Cable Consulting International

Cable Consulting International Brian Gregory BSc, CEng, MIEEE, FIEE Technical Director www.cableconsulting.net Alan Williams BSc, CEng, MIEE Senior Consultant 1

FEASIBILITY STUDY for 500 kv AC UNDERGROUND CABLES for use in THE EDMONTON REGION of ALBERTA, CANADA for the AESO Cable Consulting International 2

Topics Feasibility study Study contributors 500 kv Study project functional requirements Feasibility of 500kV underground cables Feasibility of power rating Supplier capability and experience 500 kv project size Project specific requirements Reliability Power losses Estimated costs Project risks Project schedule Recommendations for next steps Summary 3

Study contributors Feasibility study Principle investigators: CCI (Cable Consulting International) The findings and recommendations are CCI s Contributors: AESO (Alberta Electric System Operator) HPT (Heartland Project Team) Manufacturers Other consultants also contributed. Their names appear in the Appendices 4

AESO Provided the generic 500 kv Study Project to CCI Functional requirements Studies on electrical system Effect of reactive compensation Net Present Value of the Life cycle costs Cost of losses 5

CCI Performed the generic 500 kv Study Project: Visited Tokyo 500 kv cable circuit with AESO and HPT Scoping study: Costs and details from prospective suppliers Civil design: for the HPT to prepare costs Analysed manufacturers proposals State of the art Feasibility, risks, next steps Prepared report 6

HPT Contributions to the generic 500 kv Study Project: Typical routes Installation type Project schedule Total estimated capital cost 7

500kV cable systems suppliers Provided: Cable system designs Ampacity calculations Cable Accessories Trench configurations Technical design data Budgetary costs: Cables Accessories Delivery to Canada Supervision of installation Jointing Site testing To remain confidential: presented in a non-attributable manner Feasibility study 8

500 kv Study Project: Suppliers approached ABB Areva Brugg Exsym J-Power Systems LS Cable Nexans NKT Okonite Prysmian Siemens Silec Sudkabel Taihan Viscas 9

500 kv study project: functional requirements Generic study Route length: 65 km Two circuits: 3,000 MW Based on Heartland Project Applicable to 500 kv studies in Edmonton region of Alberta 10

500 kv study project route 11

Courtesy Prysmian 400 kv transition station 12

3,000 MW total: normal operation Feasibility study 13

3,000 MW total: contingency operation Feasibility study 14

Design loads for two circuits Feasibility study Load conditions: Peak load at any time: 3,000 MW total Average load over a year: 2,000 MW total Design of transmission system: Must take: peak load* Losses calculated on: average load * The cable must not exceed its design temperature at 3,000 MW 15

Feasibility of 500 kv underground cables 16

Feasibility of underground cables: conclusions Is an underground cable system feasible? Yes Underground 500 kv cable is technically feasible Cross linked polyethylene (XLPE) cable is best choice Proviso: manufacturers must validate cable and accessories on test to: IEC 62067: Accelerated aging prequalification for one year Special low ambient temperature test 17

500 kv cable types considered Feasibility study XLPE extruded SCFF LPP taped 18

500 kv XLPE cable has benefits of: Lowest losses of conventional cable types Solid (unpressurised) insulation: No possibility of fluid leakage from cable Lower maintenance Reduced risk of fire Alternative cable is SCFF (Self Contained Fluid Filled): Becoming obsolete Risk of fluid leakage 19

Other technologies evaluated: Gas insulated Line (GIL) Not yet proven for burial in long length circuits Some environmental concern Feasible alternative for tunnel (long length) Courtesy Siemens 20

Other technologies evaluated: Feasibility study High Temperature Superconducting Cable (HTS) Not yet sufficiently developed for high power, long length circuits with joints Courtesy NKT 21

Feasibility of power rating 22

Feasibility of power rating Can a cable system carry the 3,000 MW needed? Yes Suppliers design proposals: Largest standard conductor size: 2,500 mm 2 copper Two groups of cables per circuit Most efficient installation method: direct buried Typical design: Up to four trenches x three cables per trench = twelve cables (Study also evaluated scenarios with fewer groups of cables) 23

3,000 MW: Contingency operation Feasibility study 24

Six cables required per circuit: To carry 3,000 MW peak load in contingency operation 1,500 MW maximum per group of three cables 25

3,000 MW: Normal operation Feasibility study 26

Supplier Capability & Experience Has the cable system been used before at 500 kv? Yes, the cable has been used before at 500 kv But, no evidence to date that the offered joint types have been fully proven Three installations of 2,500 mm 2 cable with joints to date Three suppliers have this 500 kv experience 400 kv experience is a good indicator of prospective supplier capability Examples follow 27

500 kv, 2,500 mm 2, Tokyo tunnel: 2 x 40 km routes (240 km) Commissioned in 2000, 9 years good experience 4 suppliers In a warm, dry tunnel Courtesy Viscas 500 kv cable is available Courtesy J-Power Systems Extrusion moulded joint no longer offered 28

500 kv, 2,500 mm 2, Shanghai tunnel: 2 x 17 km routes (102 km of cable) To be commissioned in 2010 2 suppliers 2 types of prefabricated joint Feasibility study Courtesy Viscas Prefabricated joints on proving test Courtesy Viscas Pulling 500 kv cable into tunnel 29

500 kv, 2,500 mm 2, 2 routes in Russia, in tunnel 2 x 0.8 km routes (4.6 km of cable) Commissioned in 2008 and 2009 1 supplier 6 prefabricated joints Courtesy Nexans Outdoor terminations Courtesy Nexans Gas immersed terminations 30

400 kv, 1,200-2,500 mm 2, experience Cumulative 351 circuit km (1,053 km cable) 34 projects completed or under construction 21.3 km,1,600 mm 2, direct buried, installed 1997 11.2 km, 2,500 mm 2, direct buried, installed 2000 20.6 km, 2,500 mm 2, tunnel, installed 2005 Courtesy Brugg Prefabricated one piece joint mould Courtesy LS Cable Prefabricated composite joint 31

500 kv Project size How big is the 500 kv study project? It would be one of the largest in the world: 4 groups of cable in 20 km route require 240 km of cable ~360 joints. Equal to 40 km Tokyo circuit First application of buried, long length, large conductor 500 kv cable with joints. 400 kv buried experience is relevant. 500 kv is the highest voltage for XLPE to date 3,000 MW is a high power level. The combination of voltage and power requires a cable size at the top end of standard manufacturing ranges. Such cables are available 32

Project specific requirements 33

500 kv Project specific requirements Feasibility study Location specific: Crossing of route obstructions Highways: multi-lane and banked Pipelines: petrochemical, heated? Wetlands and streams Obstructions are normal for cable routes, but ability to maintain ampacity needs to be confirmed Low ambient temperatures Direct buried joints: -15 o C design Outdoor terminations: -50 o C design Lack of low temperature experience from suppliers. Concern about elasticity of the rubber insulation in accessories 34

Proving of performance 35

Proving of performance Feasibility study Should performance of cable system be proven before being supplied? Yes, both electrical and mechanical prequalification tests and low temperature tests must be performed Proving tests: these are normal before supply Prequalification test: one year Type test: 6 weeks Special proving tests: low temperature tests to be formulated 36

Proving of performance Feasibility study Courtesy Nexans Prequalification test Courtesy Sudkabel Type test 37

Reliability 38

Reliability Would XLPE cable system be reliable? Feasibility study Yes, Subject to performing proving tests and quality control in manufacture and installation Recommended proving and quality tests must be done Utilities are demonstrating confidence in reliability and maintenance by installing XLPE. They reduce risk by requiring high standards of design to installation Statistics of cable systems: Repair time 29 days. Faults : 1 x 10 km group 0.04-0.05 per year Dig in faults 25% of above Majority of internal failures accessories Reliability analysis needed for all equipment Service experience of XLPE cable is comparatively short and needs to be monitored 39

Power losses 40

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Fixed and Variable Losses Cable Overhead line Variable Losses Variable Losses Low load Fixed Losses High load Low load Fixed Losses High load Increasing transmitted load Increasing transmitted load 42

Power losses 43

Power losses There is a Cross over load where: cable losses = overhead line losses This occurs at approximately 1,700 MW Above1,700 MW Cable losses are lower than overhead line losses Below 1,700 MW Cable losses are higher than overhead line losses 44

Estimated costs How much would the 500 kv underground cable system cost? Different scenarios have different estimated costs: 45

Cost scenarios Feasibility study 65 km route with some underground cable: Underground route 10 km or 20 km Groups of Cables 3 or 4 Installation options: Unstaged all at same time Staged: Stage 1 some installed initially Stage 2 balance installed later Compared with all-overhead line 46

Scenario 1: FOUR Groups of Cables - Unstaged: all installed at start Feasibility study Full capacity at start: 3,000 MW 1,500 MW 1,500 MW 47

Scenario 1: FOUR Groups of Cables - Unstaged: all installed at start Feasibility study Full capacity at start: n-1 redundancy: 3,000 MW 1 group per circuit 2 groups total 750 MW 750 MW 750 MW 750 MW 48

Scenario 1: FOUR Groups of Cables - Unstaged : all installed at start Feasibility study Full capacity at start: n-1 redundancy: 3,000 MW 1 group per remaining circuit 1 groups total 1,500 MW 750 MW 750 MW 49

Scenario 1: FOUR Groups of Cables - Unstaged: all installed at start Feasibility study Full capacity at start: n-1 redundancy: 3,000 MW 0 group per remaining circuit 0 groups total 1,500 MW 1,500 MW 50

Scenario 1: FOUR Groups of Cables - Unstaged: all installed at start Feasibility study 1 x OHL circuit out of service 3,000 MW 1,500 MW 1,500 MW 51

Scenario 2: FOUR Groups of Cables total - Staged: 2 groups installed at start Half capacity at start: 2 further groups later 1,500 MW 750 MW 750 MW 52

Scenario 2: FOUR Groups of Cables total - Staged: 2 groups installed at start Half capacity at start: n-1 redundancy: 1,500 MW 1 group total 750 MW 750 MW future future 53

Scenario 2: FOUR Groups of Cables total - Staged: 2 groups installed at start Half capacity at start: n-1 redundancy: 1,500 MW 0 group total 1,500 MW future future 54

Scenario 3: THREE Groups of Cables total - Unstaged: All installed at start Full capacity at start: 3,000 MW Includes GIS switches 1,000 MW 1,000 MW 1,000 MW 55

Scenario 3: THREE Groups of Cables total - Unstaged: All installed at start Full capacity at start: n-1 redundancy: 3,000 MW 1 group total 1,000 MW 1,000 MW 1,000 MW 56

Scenario 3: THREE Groups of Cables total - Unstaged: All installed at start Full capacity at start: n-1 redundancy: 3,000 MW 0 groups 1,500 MW 1,500 MW 57

Scenario 3: THREE Groups of Cables total - Unstaged: All installed at start 1 x OHL circuit out of service 3,000 MW Includes GIS switches 1,000 MW 1,000 MW 1,000 MW 58

Scenario 4: THREE Groups of Cables total - Staged: 2 groups installed at start Half capacity at start: 1 group installed later 1,500 MW Includes GIS switches 750 MW 750 MW 59

Scenario 4: THREE Groups of Cables total - Staged: 2 groups installed at start Half capacity at start: n-1 redundancy: 1,500 MW 1 group total 750 MW 750 MW future 60

Scenario 4: THREE Groups of Cables total - Staged: 2 groups installed at start Half capacity at start: n-1 redundancy: 1,500 MW 0 group total 1,500 MW future 61

Scenario 4: THREE Groups of Cables total - Staged: 2 groups installed at start 1 x OHL circuit out of service 1,500 MW Includes GIS switches 750 MW 750 MW 62

Estimates of cost: types of costs Costs estimates prepared in TWO different ways Estimated capital costs: Initial purchase cost Estimated Net Present Value of life cycle costs A single number that expresses the estimated 40 year stream of costs in terms of an equivalent lump sum paid today Includes all costs for: constructing, owning, operating and maintaining the system (including spares) cost of energy losses All cost estimates in 2009 $ million CAD 63

Estimated capital project cost: 65 km (2009 $ million CAD) Unstaged 10 km cable 20 km cable OHL Scenario: 1 4 groups 3 groups 4 groups 3 groups 2 3 4 1 2 3 4 64

Estimated capital project cost: 65 km (2009 $ million CAD) Unstaged and Staged (Stage 1 and Stage 2) 10 km cable 20 km cable OHL Scenario: 1 2 4 groups 3 groups 4 groups 3 groups 3 4 1 2 3 4 65

Estimated capital project cost: 65 km (2009 $ million CAD) Unstaged and Staged (Stage 1 and Stage 2) 10 km cable 20 km cable OHL 4 groups 3 groups 4 groups 3 groups Scenario: 1 2 3 4 1 2 3 4 66

Estimated capital project cost: 65 km (2009 $ million CAD) Unstaged and Staged (Stage 1 and Stage 2) 10 km cable 20 km cable OHL 4 groups 3 groups 4 groups 3 groups Scenario: 1 2 3 4 1 2 3 4 67

Estimated capital project cost: 65 km (2009 $ million CAD) Unstaged and Staged (Stage 1 and Stage 2) 10 km cable 20 km cable OHL 4 groups 3 groups 4 groups 3 groups Scenario: 1 2 3 4 1 2 3 4 68

Estimated NPV of life-cycle cost: 65 km route Unstaged and Staged PV of power losses in red 10 km cable 20 km cable OHL Staged Staged Staged Staged 4 groups 3 groups 4 groups 3 groups Scenario: 1 2 3 4 1 2 3 4 69

Estimated capital cost for 65 km route: by component (include 2x double circuit) X 2 X 2 X 2 Full length 70

Estimated capital cost: by component Feasibility study (2009 $ million CAD) 20 km cable, 4 groups, Staged Installation (example) X 2 X 2 X 2 Full length Stage 2 Stage 1 71

Project risks 72

Project risks What are the project specific risks? There are three risks: Feasibility study 1) Inability of 500 kv accessories to operate at Edmonton winter temperature Preventative Gather low temperature information from manufacturers Draft low temperature test specification Require manufacturers to perform this test Remedial Install joints at greater depth This may require an additional group of cables to meet 3,000 MW requirement Install cables in tunnel with controlled air temperature 73

Project risks What are the project specific risks? Feasibility study 2) Uncertainty of actual minimum winter temperature Preventative Field trials to measure ground temperature Remedial: Increase accessory design temperature margins Evaluate trace heating Install cables in tunnel 74

Project risks What are the project specific risks? Feasibility study 3) Long time required to repair cable in winter Preventative Specify the maximum winter repair time requirement to suppliers in the Request for Quotation Develop a winter repair procedure Design and build mobile heated habitat* for winter repair use Perform trials to prove the winter repair procedure Install more groups of cable to allow longer repair time Remedial Contingency switch the load onto parallel circuit Repair the accessory when the ambient temperature rises *Note: use of mobile jointing habitats is normal in temperate climates 75

Project schedule 76

Project schedule How long would it take to manufacture and install? 10 km, 4 groups Unstaged 57 months Staged (stage 1 only) 46 months 10 km, 3 groups Unstaged 57 months Staged (stage 1 only) 46 months 20 km, 4 groups Unstaged 57 months Staged (stage 1 only) 57 months 20 km, 3 groups Unstaged 57 months Staged (stage 1 only) 57 months 77

Recommendations for next steps 78

Recommended Next steps What are the next steps in evaluating underground cable? Refine and optimize cable system: Investigate joint low temperature protection by installation at greater depth Detailed designs for obstruction crossings. Is ampacity OK? Quantify reliability and availability for all circuit components Refine accuracy of the cost estimates Discussions with cable suppliers to agree: Normal proving tests Specific proving tests Discussions with cable suppliers on schedule shortening: Is evidence available for 500kV XLPE : Existing electrical and mechanical prequalification and type tests Ongoing installations and tests Low temperature test and service experience 79

Summary 80

Summary What are the main findings? Feasibility study 500kV, 3,000 MW, underground cable is feasible The power rating is feasible for normal burial depth. A study of specific obstruction crossings is required: Dimensions and temperatures Their effect on circuit power ampacity XLPE insulated cable is the best choice. Service and test experience exists for 500kV XLPE cable and terminations in temperate climates. No evidence exists of tests on joints at Edmonton low winter temperatures Evidence of tests is essential. (Continued) 81

Summary What are the main findings? Feasibility study Edmonton low winter ambient temperature is a project specific risk to the joints and terminations. Low temperature testing is essential. Ground temperature with depth to be measured: Winter Summer Cable optimization: ampacity benefits of: Cyclic rating study Lower summer ground temperatures at depth 82

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