Preventive Cable O&M Key Strategy for Offshore Wind Developers According to Latest Report (UK)

Export and inter-array cables are exposed to a hostile, high-risk environment during a wind farm’s operational life. Given that they comprise a hefty portion of an offshore wind farm’s capital expenditure costs, preventive maintenance for submarine conductors should be a priority for operators, according to the latest Offshore Operations and Maintenance report from Wind Energy Update.

Roughly 27% of an offshore wind farm’s capital expenditure is ploughed into cable, cable installation and grid connection. For a generic park size of 500MW, a capital investment of €72 million is expected to be spent on export cables, and €24 million on inter-array conductors.

These costs are augmented by precautionary measures, say the report’s authors. An estimated €840,000 is required for J-tube seals, bend restrictors, stiffeners and cable mats, alone, simply to minimise premature deterioration and failure.

An up-to-date, exhaustive breakdown of submarine cable CAPEX, coupled with a holistic overview of offshore wind farm cable failure is merely a fraction of the offshore O&M topics covered in Wind Energy Update’s Offshore Operations and Maintenance information-packed report.

 Mapping the failure landscape

A wide range of variables can affect the lifecycle and reliability of subsea cabling, with a significant impact on operational expenditure. Seabed conditions, wave action and tidal effects, coupled with ship transit and fishing activity take a heavy toll on the submarine conductors. As such, the level of exposure of conductors should be a critical design driver, stress the authors of the latest Wind Energy Update Offshore O&M report.

Fortunately for operators, many variables such as dragged anchor, plough tipping, water damage, j-tube damage and cable faults, among other things, are insurable. However, activities around the offshore wind park will likely lead to considerable seabed disruption, warns the report.

For developers and operators to accurately assess the impact of maritime activities on cable faults, disruption should be expected and accounted for. Bottom fishing, for example, is widespread on most continental shelves and adjacent continental slopes, and can be expected to have a significant impact on export cable integrity, say the report’s authors.

Best practice in the making.

Because the offshore wind industry is at a nascent stage, mature and proven maintenance models have yet to emerge. As such, the report highlights areas to which careful attention should be paid. Cable integrity monitoring, spare cable, and joint availability, cable re-laying, joint/splicing expertise availability are among the key recommendations set out in Wind Energy Update’s latest report.

Providing a comprehensive overview of an offshore wind farm’s cable fault landscape, the Wind Energy Update Offshore Operations and Maintenance report lists noteworthy incidents where invaluable lessons learned can help shape cable O&M plans. The key, say the authors, is to avoid repeating events such as that incurred during the construction phase of Horns Rev I. In this particular incident, a construction vessel’s anchor hit an export cable that lay bared on the seabed, resulting in a staggering unforeseen cost of €2 million.

For a comprehensive overview of offshore wind industry O&M experience to date, look no further than Wind Energy Update’s Offshore Operations and Maintenance Report. This year’s indispensable O&M guide for offshore wind developers and operators provides a thorough treatment of today’s offshore wind turbine component failure landscape and their subsequent impact on O&M activities and costs.

By Scott MacDonald

[mappress]

Source: windenergyupdate, November 28, 2011; Image: globalmarinesystems