AC distribution tower wire denotation/ arrangement.

Thread Starter

supermankid

Joined May 26, 2013
54
I did some research on AC distribution system. It is amazing how they maintain constant voltage and
frequency from the generator.
I couldnot find good informaton on the transmission towers though!!!
They carry three phase current but why are there 6 or so hangers as shown in the picture attached?
and on one hanger there is again bunch of wires.
Could someone explain the wires arrangement in AC distribution towers or provide link to good source.
Thanks in advance.

pylon_ds_1024.jpg

Moderators note: reduced image size
 
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alfacliff

Joined Dec 13, 2013
2,458
the "groups" of wires on each insulator are carrying the same phase, just paaralelled for more current carrying. the six conductors are just three phase with two circuits. the four wires per phase allow for more current with less weight than one larger conductor. and less heating of the conductor.
 

Hypatia's Protege

Joined Mar 1, 2015
3,228
the "groups" of wires on each insulator are carrying the same phase, just paaralelled for more current carrying. the six conductors are just three phase with two circuits. the four wires per phase allow for more current with less weight than one larger conductor. and less heating of the conductor.
Indeed! Intriguingly the 'skin effect' (q.v.) comes into play at even ELF... Hence surface area often 'trumps' (or seriously 'competes' with) cross section...
 
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alfacliff

Joined Dec 13, 2013
2,458
which would have more surface, 4 conductors spaced apart paralelled, or one with the same amount of copper? and skin effect usually is considered to be a problem above 100 khz or so. which would have more air cooling effect? around here there is usually two paralled conductors around 1.25 inch thick or so. on the 354 kv lines. they start with single conductor, and then add more as the load increases.
 

AnalogKid

Joined Aug 1, 2013
10,987
When I was but a wee lad in power generation and distribution class, 765 kV lines still were fairly new. Obviously, a single conductor could replace the four conductors in a box, but it would arc into the atmosphere. For the same operating voltage and current, the box arrangement is lighter, has a lower wind load, and a much higher arc potential. In terms of calculating its ability to arc or not arc, the box has the same effective diameter as a single conductor with a diameter equal to the diagonal of the box.

Each of the cables is ACSR - Aluminum conductor, steel reinforced. The lower power sample I remember had steel aircraft cable down the center, oiled paper spiraled around that, a layer of aluminum conductors spiraled around that, then the outer jacket. Today's are bigger.

https://en.wikipedia.org/wiki/Aluminium-conductor_steel-reinforced_cable

ak
 

crutschow

Joined Mar 14, 2008
34,285
which would have more surface, 4 conductors spaced apart paralelled, or one with the same amount of copper? and skin effect usually is considered to be a problem above 100 khz or so. which would have more air cooling effect? around here there is usually two paralled conductors around 1.25 inch thick or so. on the 354 kv lines. they start with single conductor, and then add more as the load increases.
4 paralleled. That's why they use Litz wire at high frequencies.

The skin depth at 60Hz [current drops to 1/e (37%) of the surface value] is 0.36" which is much less than the radius of the transmission line wires.
 
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