OPTIMAL%20CONTRIBUTION%20OF%20DISTRIBUTED%20GENERATION

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OPTIMAL CONTRIBUTION OF DISTRIBUTED GENERATION

• IN MEDIUM VOLTAGE GRIDS
• DURING A FAULT,
• NOW AND IN THE FUTURE

Alliander S. van Loon, F. Volberda, F.
Provoost Enexis J. Morren Session 3 0092
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Introduction

• Distribution System Operators (DSO) within The
  Netherlands

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Introduction

• Increasing DG in MV-grids
• Connected by step-up transformer
• Direct connection

MV
LV
Gen
Gen
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Introduction

• Conflicts
• Selective tripping ? time grading (gt300ms)
• Voltage dips ? unwanted disconnection of DG
• No support grid codes (MV and lt 5 MVA)
• E.ON grid code FRTHV-grids, lt150 ms

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Introduction

• Is there a need for smarter protection schemes in
  MV-grids?

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Present protection scheme

• A voltage dip / frequency change ? disconnect DG
• More DG ? more power lost
• Over-/under- voltage ? damage to equipment

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Present protection scheme
150/10 kV substation

• Example
• 2 phase fault
• DG protection
• DSO protection

21
27
27
27
G1
G2
G3
Undervoltage
27
Distance relay
21
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Present protection scheme
DG disconnect
Fault

• Example
• Duration fault 1060 ms

Network protection
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Present protection scheme

• Example
• Power swing HV/MV transformer

12 MW
-6 MW
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Expectations DSO

• Stability
• Reliability
• Fully selective protection scheme
• Safety of personnel
• Security of supply
• Prevent damage to equipment
• Worst case
• Under- and/or over-voltage

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Smarter grids

• A smart grid needs a smart protection

Change grid Influence grid Cost
Scenario 1 Low Low Low
Scenario 2 High Medium High
Scenario 3 Medium Medium Medium
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Conclusions

• Increasing DG ? new protection scheme
• Fast disconnection of faults
• Shorter voltage dips
• Prepare the MV-grid now for future grids
• Change protection of dedicated feeders
• Allow contribution of large DG

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A smart grid needs a smart protection!
E M C2
Energy Measurement Control Communication
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Scenario 1
DG must stay connected
DG must disconnect
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Scenario 1
HV/MV substation
Undervoltage
27
27
27
27
G1
G2
G3
Non-dedicated feeders
Dedicated feeders
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Scenario 2
DG must stay connected
DG must disconnect
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Scenario 2
HV/MV substation
87
Undervoltage
27
27
27
27
Differential
87
G1
G2
G3
LOM
LOM
LOM
Loss of mains
LOM
Bi-directional
Non-dedicated feeders
Dedicated feeders
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Scenario 3
HV/MV substation
87
Undervoltage
27
27
27
27
Differential
87
G1
G2
G3
LOM
LOM
Loss of mains
LOM
Bi-directional
Non-dedicated feeders
Dedicated feeders
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