Background Scottish Hydro-Electric Transmission Ltd (SHETL) is proposing a new 275 kilovolt (kv) (1 kilovolt = 1000volts) double circuit overhead line (OHL) between the Dounreay sub station and the new Spittal substation via the new Thurso South substation. This new OHL will replace the existing 132 kv double circuit OHL. In addition SHETL is proposing to construct a new 132 kv OHL which would run in parallel with the existing 132 kv OHL between the new Spittal substation and an extension of the existing Mybster substation. This proposal is part of the reinforcement of the electricity transmission network, envisaged by the National Planning Framework (NPF2) and the Energy Networks Strategy Group. Analysis of the existing transmission network in the north of Scotland identified the need for increased network capacity to facilitate the transmission of renewable generation projects north of Beauly including onshore/offshore wind and marine and tidal generation. This increase in network capacity can only be achieved by undertaking reinforcement of the transmission network in the north of Scotland. The diagrams below provide an indication of the extent of the proposed generation developments in the area. This is one of several elements of work to reinforce and extend the transmission system in the area, referred to collectively as the Caithness, Moray, Shetland (CMS) transmission reinforcements. Other elements include multi-terminal high voltage direct current (HVDC) links. This poster presentation is in relation to the new 275kV and 132kV OHL between Dounreay and Mybster, the new Thurso South substation and the extension works to the existing Mybster substation. Growth in Renewable Energy Generation Offshore Renewable Generation Onshore Renewable Generation Hydro Power Activity (December 2011) Highland Windfarm Development (May 2012) 1
Project Description The aim of the project is to strengthen the high voltage network in Caithness with the replacement/upgrade of the existing 132 kv overhead line (OHL) between the substations at Dounreay, Thurso and Mybster with new higher capacity infrastructure. The main elements of the project are as follows: Construction of a new double circuit 275 kv OHL (lattice steel tower) from the Dounreay substation to the proposed 275/132 kv substation and HVDC converter station at Spittal, via a new substation near Thurso (c. 26km). This will replace the existing 132kV OHL between Dounreay and Spittal. Project Overview Map Legend Dounreay to Thurso South 275 kv Thurso South to Spittal 275 kv Spittal to Mybster 132 kv Connection of the new 275 kv OHL to the new 275 kv / 132 kv Gas Insulated Switchgear (GIS) substation at Dounreay, which is currently under construction via a different project. Construction of the new Thurso South 275 kv / 132 kv / 33 kv substation, and associated works to connect the existing 33kV distribution infrastructure to the new substation. Connection of the new 275 kv OHL to the new 275/132 kv substation and HVDC converter station at Spittal, which is currently being progressed via a different project. Construction of a new double circuit 132 kv OHL (lattice steel tower) between the new Spittal 275/132 kv sub station and HVDC converter station and the existing Mybster substation (c. 4km). This will run in parallel with the existing 132 kv OHL between the Spittal substation and the existing Mybster substation. Construction of 132 kv infrastructure at the existing Mybster substation. These works will be adjacent to the north of the existing substation. Connection of the new 132 kv OHL to the new 275/132 kv substation and HVDC converter station at Spittal, and to the new 132 kv infrastructure at the existing Mybster substation. The project overview map is presented opposite. Consultation Process As well as endeavouring to select the best possible route for the proposed overhead line reinforcement, we want to keep everyone affected by the proposal informed of our intentions. We firmly believe that early and regular communication and consultation with those likely to be affected by the proposal forms a critical part of its development. A route for the new overhead lines, shown on the plan above, was selected by undertaking a series of studies to determine technical feasibility, economic viability, land use and any environmental constraints. These were then reviewed together to identify the preferred route that balanced each of these considerations. As part of the environmental studies we are consulting with the Highland Council, statutory and non-statutory bodies and other interested parties to collect many types of baseline information including landscape and visual amenity, nature conservation, cultural heritage, archaeology and land use. We also undertook a similar site selection process to determine the preferred site for the new Thurso South substation. This was presented at a public exhibition held in February 2012. Following this event, the proposed site was selected and a Proposal of Application Notice submitted to the Highland Council as part of the Town & Country Planning (Scotland) Act 1997 major development obligations. Have Your Say This exhibition is your opportunity to comment on and ask questions about our proposals so far. We would greatly appreciate it if you would take the time to fill out our short questionnaire and post it in the comments box. Alternatively, you can write to: Lisa Kelly Scottish Hydro Electric Transmission Ltd 10 Henderson Road Inverness IV1 1SN Please submit your comments on the OHL works by Monday 16th July 2012. Project program The current programme for the project is shown below: Develop and compare sub station sites / route options Complete Identify preferred sub station sites Complete Undertake public exhibition for preferred sub station sites Complete Submit Proposal of Application Notice for sub station site Complete Identify preferred route for overhead lines Complete Publish consultation document on overhead lines Complete Undertake public exhibition for all project elements July 2012 Refine the preferred route and select a proposed route July 2012 Complete Environmental Impact Assessment October 2012 Apply for consents November 2012 Start Construction Early 2014 Phased completion and commissioning 2015-2016 Dismantling of the existing 132 kv lines 2016-2018 2
Overhead Routing Study Process The Route Selection Process We have worked closely with a team of environmental consultants and overhead line engineers to identify a technically feasible (both in terms of constructability and long term maintenance), economically viable, new transmission OHL which gives rise to: least disruption to the amenity of people living and working in the area; least impact on the physical and natural environment, and on nationally important species, habitats and cultural assets; least disruption to current land use and management practices; and least disruption to existing and proposed infrastructure and other economically beneficial uses of land. Legend Dounreay to Thurso South 275 kv Thurso South to Spittal 275 kv Spittal to Mybster 132 kv Dounreay to Thurso South 275 kv A number of 2km wide route corridor options were assessed, taking into account the technical requirements to connect to the existing electricity network. A process of analysis and comparison of potential routes within the 2km corridors was then followed. The assessment has been based on : detailed baseline data on land use and environmental character and sensitivity, obtained from desk sources and site visits; identification of potential effects, to inform strategies for enhancing positive outcomes and for avoiding, reducing, controlling or offsetting potentially undesirable or significant negative outcomes; initial consultations with key stakeholders to inform the above and the subsequent refinement of the routing study and selection of the preferred Thurso South to Spittal 275 kv Spittal to Mybster 132 kv The Preferred Reinforced Transmission Route A preferred route for the proposed reinforcement is shown on the accompanying plans. The final, proposed route will be determined after this detailed consultation and will be subject to an environmental impact assessment. The preferred route has been identified, which on the basis of the route selection process is considered to represent the optimum balance of technical, economic and environmental feasibility. The precise route alignment of the OHL and the location of individual towers will be determined following completion of ongoing detailed surveys to identify engineering, land use or environmental constraints which may require localised modifications to the route. Towers The OHL will be constructed using self-supporting lattice steel towers. The towers used for the 275 kv OHL will vary in height between 32m and 52m to accommodate changes in topography and where the line crosses roads and rivers, although the height will generally be in the region of 40m. The 132kV OHL towers will vary in height between 23m and 38m, although the height will generally be in the region of 28m. The spacing between towers will vary depending on topography, altitude and land usage. The height and distance between towers will be determined later in the design process; however the spacing will be generally in the range of 260-360 m for the 275 kv towers and 200-300 m for the 132 kv towers. Construction High voltage OHL construction typically follows a standard sequence of events which are: complete pre-construction surveys, as required by a construction environmental management plan; establish access (including any necessary vegetation management); install tower foundations; assemble and erect towers; erect temporary scaffolds and protection to roads, railways and rivers; erect conductors (wires); dismantle and remove temporary scaffolds and protection; and, re-instate tower sites and remove temporary access tracks. 33123 5486 It is anticipated that the construction programme will last approximately 34 to 36 months. We would hope to start in January 2014 to allow the completion of construction by December 2016. The detailed construction phasing and programme will be subject to change as the design progresses and also due to necessary consents and wayleaves being agreed. On completion of the commissioning the existing lattice steel towers between Dounreay and Spittal will be removed. 3
Proposed Dounreay - Mybster 275 kv / 132 kv Route Selection - Dounreay to Thurso South 275 kv New Thurso South substation This part of the preferred route follows an alignment between the Dounreay substation and the new Thurso South substation at a location near Geiselittle. It runs parallel to and approximately 90 m north of the existing Dounreay-Mybster 132 kv OHL from Dounreay, until it reaches the crossing of the B870 at Moss of Geise. It traverses on to the south side of the existing 132 kv line at this point (the existing 132 kv OHL will ultimately be removed), turning slightly to the north east to cross the railway line and River Thurso at a point approximately 350 m south of the existing 132 kv OHL, terminating at the new Thurso South substation. Route Selection - Thurso South to Spittal 275 kv Route Selection - Spittal to Mybster 132 kv New Thurso South substation New Spittal substation New Spittal substation This part of the preferred route follows a route between the new Thurso South This part of the preferred route runs between the new Spittal substation and the substation near Geiselittle and the new Spittal substation. existing Mybster substation. It initially runs south east from the new Thurso South substation before turning It runs in parallel to the existing Dounreay-Mybster 132 kv OHL, on the east side. southwards at Todholes Farm to cross the railway line and River Thurso. It then turns The existing 132 kv OHL would remain between Spittal and Mybster following to the south east to cross the river again approximately 500 m north of Hoy and Braal construction of the proposed 132 kv OHL. Holdings before turning to run north to south, from where it runs parallel to the existing 132 kv OHL until it reaches the new Spittal substation. 4
Thurso South Substation - Background Project Overview Map A new 275/132/33 kv substation is required as part of the Caithness Transmission Reinforcement. The substation will connect the new 275kV OHL to the high voltage 33kV distribution network at the existing Thurso substation. There will be new underground cabling from the substation for the connections into the existing 33kV network. SHETL previously identified four possible sites for the substation, which were the subject of a site selection process. This involved undertaking a series of studies and identifying the most suitable site, balancing technical and environmental issues, effects on local community, land ownership and land use issues, and overall network economics. Discussions were held with the Highland Council, statutory and non statutory bodies in order to gain a greater understanding of the key factors likely to influence development at the site. A public exhibition was also held in February 2012 to seek comments from the other interested parties. Indicative Electrical Layout Indicative Electrical Layout Thurso South Substation Description A new access will be constructed from the A9 to the north-east of the proposed site. The footprint of the proposed substation and associated infrastructure would be approximately 9.1 Hectares including embankments. The construction area would be 21.5 Hectares. The tallest structure within the site will be the proposed control building which would be of an agricultural type structure, approx. 35m x 20m x 10m high. The site would include parking and manoeuvring space for operation and maintenance of the facility. Existing trees will be retained for screening purposes and further landscaping will be placed in appropriate places on site. This will be determined following the landscape and visual assessment. 5
Mybster Substation - Background Project Overview Map The new 132 kv infrastructure at the Mybster substation is required as part of the Caithness Transmission Reinforcement, due to generation developer connection requirements to the transmission network. The existing transmission lines between the Mybster substation and the proposed Spittal substation are already at capacity. Reinforcement is required to increase security of supply and to connect new generation to the 275kV network at Spittal rather than install a number of separate overhead lines and/or cables for each connection. The extension of the existing substation as opposed to a new substation is driven by the requirement for the existing developer connections to be diverted onto the new OHL (Spittal to Mybster 132 kv). This also reduces the need for further infrastructure to make the connections to the new OHL. As a result, no site selection process was required. As part of the environmental studies we are consulting with the Highland Council, and other key statutory bodies to collect many types of baseline information including landscape and visual amenity, nature conservation, cultural heritage, archaeology and land use. A pre planning meeting with the Highland Council has been undertaken, and the Proposal of Application Notice (PAN) has been submitted. Mybster Substation Description Indicative Electrical Layout Mybster Extension Works Description The works involve extending the existing 132kV/33KV Mybster substation to the north. A new access will be constructed off the A9. The footprint of the proposed extension will be approximately 3 Hectares. The height of the perimeter fence will be 2.4m, the highest 132kV busbar will be approximately 7m and the highest 132kV tower 40m. The site would include adequate parking and manoeuvring space for operation and maintenance of the facility. The control building would be of an agricultural / industrial type structure, approximately 33m x 20m x 7m high. 6