Upgrade plan to boost power line

Higher transmission towers proposed on route

Details of major works planned to upgrade a power line passing through Perth and Kinross have been published.

Scottish Hydro Electric Transmission has applied for consent from Scottish ministers to replace overhead transmission lines measuring over 100 miles between Kintore north east of Dyce and Blairingone south west of Powmill.

The existing 275kV overhead line (OHL) enters Perth and Kinross at its border with Angus near Kirriemuir then runs in a south westerly direction between Blairgowrie and Coupar Angus on its way down to Perth.

Then it crosses the River Tay south west of Stormontfield and skirts around the western edge of the city.

The line then heads in a more south easterly direction through villages like Glenfarg, before turning south west again and passing close to places like Drum and Crook of Devon before reaching Blairingone.

SHE Transmission wants to increase the operating capacity of the line to 400kV as it considers its current capacity “is not sufficient” to accept electricity generated by new renewable energy projects.

The company is proposing to replace existing conductors and insulators, add extra steelwork to 73 towers along the route to increase their height, complete tensioning work to the ‘earthwire’ which runs along the top of the towers and strengthen any towers needing upgraded.

SHE Transmission has notified the local authority of the planned work and over 60 documents relating to the project have now been published on the council’s planning portal.

A non-technical summary of the proposed upgrade says enabling works will involve the creation of temporary site compounds for storing equipment and materials, with a minimum of three main compounds needed along the route as well as a “rolling” arrangement of smaller subyards.

The summary also says of the main upgrade works: “The towers along the route would be grouped into ‘sections’; typically five-15 towers. The towers at each end of the section would be set up with a winch and tensioner equipment and the new conductor on one side and a cable drum on the other.

“The machinery would be set up within a designated safety zone with temporary surfacing to protect workers from electric shock.

“The existing conductor would be pulled in via the winch onto a reel drum, which in turn is connected to the new conductor at the opposite side and therefore replaces the conductor between the towers as it is pulled through.”

The summary adds: “To ensure the required ground clearance is maintained following the replacement of the conductors, 73 towers would be extended by up to 10 per cent of their existing height.

“To achieve this, the OHL would be transferred to a temporary mast or tower structure, which would be installed within 100m of the tower to be extended. This allows electricity transmission to be maintained while the works are undertaken.

“A crane would be used to lift the top part of the tower and a new section of steel work would be installed. Following this, the OHL conductors would be placed back onto the tower and the temporary mast would be removed.”

The summary goes on to say “essential woodland felling” will have to be carried out in a number of locations to increase the operational corridor of the line, but this will be “off-set through off site compensatory planting”.

It also says a recent study identified there is the potential for the works to have “direct physical impacts” on 192 heritage “assets” along the route of the line but with mitigation in place “no significant effects are predicted”.

The documents adds: “Mitigation to potentially reduce these impacts will need early and proactive consultation with Historic Environment Scotland and Perth and Kinross Heritage Trust.”

All the documents are available for inspection on the council’s website.