| Precise manufacturing techniques and know-how are required all through the process to ensure the reliability of Milliken cables. Pourtier has been involved in power cable development for a very long time, and designs and manufactures a variety of equipment used at different stages of the process.
The conductor generally consists of 4, 5, 6 or 7 segments. Each segment is made up of wires stranded and shaped in the Pourtier Rigid Strander type RFS 630. Tension on each copper wire is automatically controlled between the full bobbin and empty bobbin and is adjusted from the control desk during machine operation.
Sophisticated rotating heads ensure the necessary high quality of compacting, shaping and pre-spiralling of the conductor. Special know-how is used for the design of compacting and shaping rollers as well as for the segments to avoid sharp corners or edges. The conductor must be free of particles that would contaminate the semi-conductive screens, causing high stress points at the surface of the semi-conductive screens.
The Pourtier Drum Twister (for drums up to 4000 mm / 30 tons) includes smooth deviation angle for the segments as well as for the laid-up conductor (resulting in a longer take-up frame). The tension control on each segment, the relative position of which is automatically adjusted, ensures a perfect geometry of the finished conductor; each pay-off reel is driven to maintain a constant tension. Sensors control the position of the segments and give feed-back to each rotating pay-off stand whose rotation speed is automatically adjusted: no pressure or forcing is exerted on the segment.
When laid-up, the segments form a tight, close-fitting construction. They are then taped together with semi-conductive and metallic tapes to prevent any movement during further processing.
Copper screening wires are applied over the insulated cable core. Below and above screen wires, cushioning tapes (used to cope with the expansion of the cable core under operating conditions) and semi-conductive tapes are also applied. Steel tapes are finally applied for cable protection.
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