Wind farm operators announce changes to onshore cable proposals

Vattenfall, the Swedish state-owned energy group behind two large offshore wind farms off the Norfolk coast, has revealed it will now use advanced technology that requires a narrower onshore cable corridor and avoids the need to build relay stations.

If all wind farm projects are approved, the underground cable routes will cross in an arable field owned by Salle Estate to the north of Reepham, adjacent to the B1145, near the junction with the road to Salle

The 60 km onshore cable route from Happisburgh on the coast passes through the Reepham district and crosses that of a proposed scheme by Ørsted just outside the town.
Vattenfall said it will now opt for high voltage direct current (HVDC) cable technology to connect Norfolk Vanguard and its sister project Norfolk Boreas to the National Grid at Necton.
The wind farm developer said it has made the strategic decision to back HVDC as it believes it will be cost competitive with the existing high voltage direct alternating (HVAC) technology by the early 2020s, when the projects are planned to start construction.
In its interim consultation report published earlier this week, Vattenfall noted that using HVDC transmission technology means the width of the onshore cable corridor can be reduced from around 100 metres, in line with HVAC requirements, to 45 metres.
This will allow the company to avoid sensitive, historical sites, such as the archaeological remains of the former St Mary’s chapel in Kerdiston.
Further, the use of long-range horizontal direction drilling (HDD) will avoid impact on county wildlife sites and a number of important local amenity and tourism sites, such as the Marriott’s Way, by adding further sections of trenchless crossing.
The consultation report follows feedback from nearly 800 individuals and organisations and a number of exhibitions across Norfolk.
Gunnar Groebler, head of Vattenfall’s wind business area, said the decision to deploy HVDC is “kinder to the environment and local people”.
Ruari Lean, Norfolk Vanguard project manager, added: “We have listened very carefully to what local people told us about our plans for Norfolk Vanguard.
“In combination with our strategic review of transmission technology, the concerns raised by local people have influenced our decision to adopt pioneering HVDC infrastructure for Norfolk Vanguard.
“By backing HVDC technology, we will minimise the impact on people and the environment, while keeping the cost of electricity down for the British consumer.”
Vattenfall will submit its final plans for Norfolk Vanguard to the Planning Inspectorate in June. The group’s Norfolk Boreas, another 1.8 GW offshore wind farm, is following Norfolk Vanguard in the planning process.
Meanwhile, Ørsted (formerly Dong Energy) has yet to announce whether it will use HVDC or HVAC technology.
The Danish energy group said: “Use of DC technology for offshore wind farms is still maturing and there are certain risks associated with solely taking forward DC technology at this stage.
“Due to current uncertainty, a decision on which transmission system to adopt will not be made until post consent after extensive engagement with potential system suppliers has taken place.”
The company’s Hornsea Project Three offshore wind farm, which has a planned capacity of 2.4 GW, will run from Weybourne on the coast to hook up to the National Grid at an existing substation at Swardeston, south of Norwich.
All the current wind farm proposals that will affect Norfolk have raised widespread concerns about the impact on the rural landscape and ecologically sensitive sites, disruption from construction traffic, road safety and damage to wildlife.
While not willing to commit to the HVDC technology until after it has received planning permission, Ørsted has, however, announced that it will reduce the construction from three to two phases.
This will reduce the maximum duration over which onshore construction works would take place from eleven to eight years. It has also finalised the route of the 80-metre-wide cable corridor (see the map for the Reepham area below).
Stuart Livesey, project development manager, emphasised that this will not mean eight years of continuous construction: works in any one section of the cable route would be completed “within a matter of months”.
Mr Livesey continued: “We are delighted that we’ve been able to incorporate so much of the feedback received into the final design.
“The views of local communities and stakeholders are of great importance to us, and we have taken these into account to reduce or remove areas of concern.”
Ørsted is due to submit its application for Hornsea Project Three to the Planning Inspectorate in the second quarter of 2018.
If successful, construction is expected to start in 2020, making it the world’s biggest wind farm, joining the Hornsea Projects One and Two, which are already under way.
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Ørsted has finalised the route of the 80-metre-wide cable corridor through Reepham

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