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Cabling on double twist XLPE Cables

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2 years 6 months ago - 2 years 6 months ago #2939 by Ing Enrico Conte
Trying to cable 4x XLPE Cables with a double twist buncher, we're facing problems and difficulties. We expected a behavior similar to PVC, where we do not have any particularly problems using bows with eyelet, but it is not so. The single cable is unwound with a motorized pay-off and dancer.

Any suggestion ? Lubrication ? Bows with roller or eyelet ?

Thanks in advance for any help.
Enrico
Last edit: 2 years 6 months ago by Peter J Stewart-Hay.

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2 years 6 months ago #2940 by Peter J Stewart-Hay
Hello Enrico,

As you well know, double twist cablers are rigid by design so three fundamental things are required for successful cabling.

Since each insulated conductor gets two axial 360 degree twists for each rotation of the take-up bows:

1 - The rigidity of the insulated conductor must be as low as possible. This means that the smaller the diameter of each insulated conductor, the easier it will be to cable the product.. The conductor material should also be annealed copper and not aluminum or an aluminum alloy. This is regardless of where the double twisting occurs but ideally it would be before the twisted cable enters the take-up bow.
2 - The length of lay of the twisted cable should be as long as possible.
3 - The design of the take-up should be optimized for the twisted cable. That means smooth and easy geometry of the bows which should be outfitted with rollers and good sized diameter pulleys to align the twisted cable as it both enters and exits the bow.

I think it would be almost impossible to double twist triple insulated conductors as the axial twisting would leave the cable essentially "alive" with inbred stress.

Since we have no other information as to the size range of the XLPE insulated conductor and the voltage rating, this is essentially all the information we can provide.

Regards,
Peter J. Stewart-Hay Principal
Stewart-Hay Associates
www.Stewart-Hay.com
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2 years 6 months ago - 2 years 6 months ago #2941 by Ing Enrico Conte
Hi Peter,

Thanks a lot for your prompt reply.
Regarding the single cable that we're trying to laying up in a 1250 double twist buncher, the single cable is a class 2 stranded copper conductor 16 square mm, not compacted, single layer insulated XLPE for LV application. The lay-length is bigger than 400mm. Pulleys have large diameter (Larger than 400mm or 15.75 inches.) and we're using 4 single motorized pay-off with dancer.
The main problem regards that in the assembled cable we have seen some damage in the insulation covering the conductor. I think that the problem could be in the bow (with carbide eyelets)

What do you think ?

Thanks again to all for the help

Enrico
Last edit: 2 years 6 months ago by Peter J Stewart-Hay.

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2 years 6 months ago - 2 years 6 months ago #2943 by Peter J Stewart-Hay
Hello again Enrico,

Thanks for the additional information.

This is a large and heavy cable as it is comprised of 4 x No. 6 AWG copper conductors with XLPE insulation. There is a lot of centrifugal force on the bow from the weight of the cable.so I would think that eyelets are out of the question. Rollers with wear plates attached to the bow in between the rollers would be used instead. Moreover the bow components must be designed so that the cable insulation can never touch the roller mounts or the wear plate mounts.

You might want to look at Bow Technology from the Gauder Group in France for a great solution. They specialize in high tech bows. They will be at stand 10E40 at the wire 2016 show.
en.bowtechnology.com/Site.aspx

Cheers

Regards,
Peter J. Stewart-Hay Principal
Stewart-Hay Associates
www.Stewart-Hay.com
This email address is being protected from spambots. You need JavaScript enabled to view it.
Last edit: 2 years 6 months ago by Peter J Stewart-Hay.

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