about high voltage direct current transmission

1. HVDC Transmission
INTRODUCTION
•Now a days large blocks of power are
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needed to be transmitted.
•There arises some technical problems
of transmitting power to such a long
distance using ac.
•In the view of the draw backs of ac the
HVDC transmission has come into
picture.
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2. HVDC Transmission
•The first dc link was set up in 1954 in
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between Swedish main land and the island of
Gotland.
•The use of an HVDC link in an ac system
requires converter stations at each end of the
line.
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3. HVDC Transmission
ADVANTAGES
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Advantages of dc
transmission
Technical Economic
Advantages Advantages
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4. HVDC Transmission
Technical Advantages
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• 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.
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5. HVDC Transmission
•No limits in transmitted distance
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•Direction of power flow can be changed
very quickly
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6. HVDC Transmission
Economic advantages
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•DC lines and cables are cheaper than ac lines or
cables.
•The towers of the dc lines are narrower, simpler
and cheaper compared to the towers of the ac
lines.
•Line losses in a dc line are lower than the losses
in an ac lines.
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7. HVDC Transmission
Technical Seminar Presentation
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8. HVDC Transmission
Comparison between the prices of AC & DC
Transmission
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9. HVDC Transmission
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Types of DC links
Monopolar Homopolar
Bipolar
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10. HVDC Transmission
Monopolar link
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11. HVDC Transmission
Bipolar Link
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12. HVDC Transmission
Incorporating HVDC into AC systems
• Two terminal DC link point to point
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transmission.
• Back to Back DC link
• DC line in Parallel with AC link.
• Multi-Terminal DC link.
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13. HVDC Transmission
CONVERTER STATION
EQUIPMENT
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• Thyristor valves
• Converter Transformer
• DC Reactor
• Harmonics Filtering Equipment
• Control Equipment
• Reactive power compensation
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14. HVDC Transmission
GROUND RETURN
• Most dc transmission lines use ground return for reasons
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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.
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15. HVDC Transmission
PROBLEMS
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• 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.
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16. HVDC Transmission
EARTH ELECTRODE
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• 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.
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17. HVDC Transmission
RECENT ADVANCES
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• GTO’s have come into use.
• Use of active ac and dc filters.
• Advanced fully digital control systems using
optical fibers.
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18. HVDC Transmission
CONCLUSION
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• 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%.
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19. HVDC Transmission
Technical Seminar Presentation
Thank you!
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