Creation of an underground electric link to the Calvados wind farm
In March 2021, building works began to the wind farm off the Calvados coast, with commissioning scheduled for 2024. RTE entrusted SADERTELEC with the creation of the project’s dual electric land link. Works were carried out in synergy with the Rouen RD up to February 2022.
Very High Voltage
Located 10 to 15km off the Courseulles-sur-Mer coastline, this wind farm will consist of 64 wind turbines capable of producing 450MW, i.e. 90% of the power needs of the Calvados area (approximately 630,000 inhabitants). Its production will be transported to the Ranville electrical substation via a dual three-phase 225,000-volt link, which extends 15km offshore and 24km underground onshore, with the intersection point at Bernières-sur-Mer.
From this landing point to Ranville, SADERTELEC’s task, with the support of the Rouen RD teams, is to build the underground facilities for the wind farm’s electrical cable and control network, with 36 cable and connection pits, and to lay 108 electric cable reels averaging 1.4km in length using the unwinding-traction technique.
SADERTELEC has been a shining example of in-house cooperation since its creation. Specialised in RTE works, this expert entity operates throughout France and calls on the support of the Group’s local resources whenever possible. For these works, the largest project entrusted by RTE to SADERTELEC to date, the Rouen RD teams carried out most of the excavation, civil engineering and backfilling works.
Rouen RD excavates, builds and pours
In concrete nozzle blocks poured on site, the two electric links are laid along symmetric, parallel and individually insulated paths. Each link is three-phase, and therefore composed of three 200mm-diameter PVC sleeves, lined with three 50mm-diameter PVC sleeves housing the optic fibre. These blocks were sized by RTE and built according to a strict protocol of precise measurements. A protocol followed to a T on a daily basis by the Rouen RD teams, organised in workshops and progressing at an average rate of 60m per day: opening, shoring, laying of supports and sleeves, concrete casting, shoring removal and backfilling. Within 11 months, the total contents of 2000 concrete mixer trucks will have been poured on site.
In addition to steering the works and building most of the 36 connection pits, the SADERTELEC teams are also laying this imposing underground facility, and from pit to pit, 108 cable sections, mainly in aluminium (ø 1,600mm² and 2000mm²), with a small proportion of enamelled copper (1,600mm²). Delivered in reels weighing 24 to 32 tonnes, they are laid under supervision using the unwinding-traction technique, a demanding method which prohibits any form of damage to the cable or its protective tube.
To manage this sensitive phase, SADERTELEC is equipped with the latest generation of high-performance equipment: reel jacks, a traction unwinder and a 150KN winch holding the reels of Dyneema® traction cables, which are lighter and more resistant than steel.
Safety: a joint concern
While SADE Group operators are naturally vigilant as to risk prevention and work safety, they are nevertheless subject to frequent inspections by RTE and its agents. Work safety is joint concern, and these inspections provide an ideal opportunity for discussion and the continuous improvement of processes.
SADERTELEC’s expertise, SADE’s solid national network and the teams’ ability to work in total synergy are all strengths. They enable us to respond to RTE’s needs on a nationwide level, with the resources and know-how to guarantee high quality and compliant lead times.