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TB 713 2018 Designing HVDC grids for optimal reliability and availability performance

This Technical Brochure addresses the question of how to design a DC grid to achieve optimal reliability and availability performance. The starting point was to consider a suitable metric which could be used to assess the reliability and availability performance of the grid. Anticipating that a DC grid may not have an overall “architect”, the brochure considers the evolution of the grid from smaller radial and meshed multi-terminal systems and the factors which need to be considered when incorporating such building blocks to ensure that the grid can achieve high levels of reliability and availability. The technologies used at the AC to DC converter stations and at DC switching stations are discussed in the brochure in terms of their impact on the grid. The interconnecting medium between grid stations, whether overhead transmission lines, underground cables or submarine cables, will also have a major impact on the grid in terms of their susceptibility to internal or external faults. The design of a DC grid will require analytical techniques to assess whether the evolving grid is able to achieve the desired levels of reliability and availability performance. The brochure includes an example of such a study, based on a deterministic evaluation of a DC grid test model, to illustrate the impacts of specific outage conditions on the energy not served by the grid. This study is presented as an illustrative example only and is not proposed as the methodology for future evaluations of DC grids, as other methods, including probabilistic techniques, may be adopted

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TABLE OF CONTENT

EXECUTIVE SUMMARY

ABBREVIATIONS AND ACRONYMS

1. INTRODUCTION

   1.1 BACKGROUND

   1.2 DC GRIDS

   1.3 CIGRE ACTIVITIES

   1.4 CENELEC ACTIVITIES

   1.5 CONTENTS OF THE TECHNICAL BROCHURE

   1.6 SUMMARY

2. DEFINITIONS OF RELIABILITY AND AVAILABILITY

   2.1 RELIABILITY

   2.2 AVAILABILITY

   2.3 RELIABILITY ASSESSMENT METHODS

   2.4 CALCULATION METHODS

   2.5 AVAILABILITY ASSESSMENT FOR DC GRIDS

3. GRID CONFIGURATION AND EXPANSION

   3.1 GRID CONFIGURATION

   3.2 GRID EXPANSION

   3.3 INTRODUCING DC BREAKER IN A RADIAL SYSTEM

4. CONVERTER STATION TOPOLOGIES

   4.1 INTRODUCTION

   4.2 SYMMETRICAL MONOPOLE

   4.3 ASYMMETRICAL MONOPOLE

   4.4 BI-POLE SYSTEMS

   4.5 ASYMMETRICAL BI-POLE SYSTEMS

   4.6 MIXED TOPOLOGIES

   4.7 ASSESSMENT OF RELIABILITY AND AVAILABILITY ISSUES

5. OVERHEAD LINE CONFIGURATIONS

   5.1 INTRODUCTION

   5.2 DC TRANSMISSION LINE CONFIGURATIONS

   5.3 DC TRANSMISSION LINE DESIGN CRITERIA

   5.4 MAINTENANCE AND SPARE PARTS OF DC TRANSMISSION LINES

   5.5 EMERGENCY RESTORATION STRUCTURES

   5.6 RELIABILITY AND AVAILABILITY OF DC TRANSMISSION LINES

6. CABLE INTERCONNECTIONS

   6.1 INTRODUCTION

   6.2 HOW TO MAXIMISE MTTF FOR CABLE SYSTEMS

   6.3 HOW TO MINIMISE MTTR FOR SUBMARINE CABLE SYSTEMS

   6.4 DETECTING THIRD-PARTY DAMAGE

7. CONVERTER AND SWITCHING STATION ARRANGEMENTS

   7.1 INTRODUCTION

   7.2 CONVERTER STATIONS

   7.3 SWITCHING STATIONS

   7.4 ASSESSMENT ON RELIABILITY AND AVAILABILITY ISSUES

8. PROTECTION

   8.1 INTRODUCTION

   8.2 DEFINITION OF PROTECTION SYSTEM RELIABILITY

   8.3 MAXIMISING GRID PROTECTION SYSTEM RELIABILITY

   8.4 ASPECTS OF A GRID PROTECTION TO SUPPORT GRID RELIABILITY AND AVAILABILITY

   8.5 AC PROTECTION SYSTEMS THAT COULD BE APPLIED/ADAPTED TO THE HVDC GRID

9. CONVERTER STATION OPERATION

   9.1 DC GRID CONTROLLER

   9.2 CONVERTER STATION CONTROLLER

   9.3 OPERATIONAL PLANNING

   9.4 AC/DC INTERACTION

   9.5 DC SWITCHING

   9.6 STABILITY CONTROLS

   9.7 DC GRID GROUNDING

   9.8 AUXILIARY POWER SUPPLY AND BLACK START

10. SPARES AND MAINTENANCE

   10.1 INTRODUCTION

   10.2 GENERAL MAINTENANCE AND SPARES STRATEGY

   10.3 SPECIFIC COMPONENT CONSIDERATIONS

   10.4 LIFECYCLE CONSIDERATIONS

   10.5 TRAINING AND DOCUMENTATION

   10.6 SUMMARY

11. MODEL AVAILABILITY STUDIES

   11.1 INTRODUCTION

   11.2 DC GRID ANALYSED

   11.3 RELIABILITY MODELING

   11.4 RELIABILITY ANALYSIS OF DC GRIDS

   11.5 SUMMARY

12. CONCLUSIONS

13. REFERENCES