Tram cables to go up during summer

The Edinburgh Trams project team and contractors are making final preparations to install overhead and underground cabling for the city centre section of the tram line.

This final major piece of construction work requires significant access to the tram route, so existing work sites between Haymarket and the West End and at York Place will remain. This will allow work to be done soon after road works are completed.

Cables will be installed on Princes Street and on St. Andrew Square during a series of night shifts. It's expected that overhead cabling will start in mid June from York Place at Broughton St, working west towards Haymarket.  The full programme which includes underground cabling is scheduled for completion in the Autumn.

Transport Convener Lesley Hinds said:

"Good progress continues all along the tram route and we're now approaching a stage, in the city centre, where road works are nearly finished. This will be a welcome sight to traders, residents and visitors to the area this summer. 

"This cable installation programme is the final major piece in the construction jigsaw but it's a significant project which requires time. Contractors will carefully hang power wires overhead at the correct tension and they'll pull miles of power cables and communication lines through underground ducts.

"Once this is done we'll be closer to the rigorous testing phase which will fully prepare the system and the people of Edinburgh Trams for service next year."

Transport Minister Keith Brown said:

"The project is entering a crucial phase and the installation of overhead and underground cabling in the city centre section is another key milestone. I wish everyone involved in carrying out this complex operation over the summer well.

"The continued patience of local residents and businesses is to be applauded. They are hopefully now starting to see some tangible progress ahead of the crucial summer tourist season.”

Cable installation process

1. Erect overhead line poles. (work well underway) There are two types of overhead line poles – those installed between the tracks, and those at the side of the tracks.

2. Install building fixings along the route in areas where the installation of an overhead line pole is not appropriate.

3. Install span wires. These run between building fixings and the side poles.

4. Install and tension the power wires. These wires provide power to the electric motors on board the trams though a pantograph which connects the overhead line to the tram vehicle. 

This installation is carried out using a set of specialist road/rail vehicles to draw out the wires from vehicle mounted cable drums. Wires are lifted to the correct height and attached to cantilevers from the overhead line poles. The power wires vary in height between 5.8m and 6.2m.

Contractors will also install underground cabling at the same time. 750V DC power is fed into the overhead power wires by a network of underground cables from a series of substations across the route. The underground cables are pulled through pre-built ducts running between a network of manholes along the route. 

In addition to the underground transmission cables, there are a series of communication systems and other cables to be installed within the network of underground ducts which line the route.

This overhead and underground cabling work will begin once road and track works are completed.

Once on-street works and overhead cabling work has been completed, a programme of rigorous testing and commissioning will take place in early 2014 to prepare the system and the service for operation. However, any scheduled completion dates can be impacted upon by weather conditions or other unexpected circumstances.

The project remains in line with the revised budget (£776m) approved by the Council in September 2011, with work either ahead of schedule or in line with the revised timescale reported in December 2011.

The tram project team will report to Council in September 2013 with an update on project timescales.

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