I noticed that the new lines (14,400 volts I believe) they ran on the high voltage towers next to the industrial park here are not the same style as the old lines.
The new lines seem to be a twisted pair instead of a single conductor. One twist about every four feet. The setup is still the same, three conductors (one per phase) on each side of the tower spaced about 10 feet apart.
So, what`s up with the twisted pair?
Have something to do with line loss? Hysteresis losses?
(Each cable in the twisted pair seems to be about the same size as the original single cable however I have no ideal how thick the new insulation is so the size of the cables may be decieving.)
Don’t know the answer, but just thought i’d point out that high voltage lines don’t have insulation on the cables. The air gap provides the insulation.
Nor are 14.4 kV conductors separated by 10 feet. Nor are they strung on towers.
Wanna reconsider the question? Post a photograph or something?
Your`re right, that was a trick question.:smack:
The underground loop that feeds the industrial park is 14,400.
The lines on the towers themselves are sort of a greyish color and they look to be coated with something, if not some sort of insulation then what? Standing on the ground I cant make out any strands in the cables and I rather doubt that they are a single conductor, although correct me if Im wrong.
Anyway, the crux of the question was why are there two twisted cables instead of one?
Strength? Anyone know for sure what improvements there might be with this arrangement?
The conductors are most commonly referred to as T-2 (for twisted 2-cable conductor). You see these all over the Midwest and they are used to prevent ‘line galloping’ which usually occurs on windy days when the conductors are covered in ice, but can happen pretty much any time if the conditions are right. For those interested, galloping can be seen Here. There are different sizes, but the majority that i have seen are twin 4/0 ACSR. They are not limited to strictly distribution voltages, i’ve seen T-2 used up to 161KV.
Basically, the profile of the twisted pair breaks up the airflow and prevents the lines from galloping. Prior to use of T-2, spoilers and dampners were the most common way to handle this galloping. Line galloping can cause physical damage to conductors, structural damage to poles and towers due to varying stresses and, in extreme cases, flash-overs on EHV lines.