205. Other factors that need to be taken into account when considering an offshore crossing are:
HVDC cables crossing HVAC cables are required to be perpendicular to prevent induced currents resulting in thermal hotspots and de-rating of the cable.
Avoid existing offshore cable joint locations (100m boundary) as these sites are more prone to failure and as such there exists a greater possibility for a requirement to recover the cable in the future.
Avoid existing crossings of cables and pipelines to prevent triple crossings which increase risk and difficulty of recovery should any of the elements require repair.
206. In addition, sand waves can result in scouring of the cable or the cable being laid in suspension over time. To prevent this, the cable would ideally be placed in the troughs of sand waves, if this is not possible; an alternative would be to dredge the top of the sand waves.
207. It is anticipated that where the East Anglia THREE export cable would cross existing cable or pipeline concrete mattressing, fronded concrete mattressing, rock dumping, bridging or gravel bags would be used for protection. The total maximum height of a cable crossing is predicted to be 4m for crossing a pipeline; however the majority of crossings will be much smaller in height, around 1.5m.
5.4.11.12 Inter-array cables indicative electrical layout
208. Inter-array cabling within the East Anglia THREE would be between 160 and 550km depending on the final layout of the turbines. Cables between turbines would typically be laid along the shortest separation between the turbines and longer cables would be laid between the last turbines of the array up to the offshore substation. The electrical layout would be designed to minimise length of cable, number of cables and electrical losses.
5.4.11.13 Inter-array cables: cable type, diameter, insulation, armour EMF / heat generated
209. The inter-array cables connect the wind turbines into strings and then connect the strings to the offshore substation platform(s). The cables between adjacent wind turbines are relatively short in length, typically in the range of 675m to 2km. However, the cables between the offshore substation(s) and the wind turbine strings would be longer and possibly up to 10km in length. The components of an inter- array cable are presented in Diagram 5.9.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 5 Description of the Development Page 47
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114