conductor bundles

[chopficaro2]

http://www.kabculus.com/capacitance-and-inductance-matrices/node7.html

this short page describes conductor bundles, which are power transmission lines hung paralell to eachother. i think the page is trying to explain why, when they are hung that way that they reduce impedance per meter, but i dont get it. i understand all the variables they are using except what it is they are calculating.
r is an approximation for the radius of the conductors' cross section (i think)
R is how far away the cables are hung from the center of the bundle (i think)
e0 is the permeability of free space

potential? that means voltage right? why are they using the greek letter for angle? why isnt it 120v rms?
and what is a2 and a4? equivalent radius?

 

[alehman]

Your link treats the capacitive (voltage) effects of bundled conductors, but you also need to deal with the inductive effects. I suggest you try to find a text on transmission lines for a complete treatment of the subject. "Power System Analysis" by Stevenson (see FAQ) is a good source for this information.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[chopficaro2]

thank you, now i know where to look

 

[chopficaro2]

but wait, the page is about the relations between the wires, and there shouldn't be any capacitance between the wires because they are carrying the same voltage in parallel. the only capacitance should be between the wires and the ground.

 

[m3ntosan]

a represents the conductor radius, a2 for the twin bundle and a4 for quad bundle.

http://en.wikipedia.org/wiki/Scalar_potential

May you grow up to be righteous, may you grow up to be true...

 

[chopficaro2]

a conductor radius? u mean the distance from the center of the brace to where the cables are hung? then what is R?
so now we have 3 radius values, r, R and a? what are these distances of? from where to where?

 

[alehman]

a is called the geometric mean radius, which is a sort of equivalent to the conductors in the bundle. r is the radius of the conductors, R is the radius of the bundle (assuming it's symmetrical). All explained in Stevenson.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[chopficaro2]

Thank you.

 

[NAZ55]

I disagree with alehman's description.

r is the radius of a single conductor in a bundle
R is a geometric mean radius a.k.a GMR of the bundle
a is the radius of a conductor which effectively replaces the whole bundle.

 

[alehman]

I was simply quoting the OP's linked article:

where r is the conductor radius and R is the radius of the bundle circle (which contains all the centres of the conductors in that bundle)

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.