A Post Bipole III Concepts Review

Transcription

1 Potential Use of Submarine or Underground Cables for Long Distance Electricity Transmission in Manitoba A Post Bipole III Concepts Review Report of the Concepts Review Panel March 17, 2011 (Revised April 4th, 2011)

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3 Potential Use of Submarine or Underground Cables for Long Distance Electricity Transmission in Manitoba A Post Bipole III Concepts Review Report of the Concepts Review Panel David Farlinger, P.Eng., F.E.I.C. (Principal, CMC Consultants Inc.) Panel Chair Allen MacPhail, P. Eng. (Principal Engineer, Cabletricity Connections Ltd.) John Ryan, Ph.D. (Retired Professor of Geography and Senior Scholar at the University of Winnipeg) Ed Tymofichuk, P. Eng. (Vice President Transmission, Manitoba Hydro) Paul Wilson, P. Eng. (Managing Director, Subsidiary Operations, Manitoba Hydro International Ltd.) Report of the Concepts Review Panel - 1

4 Revisions Rev Description Date 1 Finding 12 amended, pages 16 and 103 Finding 15 amended, pages 17 and 104 April 4, Manitoba Hydro

5 Third Party Disclaimer The content of this document is not intended for the use of, nor is it intended to be relied upon by any person, firm or corporation, other than Manitoba Hydro. This document is restricted to the use of Manitoba Hydro. The written authorization of Manitoba Hydro must be sought regarding any use of this document. Manitoba Hydro denies any liability whatsoever to any parties for damages or injury suffered by such third party arising from the use of this document by the third party, without the express prior written authority of Manitoba Hydro. Copyright 2011, Manitoba Hydro Report of the Concepts Review Panel - 3

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7 Acknowledgements As Chair of the Concepts Review Panel I want to thank and acknowledge the Panel members professionalism, expertise, and diligence in the challenging work that culminated in this report. Specifically, I would like to thank John Ryan Ph.D., who through his research and publications put the idea of an underwater cable on the public agenda and who developed several concepts for transporting long lengths of cable by train, Allen MacPhail P. Eng., an internationally recognized expert in high voltage power cable applications, for his contribution to many areas of the report, as well as Paul Wilson P. Eng., Managing Director of Manitoba Hydro International Ltd. and Ed Tymofichuk P. Eng.,Vice President Transmission of Manitoba Hydro who both brought their extensive experience and expertise in High Voltage Power Transmission to the Panel and the writing of the report. I would also like to thank Shane Dew P. Eng. of Manitoba Hydro for his administrative support and untiring efforts in his role as Administrative Assistant to the Panel. As well, I wish to extend my thanks to technical staff of Manitoba Hydro and Manitoba Hydro International for their support throughout this review, specifically to Jason West for his skillful portrayal of models illustrating the train transport of submarine cable in long lengths, to Sarah Wach for drafting the AC and DC route maps for the report and to Dean Reske for compiling estimates of the cost of various electrical installations. David Farlinger P.Eng., F.E.I.C. Panel Chair Report of the Concepts Review Panel - 5

8 Table of Contents Third Party Disclaimer Acknowledgements...5 Executive Summary Findings and Conclusions Foreword Glossary Introduction Transmission Line and Cable Routes Route 1 AC or DC Overhead across Cedar Lake Route 2 AC or DC Underground through Grand Rapids West Route 3 AC or DC Underground East Route 4 DC Submarine and through Eastern Interlake Route 5 DC Two Segments of Submarine Exiting at Traverse Bay Route 6 AC Two Segments of Submarine Exiting at Traverse Bay Grand Rapids Congestion Issues Cable System Performance Description of Cable Types for Underground Transmission Laminar, or Lapped Dielectric Extruded Dielectric Description of Cable Types for Submarine Transmission Maturity of State-of-Engineering of 500 kv Cable Technologies in Use World-wide Today Maturity of 500 kv AC Underground Cable Systems Maturity of 500 kv AC Submarine Cable Systems Maturity of 500 kv DC Submarine Cable Systems Maturity of 500 kv DC Underground Cables Conclusions about Maturity of 500 kv Underground and Submarine Cable Systems Performance of AC and DC Cables Operating at 500 kv Conditions Imposed by the Natural Environment AC Transmission Capacity DC Transmission Capacity Cable System Reliability Life Expectancy of Cable Systems Operation and Maintenance Requirements for Cable Systems Literature Review of Current Research for Further Technological Development of 500 kv Cables System Impacts Considering Long Cables Thermal Properties and Ampacity of Cables Compensation of Long AC Cables Submarine Cable Transportation by WATER and Land Transporting long lengths of 500 kv AC or DC submarine cable by ship Transporting long lengths of submarine cable via rail Transportation of short lengths of submarine or underground cable Cable Installation Submarine Cable Installation Manitoba Hydro

9 5.1.1 Cable Laying Barge Submarine Cable Trenching Cable Jointing Operation Cable Laying Procedure Cable Laying Schedule Underground Cable System Installation Civil Work Cable Transportation Cable Installation Cable Jointing and Terminating Transition and CompensATion Stations Transition Stations 500 kv AC Transition Stations 500 kv DC Compensation Stations 500 kv AC Shore Landing Ice Scouring Cost Comparisons Interpretation of Estimate Results Regulatory Issues Licencing Regulatory Issues with Lake Winnipeg Routing Project Risks Design Risks System Operation Risks Benefits and advantages of underground and submarine cable installations Findings and Conclusions References Appendix 1: Terms of Reference Appendix 2: Panel Members Appendix 3: Long AC Cable CompensATion Appendix 4: Cable Transportation Proposal 1 Transporting long sections of submarine cable by train Proposal 2 Transporting Long Lengths of Submarine Cable by Train Proposal 3 Transporting long sections of DC submarine cable with extruded insulation by train, coiled on widened flatcars Proposal 4 Transporting DC cable with extruded insulation on widened flatcars in a figure 8 pattern Appendix 5: 500 kv Global Cable System Applications Appendix 6: Differences Between AC and DC Cable Technologies Appendix 7: Grand Rapids Bottleneck Appendix 8: Cable Laying Schedule Appendix 9: Bipole I and Bipole II Reliability, Report of the Concepts Review Panel - 7

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11 Executive Summary In September 2009, Manitoba Hydro appointed a Concepts Review Panel to investigate the potential future use of submarine or underground cables for long distance hydro-electric transmission. This report reviews 500kV AC and DC submarine and underground concepts for a potential transmission line extending from the lower Nelson River to the Winnipeg vicinity with no certainty regarding timing, except it could be a number of years beyond BPIII. For purposes of this Panel s review, and for completeness, it was assumed that this fourth major transmission line from northern generation to southern load centres could be either DC or AC. To conceptually examine the use of cables in a post-bipole III link, six illustrative routes were developed. One route is an all overhead line and serves as the base reference case while the five others each employ a segment or segments of submarine or underground cable along with overhead lines, and are referred to as hybrid lines. Significant additional engineering research and study would be required to confirm the merits and validity of one or more of the conceptual routes employing cables, or to determine possibly superior routes. Details of the routes studied in this report are described in the following Tables 1 and 2, and are shown on Maps 1 and 2 accompanying the report, as well as Figures 1 through 6. Report of the Concepts Review Panel - 9

12 Table 1: Cable Route Option Length and Number Route Option Mode OH Route Length (km) UG Route Length (km) UG Cable Numbers Total UG Cable Length (km) Submarine Route Length (km) Submarine Cable Numbers Total Submarine Cable Length (km) 1 AC OH DC OH AC 2 DC 3 AC 3 DC 4 DC 5 DC 6 AC OH-UG Hybrid OH-UG Hybrid OH-UG Hybrid OH-UG Hybrid OH-Sub Hybrid OH-Sub Hybrid OH-Sub Hybrid Manitoba Hydro

13 Table 2: Transmission Line Route Details Route Advantages Disadvantages 1 AC or DC 2 AC or DC 3 AC or DC 4 DC 5 DC This would be an AC or DC overhead line with no underground or submarine cable and no cablerelated reactive compensation equipment and thus inherently more reliable. A 500 kv AC transmission interconnection between northern generation and the southern system would strengthen the AC system in the south. After connecting to the Grand Rapids underground cable, the overhead line would be at least 50 km away from Bipole I-II all the way to the Winnipeg area. No novel transport methods required. A 500 kv AC transmission interconnection between northern generation and the southern system would strengthen the AC system in the south. No novel transport methods required. There would be adequate lake sediment for the entire length of the submarine cable, thus no mechanical barrier protection required for the submarine cable (no rock cutting, rock dumping, or protective mattresses). There would be adequate lake sediment for the entire length of the submarine cable thus no mechanical barrier protection required for the submarine cable (no rock cutting, rock dumping, or protective mattresses.) Requires two long overhead spans between islands and mainland of about one km in Cedar Lake. Location of island hops less than 20 km from Bipole I-II at Grand Rapids. Permission is required for overhead line to cross about 20 km of protected area park along the east shore of Lake Winnipegosis. Permission is required for overhead line to cross about 20 km of protected area park along the east shore of Lake Winnipegosis. 500 kv AC cable systems of this length have never been installed anywhere in the world. The impacts on the transmission system are not known and need more study. Cable-related reactive compensation equipment needed for AC alternative. A tunnel would be required at Grand Rapids. The overhead line would be less than 30 km from Bipole I-II as it goes around the Peguis Reserve. 500 kv AC cable systems of this length have never been installed anywhere in the world. The impacts on the transmission system are not known and need more study. Cable-related reactive compensation equipment needed for AC alternative. To get to the Warren Landing site, the OH line from the Nelson River Generating Area would have to cross the Nelson River with a long span of about 1 km. The OH line would be less than 30 km from Bipole I-II as it goes around the Peguis Reserve east of Lake St. Martin. Dredging of the lake bottom and river at Powerview/Pine Falls may be required for barge access to rail siding. Disturbance of lake bottom sediment. To get to the Warren Landing site, the OH line from Nelson River Generating Area would have to cross the Nelson River with a long span of about 1 km. Dredging of the lake bottom and river at Powerview/Pine Falls may be required for barge access to rail siding. Disturbance of lake bottom sediment. Report of the Concepts Review Panel - 11

14 Table 2 (continued) Route Advantages Disadvantages 6 AC A 500 kv AC transmission interconnection between northern generation and the southern system would strengthen the AC system in the south. There is little sediment along the entire east shore of Lake Winnipeg, extending in places for about 30 km off shore. Throughout this area the lake bottom has rough rocky terrain. Because of the required short lengths of AC cable, about 200 km of AC cable would have to be laid near the shore on this unfavourable terrain. Because of the lack of sediment, the cable would have to be covered by rock dumping or protective mattresses. Only the 50 km line from Riverton to Traverse Bay would be covered by sediment. 500 kv AC cables of this length have never been installed anywhere in the world. The impacts on the transmission system are not known and require further study. Cable-related reactive compensation equipment needed. Disturbance of lake bottom sediment. Very complex operating a hybrid link with these components. Performance of AC and DC cables operating at 500kV in other commercial projects is examined along with cable system reliability and life expectancy. With respect to AC or DC submarine cables, because of lack of data, it is not possible to accurately determine failure rates. Despite this, in the case of DC MI cables, it should be expected that they would experience some faults during their lifetime. With regard to DC XLPE cables, there is still no 500 kv cable system in service and the expected date of maturity for this cable is at least 15 years away, hence at this stage it has no failure rate. As for AC XLPE underground cable, a cable failure may be expected approximately every 3 to 11 years depending on route length. For DC XLPE underground cable, a cable failure may be expected approximately every 4 to 17 years depending on route length. However, the Panel recognizes that there is a great deal of variability in these results due to the lack of quality data. The prime reason for this is that the electrical power industry has limited service experience on 500 kv underground or submarine cables. Route Option Table 3 illustrates the worst case and best case cable service reliability based on known CIGRE survey data for all cables except AC and DC submarine cables. The best case uses only internal failures while the worst case takes into account external failure statistics. The Panel acknowledges that these worst case failure rates may be overly pessimistic. Table 3: Estimated Cable System Failure Frequency Ranges (Worst case Best case) Installation Mode Failure Frequency Range (No Long Trains) (years) Failure Frequency Range (Long Trains) (years) Line 2 AC Land Line 2 DC Land Line 3 AC Land Line 3 DC Land Line 4 DC 1 Water?? Line 5 DC 1 Water?? Line 6 AC 1 Water?? Note 1: A Failure Frequency Range for routes 4, 5 and 6 cannot be determined because of lack of data Manitoba Hydro

15 Maturity of cable types and systems for AC and DC submarine and underground transmission were reviewed. Maturity of cable systems in 2010 and as forecast for 2025, are summarized in Table 4. Table 4: Cable options and upper voltage limits for mature AC and DC underground or submarine applications in 2010 and 2025 Cable Application Unpressurized Mass Impregnated MI Unpressurized Cross-Linked Polyethylene XLPE It can be assumed that XLPE insulation cables will be available for AC and DC underground and submarine applications in MI insulation cables will also continue to be available for submarine cable applications in 2025 for DC. Costs and reliability data in 2025 would ultimately determine final submarine cable type selection. System design impacts resulting from the use of long cables are discussed. High voltage reactive compensation devices are necessary to enable maximum transmission of power through long AC cables and to control voltage, which could otherwise exceed equipment and cable ratings under some operating conditions. For DC cable systems compensation devices are not necessary. Transportation concepts were developed, whereby cables would be transported by ship from an overseas manufacturing facility to a port in Canada, transferred and transported in long lengths of up to 100 km by train (in two approximately 50 km lengths), and off-loaded to a barge on Lake Winnipeg or nearby storage turntables. Four rail transportation concepts were developed. The concept considered by the Panel to have the best potential for future success is described further in this report. The panel concludes that transportation of long continuous lengths of cable using multiple rail flat cars would need Unpressurized Mass Impregnated MI Unpressurized Cross-Linked Polyethylene XLPE AC Underground Not Applicable 500 kv Not Applicable 600 kv AC Submarine Not Applicable 420 kv Not Applicable 500 kv DC Underground 450 kv 150 kv 600 kv 500 kv DC Submarine 450 kv 150 kv 600 kv 500 kv to be carefully researched and studied by railway engineers and cable manufacturing experts. Feasibility is not yet proven. Installation of both submarine and underground cables is discussed in the report. A comparison of using continuous long lengths of cable versus shorter lengths of cable on reels for submarine applications is also discussed, in the event that train transportation of long cables is shown to be unrealistic. Risks and regulatory issues associated with use of submarine cables in Lake Winnipeg are numerous and extensive as they relate to initial installations, operation, maintenance, transmission line reliability, system reliability and to the environment. These include: Complex licensing and regulatory issues Loss in system reliability due to a failed cable (mitigatable using spare cables and special mechanical protection). Costly manufacturer warranties due to remote locations and unproven rail transportation Lengthy route siting process Complex system operations for hybrid overhead-submarine or overheadunderground systems Report of the Concepts Review Panel - 13

16 Possible failure of joints and terminations when exposed to extremely low ambient temperatures (-40 C and below) Cable quality at point of manufacture and at point of delivery Possible cable damage due to abnormal number of multiple transfers and handling of cables between factory and installation Cable integrity after laying in water in unenergized state for several years prior to commercial use Possible in-service damage due to lake bottom ice scouring, shoreline erosion and other natural hazards Environmental impacts due to trenching hundreds of kilometres of lake bottom Installation delays due to adverse weather conditions on Lake Winnipeg Cable laying seasons for AC submarine cables could be as long as three summers. For DC submarine cables, installation may take 1.5 to 2.5 summers depending on route. Using cable on reels instead of long train transportation could double this installation time. Manufacturing capacity of two submarine or underground cable suppliers may be required to meet this schedule. Concept costs are estimated and summarized in the following Table 5 extracted from the report. Important assumptions are listed beneath the table. Table 5: Cost Comparisons (labour and material only) Route Type Description Overhead Route Lengths (km) Cable System Total Cost Estimate (M$) Cost Premium above Base (M$) 1 DC All overhead via Cedar Lake 1, , (DC Base) 2 DC 3 DC 4 DC 5 DC O/H with U/G along east side of Lake Winnipegosis O/H with U/G along west side of Lake Winnipeg O/H along west side of Lake Winnipeg with submarine section (long length shipping) O/H with two submarine sections exiting at Traverse Bay (long length shipping) 1, ,200 1, ,092 1, , AC All overhead via Cedar Lake 1, , (AC Base) 2 AC 3 AC 6 AC O/H with U/G along east side of Lake Winnipegosis O/H with U/G along west side of Lake Winnipeg O/H with two submarine sections exiting at Traverse Bay (long length shipping) 1, ,200 1,942 1, ,092 2,387 1, ,268 1, Manitoba Hydro

17 Assumptions and notes: 1. Costs are expressed in 2010 CAD dollars kv AC overhead line is single circuit capable of 1000 MW kv DC overhead line is similar to Bipole I-II construction. 4. DC underground cables are XLPE. 5. DC submarine cables are MI due to maturity 6. AC underground cables are XLPE. 7. AC submarine cables are XLPE. 8. For underground options, cables would be shipped from Thunder Bay to site by truck (4.0km cable/truck for DC; 1.8 km cable/truck for AC). 9. For submarine options with no long train shipping, cables would be shipped from Thunder Bay to Powerview/Pine Falls by rail (1.8 km cable/car for DC; 1.2 km cable/car for AC). 10. For submarine options with long train shipping, cables would be shipped from Montreal, Prince Rupert or Vancouver, a maximum distance of about 2500 km. 11. MH Project Management and Engineering costs not included. 12. Contingencies not included. 13. Interest during construction not included. 14. Insurance for cable transportation not included. 15. Converter costs for DC alternatives not included. 16. Static VAR compensator for AC alternatives not included. 17. Cable manufacturing capacity is assumed available. 18. Taxes and import duties not included. 19. Estimates are Class 5, as defined by AACE International, to be used only for concept screening purposes with low project definition. Class 5 estimates typically have accuracies in the following range: Low: -20% to -50% High: -30% to +100 % 20. All estimates contain only labour and material. Report of the Concepts Review Panel - 15

18 Findings and Conclusions 1. System studies indicate that with Bipole III (LCC) in service, the Manitoba Hydro power system would experience network frequency stability problems with an additional LCC HVDC transmission link. Therefore it is very unlikely that a fourth HVDC (LCC) bipole would be implemented in Manitoba [19]. 2. The same studies have concluded that additional north-south 500 kv AC transmission would be recommended to integrate the next major northern generation plant [19]. 3. With current cable technology and unproven cable transportation methods, an AC submarine cable under Lake Winnipeg is not a viable option at this time. 4. Assuming in the foreseeable future that the Manitoba Hydro system develops to accommodate a fourth Bipole of any mode (overhead or hybrid), and together with further research and technological advances, a DC submarine or underground cable may be a viable option. 5. Future transmission development should proceed on the basis of overhead, underground and submarine in that order of preference. Studies and circumstances at the time would determine the actual choice. 6. Once all overhead and underground options have been exhausted, further research on long length cable transportation by train, related transportation handling and installation may be initiated. 7. Based on years of operating experience with long transmission lines in Manitoba, an overhead transmission line should have a higher reliability than a hybrid line. 8. A hybrid 500 kv AC line with several cable sections and associated multiple transition and compensation stations would be difficult to operate. 9. A hybrid 500 kv AC line may degrade system reliability, as compared to an overhead line. This potential degraded level of reliability may impact the reputation and value of Manitoba Hydro s product. 10. An underground AC or DC cable system failure can be expected approximately once every 3 to 17 years. A lack of meaningful industry data for AC and DC submarine cables prevents determination of statistical failure rates. 11. The repair time for underground cables is considerably less than for submarine cables. A spare cable for submarine and underground options would minimize forced outage times. 12. All hybrid options have cost premiums compared to overhead lines. Any of the solutions using cables result in incremental cost increases of about $0.36B and could be as high as $1.58B, assuming that long submarine cables could be successfully transported by train. A reference of cost premiums for submarine cabling over an equivalent length of overhead line is presented in Section 7, Table 20: Cost Premiums for Equivalent Line Lengths. These are represented as ratios: submarine segment (cost per route km) overhead segment (cost per route km) For Route 4 DC the ratio is 6.6, for 5 DC it is 6.8 and for Route 6 AC it is This means that on an equivalent length basis the submarine options are 6.6 to 11.9 times costlier than an overhead line. These estimates and ratios that express the premiums include labour and material only Manitoba Hydro

19 13. Routing through Grand Rapids would require detailed engineering studies. Underground segments, including a tunnel, are required to alleviate issues with congestion and proximity to existing Bipole lines. 14. With present technology, estimates indicate that short length submarine cables shipped on reels would take twice as long to splice and lay compared to long train shipping methods. Using reels for shipping submarine cable would be more expensive, impractical and is not recommended. 15. The least costly hybrid DC or AC route would be approximately 1.5 and 2.8 times more expensive respectively, than the base case overhead route, assuming long train shipping is feasible. 16. The base case DC overhead line is the most economic option, despite being longer than other DC conceptual routes. A base case AC overhead line would cost approximately 27% more than the base case DC overhead line. 17. Installation time of DC submarine cable would range between 2 to 3 years, depending on route alternative and assuming long train transportation. For AC submarine cable it would be about 4 years. 21. The life expectancy of an overhead line is approximately 100 years. Life expectancy for an underground or submarine cable is approximately 40 to 50 years. Therefore a complete cable system replacement could be anticipated about half way through the life of overhead line sections. 22. VSC HVDC technology, if only implemented as a future fourth HVDC Bipole transmission line, would not improve the vulnerability to common mode faults. Assuming that there are no technological developments or system developments that would remove system constraints to allow a fourth Bipole and given the operating complexities and reliability risks of a hybrid AC transmission line, an overhead AC line should be considered first. 23. With a low probability of HVDC being implemented, and the costs, reliability, complexity and operating difficulties associated with hybrid AC lines, the preferred post-bipole III option is therefore overhead 500 kv AC. 18. The complete manufacturing capacity of two cable suppliers may be required to meet this schedule for submarine cables. 19. The world s ocean going cable laying fleet does not have access to Lake Winnipeg. A suitably equipped cable laying barge would need to be constructed locally and launched. 20. A dock and cable handling facilities would need to be constructed on a Lake Winnipeg harbour. Report of the Concepts Review Panel - 17

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21 Foreword This report explores and reviews 500 kv AC and DC submarine and underground cable application concepts for a possible post-bipole III 1000 MW transmission line from the lower Nelson River to southern Manitoba. The new link is not expected to be required before 2025, based on domestic load growth forecasts. Some of the concepts include application of cable technologies at voltage levels higher than presently commercially available. They also include untested and unproven methods of transporting long continuous lengths of submarine cables on trains to Lake Winnipeg. Although some concepts could be considered unproven and risky today, there are reasonable probabilities of development prior to The Concept Review Panel s Terms of Reference did not include investigating and describing how a hybrid AC or DC transmission line with overhead and cable segments would be reliably integrated into the existing power grid. Many long submarine cable links in other parts of the world are primarily for opportunity sales of electricity (merchant trade) between countries. But the main purpose of an additional northsouth link in Manitoba would be to serve the domestic load in a reliable and economical manner. In addition, most, if not all other long submarine cable links are in salt water bodies not subject to freezing. However, Lake Winnipeg s surface is frozen during winter, making repairs impractical for approximately six months of the year. Therefore, consequences of a submarine cable failure may not be as critical elsewhere in the world as in Lake Winnipeg. It is also significant that there have been no significant Extra High Voltage submarine cable applications anywhere in the world, where ocean-going freighters or cable laying vessels did not have ease of access. In order to better develop, explain and evaluate the various concepts, transmission line routes were defined for comparison purposes. These routes are by no means final and should be considered as illustrative only. No field work was conducted for any of the example routes. Furthermore, the Panel did not concern itself with the preliminary preferred routing of Bipole III. 1 The report contents reflect the consensus of the panel members. Because of the speculative nature of future cable technology development, uncertainty about future routes and limited Terms of Reference to provide engineering detail, the report must be considered as conceptual in nature. 1 The preliminary preferred routing for Bipole III was announced on July 29, Report of the Concepts Review Panel - 19

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23 Glossary AC Ampacity Bipole Capacitive Effect Coupling Coil Alternating electric current that is a periodic function of time. The maximum value of electric current which can be carried continuously by a conductor, a device or an apparatus, under specified conditions without its steady-state temperature exceeding a specified value. A common HVDC transmission configuration where a pair of conductors is used, each at a high potential with respect to ground, in opposite polarity. The coupling between electric or circuit elements, by which a voltage between the terminals of one of them gives rise to an electric charge in another element To wind into continuous regularly spaced series of rings, one adjacent to the other where allowed. A coil produces a twist in the cable. Compensation A special purpose substation Station to provide reactive power compensation to high voltage underground, submarine, or overhead AC transmission lines. DC EHV A continuous flow of current that is not periodic as a function of time. Extra High Voltage - the voltage range between 220 kv and 500 kv Fault Fault Level Fetch Hybrid line Joint LCC Monopole The state of an item characterized by inability to perform a required function The amount of fault current available at a particular location on an electrical network, measured in MVA or ka. The distance a wind blows unobstructed over water, especially as a factor affecting the build-up of waves. A transmission line that is a combination of overhead and underground or submarine sections. A splice or joining of two underground or submarine cables forming a continuous current carrying path that maintains the electrical and insulation integrity. HVDC transmission using Line Commutated Converters. Changing power flow direction requires polaritry reversal. Is a common HVDC transmission configuration. One of the terminals of the rectifier is connected to earth ground and the other terminal, at a potential high above or below ground, is connected to a transmission line. The earthed terminal may be connected to the corresponding connection at the inverting station by means of a second conductor. Report of the Concepts Review Panel - 21

24 Reactor Reactive Power Compensation Two-terminal device characterized essentially by its inductance. Devices or systems that provide reactive power in high voltage AC networks to control voltage and optimize the transmission of power. VSC HVDC transmission using Voltage Sourced Converters where AC is converted to a DC voltage, or DC voltage is converted to AC. Unlike LCC converters, VSC converters can change power flow direction without polarity reversal. Reeling To wind cable on to adjacent spools directly from one to another. A reel does not produce any twists in the cable. Short Circuit Capacity The highest electric current which can exist in a particular electrical system under short circuit conditions. It is determined by the voltage and impedance of the supply system, affected by switching configurations. Termination Specially prepared cable end providing a seal to the external environment, maintaining internal cable pressure, if any, and controlling electrical stress for the transition between cable and external insulations (usually to air in the case of outdoor terminations). Transition Station A substation dedicated to management of the transition from overhead to underground or submarine cables Manitoba Hydro

25 1 Introduction The subject of this report is the use of submarine or underground power cables as part of a fourth major north south 500 kv transmission line in Manitoba. Bipoles I, II, and the planned Bipole III comprise the first three major northsouth transmission links. The fourth, post-bipole III line is not expected to be required before approximately 2025, based on domestic load growth forecasts and system reliability needs. All activities related to the generation, transmission and distribution of electricity in Manitoba are governed by the Manitoba Hydro Act and the Manitoba Hydro Electric Board, which oversees the operations of the Manitoba Hydro Corporation. The Board is appointed by the Provincial Government. Manitoba Hydro s mission is to provide for the continuance of a supply of energy to meet the needs of the province and to promote economy and efficiency in the development, generation, transmission, distribution, supply and end-use of energy. In Manitoba approximately 70% of all power generated in the province is transmitted from the north via two high voltage 500 kv direct current (DC) lines. They share a common rightof-way, which is a reliability concern. Each line is approximately 900 km long, from two sites on the Nelson River to the Dorsey converter station just northwest of Winnipeg. Manitoba Hydro is presently designing a third DC line (Bipole III) and activities have been well documented over the past several years [18]. Routing of this transmission line, critical to Manitoba s electricity reliability and security, has been controversial. Although initially there was preference to route the line east of Lake Winnipeg for economical, technical, and reliability reasons, the Provincial Government s decision to protect this boreal forest region, precluded a route east of the lake. In 2008 Manitoba Hydro began a lengthy process of environmental assessments to locate a route generally west of Lake Manitoba and Lake Winnipegosis. An Interlake Route between Lake Winnipegosis and Lake Winnipeg was considered, but weather risk assessment studies showed that: locating the Bipole III transmission line on the East Route or West Route would significantly reduce the likelihood that all three lines would be exposed to the same extreme weather conditions, compared to locating Bipole III on the Interlake Route. In summary, the larger the separation distance between the lines, the greater the reduction of common event risk. [2]. The receipt of a licence for Bipole III is scheduled and expected in the fall of Bipole III is scheduled to be in service five years later. Concepts for possibly implementing the post- Bipole III link using submarine or underground cable segments are discussed in this report. The fourth major transmission link will be to accommodate the Gillam Island generating station, a 900 MW development. In early 2008, retired University of Winnipeg geography professor Dr. John Ryan wrote several articles promoting the idea of installing a portion of the Bipole III line under Lake Winnipeg. He generally explored the feasibility of transporting and installing long sections of submarine cables in a land-locked lake, inaccessible by specialized ocean-going cable laying vessels [12]. Dr. Ryan proposed a concept of using long trains with specially modified flat cars linked to hold long cable lengths in a continuous looping method. The cable would arrive by ship from a factory at a port such as Thunder Bay, Montreal, Vancouver or Prince Rupert and be transferred to a special unit train, transported to the Lake Winnipeg area, off-loaded onto a specially built barge equipped for cable laying, and subsequently Report of the Concepts Review Panel - 23

26 installed on the lake bottom. The complete process would need to be validated by submarine cable manufacturing and installation experts, as well as professional railway engineers. The risks associated with transportation, multiple handling and laying of cables, as well as future reliability, maintenance and repairing of the cables in the middle of Lake Winnipeg are identified in this report. Besides technical problems, risks and costs associated with unproven submarine cable transportation systems, there are additional complexities because some possible route alternatives could make partial use of underground cables instead of submarine cables. They would avoid difficulties associated with overhead lines and geographical restrictions, for example through the congested Grand Rapids area. Historically, Manitoba Hydro and other utilities around the world have built high voltage transmission lines overhead, provided land for rights-of-way was available. Such designs, using AC or DC transmission, are the most economical method of transporting bulk electric power over long distances and have a proven record of acceptable reliability at minimum cost. Today the highest voltage overhead line in the world is in China. It operates at +/-800 kv DC and was commissioned in June There are many 765 kv AC overhead lines operating in the world including in Quebec and the United States. In congested urban areas where AC systems dominate and overhead systems are impractical, transmission lines have been placed underground. For water crossings beyond the reach of overhead lines, AC submarine cables are used. 500 kv AC submarine cable systems spanning distances of approximately 30 km and using pressurized insulations, have been in service for over 25 years. Where wide water bodies separate regions by more than 50 to 75 km, AC transmission at the 400 to 500 kv level is usually not feasible. However, DC submarine cable systems provide practical alternatives. The highest operating voltage submarine DC cables in Canada are the +/-300 kv Vancouver Island cables, commissioned in 1969 and 1975 (total cable length = 5 x 32 km). The highest operating voltage DC underground cables in Canada are the +/- 450 kv cables in the Radisson-Nicollet tunnel link under the St. Lawrence River in Quebec, commissioned in 1992 (total cable length = 6 x 5.1 km). The highest voltage DC submarine cable in North America is the 500 kv Neptune link between New Jersey and Long Island, New York, commissioned in 2007 (total cable length = 1 x 105 km). The Manitoba Hydro system presently has one of the highest penetrations of high voltage DC into a local AC network in the world. With the future development of Keeyask and Conawapa, the three bipole system could be loaded up to 5500 MW. Because of the tight electrical coupling between the HVdc converters, a fault in the northern AC collection system, or in the southern Manitoba AC network, can cause the temporary loss of all the DC power for the duration of the fault. This temporary loss of power causes the frequency of the southern system to decay rapidly during the fault due to the low inertia in the southern Manitoba network. Inertia is normally provided by nearby synchronous generators but in the case of Manitoba it is also provided by local synchronous condensers. The susceptibility of the HVdc bipoles to interruption in power delivery due to an AC fault places a limit on the HVdc penetration level in southern Mantioba. Studies have demonstrated that the addition of Bipole III, loaded with Keeyask and Conawapa generation, increases the DC to that penetration limit. As a result, there appears to be many reliability advantages if a post Bipole III north-south link was developed at 500 kv AC, rather than DC [19] Manitoba Hydro

27 With these technical, political and economic issues in focus, Manitoba Hydro appointed a Concepts Review Panel, to examine the potential use of 500 kv submarine and underground cables for long distances in Manitoba. The detailed Terms of Reference of the Panel (i.e. Purpose of the Panel and Items of Concern) are contained in Appendix 1 and summarized below. Discuss feasibility of underground and underwater 500 kv cables for possible use in a future North-South Transmission line in Manitoba, post Bipole III. Review maturity of the state-of-engineering of 500 kv cable technologies in use worldwide today. Research performance of cables operating at 500 kv. Research the causes of failure of 500kV cable systems world-wide. Review the literature on current cable research for 500 kv cables and the effects of very long cable lengths on the power system. Discuss concepts for transporting very long sections of cable on land and over landlocked inland waterways. Identify the concept with the highest feasibility for long-length transportation and installation that may need to be advanced for further research and investigation by world experts. Address cost implications of any concepts that may have merit. Membership of the Panel is described in Appendix 2. In order to achieve the Panel s mandate, members collectively and conceptually investigated cable transportation methods by rail and road, possible cable system types and implications of applying them to illustrative transmission routes for comparison purposes. The concepts review and report is not about routing or route selection as the routes depicted in this report are for illustrative purposes only. Example routes were comprised of an overhead line, and several hybrid lines with segments of overhead and submarine or underground cables. With these example routes established, scenarios could be conceptually engineered, characterized and ranked in terms of cost and performance. Cable system performance issues were explored to determine their present maturity and anticipated failure rates when applied to the example route scenarios in A detailed discussion of example transmission routes is provided in Section 2. Report of the Concepts Review Panel - 25

28 26 - Manitoba Hydro

29 2 Transmission Line and Cable Routes The Panel examined a number of example route options for the next transmission line from the Nelson River generating station area to southern Manitoba, following commissioning of Bipole III. The northern terminus was assumed to be Gillam Island and the southern terminus assumed to be Riel Substation, for illustrative purposes only, to provide a basis for line length calculations. It was assumed that the fourth Nelson River line would have a capacity of 1000 MW and for completeness, options were studied for AC and DC, notwithstanding that a stronger AC network is desirable at the receiving end to improve system stability. 2.1 Route 1 AC or DC Overhead across Cedar Lake This route, which begins at Gillam Island on the Nelson River, passes through several Provincial and Aboriginal Resource Management areas, and along the western edge of the Grand Rapids area. The route would then extend along the eastern side of Lake Winnipegosis and then on to the Winnipeg area. The total length of the route would be 1273 km. The closest distance between it and the Bipole I-II corridor is about 17 to 25 km but the total extent of this section is only about 100 km or 10% of the line length. In addition to an entirely overhead route option for either AC or DC, two of the conceptual routes contain underground cable segments for AC or DC and three routes contain submarine cable segments (two for DC and one for AC). Extensive engineering studies will be required to confirm the ultimate merits and validity of any route and concept, with the distinct possibility that variations may ultimately be shown to be superior. Churchill MANITOBA Gillam Gillam Island Hudson Bay Detailed maps of both the AC and DC route options are provided at the end of this report (Map 1: DC concept routes and Map 2: AC concept routes). Flin Flon Thompson The Pas Grand Rapids Brandon Selkirk Winnipeg Figure 1: Route 1 AC or DC Overhead across Cedar Lake Report of the Concepts Review Panel - 27

30 2.2 Route 2 AC or DC Underground through Grand Rapids West This route is a hybrid overhead underground cable overhead line. It begins generally at Gillam Island and extends overhead to the north of Lake Winnipeg, where it transitions to an underground cable that would follow the Bipole I-II corridor through the Grand Rapids area, then veers to the eastern edge of Lake Winnipegosis. From there it would transition back to an overhead line and proceed to the Winnipeg area. The main purpose for using cables for this route is to avoid common mode failure of the new line and existing Bipole I-II lines due to extreme weather events. The closest distance between the new and existing overhead lines is about 50 km. It is assumed that a tunnel would be used to carry cables under the Saskatchewan River at Grand Rapids tailrace and spillway. The total length of the route would be 1200 km with one underground segment of 175 km. Tunnel length is assumed to be about 0.6 km. The AC solution would have reactive compensation equipment at each overhead/underground transition station and at two intermediate stations in the underground segment. A spare cable would be provided to improve reliability in case of a cable failure. Flin Flon The Pas Churchill MANITOBA Thompson Grand Rapids Gillam Gillam Island Hudson Bay Brandon Selkirk Winnipeg Figure 2: Route 2 AC or DC Underground through Grand Rapids West 28 - Manitoba Hydro

31 2.3 Route 3 AC or DC Underground East This route is a hybrid overhead underground cable overhead line, beginning at Gillam Island and then proceeding overhead to the north of Lake Winnipeg where it would connect to an underground cable. The cable would follow along the Bipole I-II corridor through the Grand Rapids area then veer to the western edge of Lake Winnipeg. From there it would transition back to an overhead line and extend to the Winnipeg area. The total length of the line would be 1093 km with one underground segment of 263 km. The AC solution would have reactive compensation equipment at each overhead/underground transition station and at three intermediate stations in the underground segment. A spare cable would be provided to improve reliability in case of a cable failure. Flin Flon The Pas Churchill MANITOBA Thompson Grand Rapids Gillam Gillam Island Hudson Bay Brandon Selkirk Winnipeg Figure 3: Route 3 AC or DC Underground East Report of the Concepts Review Panel - 29