The working group started in 2014, there were 9 WG meetings. The draft comprising more than 50,000 words and more than 150 pages, was submitted to SC B1 for review at the meeting in Paris 2016. Comments were received and the format changed to the new format in Jan 2017. It was published as TB 680 in 2017. A Tutorial is being presented for the SC B1 meeting in 2017. Definition of a long length of insulated cable:- “is one where the load due to the capacitive current needs to be taken into account in the system design. Typically this would be 40 km for voltages less than 220 kV and 20 km for voltages above 220 kV”

There are currently more than 80 examples of such long length HV & EHV cable links in the world today and the rate of growth is exponential .

Implementation of Long Lenght HV & EHV AC cable links

Convener: Ken Barber (AU) <ken.barber@nancable.com.au> Secretary: Gert Aanhaanen (NL) <Gert.Aanhaanen@tennet.eu>

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Membership of working group

Australia Ken BARBER

Switzerland Peter BRACHER

Italy (1) Stefano LAURIA

Italy (2) Sebastian DAMBONE SESSA

China Ying WANG

Japan (1) Hiroshi SUYAMA

Japan (2) Takayoshi YAMAMOTO

U.K. Francis WAITE

Canada Harry ORTON

Korea Jung-Nyun KIM

Sweden Christer AKERWALL

Norway Fabien RENAUDIN

Spain Jose Maria DOMINGO

France (1) Frederic LESUR France (2) Marc BOEDEC

Australia Naveed Rahman

India Saibal Kumar GHOSH

Denmark Unnur Stella GUDMUNDSDOTTIR

Netherlands Gert AANHAANEN

U.S.A. David LINDSAY

Germany Volker WERLE

Ireland Paul MORAN

MEETINGS:-

The first meeting was held in Japan in May 2014, then Paris,

Netherlands, Australia, U.K., Norway, Spain and China with the last

meeting in Fort Lauderdale – USA in April 2016.

Introduction to Long length AC Cable systems

• Why is there now such a significant interest in Long Length AC transmission Power Transmission by insulated cables. Some of the reasons being:-

Now very possible with new cable designs and materials

Need to transfer power from renewable energy sources to the grid in the most economical manner

Need to provide electric power to remotely located plants

Often there are difficulties in obtaining approvals for OHL

Cable offers quicker implementation time than using OHL

Now a lower cost differential between Underground and OHL

Avoids problems and costs with OHL e.g. R.I.

Need for lower system/network power losses

Reliability of supply in extreme weather conditions.

Environmental issues and community support

Property valuations are reduced with OHL impact

Off-shore AC connection to land & Interconnection of Platforms

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The Whole Cable Life Cycle & B1.47

Design

Construction

Operation

Removal

System design: WG B1.39 & B1.40(TB 610)

WG B1.50

Rating, Ampacity: WG B1.35 WG B1.41

Cable & Accessories design: JWG B1.B3.33 (TB 605) JWG B1.B3.49 WG B1.51 WG B1.51

Construction, Installation: WG B1.34 WG B1.44 WG B1.48

Monitoring, Diagnostics: B1.38

Testing: WG B1.28 WG B1.42 &B1.43 TBs 622 and 623 WG B1.46

Operation, Maintenance, Reliability Upgrading: WG B1.11 (TB 606) WG B1.37 WG B1.41 WG B1.45 WG B1.52 W

WG B1.47

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Progress with the introduction of long length AC cable links

Years1 Period Projects Links km Cable km

1967 1997 30 years 13 398 458

1997 2007 10 years 12 538 682

2007 2012 5 years 20 1122 1343

2012 2015 3 years 22 1349 1947

2015 2018+ From 2015 14 703 1216

Total 81 4111 5645

Cable circuit km – 50 years from 1967 – 2017 5

CURRENT STATE of DEVELOPMENT Reasons for Growth in demand

Possible 50 years ago but now more practical with new cable designs, materials, accessories & installation methods

Improved overall performance of cables and accessories

Cost of supply and installation significantly lower

Availability of Monitoring systems

Net effect is improved reliability of supply

Transfer power from renewable energy sources to the grid

Demand for offshore wind farms

Limited space on Offshore platforms for other options

Need to provide electric power to remotely located plants

New Mine sites, Desalination plants

Need for lower network losses – net effect on energy cost

Difficulties in obtaining approvals for Overhead Lines (OHL)

Quicker implementation time than using OHL

Environmental factors

Climatic conditions and security of supply

Avoiding noise from Overhead lines

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Format of the Technical Brochure • Introduction - Terms of Reference – Executive Summary.

• 1. Current State of Development

• Reasons for growth, Cable design trends and cable types, New Installation trends, Associated equipment and Reliability of supply.

• 2. Challenges for Implementation

• Effect on the grid, Protection systems, Voltage effect, Harmonics, Mitigation of EMF and Life time expectancy.

• 3. System Design

• AC-DC comparison, Compensation, Sheath Voltages, Thermo-Mechanical issues, EMF, Maintaining Circuit Ratings, Limiting induced voltages and future systems.

• 4. Installation

• Selection of cable, routes & planning, Installation methods, Transport and Testing

• 5. Monitoring

• Temperature, Condition e.g. P.D. and condition of SVL’s, damage in service, etc.

• 6. Maintenance

• Route information, Land, Submarine, Fault location, Rapid repair options

• 7. Practical Experience of Long AC links – Review world experience

• Examples from the working group member countries & worldwide experience

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Long length AC links by Country Country of System Region Number of System

First year commissioning

last year commissioning

Cable Length (per circuit)

Total cable length in system

AUSTRALIA ASIA-PACIFIC 2 2000 2010 116 116

BELGIUM EUROPE 2 2010 2012 94 94

CANADA NORTH AMERICA 2 1984 2008 76 114

CHINA ASIA-PACIFIC 1 2009 n.a. 32 32

DENMARK EUROPE 5 1997 2012 308 355

FRANCE EUROPE 6 2009 2018 214 279

GERMANY EUROPE 4 2008 2014 229 229

ITALY EUROPE 2 2014 2015 173 221

JAPAN ASIA-PACIFIC 9 2000 2016 267 590

KOREA ASIA-PACIFIC 1 T.B.A. n.a. 22 66

NETHERLANDS EUROPE 2 2015 2016 122 244

NORWAY EUROPE 4 2010 2017 399 399

QATAR MIDDLE EAST 1 2016 n.a. 102 203

SAUDI ARABIA MIDDLE EAST 5 2006 2015 246 317

SPAIN EUROPE 5 1973 2015 297 424

SWEDEN EUROPE 3 1973 2000 162 162

TANZANIA AFRICA 1 2010 n.a. 75 75

THAILAND ASIA-PACIFIC 1 2011 n.a. 55 55

TUNISIA AFRICA 1 2005 n.a. 25 25

UNITED ARAB EMIRATES MIDDLE EAST 2 2006 2018 189 189

UNITED KINGDOM EUROPE 14 1967 2015 646 1157

UNITED STATES OF AMERICA NORTH AMERICA 7 1967 2008 207 245

VIETNAM ASIA-PACIFIC 1 2013 n.a. 56 56

TOTAL 81 4111 5645

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Long Length AC links by Voltage and Power transfer

Voltage Level Number of

System

Cable Length

(per circuit)

Total cable

length in system

U0 ≤170kV 36 2446 3222

170kV≤ U0 ≤380kV 34 1298 1860

U0>380kV 11 367 563

TOTAL 81 4111 5645

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Voltage Level Number of System Cable Length

(per circuit)

Total cable

length in

system

Average cable

km / Project

Power <100MVA 10 856 856 86

Power <200MVA 17 1100 1401 82

Power <300MVA 8 536 729 91

Power <400MVA 4 136 224 56

Power <500MVA 5 229 294 59

Power <600MVA 3 89 225 75

Power <700MVA 11 467 772 70

Power <800MVA 5 142 142 28

Power <900MVA 2 52 103 52

Power <1000MVA 1 22 22 22

Power <1500MVA 5 173 378 76

Power <2000MVA 3 87 171 57

Power >2000MVA 3 87 195 65

Summary of some of the challenges for Implementation

• Cable Design • Choosing the best cable design for each specific Link

• System design issues • Selecting the best voltage • Consider frequency of supply e.g. 60, 50 or 16 Hz. • Matching the power rating for hybrid circuits • Acceptance of cyclic ratings – thermal delay for cables • Protection system arrangements - Cable vs. OHL, • Controlling EMF – but easier for cable than OHL , • Controlling future changes in route to ensure circuit rating • Amount of reactive compensation and location • Impact on other network components • Sheath bonding for long lengths – acceptance of higher

voltage levels • Reliability - longer repair times for underground cable

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Summary of challenges for Implementation (cont.)

• Installation • Rights of way. • Remote areas – transportation issues • Inductive coupling with OHL – safety • Thermal mechanical forces from long straight cable

lengths • Commissioning – Testing- voltage & frequency.

• Monitoring • Long distance Distributed Temperature Sensing with

OFC • Monitoring of Sheath Link box SVL’s • Sheath condition monitoring. • Control of route condition AIS and Acoustic

• Maintenance • Fault location methods and automation • Access to route information – GPS data • Methods to reduce repair times - outage in case of cable

damage

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SUMMARY • Prior to starting this work we felt that there were very few

examples of LONG AC CABLE LINKS but we found that is certainly not the case.

• In many countries LONG AC LINKS appear not to have been considered practical and this appears mainly to based on a lack of knowledge of what can be done in the most cost effective manner.

• We have tried to write the TB in a language that can be understood by a very wide audience, because it is now very clear that the demand for such links will be quite substantial.

• We expect this demand will grow even more significant and suggest the CIGRE should be seen as a source of knowledge and practical advice which can avoid future problems.

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