Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
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<strong>Review</strong> <strong>of</strong> <strong>Cabling</strong> <strong>Techniques</strong> <strong>and</strong> <strong>Environmental</strong> <strong>Effects</strong> <strong>Applicable</strong> to the Offshore Wind<br />
Farm Industry – Technical Report<br />
Table 3.16: Cable Installation Experience <strong>and</strong> Feedback on Recently<br />
Installed Offshore Wind Farms<br />
Wind Farm Cable Route Soil Conditions Burial Depth <strong>and</strong><br />
Method<br />
Arklow Bank Export Cables Superficial<br />
sediments<br />
overlying harder<br />
sediments which<br />
are believed<br />
to possibly be<br />
glacial till.<br />
Nysted<br />
(Denmark)<br />
74<br />
Export Cables<br />
<strong>and</strong><br />
Inter-Array<br />
Cables<br />
Horns Rev Inter-Array<br />
Cables<br />
It is believed<br />
there are a<br />
variety <strong>of</strong> seabed<br />
conditions across<br />
the site.<br />
A subsea cable plough<br />
was used to bury the<br />
export cables.<br />
A variety <strong>of</strong> installation<br />
techniques were<br />
employed. Jetting was<br />
used in areas <strong>of</strong> looser<br />
substrates which included<br />
s<strong>and</strong>s, silts <strong>and</strong> clays with<br />
shear stress less than<br />
75kPa. Pre-trenching <strong>and</strong><br />
backfilling was used to cut<br />
through areas <strong>of</strong> harder<br />
substrate with back-hoe<br />
excavators working from<br />
a shallow water jack-up<br />
barge.<br />
Feedback Information<br />
(where available)<br />
It is understood that surveys<br />
undertaken post installation<br />
indicated localised exposures<br />
<strong>of</strong> cables. This was possibly<br />
caused by scouring <strong>of</strong><br />
the superficial sediments<br />
adjacent to the bank. It is also<br />
understood that the export<br />
cable suffered a fault resulting<br />
from an anchor contact with<br />
a repair being completed<br />
within one week. Further cable<br />
protection methods are under<br />
consideration.<br />
It is understood that the<br />
cable installation <strong>and</strong> burial<br />
were successfully completed.<br />
However, the burial operations<br />
took a considerable period <strong>of</strong><br />
time owing to poor weather.<br />
The <strong>of</strong>fshore spread does<br />
not appear to be particularly<br />
weather resistant potentially<br />
which explains the apparently<br />
protracted operations.<br />
- - It is understood that the<br />
installation contractor<br />
encountered difficulties<br />
whilst installing <strong>and</strong> burying<br />
the inter-array cables. It is<br />
thought that the wave climate<br />
proved problematic during the<br />
installation operations <strong>and</strong> it<br />
is believed that divers were<br />
subsequently employed to<br />
bury the cables which were left<br />
exposed, particularly close to<br />
the <strong>of</strong>fshore structures.