Table 9.1. Worst Case Assumptions for EMF Impact


Operation


Impact 1: Changes to background EMF


Installation of up to: 550km AC inter-array cables (75kV)


195km HVAC export cables between collector and converter stations (275kV)


620km of HVDC export cables (600kV) (320kV realistic worst case) Cables buried to a depth of 0.5 –5 m


Note: that there would be up to two cables to interconnect the proposed East Anglia THREE and East Anglia ONE projects. The cables would be subject to detailed design and future technology developments. Each would be up to 90km in length. The locations where these interconnections join the East Anglia ONE electrical infrastructure would be identified following detailed electrical design and would be dependent upon the location of the East Anglia ONE converter stations. These cables have not been assessed as part of the worst case and once interconnection cable routeing has been determined they will be added into the assessment.


42.


For the proposed East Anglia THREE project, three core AC cables would be used for both the inter-array cables and the high voltage alternating current (HVAC) export cables that connect the offshore collector and offshore converter stations (see Chapter 5 Project Description section 5.4.11). Array cables are likely to be rated between 33kV and 75kV; cables between the offshore collector and converter stations could be rated up to 275kV.


43.


EATL propose to use high voltage direct current (HVDC) cables to export power to the shore with 320kV bipole HVDC cables most likely to be used.


9.8.3 Embedded Mitigation Specific to EMF 44.


45.


All cables would be sheathed and armoured, which would prevent the propagation of electric (E) fields into the surrounding environment.


Inter-array and export cables would be buried where possible. Cable protection measures would be applied in areas where burial is not possible, for example at cable crossings and in areas of hard ground.


9.9 Assessment Methodology – EMF


9.9.1 Legislation, Policy and Guidance 46.


47.


The assessment of potential impacts of electromagnetic fields has been made with specific reference to the relevant NPS (EN-1 and EN-3).


EN-3 refers to the assessment of EMFs in relation to fish (Paragraph 2.6.75). The document suggests that where mitigation is applied, it is expected that the residual


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Chapter 9 Underwater Noise Page 13


The maximumlength and maximum rating of cables within the East Anglia THREE site and offshore cable corridor.


Key design parameters forming the worst case scenario


Rationale


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