All electrical work at the new Thurso South substation has now been completed, preparing the way for the energisation of the first section of upgraded 275 kilovolt (kV) overhead line in Caithness.

Thurso South substation is located near Geiselittle, west of the A9, two miles south of Thurso. Its equipment enables power to be transferred between circuits operating at 33kV, 132kV and the new 275kV spine of the transmission network that runs between Dounreay and Spittal. Construction of the substation began in June 2015 and, at its peak, saw a workforce of 220 employed on the site.

The upgrade to the spine of the onshore transmission network in Caithness is a key element in the wider Caithness-Moray transmission reinforcement which is being delivered by Scottish and Southern Electricity Networks (SSEN).

SSEN Lead Project Manager for the substation, Ian Clark, said:

“It’s a privilege to be involved with a project like this, improving infrastructure for the Highlands while working in, and supporting, the economy of the local community. We’ve had some significant challenges over the two years of construction, but we couldn’t have asked for more support and understanding from residents in the area.

“We’ve benefited a great deal from having a strong presence of locally based staff on the site. Almost half of the workforce has been drawn from Caithness, Sutherland or Wester Ross. Many have been part of the core team involved from the early weeks and will now see the site through to energisation.

“Close team-working between SSEN, our lead contractor Balfour Beatty and the wider supply chain has been vital in dealing successfully with the many issues and interfaces involved. The result is the timely delivery of a substantial new piece of strategic infrastructure which will serve a vital purpose for many decades to come.”

The construction of the new substation has involved 80,000 cubic metres of fill material – enough to fill 32 Olympic-sized swimming pools. 75,000 metres of cabling has been installed within the site, connecting 240 items of plant, 72 control panels and 4 transformers.

The high-point of the construction involved the landing at Scrabster Harbour of 2 supergrid transformers, comprising 6 large transformer sections and 14 HGV loads of crates with a combined weight of 700 tonnes.

The transportation through Thurso Town was carefully coordinated via engagement with the police, Transport Scotland and the Highland Council. The timings of the journeys were planned to minimise disruption to the town, with many locals who witnessed the transit enjoying the spectacle.

SSEN Site Supervisor, Billy Jappy, a local to Helmsdale said: “No matter how often you see it, it’s always incredible to watch the precision with which these huge vehicles are handled during delivery of such large pieces of equipment.”

One of the first activities on site was to establish the extensive 500 metres network of ponds, ditches and check dams in order to provide a temporary water management system. With some parts of the site within just 100 metres, the system was of vital importance to protect the tributaries and the river itself. The Thurso River is not only a site of special scientific interest (SSSI) but also a designated Special Area of Conservation (SAC) and renowned salmon fishery. The water management of the site has been a significant success given the amount of earthworks that have taken place and the very wet winters experienced.

Mr Tim Hawse, River Manager, Thurso River Ltd said: “It is always a slight concern for us when we see a project of this size happening relatively close to the watercourse, however the contact from the project has been really good and the surface water management has been completely successful.”

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