FAULT CLEARANCE FOR ZHOUSHAN HVDC SYSTEM

Ting An (PhD CEng FIET)

国网智能电网研究院Smart Grid Research Institute, SGCC

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FAULT CLEARANCE OPTIONS2

3 CASE STUDY

4 CONCLUSIONS

TABLE OF CONTENTS

INTRODUCTION1

INTRODUCTION

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A DC network with a plurality of converters

Partially meshed Partially radial an overlaid network 5

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DC Grid Definition

CIGRE B4.52 WG – HVDC Grid Feasibility StudyCIGRE B4.52 WG – HVDC Grid Feasibility Study

INTRODUCTION

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INTRODUCTION

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ABB - Hybrid DC Breaker *ABB - Hybrid DC Breaker *

* ABB published paper BOLOGNA 2011

INTRODUCTION

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SGRI - H-bridge Cascaded DC CB *SGRI - H-bridge Cascaded DC CB *

Transfer Branch

Arrester Banks

Main Branch

UFD

Voltage 200kV Nominal current 1.2kAProspective fault rise 3.6kA/ms Nominal loss <0.01%Limited current 18kA Time to interrupt 3ms

Three branches - UFD, H-bridge modular & SAsBidirectional fault current limitation and interruption

UFD opens at current zero (2ms)Low stress and loss

Breaker reclose function

* Presented by SGRI during CIGRE 2014in Paris

FAULT CLEARANCE OPTIONS

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Three possible solutions to clear DC faultsSolution 1 - DC Circuit Breakers (DC CBs) FC time < 5ms Minimal disturbance Half bridge converters (HBCs) STATCOM functionalitySolution 2 - Blocking Converters (BC)+DC Disconnector (DCD) FC time > 30ms Disturbance to the whole grid STATCOM functionalitySolution 3 - Half Bridge (HBCs) + ACCBs+ DCD FC time > 70ms Disturbance to the whole grid No STATCOM functionality

FAULT CLEARANCE OPTIONS

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Option DC CBs BC + DC SWHBC + AC

CBs + DC SW

Fault clearance

time< 5ms >30ms >70ms

STATCOM functionality Yes Yes No

Losses Medium High Low

Cost Medium High* Low

Technical & Economic Comparison

CASE STUDY

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Zhoushan400MW

Daishan300MW

Sijiao100MW

Yangshan100MW

Qushan100MW

Zhoushan400MW

Daishan300MW

Qushan100MW

Yangshan100MW

Sijiao100MW

46km

17km

39km

32.3km

46km 17km39km

32.3km

In service 4th July 2014Rated capacity 400/300/100/100/100 MW

Rated DC voltage ±200 kV

• Power supply to islands• 5-terminal radial network• No redundancy• AC CBs to clear DC side faults

Current status

• Transform to HVDC grid• Reduce line losses• Provide redundancy for Zhoushan• DC side fault clearance

Upgrade plan

CASE STUDY

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• 3 protection zones

• 4 DC CBs in tie-lines required

• Option 4: BC

• Option 5: HBC

Zhoushan

Daishan

SijiaoYangshan

QushanDC

breaker

• Op 1: HBCs, no DC CBs

• Op 2: BCs, no DC CBs

• Op 3: HBCs, two DC CBs for each DC

Options 1, 2 & 3 Options 4 & 5

Zhoushan

Daishan

SijiaoYangshan

QushanDC

breaker

CASE STUDY

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Option Protection zones

No. of DC CBs Converters Cost ratio STATCOM

functionality

1 1 0 HBC: 5 1.0 No

2 1 0 BC: 5 1.40 Yes

3 1 10 (x2) HBC: 5 1.45 Yes

4 3 4 (x2) BC: 5 1.54 Yes

5 3 4 (x2) HBC: 5 1.18 No

Technical & Economic Comparison

CONCLUSIONS

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• Both technologies of DC circuit breakers and the blocking converters can be used to clear DC side faults

• Using DC circuit breakers is the best option technically but may not be the preferred option economically

• Using blocking converters needs DC switchgear to isolate faulted section which increase the fault clearance time

• Dividing DC grid into multiple zones can reduce the need of number of DC circuit breakers and affected area of the grid

• Dividing DC grid into multiple zones may be the preferred option technically and economically

Paris Palais des Congrès

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