Submarine cable: industry progress

Davide Pietribiasi – Luigi Colla

27.06.2019
AGP21 TGEG19, Versailles, France
 HVDC FOR CABLE INTERCONNECTIONS
What will be required?

Sources: Forecast demand and manufacturing capacity for HVAC and HVDC underground and submarine cables, ENTSOE-E/Europacable
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Electricity transmission of tomorrow underground and subsea cables in Europe, Europacable
HVDC FOR CABLE INTERCONNECTIONS

State-of-the-art cable designs for submarine interconnections

•320kV extruded cables installed and in operation for distances up to 300km
•400kV extruded cables recently introduced, potential up to 500km
•525kV lapped cables installed and in operation for distances up to 700 km

Typically bundled with optical cables, to combine energy and

telecom transmission: different types of system configurations
Need for (unrepeated, repeated with passive amplifiers, repeated with active
fully amplifiers) depending on link length
integrated
network
solutions New generation of cable laying vessels able to match with long
installation campaign lengths, minimize number of joints and reduce
installation time

Monitoring, preventive maintenance and readiness to repair – integrated

monitoring in the cable design

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HVDC FOR CABLE INTERCONNECTIONS
Extruded cables

 Completed pre-qualification tests at 525kV

HPTE XLPE
for land systems
 XLPE (commercial compound)  ±525 kV @ 90 °C  ±525 kV @ 70 °C
 HPTE (high performance thermoplastic
elastomer)
 Large cross sections tested
(2500mm2/3500mm2)
 Power up to 3GW
 Now moving to submarine

Is the future of HVDC for thermoplastic

materials?
• High operating temperature
• No by-products
• No space charges
• No degassing
• Fully recyclable

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HVDC FOR CABLE INTERCONNECTIONS
Lapped cables

NSN – UK/NO
HVDC ± 515 kV 1800mm2 Cu

SKAGERRAK4 - DK
HVDC ± 525 kV various sizes
SAPEI - IT
HVDC ± 500 kV various sizes
ITALY GREECE – IT/GR
HVDC + 400 kV 1250mm2 Cu
BASSLINK - AU
HVDC + 400 kV 1250mm2 Cu

NEPTUNE - US
HVDC + 500 kV 2100mm2 Cu

WESTERNLINK - UK
HVDC ± 600 kV various sizes

MANUFACTURING INSTALATION EXPERIENCE SERVICE EXPERIENCE HIGHEST VOLTAGE

EXPERIENCE

7 interconnectors 20 years 525kV

>4000 km above 400kV operational experience with MI
of installed DC MI cables above 400kV (Italy-
Deepest installations Greece)
600kV
1650m (SAPEI)
with MI PPL

Longest connections
740km (NSN)
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 HVDC FOR WINDFARMS
What will be required?

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Sources: Windenergy, 2017; Policy paper “Offshore wind Sector Deal” by UK Department for Business, Energy & Industrial Strategy
HVDC FOR WINDFARMS
Extruded cables

CONSOLIDATED CABLE DESIGN FOR

SUBMARINE SECTION

Copper conductor
XLPE based insulation for 320kV
Lead sheated
Single wire armoured (shallow waters)
Cross section transitions

CONSOLIDATED CABLE DESIGN FOR

LAND SECTION

Aluminium conductor
XLPE based insulation for 320kV
… almost 10 years Welded aluminium sheated
service experience
at 320kV…
… what does it
mean translated
in numbers?
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HVDC FOR WINDFARMS
Extruded cables

MANUFACTURING EXPERIENCE INSTALLATION EXPERIENCE

>1600 km 11 projects
of installed DC extruded submarine cables connecting HVDC offshore windfarms

>2500 km >1000 joints

of installed DC extruded land cables between offshore and onshore

POWER

900 MW highest rating for a DC extruded

1200 MW new power requirement
submarine cable

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HVDC FOR WINDFARMS
Extruded cables

Work for the future

1. Up to 2GW power for each windfarm connection

Requires qualifications up to 525kV and cross sections >2500mm2

2. System solutions
System optimization since tendering phase, exploiting benefits of
integrated supply&installation; closer interfaces with
converter/platform suppliers

3. Hybrid solutions
New windfarm concepts; decreased installation corridors

4. Security of the power supply

System redundancy/backups, cable requirements in case of
multiterminal systems, revision of insulation coordination
requirements (CIGRE dedicated WGs)

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 AC SUBMARINE
MV THREE CORE HV THREE CORE HV SINGLE CORE

CHARACTERISTICS

Self Contained Fluid

Insulation EPR or XLPE XLPE XLPE
Filled

Maximum voltage 72.5 kV 245 kV 420 kV 525 kV

Maximum power
90 MVA 400 MVA 1000÷1200 MVA 1200 MVA
per circuit

Not limited by cable Not limited by cable Not limited by cable ~ 60 km due to hydraulic
Maximum length
technology technology technology system limits

NOTE 1: Submarine cables may have different armouring design mainly depending on water depth
NOTE 2: rating depends on ambient and installation parameters

Presentation title | Client’s name or Subtitle | DD Month Year 10

 SUBMARINE AC TECHNOLOGY MILESTONS

60 kV Oil 60 kV 3C First 525 kV 150 kV 400 kV

Filled EPR Oil Filled EPR XLPE

1949 1966 1972 1982 1984 2000 2001 2006 2015 2017
220 kV Oil First 400 kV 150 kV 3C 230 kV 230 kV 3C
Filled Oil Filled XLPE XLPE XLPE
insulated

Presentation title | Client’s name or Subtitle | DD Month Year 11

CHALLENGING TRENDS

 Deeper water

 Longer distance

 Higher power rating

 Higher efficiency

 Dynamic cables

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WATER DEPTH > 3000 M
On going developments and tests confirm the feasibility
of HV submarine power cables at water depth up to 3000
m and beyond.

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50Hz – 220 kV Grid Connection
Offshore Wind Park Cluster “Westlicher Adlergrund”

Main features
 Nos. 3 connections approx. 90 km long
 300 MW per cable
 3x1200 mm2 Cu 220 kV XLPE

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 Dardanelles Strait (Turkey) 400 kV circuits

Main features
 N. 4 circuits. Each 4 km long
 1000 MW per circuit
 1600 mm2 Cu 400 kV XLPE

EUROPE Tunnel ASIA

Seabed

400 kV AC Sea/Land Sea/Land AC400 kV

network joints joints Overhead network
Overhead line
line Cable/OHL Cable/OHL
transition transition
station
0.6 km 4.0 km 0.1 km station

Scope of Work
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PRYSMIAN DYNAMIC CABLES
SANTA YNEZ PROJECT

USA - California
 Year of installation: 2015
 Power: 2 x 34 MW
 Cable: 3 core EPR insulated 46 kV
- Able to withstand repetitive dynamic forces
- Superior fatigue resistence & mechanical performence
 Overall Length: 44 km static cable + 4 km dynamic cable
 Completed full-size flex fatigue test
KINCARDINE PHASE I KINCARDINE PHASE II

 Scotland – Kincardine  Scotland – Kincardine

 Year of installation: 2018  Year of installation: 2020
 Power of 2MW (pilot)  Power of 50MW (total)
 Water Depth: 80m 5 WTG – 9,5MW each
 Overall Length: 16km  Water Depth: 80m
Static  Overall Length: 18km Static
+ 2km Dynamic (single + 1km Dynamic (single factory
factory lenght) lenght) + 5 inter-array
Cable Description (dynamic): dynamic
cables
 3x500mm² Cu
 19/33 kV EPR
 1x30 SM FOC
 DWA https://www.windpoweroffshore.com/article/1497569/fir
st-power-kincardine-floating-project
PROVENCE GRAND LARGE (PGL)
 France, Provence
 Year of award 2019
 Power of 24MW (pilot)
 Water Depth: average 99m
 Length: 19 km of Static Export Cable and 3km of
Submarine Dynamic Inter-Array Cables

Cable Description
(dynamic):

 3x150mm² Cu
 38/66 kV EPR
 1x48 SM FOC
 DWA
https://www.sbmoffshore.com/wpcontent/uploads/2
013/09/SBM-Offshore-wind-floater.jpg
Thank you