Pipe type cable made from three stranded 110 kV XLPE cables simplifies redevelopment work

Hanover, April 16, 2007 – The 110 kV XLPE*)pipe type cable, which Nexans presented last year at the Hannover Messe, has since then proved it can be installed economically: in two redevelopment projects it is now serving as a technical and commercial alternative to paper-insulated cables.

Improved materials permit comparable dimensions
The pipe type cable was specially designed for insertion into existing cables, including as a replacement for gas pressure cables with paper insulation. To do this, it has three fully-fledged 110 kV XLPE cables with a copper wire screen and an aluminium laminated sheath, which, when stranded, have approximately the same dimensions as a paper-insulated cable. The stranding can also accommodate other elements, such as LWL cables**) for data transmission or temperature monitoring.

The compact diameter of the pipe cable was possible as current materials and manufacturing processes allow smaller XLPE wall thicknesses while retaining the same insulation effect. The whole cable has an armouring made from flat steel wires which allows it to be pulled further into even longer pipe systems.

Higher level of current transportation possible than with paper-insulated cables
The advantage of the new XLPE cable system compared to a paper-insulated pipe type cable is the higher permissible conductor temperature. This means the transmission ability is higher with the same sized conductor cross section.

Practical suitability of the cable tested in two cases
The pipe type cable was first used between a 110 kV block transformer and an outdoor switchgear unit in order to replace almost 500 m of esternal gas pressure cable. In the course of the redevelopment, superfluous bends in the pipe were adjusted, the trifurcating boxes in the ground were reinstalled and the individual cores were laid in the ground. The adjustment of the course of the pipe substantially reduces the sum of angles of the bends in the pipe, which reduces the force required to insert the pipe type cable. In this case, an additional advantage of the pipe type cable was used: it does not require gas tightness and the 110 kV cables can be laid as underground cables without any problems.

A second installation of the pipe type cable including straight joints was used for the 960 m long connection between an outdoor switchgear unit and an overhead line here, the old gas pressure cable was removed without altering the steel pipe. Other projects are planned. The Nexans team will be talking about their experiences at the Hannover Messe (April 16 to April 20) in hall 12 at stand D06.
*) XLPE = crosslinked polyethylene; **) LWL = fibre optic cable

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