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 3.4: Typical Cross Section of a Double Armoured Cable (used in areas subject to a high risk of hostile seabed intervention) 3.4.6 ROCK ARMOURED CABLE Rock armoured cable is a double armoured cable where the outer layer of contrahelically laid armour has a tight pitch angle which results in a tight packing of the armour wire around the cable. This armour type provides a very stiff outer protection to the cable core and this type of cable would typically be employed where the cable would be laid over rocky outcrops in shallow water, where the cable was perceived to be at high risk from abrasion damage, or other localised risks resulting from a surface laid cable in a shallow water environment. 3.5 Power Cables Power cables are defined as subsea cables which are used to either import or export power capacity. For example, there are a number of installed subsea power cables between the UK and France which allow for such power exports and imports. Similar systems are used to connect island settlements around the UK such as the Scottish Isles and the Isle of Wight. These cables are large diameter cables with similar characteristics and behaviour to the export cables associated with offshore wind farm developments. 26
Cable types and installation techniques Power cable diameters can range from 75mm in diameter up to 240mm in diameter. The larger size being associated with 132kV export cables from offshore wind farm developments currently under consideration for Round 2 developments. 3.6 Flowlines, Umbilicals and Small Diameter Pipelines Flowlines, umbilicals and small diameter pipelines have been included in this review on the basis that some of the burial systems and other cable protection methods are commonly applied to this group of subsea products. These products fall into the larger diameter category (usually at least 200mm diameter) and are typically used to connect remote wellheads to offshore platforms and to provide interconnect facilities between offshore installations. As well as containing fibre optics and power cores, these products have tubing within the make-up of the product which can be used for chemical injection and hydraulic power. The flowlines and umbilicals, by the nature of their make-up, are constructed using a specialist manufacturing process, are heavy, have stiff properties and also have a large minimum bend radius. 3.7 Background to Safe Installation and Protection of Subsea Cables This section sets out the history and background to the need for protection methods for subsea cables. 3.7.1 THE NEED FOR CABLE PROTECTION Cable burial and other protection measures are used to ensure cables are adequately protected from all forms of hostile seabed intervention. If a cable is not adequately protected, damage can and will occur. Figure 3.5 illustrates the results of seabed deployed fishing gear becoming entangled with an unprotected cable system. Figure 3.6 shows a typical deployment of bottom trawl fishing gear and Figure 3.7 shows how a trawl or otter board can potentially engage and snag a subsea cable giving rise to the damage as illustrated in Figure 3.5. 27
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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