STRINGING CONDUCTOR ON F TSP’...•When the other side is strung, the span will be back to the...
Transcript of STRINGING CONDUCTOR ON F TSP’...•When the other side is strung, the span will be back to the...
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STRINGING CONDUCTOR ON
FLEXIBLE TSP’S
Douglas ProctorPLS-CADD User Group Meeting
June 2 – 4, 2015
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Line Map118⁰ 89⁰
UPRR crossing
I-5 Crossing
21⁰
14⁰
66⁰
52⁰
18⁰
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• Double Circuit Line• Poles Directly Embedded• 19 Poles• 14 angles• 1 Interstate Crossing• 1 UPRR Crossing
Study Project
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Project Installation
• Rake to allow for deflection
• Setting the embedded sections
• Order of Construction– UPRR
– Interstate
• Order of Stringing and sagging– Both Circuits
– One at a time
• Final adjustments
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Stringing on TSP’s
• Poles deflect– Deflection shortens span– Tension reduced
• Angles– Rake on bisector– String through and cut in
• Controlling Stringing – Several Methods– Stringing Charts– Project Specific Stringing Data– Trial and Error
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Tradition (an aside)
• Grandfathered Standards• Must use or merely a resource?• What if they are wrong?
• Contractor’s problem• It’s in their contract• Who suffers if they don’t do it right?
• Should we write new standards (internal to the Utility)?• It is a daunting task to change a standard• Maybe we can be clever and re-interpret the existing ones?
• It’s a special case to be solved in the field.• Is it really?• Fireman to the rescue, again?
• Question• What standards do you follow?
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Challenges
• Large Angle in UPRR Span
• Short Duration for I-5 Crossing
• Sag Charts– Communication to Contractor
– Initial Data
– Sag Check Data
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Setting Procedure• Angles and Deadends That are not Terminals
– Rake on bisector
– String Through
– Cut in
– Sag
– Add Jumpers
• Large Angle Deadends– Rake on bisector
– String to both sides
– Sag one side
– Sag the other
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• The sags and tensions are readily determined for a rigid structure.
• Therefore, the unstressed length can be determined for the rigid structure case.
• However, the structure is not rigid.• Deflection changes the span.• The unstressed length stays the same.• What is the sag and tension at
equilibrium?
Working on Another Idea
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• The sags and tensions are known for a rigid structure.
• Therefore, the unstressed length can be determined for the rigid structure case.
• However, the structure is not rigid.• Deflection changes the span.• The unstressed length stays the same.• What is the sag and tension at
equilibrium?
Stating The Problem
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Span
Tension
Deflection
• Unstressed Length
• Poles Plumb
• No Deflection
• Using Known Tension
Known Parameters
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Span
Tension
Deflection
• Span at Equilibrium
• Tension at Equilibrium
• Deflection at Equilibrium
Unknown Parameters
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EXAMPLE
STRUCTURE
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Deflections• Tip deflection from PLS-POLE = 21” at 60⁰ F• Procedure Investigated
– Move pole 12 21” toward pole 13 to simulate deflection– Results unrealistic
Tension after move566 lb
Tension before move4683 lb
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Deflections Considering Equilibrium
• The reduction in tension due to the deflection of pole 13 drops rapidly.
• An imbalance is created at pole 12, which also deflects and so on down the line.
• The unstressed length was determined from the rigid case
• The tension can be determined for the reduced span length
• When the other side is strung, the span will be back to the original length at design tension.
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PLS CAD tools• Equaling Tensions at Poles
• Flexible Pole Models
• Sections must be clipped in
• Find Tension using “Sag-Tension” under sections
• Find Unstressed Length under “section modify”
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What’s Next• Updating the Construction Specification
• Prepare Sag Charts
• Check Sags after Construction
• Continue to Develop a workable analytical method to include deflection dynamically
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Summary
• Construction will proceed using the techniques described
• The dynamic deflection analysis is a work in progress
• I still use a graphical method– Trial and error adjusting span lengths until
unstressed lengths result in equalized tensions
• Why haven’t we had many more problems?– TSP’s are very forgiving– They move to where they are most comfortable.
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QUESTIONS AND
DISCUSSION?