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Scottish Hydro-Electric Transmission Limited (SHETL) has compiled a Report on Consultations Document to provide a summary of the consultation process undertaken and to provide a project update for its proposed new electricity connection from Lewis to mainland Scotland.

The proposal is for the development of a new electrical circuit on Lewis, a subsea connection to the mainland and an underground cable to Beauly substation in Inverness-shire

The indicative proposed routes are included in the Report on Consultations document.

October 2008

If you would like a copy of the full environmental appraisal, please write to SHETL at the address below, enclosing a cheque for £50 for a paper copy (three large volumes) or £5 for a CD copy. Please make your cheque made payable to Scottish and Southern Energy plc.

Andrew Robertson
Scottish Hydro Electric Transmission Limited
Inveralmond House
200 Dunkeld Road
Perth PH1 3AQ

July 2008

Lewis infrastructure and subsea section (March 2007)

Consultation document March 2007 (1.40 MB)
Fig 2.1 Land based study area (846 KB)
Fig 2.2 Marine study area (398 KB)
Fig 2.3 Typical woodpole designs (191 KB)
Fig 4.1 Cultural heritage sites (813 KB)
Fig 4.2 Landscape character (780 KB)
Fig 4.3 Environmental designations (953 KB)
Fig 4.4 Proposed marine national park (591 KB)
Fig 4.5 Locations of known wrecks and charted obstructions (403 KB)
Fig 5.1 Proposed route options (968 KB)
Fig 5.2 Proposed route options (553 KB)
Fig 6.1 Preferred route land (916 KB)
Fig 6.2 Preferred route land (924 KB)
Fig 6.3 Preferred route marine (441 KB)

Consultation Document (December 2006)

Consultation Document (437 KB)

PCS-SSE - Western Isles HVDC GB Connections Options (609 KB)

West Coast Interconnector Initial Route Feasibility Study (5.78 MB)

Consultation Doc Fig 2.1 (386 KB)

Consultation Doc Fig 2.2 (127 KB)

Consultation Doc Fig 2.3 (162 KB)

Consultation Doc Fig 2.4 (54 KB)

Consultation Doc Fig 4.1 (329 KB)

Consultation Doc Fig 4.2 (797 KB)

Consultation Doc Fig 5.1 (863 KB)

Consultation Doc Fig 5.2(A) (661 KB)

Consultation Doc Fig 5.3 (460 KB)

Consultation Doc Fig 5.4 (495 KB)

Consultation Doc Fig 5.5 (406 KB)

Consultation Doc Fig 5.7 (421 KB)

Consultation Doc Fig 5.8 (920 KB)

Consultation Doc Fig 5.9 (835 KB)

Consultation Doc Fig 5.10 (826 KB)

Consultation Doc Fig 5.11 (762 KB)

Consultation Doc Fig 5.12 (795 KB)

Consultation Doc Fig 5.13 (764 KB)

Consultation Doc Fig 6 (692 KB)

Consultation Doc Fig 6.1 (792 KB)

Consultation Doc Fig 6.2 (837 KB)

Consultation Doc Fig 6.3 (857 KB)

Consultation Doc Fig 6.4 (850 KB)

Consultation Doc Fig 6.5 (958 KB)

Consultation Doc Fig 6.6 (976 KB)

Consultation Doc Fig 7.1 (819 KB)

Consultation Doc Fig 7.2 (827 KB)

Consultation Doc Fig 7.3 (874 KB)

Consultation Doc Fig 7.4 (967 KB)

Consultation Doc Fig 7.5 (963 KB)

Consultation Doc Fig 7.6 (471 KB)

Preliminary Consultation Documents

Preliminary Consultation Document (78 KB)

Overhead Line Study Area Map Figure 1 (October 2004) (385 KB)

Subsea Cable Study Area Map (379 KB)

SHETL's report on the Preliminary Consultation (February 2005)

In October 2004, Scottish Hydro-Electric Transmission Ltd (SHETL) asked for views to assist with the selection of a preferred route corridor for a 400,000 volt electricity transmission line between the north west of Scotland and the Western Isles – should it be necessary to accommodate output from renewable generation schemes which may be developed on the Western Isles. The purpose of this report is to advise the work that will now be done in the light of that consultation exercise, and to summarise the issues in respect of placing high voltage electricity infrastructure under ground.

Two possible route corridors
The ‘Preliminary Consultation Document’ set out five possible route corridors and summarised the environmental issues relating to electricity transmission developments. SHETL received and analysed over 300 comments on the document. Following this preliminary consultation process, SHETL has decided to undertake further environmental and technical work in respect of two possible route corridors:

Beauly/Shin/Melvich
Beauly/Garve/Ullapool

The Beauly/Garve/Ullapool corridor has clearly been prominent in this process for some time. The Beauly/Shin/Melvich route requires further consideration following suggestions from a number of consultees that other north of Scotland developments are included in a wider strategic evaluation of the options and their impacts.

SHETL does not intend to undertake further work on the other three route corridors discussed in its Preliminary Consultation Document at this stage.

The underground issue

A number of respondents to the Preliminary Consultation Document suggested that a new electricity transmission line should be placed underground. SHETL understands the sentiment behind this suggestion and believes it may be helpful at this stage to outline the technical and economic issues for transmitting power of this order of magnitude over long distances.

Alternating current/direct current
Public electricity supplies use alternating current (AC) while systems with batteries use direct current (DC).

For normal power supplies AC is used because it is relatively easy and economic to create a branched network and to transform between different voltages – high ones to transmit over long distances and lower ones for use in homes and offices. DC can also be used over long distances - but can only provide a single point-to-point link and requires very expensive equipment to change it back into AC for connection to the rest of the electricity network.

Accordingly, different types of cable are chosen depending on the application:

Underground AC cables are common at low voltages but very rare at high ones. 400,000 volt AC cables require a large trench of about 25m width overall and cost between 10 and 25 times more than overhead lines of the same voltage and capacity. The AC technology is the one that must be used in replacing the existing electricity transmission line connecting Beauly and Denny.

Application to a possible Western Isles connection

Any high capacity underwater link from the Western Isles to the North of Scotland would use a DC cable. This has to be used for any significant length of subsea route to keep electrical losses to an acceptable level. The laying of subsea cables is very expensive, especially over long distances. The subsea cable approach was rejected when it was put forward as a solution for linking the Western Isles to England because of the high cost and its inability to collect or deliver power to any other source over the length of the route.

Placing DC cables under ground is also a difficult task but is less expensive than AC cabling and may have less environmental impact. However, the inflexibility for interconnection and the costs of the converter stations normally make this unrealistic, but if a cable is used for a point-to-point link in combination with a subsea section where the converter costs are already included, it may become viable.

For the Western Isles connection, another possibility, therefore, is to continue the DC link from the point at which it arrives onshore to a point nearer Beauly. For this reason, SHETL will undertake further environmental and technical studies on this option as well.

Next steps
The Preliminary Consultation Document marked the first stage in the overall process and a first opportunity for formal comment on the possible development. This process will continue in due course with the publication of a Consultation Document on the preferred route when it is identified. That document will set out in more detail the outcome of the preliminary consultation process and of the further technical and environmental studies that are being undertaken. It is expected that it will be published later this year.

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