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The challenge of choosing the rightmethod for surveying power cables
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Submarine power cables
Hydro 16 09.11.2016 Rostock
Wind farm
Inter- array
export cable
Power supply
Islands
Offshore constructions
Inter country
NorGer
BritNed
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HVAC (high voltage alternating current) HVDC (high voltage direct current)
HVAC vs. HVDC
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Gotland 1 1954, 98km NorNed 2015, 580km
HVDC cable
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Anchor strikes, dragging
fishing equipment
Poor planning Erosion
2K Criterion
Burial of cables
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The burial of cables decreases the risk of external damage and furthermore fixes the cable to its
projected position.
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Passive Systems
Fixed baseline, triangulation
Range – Altimeter = Depth of burial (DOB)
Detection systems
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Detection Systems
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Active Sytem
- Acoustics
- Pulse induction
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Detection Systems – Comparison Matrix
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HVAC HVAC HVDC HVDC widely easy toin operation out of service in operation out of service tested operate
Teledyne TSS 350tone detection
passive Optimal Ranging
Field Sense
tone detection passive
Teledyne TSS 440pulse Induction
active
Innovatum Smartrak 9gradiometer
passive
Pangeo SBIacoustic
active
System Technology
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Passive Systems assume a radial electric field.
Challenges
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Passive Systems assume a radial electric field.
3-core cables behave comparable to 1 coreconductors
Challenges
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Passive Systems assume a radial electrical field.
3-core cables behave comparable to 1 coreconductors
Electrical field is disturbed by seabed and seawater flow.
Challenges
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Passive Systems assume a radial electrical field.
3-core cables behave comparable to 1 coreconductors
Electrical field is disturbed by seabed and seawater flow.
2-core cable design is conflicting with the radial electrical field model
Challenges
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Accuracy requirements of federal- or private clients are derived from cable tracking specs.
Vertical-, horizontal accuracy of tracking system itself
Multisensor system is involved:
- DGNSS
- USBL system
- Altimeter readings of seabed
- Tidal effects
- Pressure sensors
- Latency effects
Accuracy
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Seabed difference as burial survey
Hydro 16 09.11.2016 Rostock
Epoch
Cable lay (by barge)Cable lay (by barge)
1st by survey vessel1st by survey vessel
2nd by survey vessel
2nd by survey vessel
3rd by survey vessel
3rd by survey vessel
Classic approach
cable location from laying bargecable location from laying barge
cable tracking surveycable tracking survey
cable tracking surveycable tracking survey
cable tracking surveycable tracking survey
Time consuming / higher costs
MBES seabed difference
Cable location from laying barge
+MBES
Cable location from laying barge
+MBES
cable tracking survey + MBEScable tracking survey + MBES
MBES differenceMBES difference
cable tracking surveycable tracking survey
Faster / possible cable impacts detectable
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Summary
Hydro 16 09.11.2016 Rostock
BoundaryConditions
Methods and their
Limitations
Tool Selection
Baseline or MBES difference
survey
Equipment Carrier
Data processing and review
Presentation of results
ReportCharts
Thank you for your attention
M.Sc. Oliver Anders
FUGRO OSAE GmbH, Bremen
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