stranded conductors
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Stranded conductors and
Bundled conductors
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Stranded conductor
What is Stranded conductor?
Instead of a single rounded conductorstranded conductors made from conductors of
smaller radii are used. Group of small radii
conductors is known as the Stranded
Conductor.
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Stranded Conductor
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Advantages of stranded conductor
over single rounded conductor
The stranded conductor has larger surface area
so the electric field strength near the conductor
surface is reduced. As a result the stranded
conductor is less likely to experience corona.
Simultaneously it has irregular surface so the
corona effect will be more pronounced.
It depends upon the factor which is moreaffecting that has to be taken into consideration.
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The stranded conductor is more flexible than a
single rounded conductor of equal capacity.
For higher capacity conductor the conductor
diameter may become large enough that use
of one single conductor of large diameter
becomes non-flexible.
Stranded conductors have more mechanical
strength.
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Types of stranded conductors
Three types of conductors are mainly used for
transmission purposes:
All Aluminum Alloy Conductor (AAAC)
Aluminum Conductor Steel Reinforced (ACSR)
Aluminum Conductor Alloy Reinforced (ACAR)
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Bundled Conductor
What is bundled conductor?
In high capacity transmission lines instead ofone conductor (ACSR/AAAC conductor) per
phase, two, three or four conductors are used.
This is called bundled conductor.
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http://1.bp.blogspot.com/_U3umjVzCXTA/TRg08Kb-ZhI/AAAAAAAAAUk/O_EmGTxx9lE/s1600/ACSR+bundled+conductor.jpg -
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http://2.bp.blogspot.com/-LcUjpub5eR8/Tse2clY9oII/AAAAAAAAADA/aIWouqjqNLY/s1600/bundled.jpg -
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Advantages of Bundled Conductors
Bundled conductors per phase reduces the
voltage gradient in the vicinity of the line. Thus
reduces the possibility of the corona discharge.
Improvement in the transmission efficiency asloss due to corona effect is countered.
Bundled conductor lines will have higher
capacitance to neutral in comparison with singlelines. Thus they will have higher charging currents
which helps in improving the power factor.
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Bundled conductor lines will have highercapacitance and lower inductance than ordinarylines they will have higher Surge ImpedanceLoading (Z=(L/C)1/2). Higher Surge ImpedanceLoading (SIL) will have higher maximum powertransfer ability.
With increase in self GMD or GMR inductance perphase will be reduced compared to singleconductor line. This results in lesser reactanceper phase compared to ordinary single line.
Hence lesser loss due to reactance drop.
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Vibrations and dampers
Aeoline vibrations Galooping or Dancing
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Vibration dampers
To reduce the vibrations dampers are used.
Widely used dampers are Stock bridge
dampers
A Stockbridge damper is a tuned mass
damper used to suppress wind-induced
vibrations .
http://en.wikipedia.org/wiki/Tuned_mass_damperhttp://en.wikipedia.org/wiki/Tuned_mass_damperhttp://en.wikipedia.org/wiki/Tuned_mass_damperhttp://en.wikipedia.org/wiki/Tuned_mass_damper -
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http://en.wikipedia.org/wiki/File:Stockbridge_damper_(cropped).jpg -
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The dumbbell-shaped device consists of two
masses at the ends of a short length of cable
or flexible rod, which is clamped at its middle
to the main cable. The damper is designed todissipate the energy of oscillations in the main
cable to an acceptable level.
http://en.wikipedia.org/wiki/Dumbbellhttp://en.wikipedia.org/wiki/Dumbbell -
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http://en.wikipedia.org/wiki/File:Stockbridge_damper_POV.jpg