Tension force during stringing

[Bercy]

Hi all,

I am new here in forum, and I dont know my question is in the right section, but Im gonna try.
I work as a technical- qualitative inspector in the plant which produce ACSR, AAC, AAAC, conductors.
Sometimes we are solving the claim about "birdcaging" during stringing process.
We assume that this is happening because of the not properly preset the tensioner, better say, the tensioning force used during stringing is too high.
There were also found other non-standard procedures, e.g. big angles on bullwheels and pulleys, an enorm unwinding force on drum, and so on.
I was carefully read standard IEEE 524 Installation of overhead conductors and other guidelines
saying recommendations about stringing process, but nowhere I found anything about tensioning force required or needed to set up on tensioner or unwinded drum.
Can anyone advise me where I find required informations, or share yours experiences, pls.

Thanks

Bercy

 

[LiteYear]

Outside my area of expertise, but FWIW, birdcaging is more likely to occur due to compression, not tension, or twisting. So I'd be looking for jams or kinks instead.

 

[PHovnanian]

Birdcaging is caused by excessive bending of the conductor or untwisting during stringing. The former can be caused by too small traveler wheels for the conductor diameter. The latter has several causes, including misalignment of tensioner wheels or travelers with the direction of the conductor entering or leaving the equipment. This includes the alignment of the conductor reel with the tensioner, crossarm mounted traveler wheel angles not set correctly, etc. There is a correct and incorrect direction that conductors should be wrapped around the tensioners, as they impart some twist or untwist during operation depending on the conductor lay.

 

[Bercy]

Totally agree with PHovnanian. Here is quotation of bircaging from Standart IEEE 524

"As the conductor enters the bullwheel groove, the pressure of contact tends to push the loose
outer strands back toward the reel where the looseness accumulates, leading to the condition
commonly known as birdcaging, see Figure 28. If this condition is not controlled, the strands can
become damaged to the extent that the damaged length of conductor must be removed. This problem
can be remedied by allowing enough distance between the reel and tensioner to permit the strand
looseness to distribute along the intervening length of conductor and simultaneously maintaining
enough back tension on the reel to stretch the core and inner strands to sufficiently tighten the outer
strands. It is recommended that the back tension or braking tension of the conductor reel not exceed
4.5 kN since drawing down of the conductor into the lower layers on the reel may cause surface
damage. For smaller diameters and wooden reels, the back tension should be considerably less."

As you can see there is one number of tension force, better say braking tension and it is 4.5 KN,
but on the bullwheel there is much higher tension force using during stringing. I am really curious about the
differnce between braking tension on the reels and tension on the bullwheel. What is the proper ratio between the two,
or what tension force is proper to use on the bullwhhel? I know it depends on the diameter of conductor and distance
betwwen the structures.

Can anyone share installation manual, (guide for instalation ACSR overhead conductor) in .pdf.
I am also interesting about birdcaging remedies. What do you do when the birdcage occur in various of cases
(e.g.- during installation, or after final sagging, or after joining, and so on)

Thank you