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TB 684 2017 B4/C1-65 Recommended voltages for HVDC grids

This technical brochure provides guidance for system planners and designers to choose the optimal DC voltage for High Voltage Direct Current (HVDC) grids. This includes a clear technical definition for the “DC voltage” in line with current practices and standards, a list of recommended values based on technical considerations and drivers from system planning, and a flowchart to guide the selection of the optimal voltage for individual projects.

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Table of Contents

1- INTRODUCTION

2 - ASSUMPTIONS, SCOPE AND DEFINITIONS

3 - HISTORICAL PERSPECTIVE ON VOLTAGE LEVELS FOR AC NETWORKS

   3.1 - General Trends

   3.2 - Illustrations in Specific Countries

   3.3 - AC Voltage standards

4 - SURVEY OF CURRENT AND PLANNED HVDC PROJECTS

   4.1 - Drivers for choosing HVDC systems

   4.2 - Voltage Choices in Existing or Planned HVDC Links Worldwide

   4.3 - Outlook in Selected Regions

5 - CHOOSING DC VOLTAGES FROM THE SYSTEM PLANNING PERSPECTIVE

   5.1 - Drivers for choosing recommended voltages for HVDC projects

   5.2 - Benefits of choosing Recommended Voltages for HVDC projects

   5.3 - Conversion of AC to DC

      5.3.1 - Relevant aspect to consider for the AC/DC conversion

      5.3.2 - Analysis of different actions carried out around the world

      5.3.3 - Voltage aspects and final considerations on conversion

   5.4 - Point to point HVDC without Outlook to evolve to an HVDC grid

   5.5 Planning a new HVDC system near an existing system

   5.6 - Planning of new HVDC system with outlook to evolve into a DC grid

   5.7 - Operational requirements and selection of the voltage range

6 - TECHNICAL CONSIDERATIONS FOR VOLTAGE LEVELS IN HVDC GRIDS

   6.1 - Definitions of Relevant Voltage Levels and Other Limits

      6.1.1 - Definitions in standards, and proposed DC voltage definition

      6.1.2–Current practices in point to point HVDC projects

   6.2 - Overview of HVDC technologies

      6.2.1 - Converter technologies

      6.2.2 - HVDC grid transfer capability

      6.2.3 - Cable technology

      6.2.4 - Overhead line technology

      6.2.5 - DC Compact Switchgear and DC Compact Transmission Line (DC CTL)

   6.3 - Relationship between cost and voltage

7 - UPGRADING OR INTERCONNECTION OF DC SYSTEMS WITH DIFFERENT VOLTAGES 51

   7.1 - Upgrading of a DC system to another voltage

   7.2 - DC-DC conversion equipment

8 - TOOLBOX TO CHOOSE DC SOLUTIONS AND VOLTAGE

   8.1 - Recommended DC Voltage Levels

   8.2 - Toolbox

9 - CHALLENGES TO HVDC GRIDS BEYOND THE STANDARDIZATION OF VOLTAGES

10 - CONCLUSIONS AND RECOMMENDED VOLTAGES FOR HVDC GRIDS

11 - LIST OF REFERENCES

12 - APPENDIX: IMPLEMENTATION OF THE FLOWCHART