1
Compact Systems
for future HVDC Applications
Dr. Hermann Koch
Siemens AG
Erlangen (Germany)
2
Applications: Main drivers today
• Space reduction
• Interconnection of
Standardized HVDC
Offshore Transmission
Installations
• German
“Energiewende“
• Impact
• Increasing of
transmission capacities
• Efficient transmission
over long distances
• Increasing the grid
stability with new
generation structure
3
Solutions
• Point-to Point connections for strengthening of grid
and transmission of RES
• Onshore applications in a Hybrid Transmission
System
(OHL, underground Transmission)
• Offshore / Onshore Multiterminal HVDC Systems
• Overlay (Backbone) Grid incl. Onshore
and Offshore HVDC Systems
4
VSC full bridge
5
Towards a first
HVDC Systems in Germany
6
Operational stresses in gas
insulated systems
Why is it NOT possible to directly use existing AC systems for DC
voltage?
Stresses of insulators in
operation
Gas
Mechanical Stress
Current I
Gas
Chemical Stress
Thermal Stress
Gas
Impact on
Electric Stress
Grounded Encapsulation
DC insulating systems must withstand different electrical stress
compared to AC systems
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Physical Effects influencing electric
stress
Grounded Encapsulation
∆T
Ionization
Attachment
N
N
+
-
-
-
+
- -
-
-
+
-
+
+
Charge transport
and accumulation
+
+
Drift due to
electric field
+
-
N
-
Recombination
-
Field emission
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Transition from AC to DC electric
field
AC
1
0
Positive space charge
density in gas
Negative space charge
density in gas
DC
1
1
1
negative DC voltage
negative DC voltage
0
0
0
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HVDC basic investigations
Exemplary test setups
Artificial
protrusions
Dielectric limits
Temperature
gradient
Long-term testing
Charging phenomena
Surface effects
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Technical challenges for DC
insulators
• Development of insulator design allowing for control of
physical effects, particularly charging effects
• Development of suitable insulating material for DC gas
insulated systems
• Careful handling/drying of insulating parts and cleanliness
during assembly
• Definition of “equipment-specific” high voltage testing
procedures
• Approach: Application of capacitively graded
insulator based on Resin Impregnated Paper
technology
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Normalized electric field
Innovative RIP insulator design for
DCCS ±320 kV
DC field distribution
AC field distribution
Radius
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Simulation
Effect of field grading
Potential distribution
AC
DC
With field grading
High voltage conductor
High voltage conductor
Without field grading
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DC Compact Switchgear ±320kV
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Testing Strategy
• There are NO international agreed standards
for this kind of equipment.
• List of the possible dielectric tests:
–
–
–
–
DC withstand test at higher level
DC voltage with superimposed impulse voltage
Polarity reversal
Long(er) term test with specified voltage, current,
temperature and time profile
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Summary
In Addition to traditional Central Power Generation Large Scale
Renewable Energy Sources (RES) have to implemented into
Transmission Systems
•
New Transmission Solutions are needed
•
Standardization of HVDC Grids has started
in Europe
•
Compact Gas Insulated Systems for HVDC Applications
are feasible and ready for use
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Thank you very much
for your kind attention
Dr. Hermann Koch
Siemens AG
E T TI
D-91058 Erlangen, Germany
hermann.koch@siemens.com
Dr. Denis Imamovic
Siemens AG
E T TS PLM 4
D-91058 Erlangen, Germany
denis.imamovic@siemens.com