09-03-2011, 10:29 AM
PREPARED BY
SUNIT KUMAR SAHOO
SUNITS seminar.ppt (Size: 580.5 KB / Downloads: 601)
Why we need HVDC ?
ADVANTAGES
Technical Advantages
Reactive power requirement
System stability
Short Circuit Current
Independent Control of ac system
Fast change of energy flow
Lesser Corona Loss and Radio interference
Greater Reliability.
Economic advantages
Comparison between the prices of AC & DC Transmission
Monopolar link
Bipolar Link
Incorporating HVDC into AC systems
Two terminal DC link point to point transmission.
Back to Back DC link
DC line in Parallel with AC link.
Multi-Terminal DC link.
CONVERTER STATION EQUIPMENT
Thyristor valves
Converter Transformer
DC Reactor
Harmonics Filtering Equipment
Control Equipment
Reactive power compensation
GROUND RETURN
• Most dc transmission lines use ground return for reasons of economy and reliability
Ground return are used by the monopolar and the bipolar link for carrying the return current.
The ground path has a low resistance and, therefore low power loss as compared to a metallic conductor path provided the ground electrodes are properly designed.
The resistance of the ground path is independent of the depth of the line.
Typical tower structure and rights of way for alternative transmission system of 2000 MW capacity
PROBLEMS
The Design of grounding electrodes for low cost of installation and maintenance
Location and screening of electrodes so that ground currents cause negligible electrolytic corrosion of buried and immersed metallic structures.
EARTH ELECTRODE
HVDC system requires a properly designed earth electrode at each station.
The electrode is situated at a safe distance (5 to 30 km) from the station.
The earth electrode at one of the station acts as a anode and at the other end acts as a cathode.
RECENT ADVANCES
GTO’s have come into use.
Use of active ac and dc filters.
Advanced fully digital control systems using optical fibers.
CONCLUSION
Recent studies indicate that HVDC systems are very reliable.
The data collected from 31 utilities says that forced unavailability of energy due to the converter station is 1.62%
The scheduled unavailability of energy is about 5.39%.
SUNIT KUMAR SAHOO
SUNITS seminar.ppt (Size: 580.5 KB / Downloads: 601)
Why we need HVDC ?
ADVANTAGES
Technical Advantages
Reactive power requirement
System stability
Short Circuit Current
Independent Control of ac system
Fast change of energy flow
Lesser Corona Loss and Radio interference
Greater Reliability.
Economic advantages
Comparison between the prices of AC & DC Transmission
Monopolar link
Bipolar Link
Incorporating HVDC into AC systems
Two terminal DC link point to point transmission.
Back to Back DC link
DC line in Parallel with AC link.
Multi-Terminal DC link.
CONVERTER STATION EQUIPMENT
Thyristor valves
Converter Transformer
DC Reactor
Harmonics Filtering Equipment
Control Equipment
Reactive power compensation
GROUND RETURN
• Most dc transmission lines use ground return for reasons of economy and reliability
Ground return are used by the monopolar and the bipolar link for carrying the return current.
The ground path has a low resistance and, therefore low power loss as compared to a metallic conductor path provided the ground electrodes are properly designed.
The resistance of the ground path is independent of the depth of the line.
Typical tower structure and rights of way for alternative transmission system of 2000 MW capacity
PROBLEMS
The Design of grounding electrodes for low cost of installation and maintenance
Location and screening of electrodes so that ground currents cause negligible electrolytic corrosion of buried and immersed metallic structures.
EARTH ELECTRODE
HVDC system requires a properly designed earth electrode at each station.
The electrode is situated at a safe distance (5 to 30 km) from the station.
The earth electrode at one of the station acts as a anode and at the other end acts as a cathode.
RECENT ADVANCES
GTO’s have come into use.
Use of active ac and dc filters.
Advanced fully digital control systems using optical fibers.
CONCLUSION
Recent studies indicate that HVDC systems are very reliable.
The data collected from 31 utilities says that forced unavailability of energy due to the converter station is 1.62%
The scheduled unavailability of energy is about 5.39%.