Questions asked by the public

GridLink is not permitted by European Union rules to produce power or trade power transported through the interconnector.  These rules are designed to prevent any company having a monopoly on both power generation and transportation.

GridLink will own and operate the interconnector and earn income by charging a fee to other companies to send power through the interconnector.  The income earned by GridLink will be regulated by Ofgem in the UK and Commission de Regulation de l’Energie (CRE) in France.

The use of the interconnector must be offered on a non-discriminatory basis.  Power may be transported in either direction from France to UK or vice versa at any time. 

The amount of power that is transported will depend on the supply and demand for electricity.  In particular, it is expected that the interconnector will be used for the transport of excess renewable energy, such as wind or solar, or nuclear power, which becomes available when the supply exceeds the local demand or existing grid capacity.  Therefore, the interconnector will facilitate the use of low carbon sources of energy that would otherwise be unused and lost.

During the transport of electricity over long distances, a power cable loses energy due to the heating of the conductor caused by the electrical current. Additional energy is lost due to the energy demand, heating, noise and other phenomena related to the operation of ancillary equipment needed to connect the power cable to a local distribution system or consumers at each end.

The laws of electricity mean that operating the power cable at high voltage reduces the electrical current.  This, in turn, reduces the energy losses.

The amount of energy loss is influenced by the cable design and length.  Energy losses are reduced if the cable length is shorter.

Transmitting electricity as direct current has lower energy losses than alternative current because the current is uniformly distributed across the conductor.  In alternating current, the current is concentrated at the conductor surface which increases the energy losses.

Whilst direct current technology always has lower energy losses, it is more expensive to install.  Therefore, alternating current is preferred for economic reasons for transport of electricity over short distances, up to the point where the lower costs of the equipment is outweighed by the higher operational energy losses.

For GridLink, it is estimated that the total energy losses will be in the range 2% to 2.5%.  For an equivalent system operating with alternating current, the losses are expected to be 6% to 7%.

Therefore, GridLink has chosen to utilise a high voltage, direct current cable to obtain the lowest energy losses.  The relatively short cable length will also minimise the energy losses related to the interconnection.

Electromagnetic fields are generated by a power cable due to the electric current flowing through the conductor. The current produces both an electric field and a magnetic field, which are collectively referred to as electromagnetic fields (EMF).

The design of the cable, including metallic screening, lead sheathing and/or armouring, contains the electric field within the cable and prevents any propagation into the environment.  Therefore, there are no electric fields around the cable.

However, a power cable does produce a magnetic field that emanates into the surrounding environment. 

For subsea cables, a phenomenom is possible that an electric field is induced by the movement of water currents or other objects through the magnetic field.  The burial depth of the cable under the seabed prevents any measurable induced electric field caused by this phenomenon.

The magnetic field of the cable should be considered in the context of the background geomagnetic field of the Earth, which ranges from 25 to 65 μT.  At the location of the GridLink interconnector, the Earth’s geomagnetic field is approximately 50 μT.  People are often exposed to higher magnetic fields on a regular basis from portable electrical gadgets and equipment, including hair dryers, vacuum cleaners and microwave ovens.  Magnetic Resonance Imaging (MRI) used for medical diagnosis exposes patients to more than 100,000 times the background geomagnetic field.  The International Commission on Non-Ionizing Radiation Protection (ICNIRP) most stringent guideline value for limiting public exposure to magnetic fields is 500 μT, with the level to protect public health set at 40,000 μT.

The magnitude and range of a magnetic field from a power cable depends on the configuration of the cable, strength of the electric current and the density of the surrounding material.  The GridLink interconnector consists of two high voltage, direct current power cables that are bundled together. In this configuration, the electric current in each cable is flowing in opposing directions to complete the circuit.  As a result, the magnetic field produced by one power cable is equal and opposite to the other cable and they tend to almost cancel each other out.  The residual magnetic field is very small. 

With a burial depth of 1.5m on land and 2m under the seabed, it is expected that the increased magnetic field above the cable may range from no change up to 20% above the typical background of approximately 50 μT.  Any magnetic field will not be detectable within 5m to 10m from the cable. Any increase is also well below the ICNIRP guideline values and within the natural variation of the Earth’s geomagnetic field, so it has no negative effects.

The depth of burial of the cable will be determined by the type of soil, existing underground public utilities and environmental features that must be crossed.

The indicative depth of the cable is 1.5 m.  This is a typical burial depth for electricity cables.  The cable will be protected from accidental disturbance by a protective concrete layer above the cable and a warning marker buried in the soil.  It will not be possible for anything to accidentally penetrate the cable from above due to this protection.

Where the cable crosses railways, road embankments and water drainage canals, horizontal directional drilling will be used to enable the cable to pass underneath the existing infrastructure.  Such horizontal directional drilling may be 5-10 m below ground level.

The burial of the cable is shown in the illustration below:

The cable will be buried at sufficient depth to ensure that farming can continue after the cable has been installed.  The only restriction on the land will be the prohibition of new farm buildings within 5m.  All other surface land uses, including access roads, ploughing and harvesting will be unaffected.

The cable installation will require the excavation of a trench.  The topsoil will be removed and kept separate from other excavated materials.  After cable installation, the trench will be backfilled and restored with the return of the topsoil layer.

The restoration of the trench and any temporary construction areas will be carried out in a way to avoid changes to the compaction of the soil or drainage of the land.

The Environmental Impact Assessment has included a pedology study carried out by the Chamber of Agriculture.  This study will be used to inform the environmental and technical studies to ensure that the agricultural soils are properly protected during construction works and restored afterwards.

The converter station and cable installation will generate traffic during construction.  The construction traffic will comprise the typical vehicles used for all construction projects, including workers cars and mini-buses, light good vehicles and trucks.  A small number of special loads due to size or weight, such as delivery of transformers, will be required.

During operation, the converter station has a small number of employees and does not require routine delivery of any materials or consumables.  Therefore, there will be very small traffic generation during day-to-day operations.

The converter station will comprise a range of industrial buildings containing electrical equipment, together with some outside electrical equipment installed within fenced compounds.  The converter station will require 3-4 ha of land, with less than 2 ha being developed as buildings.

According to preliminary designs, the main buildings are a valve hall up to 25 m high, reactor hall up to 20 m high and other service, control and storage buildings up to 10 m high.  In addition, transformers, harmonic filters and switchyard equipment may be up to 15 m in height.

The buildings will be designed to resemble typical logistics and distribution warehouses or similar industrial buildings.  The colour scheme and building materials can be chosen to assimilate with other buildings in the area or landscape designs.

In addition to the benefits to electricity producers and consumers through improved network integration, security of supply and reduction in wholesale electricity prices, there will be local economic benefits.

The construction of the GridLink project will employ local companies and workers.  Although the main electrical equipment and cables for the converter stations are manufactured in specialist factories, local companies will be needed to supply construction materials and equipment, construction services, transport and logistics, temporary accommodation, catering, office and similar services.  The construction works will require a range of skilled construction workers and manual labourers, with a team of up to 300 workers at each converter site.  It is expected that local construction workers will be employed to carry out many tasks, including site surveys, site preparation, excavation and civil works, foundations, building erection, supply and installation of public utilities, supply and installation of general equipment, and landscape restoration.

For the offshore cable-lay activities, port facilities, berthing, victualing, refuelling and associated services will be required for the specialist cable-lay vessels and any support ships.  These are likely to be provided by the Port of Dunkerque and/or Port of Sheerness, or other nearby ports.

During operation, there will be a small number of operations personnel at the converter station sites, as well as service contracts for security, property maintenance and landscape gardening.  The operations personnel will be supplemented by maintenance engineers and support workers responsible for routine maintenance and repair, including regular major maintenance activities each year or every two years.

GridLink Interconnector Ltd will pay national corporate taxes and local business taxes, such as the Cotisation Foncière des Entreprises (CFE) in France and business rates in the UK.  These taxes are based on company revenues and/or property valuations, so they will depend on the company’s financial performance and land valuations set by the local authorities.  They are expected to make a significant contribution to local tax income.

Therefore, the provision of construction services, employment of construction and operations workers and payment of corporate taxes are expected to make a notable, positive contribution to the local economy.