Project Type: Transmission reinforcement
Location: Highland, Moray

Contact Details

Lisa Marchi
Title: Community Liaison Manager
Telephone: 01463 728072
Mobile: 07825 015507
Address: 10 Henderson Road, Inverness, IV1 1SN
Status: Operational

Project Completion

Scottish and Southern Electricity Networks has now completed the construction, commissioning and energisation of the new Caithness-Moray electricity transmission link. Constructed over a period of four years, the link uses HVDC (High Voltage Direct Current) technology to transmit power through a 113km subsea cable beneath the Moray Firth seabed between new converter stations at Spittal in Caithness and Blackhillock in Moray. The project also involved work at eight electricity substation sites and has also required two overhead electricity line reinforcement projects. 


Latest update

The NKT Victoria has now successfully complete its first cable laying campaign from Noss Head to the centre point of the Moray Firth. The below video provides an insight of the state of the art vessel being used to lay the HVDC cable between Caithness and Moray.

Caithness-Moray overview

We are installing a subsea cable, capable of carrying up to 1,200MW of electricity between Caithness and Moray. With associated reinforcement of the existing onshore network, the project represents the largest investment in the North of Scotland's electricity network since the hydro development era of the 1950s.

The cable uses High Voltage Direct Current (HVDC) technology to transport power between converter stations at Spittal in Caithness and Blackhillock in Moray. This well established technology allows the efficient transmission of large volumes of electricity across long distances.

Subsea cable installation

The HVDC circuit consists of two electrical cables (positive and negative) bundled together with a fibre optic cable used for communications between our land-based HVDC sites.

In preparation for the arrival of the cables, a specialised subsea plough will initially clear the route of boulders and subsequently create a trench to lay the cable within it. The cables will be laid from a purpose-built cable laying vessel (CLV) in two campaigns – the first from Noss to the midpoint of the cable route and the second from Portgordon to the end of the previously laid cable. This is due to the overall length of the cable route (113km) requiring a tonnage of cable in excess of the capabilities of the CLV. A subsea joint will then be constructed to connect both sections of cable to complete the circuit. At the landfalls at Noss and Portgordon, the cables will be pulled in from the CLV through pre-installed ducts connecting the land to the seabed. Various sup[port vessels and dive teams will be utilised diring these pull-ins.

Following the laying of the cables, the plough will be brought back and reconfigured to backfill the trench using the seabed material previously excavated during the trenching operation. However, the seabed is not always soft, and there may be areas where there is insufficient material to give the cable a minimum of 1m cover to protect it from unforeseeable damage such as contact with anchors. In this situation, it will be necessary to use rock supplement the protection in areas where a minimum of 1m protection has not been provided by backfill material alone. A separate vessel will return and carefully place rock on top of the cable and at the cable joint, to create a berm. From an environmental perspective, this berm may then act as an artificial reef for marine creatures to live in and over time this may become valuable habitat. 


Seal of approval

The installation of four cable ducts through the rock beneath Noss Head, north of Wick, and almost 500 metres out to sea was successfully completed in July 2016.

While the ducts were being drilled around 20 metres beneath the base of the cliffs, a specialist member of the site team regularly monitored wildlife in the surrounding area to minimise any disturbance.  The coastal environment at Noss Head supports a diverse range of species and is a popular haul-out area for both grey and common seals.  Occasional pauses in work when seals were close to the site ensured that the mammals were able to rest undisturbed by the steady progress of the drill through the rock below.

Protecting Scotland’s natural habitat

Approximately 1km off the Noss coastline, our surveys uncovered a significant horse mussel bed.

Horse mussels (Modiolus modiolus) form beds and reefs which stabilise the seabed. In large numbers, they support rich feeding grounds and a home for several other marine species and due to this they are now considered a priority habitat for the UK and Scottish biodiversity strategies and actions plans.

Caithness Landfall

Between January and April 2016, drilling took place from the land between Noss Head and Staxigoe village near Wick. Four drills were undertaken and ‘popped out’ on the seabed approximately 800m from the coastline on the seabed using a technique known as Horizontal Directional Drilling (HDD). Each drill was then lined with steel ducting and capped off awaiting the arrival of the subsea cable in 2017.

This drilling exercise came with significant technical and environmental challenges. The headland at Noss contains a significant and complex array of geological faults that could have compromised the success of the drilling operation. Careful design and planning were needed to ensure the greatest probability of success without additional drilling.                                                                                                           

Moray Landfall

Between October 2016 and April 2017, drilling will be underway from land to the west of Portgordon out to sea. These HDDs will also be lined with steel ducts and await arrival of the subsea cable in 2017.

This drilling exercise also comes with significant challenges. The total length of each drill is 1600m, and when they emerges from the bedrock under the sea bed, there will be a significant amount of overlying soft material such as sand, gravel, and cobbles which may jeopardise the integrity of the drill however, at this time, three out of the four ducts have been successfully installed again with no adverse environmental impact.

The data in this map is provided for indicative purposes only and may be subject to change. Scottish Hydro Electric Transmission plc do not accept responsibility for its accuracy, completeness or validity. The data should not be copied, reproduced or utilised externally without permission.

Who is Scottish and Southern Electricity Networks?

Scottish and Southern Electricity Networks is the trading name of Scottish and Southern Energy Power Distribution Limited, Scottish Hydro Electric Transmission plc, Scottish Hydro Electric Power Distribution plc and Southern Electric Power Distribution plc.

How are Transmission network upgrades paid for?

Investments in projects are made by SHE Transmission plc. Electricity transmission companies are authorised to recover the costs of such investments through 'use of system' charges which are levied by National Grid Electricity Transmission plc on generators and suppliers of electricity. Suppliers recover their costs from all electricity customers. In order to protect the interests of customers, the transmission companies have to demonstrate to the energy regulator, Ofgem (Office for Gas and Electricity Markets) that proposed investments are necessary, are efficient and are economical so that the charges which are ultimately levied on all electricity customers are justified.

This means SHE Transmission is subject to a funding mechanism established by Parliament and regulated by Ofgem. Cross subsidies between different businesses in the SSE group is not permitted.

How are proposals scrutinised?

The Scottish Ministers are responsible for determination of applications submitted under Section 37 of the Electricity Act 1989. Both statutory consultees and members of the public have the right to submit their representations on the application. All representations will be considered by Scottish Ministers in their determination of the application.
The Office for Gas and Electricity Markets (Ofgem), as the regulator, has to approve all investment so project proposals are developed under license conditions.
Preferred route corridors chosen will comply with revised ‘Holford Rules’ which are the recognised industry approach to routeing overhead lines amended to reflect Scottish circumstances.

How and to what extent are electricity consumers' interests considered?

SHE Transmission are regulated by the Office for Gas and Electricity Markets (Ofgem), the regulator responsible for representing consumers' interests. Electricity consumer interests are therefore one of our key drivers and this is enshrined in our statutory duties under the Electricity Act.

In particular we have a statutory duty to develop, maintain and operate an efficient, economic and co-ordinated transmission system. Since the costs of these projects will ultimately be paid for by electricity consumers, we have a responsibility to take cost into account with due weighting in a comparison against other important factors.

What is the transmission network?

It’s the highest voltage electricity network in the UK – the ‘motorway network’ of the energy world. It transmits large quantities of electricity over long distances via wires carried on a system of mainly metal towers (pylons) and large substations. Transmission voltages in Scotland are 132kV, 275kV and 400kV. Larger generation schemes usually connect to the Transmission system.

The lower voltage parts of the system are called distribution networks. In Scotland, these local networks operate below 132kV whereas in England the distribution network includes 132kV. 

Cable pull-ins at Portgordon

Cable pull-ins at Portgordon commenced at 07:03hrs this morning. The operation is expected to take until Saturday to complete, after which the Victoria will then progress onto the main cable lay operations out into the Moray Firth.

Marine Scotland Visit

The cable lay vessel NKT Victoria currently moored at Aberdeen harbour awaiting a weather window to commence the cable pull-ins at Portgordon welcomed Marine Scotland on board for a tour around the vessel.

Caithness – Moray HVDC Link project cable laying

We have now reached the point on the Caithness – Moray HVDC Link project where cable laying can commence and, subject to some external factors, intend to commence pulling in the cables through the previously installed landfall ducts at Noss Head on Saturday, 27th June 2017.

Offshore cable installation

Offshore cable installation works have commenced with boulder clearance operations at Portgordon. The Siem Ruby (the plough vessel) can be tracked by following the instructions set out below: Log into webpage

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