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Subsea Power Connections that Work

Subsea Power Connections that Work. 04 – 07 Feb 2013, Vienna, Austria. Contents. Experience History Concerns Design considerations Electrical Thermal Mechanical Conclusions. Experience. 120 years

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Subsea Power Connections that Work

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  1. Subsea Power Connections that Work 04 – 07 Feb 2013, Vienna, Austria

  2. Contents • Experience • History • Concerns • Design considerations • Electrical • Thermal • Mechanical • Conclusions

  3. Experience 120 years Power cables have been around for a long time. Designs have evolved, new materials are being used. Challenges offshore remain. 7,000 km More than 7,000 km of HV (≥ 60 kV) cables are in service (onshore, offshore), many more system-kilometres at 33 kV and below. 80% claims Many offshore wind farms have experienced problems with subsea power cables. Claim amounts related to cables top the list.

  4. Experience – “Other” Subsea Cables • Subsea interconnections ≥ 60 kV • 3,700 km AC, 3,400 km DC (2005) • ~ 50 damages in 1990-2005: • 80% in water depths < 50 m • Many on unprotected cables,e.g. through fishing and anchors • Subsea telecom cables • > 1,000,000 km in service(fibre optic, 2009) • Frequent damages, but networkbuilt with redundancies Data sources: Cigré (2009), Carter et al. (2009)

  5. Experience – Offshore Wind Energy Failure statistics not yet available Incidents in virtually every wind farm Most often during construction Sometimes during operation Strong focus on price , not enough on risk Lack of transfer of knowledge “Industry best practice” yet to be developed Data source: DNV stakeholder consultation

  6. “CableRisk” Joint Industry Project Initiative • 15 Participants • Objective • Develop a guideline for subsea power cables in renewable energy applications which • covers the cable lifecycle • provides technical guidance • improves communication between stakeholders • helps managing the risks • Timeline • Project: Aug 2012 – Jun 2013 • Industry review: Spring 2013 INCH CAPE Project responsible:

  7. Cable Projects – Appreciating Complexity Thermal Electrical Mechanical Quality checks All relevant stakeholders consulted? Started early with the planning and design? Optimised and planned with contingencies?

  8. Electrical 3 x 1 x 240 mm2 Cu 33 (36) kV, 880 m 3 x 1 x 630 mm2 Cu 150 kV, 20,500 m 3 x 1 x 800 mm2 Cu 150 kV, 1,350 m Layout MW, kV Topology selection Choice of mm2 Ampacity estimation Length R, XC Data sheets Cable choice Failure rate Basic power flow Reliability check NPV (€) p.u., Mvar Quality checks Reliability targets set? Failure rates applicable?

  9. Thermal Pel Losses w y s  th Constraints Data Cable route desktop study Site parameters Survey ,  th • Example: 3 x 1 x 240 mm2 Cu, 33 (36) kV • Cable A: 467 A (< 20°C, < 1.0 K m / W) • Cable B: 590 A (< 10°C, < 0.7 K m / W) Proposed corridor y Depth Hazards Burial assessment Electrical losses w Cooling verification Back to electrical study? s Quality checks • Site data available? • Hotspots ok? • J-tubes • Soils with low conductivity • Landfall

  10. Mechanical Radius, tension, friction Fpull Movement Cable properties Site, vessel data Foundation design Back to electrical / thermal study? Construction engineering Trials Method statements Warranty surveyor verification Insurance cover? Quality checks Installation weather dependent? Optimised for smooth installation?

  11. Conclusions • Subsea power cabling • is multi-disciplinary • has frequently been underestimated • Cable risks require assessment over whole life cycle • Industry guidance is being developed

  12. www.dnv.com Joint Industry Project: CableRiskJIP@dnvkema.com

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