Scottish Hydro Electric Transmission
Scottish Hydro Electric Transmission (SHE Transmission)
owns and maintains the high voltage electricity network
that serves the north of Scotland.
Overview of
Transmission projects
The landscape and environment that contribute to the
challenges we face also give the area a rich resource for
renewable energy generation. There is a high demand
to connect from new wind, hydro and marine generators
which rely on SHE Transmission to provide a physical link
between the new sources of power and electricity users.
Orkney
Existing infrasturcture
Recently completed
Under construction
Potential Development
In total, we maintain about 5,000km of overhead lines
and underground cables – easily enough to stretch
across the Atlantic from John O’Groats all the way to
Boston in the USA.
Our network crosses some of the UK’s most challenging
terrain – including some circuits which are over 750
metres above sea level and up to 250km long.
Shetland
Dounreay
Spittal
Western
Isles
Moray
Firth
Mossford
Beauly
Skye
Peterhead
Blackhillock
Kintore
Aberdeen
Perth
SHE Transmission is delivering a major programme of
investment to ensure that the network is ready to meet
the needs of our customers in the future.
Denny
Kincardine
Hunterston
Kintyre
Arran
East Coast Subsea Link
SHE Transmission’s recently completed Corriemoillie substation, near Garve, with Lochluichart wind farm shown in the distance.
Caithness to Moray Transmission Reinforcement
Renewable generation in the northernmost part of
Scotland, Orkney and Shetland is forecast to grow in
the years ahead to around 3 Gigawatts (3000MW).
Work was completed in early 2013 to add extra capacity
to the existing 275 kilovolt (kV) overhead line which runs
between Dounreay and Beauly, but significant further
investment is now required to accommodate additional
power generated from the wind, waves and tides.
SHE Transmission is proposing to invest around £1.3
billion in a project centred on an underground and
subsea cable between Spittal in central Caithness and
Blackhillock, near Keith, in Moray. The existing onshore
network would also be further reinforced between
Dounreay and Mybster in Caithness and – further south –
between Loch Buidhe, near Bonar Bridge, and Beauly.
Work would take place at 8 substation sites and would
include the construction of 2 converter stations at either
end of the proposed cable. The cable itself would run
for over 160 kilometres (100 miles) and be capable of
transporting up to 1200MW of electricity beneath the
Moray Firth.
Caithness-Moray project website
www.ssepd.co.uk/CaithnessMoray
Subject to approval by the energy regulator, Ofgem, the
whole project could be completed as early as 2018.
The Oyster wave energy device in use off Orkney.
Photo: Aquamarine Power
OpenHydro’s tidal machine on the dockside, ready for testing.
Photo: OpenHydro
Planned onshore and offshore wind generation
is forecast to grow.
High Voltage Direct Current
The underground and subsea cable at the heart of SHE
Transmission’s proposals would use a technology called
High Voltage Direct Current (HVDC). This is different
to the existing onshore network, which carries high
voltage electricity as Alternating Current (AC).
HVDC is a well established technology which is in growing
use all over the world – including at a number of locations
around the UK.
It allows the efficient transmission of large quantities
of electricity across long distances – with much reduced
electrical losses compared with AC. It also introduces
greater flexibility and resilience in the operation of the
network and the management of variable output from
renewable generation.
The Caithness to Moray project as a whole would keep
the amount of new onshore transmission infrastructure to
a minimum. Individual sites have been carefully selected
and designed to keep their impact on the landscape and
the wider environment to a minimum.
Careful site selection, planting and landscaping will help key sites like Spittal to blend into their
surroundings over time.
Modern Gas Insulated substation equipment within the newly built Dounreay substation. Similar
technology will be used in the construction of the AC substation at Spittal, from which electricity
will be transferred into the HVDC converter station for onward transmission.
Onshore HVDC Construction
The HVDC cable will run between two converter
stations at Spittal in Caithness and Blackhillock
in Moray.
Onshore cable burial: The project involves 48km of
onshore underground cable, from Spittal to Noss Head in
Caithness; and from Portgordon to Blackhillock in Moray.
Along this section:
The proposed layout of the Spittal site, with the HVDC converter station shown at the top right.
• A working corridor up to 20 metres wide will
be established.
• A temporary access track will be built.
• A trench will be excavated to allow installation of the
cable circuit.
• The cables will be laid in sections and ‘jointed’ in
temporary covered bays along the route.
• Once installation is complete, the soil and topsoil will be
carefully reinstated and the access tracks removed.
Directional drilling: At the cable landfalls, it is proposed
to use ‘horizontal directional drilling’ to enable the cable
to be installed with minimal disturbance to the coastline.
At the locations:
The proposed layout of the Blackhillock site, with the HVDC converter station at the bottom left.
A 20 metre working corridor will be created to allow the installation of the cable underground
between Spittal and Noss Head in Caithness; and between Portgordon and Blackhillock in Moray.
• A specialist drilling rig will bore a hole through which
the cable can be fed without disturbing the surface
of the ground.
• This method on a smaller scale can also be used at
major road and river crossings.
Offshore HVDC Construction
Some of the most challenging construction work work
takes place on the subsea section of the route. Extensive
surveys of the seabed have already been completed to
find the best route – and every stage of the installation
process will be closely monitored to ensure the cable is
buried or protected safely.
Offshore: The subsea part of the cable runs from Noss
Head, north of Wick, to a landfall near Portgordon in Moray.
• Detailed surveys of the seabed are completed to
identify the most suitable route and to minimise impact
on sensitive marine habitats.
• A specialist submarine plough is used to clear any
boulders from the seabed and then to create a trench
around 1 metre deep into which the cable can be laid.
• The cable is laid from a large specialist cable-laying
vessel and guided into the trench.
• Remotely operated vehicles are used to allow engineers
and environmental experts on board the vessel to
monitor each stage of the process.
• The submarine plough is then used to backfill the
trench, burying the cable.
• On sections where seabed conditions mean that cable
burial is not possible, a protective layer of rock will be
laid over the cable, creating an artificial reef.
Onshore network reinforcements
As well as the major sites at Spittal and Blackhillock
– and the work which will take place along the cable
route itself – further reinforcements will be completed
on two sections of the existing onshore transmission
network that serves the north of Scotland.
Dounreay to Mybster: Between Dounreay and Spittal,
the existing 132kV overhead line will be replaced by an
upgraded 275kV overhead line. As part of this project
a new transmission substation will be built south of
Thurso on the west side of the A9 and the existing
substation on the east side of the road will be dismantled.
The existing substation at Mybster will be extended and
an additional 132kV overhead line will be built between
Spittal and Mybster.
Helicopters are used in the ‘stringing’ of the conductors (wires)
on to the steel towers that support most overhead transmission lines.
Loch Buidhe to Beauly: Further south on the existing
network, two new transmission substations will be built
at Loch Buidhe, north of Bonar Bridge, and at Fyrish,
near Alness. The wires on the west side of the existing
275kV overhead line will be replaced between Loch
Buidhe and Beauly.
The combined effect of these projects is to strengthen
the network for transporting electricity from generation
sites to where it is needed – either via Spittal and the
new HVDC system; or via Beauly and the existing
onshore network.
Benefits of the project
The Caithness to Moray project has the potential to
generate significant benefits to the local, regional and
national economy during construction and operation.
It would deliver an important step towards a modern
electricity network that is ready for the future.
•D
uring the construction phase, the project would
generate hundreds of direct jobs and training
opportunities at sites in Caithness, Sutherland,
Ross-shire and Moray.
•A
wide range of businesses would benefit, both
directly through opportunities to provide services
and indirectly through the value added to the local
and regional economy.
CASE STUDY: In the first two years alone of
constructing the Beauly to Denny transmission
project, a study has estimated that the work
generated approximately £86 million in Gross Value
Added (GVA) to the Scottish economy and created
around 1,500 jobs in total.
SHE Transmission has set up an award-winning transmission trainee programme in partnership with
Inverness College UHI and Balfour Beatty to deliver the skilled workforce of the future. The class of
2013/14 successfully completed the college-based part of the course in December 2013.
• The Caithness to Moray proposals can be delivered by
2018, providing the capacity needed by the north’s
growing renewable energy industry when it is needed.
• The innovative design of the project allows for
additional HVDC connections in future, potentially
including links for Orkney and Shetland. With the first
stage in place, future works could be delivered faster
and at reduced cost.
• HVDC enables significantly more efficient transmission
of power across long distances – greatly reducing
electrical losses when compared with a conventional AC
alternative.
• The HVDC system provides greater flexibility in the
operation of the network. It allows more efficient
management of the output from renewable generation
and can also contribute to a more resilient network for
all our customers.
• The project as a whole has been carefully planned to
deliver an efficient solution which minimises impacts
on people and the environment. Its construction
would reduce the requirement for major new onshore
transmission infrastructure in the north.
Keeping the light on and supporting growth
SHE Transmission is committed to working closely with local communities to
deliver a modern electricity network that is ready to meet the challenges ahead.
Britain’s safest power company
Safety is our first priority in everything we do. We aim
to be among the safest companies in the world and will
keep looking for new ways to keep our staff, contractors
and the public safe. Last year our staff made 96 visits to
schools in their own communities to teach children how
to be safe around electricity. When it comes to safety, we
think you can’t start early enough.
Investing in skills for the future
We are committed to investing in the long term future
of our business and of the communities where we work.
That’s why we offer a range of industry-leading training
and apprenticeship programmes, with opportunities for
everyone from school-leavers to graduate engineers.
In recent years, we have also delivered an award-winning
transmission trainee programme in partnership with
Inverness College UHI and Balfour Beatty.
To find out more about our training and career
opportunities, check regularly at www.sse.com/careers.
Proud to be an active part
of the communities we serve
Our Community at Heart scheme means every member
of our staff can take a day of their time each year to
work on a community project of their choice. Last year,
around 1500 days of volunteering took place through the
scheme. If there is a community or charity project that
you think our staff might be able to help with, just ask our
team for a form and let us have the details.
If you have a question or
concern about our work,
please get in touch and
we will do our best to help:
Caithness:
Gavin Steel
SSE, 10 Henderson Road,
Inverness, IV1 1SN
E:gavin.steel@sse.com
T: 01463 728109
M:07584 313481
Moray:
Sam O’Connor
SSE, Inveralmond House,
200 Dunkeld Road, Perth, PH1 3AQ
E:sam.oconnor@sse.com
T: 01738 453224
M:07584 313059