Randstad380, Netherlands

NKT received an order for the project in 2008 from the Dutch electricity grid operator TenneT TSO B.V. At this time, it was the biggest 380 kV turnkey cable project in the world.

The Randstad region includes big cities like Rotterdam and Amsterdam, what made the project of connecting the two transfer stations of Wateringen and Bleiswijk highly challenging. Among others, the cable route had to cross two railway lines, a motorway, some sports facilities, several dikes, a river and several watercourses. Extremely varied territory profiles, soft moorland, a high water table, deep sand layers and expected submergences of up to 0.5 m in civil engineering were other huge challenges the NKT engineering teams had to face.

About 11 km of the distance were to be covered by underground cables and about 14 km by overhead lines. TenneT approached NKT for a complete solution for the engineering, production and delivery of the cable system and accessories. NKT was also to be responsible for the project management, the accessory installation and the final testing. We took care of the civil engineering and cable-laying as well, with the support of a partner.

The cable system and accessories were produced at our state-of-the-art facility in Cologne, Germany. To minimize construction time, we also designed a special logistics concept and established a storage place in the Netherlands.

We managed to overcome the challenges of the cable route. Together with TenneT and the authorities we decided to install plastic tubes through horizontal drilling to minimize adverse effects. There were drillings of up to 530 m with a total length of more than 50 km. To act in an environmentally friendly way in the complex landscape, we used a very narrow working area.

NKT provided a 380 kV connection with dual systems consisting of 132 km of 380 kV XLPE cable, partly with integrated optical fibres. Our specialists performed all installations, whereof some needed to take place simultaneously to match the project schedule.

We used our own test trailers plus two additional ones for the onsite testing, and completed the final high-voltage test at 374 kV for one hour on all cables and accessories. Partial discharge measurement was also performed on all accessories.

This successful project demonstrates our outstanding competence in handling projects to customer’s benefit by responding to their needs and providing cost-efficient, ecological solutions. The Randstad380 Zuidring project is a remarkable milestone – not only for us at NKT.