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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Cable types <strong>and</strong> installation techniques<br />
Connection voltage – Offshore wind farm projects need to be connected to<br />
regional distribution networks, rather than to the national transmission system.<br />
In Engl<strong>and</strong> <strong>and</strong> Wales, these distribution networks currently include 132kV<br />
<strong>and</strong> 33kV systems. Some <strong>of</strong> the early Round 1 <strong>of</strong>fshore wind farm projects<br />
have made connections at 33kV while several others have connections at<br />
132kV. It is probable that all Round 2 sites will secure connections at 132kV.<br />
Cable design – Three-core subsea cables using solid insulation (ERP or XLPE)<br />
are typically used for operation at voltages up to 132kV. Higher voltage cables<br />
that use oil as an insulating medium are not deemed to be environmentally<br />
acceptable owing to the potential risks associated with oil leakage in the<br />
near shore environment. The cables are typically designed to give a power<br />
transmission capacity <strong>of</strong> up to 40MW for a single 33kV cable <strong>and</strong> 160MW for<br />
a single 132kV cable.<br />
Turbine size – Offshore wind farm developers are continually looking to the<br />
turbine manufacturers to develop larger <strong>and</strong> more energy efficient turbines.<br />
The early UK Round 1 developments such as North Hoyle, used 2.5MW wind<br />
turbine generators (WTGs). Current <strong>of</strong>fshore wind farm developments are<br />
planning to use 3.0MW <strong>and</strong> 3.6MW machines <strong>and</strong> plans for a 5.0MW machine<br />
are already well advanced.<br />
Distance from shore – The use <strong>of</strong> a single 132kV cable to shore provides a<br />
cost-effective alternative to the use <strong>of</strong> three or four 33kV cables. The installed<br />
cost (per kilometre) <strong>of</strong> a single 132kV cable is considerably lower than the<br />
installed cost <strong>of</strong> three 33kV cables, but this solution requires an <strong>of</strong>fshore<br />
substation in order to step up to 132kV from the wind farm collection voltage<br />
(usually 33kV). Some <strong>of</strong> the current projects under consideration have more<br />
than one 132kV export cable to link the <strong>of</strong>fshore wind farm to shore.<br />
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