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TB 186 2001 SC 14 WG 14.20 Economic assessment of HVDC links

HVDC has been a viable technique since the 60's and has played a vital part in both long distance transmission and in the interconnection of systems. Its relative economic position has been much discussed over 30 years and this report is both an update of those considerations and a review of the present position. It reviews many aspects of transmission development common to both AC and DC transmission with a concentration on the specific aspects of DC as they give advantage or extra dimension to the long distance transmission of electrical power.

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TABLE OF CONTENTS

1. INTRODUCTION

2. GENERAL CONSIDERATIONS OF AC AND DC TRANSMISSION

      2.1 Objectives

      2.2 The Benefits of Interconnection

      2.3 Technical Considerations

            2.3.1 Long Distance Bulk Power Transmission

            2.3.2 Interconnection by AC or HVDC

            2.3.3 HVDC Multi-terminal System

3. ASSESSMENT METHODOLOGY

      3.1 Identifying alternatives for interconnections

      3.2 Technical Assessment

            3.2.1 Performance and Cost Analysis

            3.2.2 HVDC Electrodes

            3.2.3 Losses

            3.2.4 Reliability

            3.2.5 Spare Parts for HVDC

            3.2.6 AC System Strength

            3.2.7 Commutation Failure

            3.2.8 Subsynchronous Frequency Considerations

            3.2.9 Harmonic Modulation

      3.3 Tools

4. TRANSMISSION SYSTEM COSTS

      4.1 Check List of Cost Areas

            4.1.1 Engineering cost

            4.1.2 Environmental costs

            4.1.3 Implementation costs

            4.1.4 Operational Costs

      4.2 Station Costs

      4.3 Overhead Line Costs

      4.4 Stages in Expansion of HVDC Transmission

      4.5 Environmental Aspects

5. TRANSMISSION BENEFITS

      5.1 Technical Benefits

            5.1.1 AC System Support

            5.1.2 Limitation of Faults

            5.1.3 Limitation of Short Circuit Level

            5.1.4 Power Flow Control

            5.1.5 Voltage Control

      5.2 System Reserve

      5.3 Environmental Benefits

6. ECONOMIC ANALYSIS

      6.1 Factors to be Considered

      6.2 Economic Criteria and Decision Rules

      6.3 Economic Analysis Methodology

            6.3.1 DCF spreadsheet examples

            6.3.2 Cost Streams for Least Cost Ranking

            6.3.3 Avoided Cost Concept

      6.4 Coping with Uncertainty

      6.5 Non-Quantified Benefits and Costs

7. OTHER FACTORS AFFECTING A DECISION

      7.1 Risks

            7.1.1 Technical Risks

            7.1.2 Economic Risks

            7.1.3 Social and Political Risks

      7.2 Dependency and Interdependency

      7.3 Market and Institutional Arrangements

      7.4 HVDC as a Barrier

      7.5 Supplies to communities en route

8. CONCLUSIONS ACKNOWLEDGEMENT

APPENDIX I – HVDC CONFIGURATIONS

      I 1. Monopolar HVDC Systems

      I 2. Bipolar HVDC Systems

      I 3. Point-to-Point HVDC Overland Systems

      I 4. Point-to-Point HVDC Submarine Systems

      I 5. Back-to-Back HVDC Links

      I 6. AC and DC in parallel

      I 7. Switching possibilities on DC side

      I 8. Multi-terminal HVDC Systems

      I 9. Intermediate Supplies

APPENDIX II – EXPERIENCE REVIEW

      II 1. Cross Channel link

      II 2. East and West Europe

      II 3. Cahora Bassa

      II 4. Quebec - New England

      II 5. India

APPENDIX III – MINI-SPEC

      III 1. Scheme Type

      III 2. AC System for each Terminal

      III 3. DC System

      III 4. Generators

      III 5. Auxiliary Supplies

      III 6. Controls & Telecommunications

      III 7. Sites

      III 8. Site Conditions

REFERENCES