length of conductor that shortens when heated due to SMA core.
b Lower cost alternative to SLiM.
b ~30% of the range of motion of SLiM.
b Assembled rather than fabricated.
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Small Scale Prototype Testing
Full-Scale Functionality Testing
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Functionality Testing
Functionality Testing
SmartConductorControl Span Test Span
Measured Tension Height* Change in Sag Tension Height* Change in Sag Sag Differential(lbs.) (in) (in) (lbs.) (in) (in) (in)
Cold 2917 98.6 — 2925 97.5 — —Hot 2073 41.5 57.1 2202 50 47.5 9.6Predicted Tension Sag Change in Sag Tension Sag Change in Sag Sag Differential