Crossing waterways for Randstad 380

Due to the rising demand for electricity in the Randstad, Tennet, the administrator of the national electricity grid, decided to increase the current power line between the Maasvlakte and Westerlee from 150 kV to 380 kV. The name of this project is Randstad 380.

Facts and figures

Project categories
The first step in raising the transport capacity of the grid is replacing the current 150 kV oil pressure cable underneath the Caland canal and the Nieuwe Waterweg canal. The current cable was laid in 1969, and its diameter and voltage levels will not be able to cope with the transport capacity as required in the future.

Drilling

The new connection will be created through drilling, as both the Nieuwe Waterweg canal and the Caland canal are extremely busy waterways, regularly traversed by large and tall vessels. Constructing overhead lines would therefore require extreme heights. It was therefore decided to construct the 380 kV line underground in these places,
running underneath the waterways. Visser & Smit Hanab has twice realised four horizontally controlled drill holes, measuring 750 and 650 metres in length respectively. The distance between the holes is eight metres, so as to prevent problems with the power limits and temperatures.

 

The connection between the two points where the lines resurface consists of two parallel circuits. These in turn consist of three 380 kV lines with copper conductors. The
cable lengths of the circuits measure approximately 1350 and 850 metres. These lengths are unique for 380 kV lines, as are the abovementioned drilling lengths.

Installation

The installation of the lines involved the use of large cable drums (5.5 metres wide and 4.5 metres tall), a winch and cable traction machines. The cable pipes were filled with water prior to installation so as to decrease friction when drawing in the stiff cable. It was pulled through by the winch and simultaneously pushed by many small cable traction machines. Each socket was equipped with a measuring sensor, so as to monitor for any losses. All data of these measurements was transferred by means of a fibre optic cable constructed parallel to the lines. Once the cables have been drawn through, the end-fittings which connect the new lines to the national grid will be installed.
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