Subsea power connections that work
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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

Subsea Power Connections that Work

04 – 07 Feb 2013, Vienna, Austria


Contents

Contents

  • Experience

    • History

    • Concerns

  • Design considerations

    • Electrical

    • Thermal

    • Mechanical

  • Conclusions


Experience

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.


Experience other subsea cables

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)


Experience offshore wind energy

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


Cablerisk joint industry project initiative

“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:


Cable projects appreciating complexity

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?


Electrical

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?


Thermal

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


Mechanical

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?


Conclusions

Conclusions

  • Subsea power cabling

    • is multi-disciplinary

    • has frequently been underestimated

  • Cable risks require assessment over whole life cycle

  • Industry guidance is being developed


Subsea power connections that work

www.dnv.com

Joint Industry Project: [email protected]


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