Home office in the mountains thanks to high-speed optical fibre connections – and, what's more, in the idyllic Engadine, one of Europe’s highest inhabited valleys with a length of over 80 km. This is a vision that will, in future, be made a reality thanks to the joint venture between Swissgrid AG, Engadiner Kraftwerke EKW and EE-Energia Engiadina.

The positive properties of Rauspeed microducts made of high-quality HDPE virgin material, tested in internal pressure creep tests, were demonstrated in the blowing-in of fibre optic cable back in the summer of 2018: with a blowing-in pressure of 14 bar, the Plumett MiniJet™ blowing unit was used to blow in an 8.1 mm fibre optic cable along a winding route into the already laid Rauspeed 16 x 2.0 duct – and achieved an impressive blowing-in length of 5.23 km without intermediate blowing. This easily surpasses the average route lengths of 1 to 2 km in the backbone and 600 to 800 m in the building connection that cable layers usually settle on for safety reasons. As if that were not enough, the route also passed under the river Inn and a plug connector was fitted every 800 m due to manholes.

After Swissgrid AG and EKW had laid the groundwork for the extension of the high-voltage line in the beginning of 2013, EE-Energia Engiadina took the opportunity to complement this by providing the municipalities with an inexpensive fibre optic network. The 50 km long trenches created for the power lines from 2017 were also used to lay a DN 92/80 mm conduit, which established the foundation – the “backbone” – of the fibre optic network in the Engadine between Bever, Zernez and Pradella. EE-Energia Engiadina independently constructed an additional line with a length of 25 km to enable supply out of the valley from Pradella to Martina.

Several duct bundles (3 x 16 x 2.0; 3 x 14 x 2.0; 5 x 14 x 2.0) and single ducts were fed into the conduit over a total route length of 75 km in the backbone and 40 km in the feeder as well as in the drop (the last route section to the building). For the subsection between the starting point in Ftan and the end point in Gurlaina in the municipality of Scuol (Lower Engadine), a 3 x 16 x 2.0 RAUSPEED duct bundle, a 32 x 2.3 PE duct and an earth wire were fed into the previously laid conduit.

The great blowing-in result is not only due to the experience of EE-Energia Engiadina, the blowing unit and the cable. The technical characteristics of the microduct are also crucial to the success of the blowing-in process. The patented Rehau RTR grooving, which has been tested for decades, promises particularly excellent blowing-in results with low cable abrasion. The large minimum internal diameter of the Rauspeed ducts and moulded parts (plug connectors) that are tailored for narrow tolerances guarantee optimal blowing-in conditions. Not without good reason are the ducts scrutinised extremely carefully at the factory: using ball tests, pressure tests and mandrel tests, every metre of duct produced is inspected for its suitability for blowing-in.

Not only thanks to the synergies produced by simultaneously laying the conduits, but also due to the long blowing-in length, it was possible to save additional civil and underground engineering costs. Besides single-family homes, businesses, hotels and other distribution points were also connected with optical fibre and will now in future receive an improved connection at a fair price – accompanied by a wonderful view.