Experience in transporting energy through subsea power cables: The case of Iceland Svandís Hlín Karlsdóttir Faculty of Industrial Engineering, Mechanical Engineering and Computer Science University of Iceland 2013 Experience in transporting energy through subsea power cables: The case of Iceland Svandís Hlín Karlsdóttir 30 ECTS thesis submitted in partial fulfillment of a Magister Scientiarum degree in Industrial Engineering Advisors Rúnar Unnþórsson, Lektor Tómas Philip Rúnarsson, Professor Faculty Representative Magni Þór Pálsson Faculty of Industrial Engineering, Mechanical Engineering and Computer Science School of Engineering and Natural Sciences University of Iceland Reykjavik, May 2013 Experience in transporting energy through subsea power cables: The case of Iceland 30 ECTS thesis submitted in partial fulfillment of a Magister Scientiarum degree in Industrial Engineering Copyright © 2013 Svandís Hlín Karlsdóttir All rights reserved Faculty of Industrial Engineering, Mechanical Engineering and Computer Science School of Engineering and Natural Sciences University of Iceland Hjardarhagi 2-6 107, Reykjavik Iceland Telephone: 525 4000 Bibliographic information: Svandís Hlín Karlsdóttir, 2013, Experience in transporting energy through subsea power cables: The case of Iceland, Master’s thesis, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland, pp. 85. Printing: Háskólaprent Reykjavik, Iceland, June 2013 Abstract This Master’s thesis analyses the experience from subsea power cable projects in Europe to bring new aspects and gain more information and insights to this project. The main focus is on technology, reliability and environmental impact. This study of the European experience is transferred to Iceland and is evaluated as to which technology is suitable for Icelandic conditions, what to avoid and what to keep in mind, and also to evaluate the reliability of possible subsea power cables from Iceland to mainland Europe, or to Great Britain. Útdráttur Þetta meistaraverkefni fjallar um að afla reynslu af rekstri sæstrenga frá Evrópulöndunum hvað varðar tækni og áreiðanleika. Auk þess voru skoðaðar rannsóknir á umhverfisáhrifum þeirra. Aðstæður á íslenskum orkumarkaði voru skoðaðar og út frá samantekt á reynslu sæstrenga var metinn áreiðanleiki mögulegs sæstrengs frá Íslandi til Bretlands. Niðurstöðurnar veita mikilvægar upplýsingar um ákveðinn hluta af þessu stóra flókna kerfi sem sæstrengsverkefni er. Table of Contents List of Figures .................................................................................................................... vii List of Tables ....................................................................................................................... ix Variable Names ................................................................................................................... xi Acknowledgements ........................................................................................................... xiii 1 Introduction ..................................................................................................................... 1 1.1 Motivation and objectives ....................................................................................... 2 1.2 Contributions ........................................................................................................... 3 1.3 Structure of the thesis .............................................................................................. 3 2 Electric Power Systems .................................................................................................. 5 2.1 European electricity grid ......................................................................................... 6 2.2 Electric power.......................................................................................................... 7 2.2.1 AC voltage and current .................................................................................. 8 2.2.2 DC voltage and current .................................................................................. 9 2.2.3 HVAC vs. HVDC ........................................................................................ 10 2.3 HVDC systems ...................................................................................................... 12 2.3.1 Configurations.............................................................................................. 13 2.3.2 Converter station .......................................................................................... 14 2.4 HVDC cable system .............................................................................................. 14 2.4.1 Cable types ................................................................................................... 15 2.4.2 Cable structure ............................................................................................. 16 2.4.3 HVDC cable properties ................................................................................ 18 2.5 Summary ............................................................................................................... 19 3 Development of the HVDC Cable System .................................................................. 21 3.1 Cable design .......................................................................................................... 24 3.1.1 Extruded XLPE cable .................................................................................. 25 3.1.2 Mass-impregnated cable .............................................................................. 26 3.2 Joints ...................................................................................................................... 28 3.3 Laying of the cable on the sea floor ...................................................................... 28 3.4 Cable protection .................................................................................................... 28 3.5 Operation ............................................................................................................... 30 3.6 Extension of cable life time ................................................................................... 31 3.7 Summary ............................................................................................................... 32 4 Reliability ....................................................................................................................... 33 4.1 The data ................................................................................................................. 33 4.2 Definition of statistical terms ................................................................................ 34 4.3 Utilization .............................................................................................................. 35 4.4 Energy availability ................................................................................................ 36 v 4.5 Cause of damages ................................................................................................... 37 4.6 Repair cost .............................................................................................................. 39 4.7 Repair time for subsea power cable ....................................................................... 40 4.8 High-voltage subsea cable failure statistics ........................................................... 41 4.8.1 CIGRÉ study ................................................................................................ 41 4.8.2 Large HVDC cable failure rate .................................................................... 42 4.8.3 Swedish subsea power cable failure statistics ............................................. 43 4.9 Summary ................................................................................................................ 43 5 Environment .................................................................................................................. 45 5.1 Environmental impacts .......................................................................................... 45 5.1.1 Installation ................................................................................................... 45 5.1.2 Operation ..................................................................................................... 46 5.2 Summary ................................................................................................................ 47 6 The Case of Iceland ....................................................................................................... 49 6.1 Energy in Iceland ................................................................................................... 49 6.1.1 Future Possible Electrical generation and demand ...................................... 51 6.2 The Electrical Transmission System ...................................................................... 52 6.3 Icelandic experience ............................................................................................... 53 6.4 Technological evaluation ....................................................................................... 54 6.5 Availability assessment for subsea cable ............................................................... 55 6.5.1 Assessment of failure rate ............................................................................ 55 6.5.2 Outage duration