Copper wire and Copper tape in EHV Cable

[ravindranathan]

Copper wire is wound helically on the extruded insulation layer of (semicon+XLPE+semicon) in a typical MV/HV Cable.And again copper tape is wound helically on the copper wires in the opposite direction.Is there a purpose of winding these in opposite directions? Different manufacturers follow different methods..this is followed by one of the manufacturers.

 

[Compositepro]

During the winding process the torque applied to the cable cancels out. Also when tension is placed on the cable the tendency for the cable to twist will cancel.

 

[bacon4life]

Not sure if this applies to underground copper cable, though there is a great reason to do this in overhead ACSR conductors. A small single layer ACSR cable is just current carrying wires wrapped around a steel core, just like a simple inductor. The high magnetic fields in the steel core cause significant hysteresis losses in the steel core at higher amperage levels. In larger multilayer ACSR cables, each layer is wound in opposite directions to so that the magnetic fields cancel.

 

[7anoter4]

For cable conductor it is another explanation.
See-for instance: US Army Engineering Design Book Electrical Wire and Cable
chapter 1-6.2 CONCENTRIC STRANDING
Concentric stranding consists of a central core surrounded by distinct layers of strands. The only way such a stranding can be guaranteed to stay round is to either reverse the direction of the successive layers of strands, or have a different length of lay for each layer,so that the inner layer will support the outer layer and prevent the strand migration encountered in a bunched configuration. When the lay in each layer is reversed,
concentric stranding is called true concentric, and when the layers are in the same direction, each with a different lay length, it is called unidirectional concentric.
Unidirectional concentric has an advantage of much greater flexibility and flex life than the true concentric.
Lay lengths close to, but not greater than, those specified in Table 1—8 are important for flexibility and flex life. Concentric stranding is preferred to bunched to achieve more uniform wall thickness of insulation