Review of Cabling Techniques and Environmental Effects Applicable

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Review of Cabling Techniques and Environmental Effects Applicable to the Offshore Wind Farm Industry – Technical Report Figure 3.1: Diverse Range of Different Cable Types 3.3.2 EXPORT CABLES The function of the export cables is to transmit the electrical power from the offshore wind farm to the appropriate cable connection facility at the shoreline or landfall. The electrical parameters of these cables will depend on the choice made between two options: Option 1 – No voltage step-up offshore. The power produced from the offshore wind farm is transmitted to shore at the collection system voltage. With this option there is no need for an offshore substation. A number of the offshore turbine structures act as a localised hub from which the export cables then transmit the generated power back to shore. Option 2 – Voltage step-up offshore. The power produced by the wind farm is transmitted to shore at a different voltage level, greater than the collection voltage. An offshore substation, containing one or more step-up transformers, is required. The offshore substation acts as the collection point within the wind farm. The export cables then run from the offshore substation to shore. 20
Cable types and installation techniques High voltage direct current (HVDC) is not economically viable at present due to the high cost of HVDC converters, however it may, in the future, be used for sites situated further offshore. The current and future generation of export cables are likely to be rated with a voltage of 132kV. The cable is likely to be constructed with 3 core copper conductors, insulation and conductor screening, steel wire armour and either ERP or XLPE insulation with a lead sheath. The copper conductor size is typically estimated at between 300mm 2 and 1200mm 2 . The cables will contain optical fibres embedded between the cores for data transmission and communications. The range of indicative cable conductor sizes and overall dimensions which could be used for a 132kV export cable for an offshore wind farm are shown in Table 3.1. Table 3.1: Typical Cable Characteristics For 132kv Cable Details 132kV Cable Type 300 mm² 500 mm² 800 mm² 1000 mm² 1200 mm² Overall Diameter (mm) 185 193 214 227 232 Weight (kg/m) 58 68 88 100 108 MVA (approx) 127 157 187 200 233 3.3.3 INTER-TURBINE ARRAY CABLES The inter-turbine array cables are the cables which connect the offshore turbines into arrays and also connect the various arrays together. It is normal practice to cable several turbines together in an array, with each cable providing a link between two adjacent turbines. Each end of the cable is terminated onto the high voltage (HV) switchgear located within the turbine tower. Because they connect to the HV switchgear at the turbines, the operating voltage for the inter-turbine cables is limited to 36kV. These cables would also connect any offshore substation to the offshore WTG arrays. The cables between WTGs are relatively short in length (typically in the range 500m to 950m). However, the cables between the offshore substation and the WTG arrays could be longer and possibly up to 3.0km. The inter-turbine array cables will typically be 33kV, 3-core copper conductors with insulation/conductor screening and steel wire armoured. The insulation will be either dry type XLPE, wet type XLPE or a combination of both. All cables will contain optical fibres embedded between the cores. A number of conductor sizes would be used depending on the load current that the cable is required to carry. The ranges of indicative cable conductor sizes and overall diameters that may be used are shown in Table 3.2. 21
Page 1: REVIEW OF CABLING TECHNIQUES AND EN
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Page 9 and 10: Abbreviations AIS Automatic Identif
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Review of Cabling Techniques and En
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4 Physical change 4.1 Introduction
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6 Good practice measures This secti
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7 Gaps in understanding Research fo
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References Introduction Sinden, G.
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Appendix A: Standards and codes of
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Printed in UK on recycled paper. De
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