Nexans Deliver Innovative Solutions for UK Onshore Windfams

Nexans 33kv cableNexans 33kv cables for onshore windfarm projects are now available with a conductive outer skin on the protective sheath, this innovative feature assists the installer in testing for sheath damage.

This conductive outer skin feature represents one of Nexans "Windfarm Innovations Program" which covers a range of features for cables and associated services which can improve the overall efficiency of an onshore windfarm installation through reducing installation time and overall costs

The cables used to convey power between the wind turbines and the collector substations are laid directly in trenches which can often cross challenging terrain. A common problem on sites is that the cable sheaths are damaged by stones or other obstacles during laying but this damage is not discovered until the cable is buried and testing is being carried out.

On standard cables, in order to make a "sheath test" (which measures the resistance between the cables metallic screen and the outer sheath layer), the outer sheath needs to be in contact with moist soil/sand to provide a return electrode for the test. This means the test can only be performed satisfactorily once the cable is buried in the ground.

By supplying cables which have a very thin skin of conductive material, testing can be done without the need for the cables to be buried. An initial test can be made whilst the cable is still on the drum to establish whether the cable sheath is intact before beginning to lay it in the ground, the test can then be repeated as soon as the cable is laid in its’ final position before the cables are blinded with soil or sand.

Any damage to the sheath can found from the test and repaired without the expense and lost time of having to excavate the surrounding soil /sand.  A further feature is to have the sheath in a natural colour with the conductive skin as black. This assists in the identification of any sheath damage as the natural colour of the sheath is visible through the black layer at the site of damage.

The semiconductive layer is also a perfect way to detect sheath errors of cables installed in ducts. Even if the duct is dry during installation; this may change during its’ lifetime. Once water has entered a duct it normally stays there and may damage a cable with an existing sheath error in this area. With a conductive layer the cables can be tested before and after installation into ducts to be sure no sheath error is present which could reduce the cables’ lifetime.

"The cables used in onshore windfarms today are essentially the same designs as those used on powergrids, however there are some differences in the installation and operation which mean there are possibilities to optimise and innovate the cables for windfarms to accommodate the unique conditions found on windfarms. Our Windfarm Innovations Program has been developed following the experience we have in supplying many kilometres of cable to Windfarm sites to help owners,developers and installers reduce their costs" comments Philip Howell, Sales Manager for Nexans UK Infrastructure Markets.

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