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Power firm plans to bury cables

A power company has confirmed its intention to put a major high-voltage power line underground across the Highlands. However, it has again ruled out burying an upgraded transmission line down the spine of Scotland.

Scottish and Hydro-Electric Transmission Ltd (SHETL) wants to take a power line from Ullapool in Wester Ross to Beauly, near Inverness, so that electricity from the UK’s largest wind farm, planned for Lewis, can be connected to the national grid. A revised plan by Lewis Wind Power for 181 turbines was submitted to the Scottish Executive on Tuesday.

SHETL, a subsidiary of Scottish and Southern Energy (SSE), looked at five different routes to take power from the proposed wind farm to the mainland and connect to the grid. Yesterday, it published a new consultation document setting out its preferred option for the new connection, costing about £375 million.

This involves building substations on Lewis, taking underground high-voltage direct current (HVDC) cabling between the substations and the shoreline and then a subsea HVDC cable circuit under the Minch. Underground HVDC cabling would be laid between Little Loch Broom at Ullapool and a substation at Beauly.

SHETL says it has chosen to bury the cables because HVDC technology is essential for the subsea section of the route, as power losses on alternating current (AC) underground or undersea cables are unacceptably high.

A spokesman said: “The HVDC technology can be continued along the route of the entire circuit to Beauly and is an economic solution, partly because it avoids the major costs associated with the converter stations that would be required to convert HVDC transmission to AC transmission. Overall, the proposed connection is a point-to-point transmission system, for which use of HVDC technology is suitable.”

However, he said the HVDC technology is not suitable for the proposed upgrading of the transmission line between Beauly and Denny, near Stirling, which has been the subject of strong criticism.

A public inquiry into the planned upgrade is due to start in February.

“That line is part of the main interconnected transmission system,” he said. “The scheme to upgrade it features three intermediate points where it is necessary for the line to collect additional power: Fort Augustus, Errochty and Braco. It is not generally practical to connect into an intermediate point on an HVDC link. The Beauly-Denny replacement line is, therefore, proposed as an AC overhead line.”

Dr Keith MacLean, SSE’s head of sustainable development, said all comments will be considered along with an environmental assessment.

The Ullapool-Beauly plan has been strongly criticised by the protest group Highlands Before Pylons (HBP).

HBP welcomed the move to bury the cables, but said it still has “grave reservations” about the need for the line.

By John Ross