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TB 684 2017 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