HIGH VOLTAGE DIRECT CURRENT TRANSMISSION

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HIGH VOLTAGE DIRECT
CURRENT TRANSMISSION

• G.MAHESH KUMAR
• B.ANUSHA

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THE ENTIRE POWER SYSTEM IS DIVIDED IN TOTHREE
MAJOR PARTS

• Generation system
• Transmission system
• Distribution system

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DISADVANTAGES OF A.C. TRANSMISSION

• In order to provide adequate insulation and to
  avoid corona loss spacing between line conductors
  is to be kept more in over head transmission
  lines.
• amount of conductor material required is more
  over D.C. two wire system
• In long transmission lines capacitance effect
  comes into picture .due to capacitance charging
  current flows in the line even though the line is
  open circuited and produces continuous power loss.

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• Construction of A.C. transmission lines is not
  easy over D.C. lines.
• Alternators are to be synchronized before putting
  them into parallel.
• The variations in the speeds of alternators are
  to be controlled with in very low limits to keep
  constancy of frequency.

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ADVANTAGES OF D.C. TRANSMISSION

• It requires only two conductors for transmission
• No inductance, capacitance and phase
  displacement.
• There is no skin effect and hence full
  cross-section of the conductor is utilized.
• Less insulation is required.

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• Underground cables can be used because of less
  potential stress and negligible dielectric loss.
• For a given load and sending end voltage, voltage
  regulation is better for D.C. transmission line.
• No stabilizer is required.

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• WHY HVDC?
• WHAT IS HVDC TRANSMISSION?
• HOW HVDC TRANSMISSION IS DONE?

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WHY HVDC?

• Energy demand doubles for every 10-12 years.
• Interconnection of technical and economic
  advantages

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HVDC solutions have become more desirable for the
following reasons

• Environmental advantages
• Economical (cheapest solution)
• Asynchronous interconnections
• Power flow control
• Added benefits to the transmission (stability,
  power quality etc.)

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HOW HVDC IS DONE???

• The following steps are involved
• stepping up the generated A.C.
• Converting the A.C. to D.C.
• Transmission through D.C.
• Converting the D.C. to A.C. at the load side
• The main components of HVDC transmission are the
  converter stations

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The main components of a converter station are

• Thyristor valves
• VSC valves.
• Transformers
• AC Filters and Capacitor Banks
• DC filters

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The HVDC Converter station
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Cost Structure of HVDC Transmission
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Advantages of HVDC Systems

• The need for ROW is much smaller for HVDC than
  for HVAC for the same transmitted power.
• The environmental impact is smaller with HVDC.
• Direction of power flow can be changed very
  quickly.
• No limits in transmitted distance.
• HVDC can carry more power for a given size of
  conductor.
• Very fast control of power flow.

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Limitations of HVDC

• Terminal equipment like valves have little
  overload capacity.
• Harmonics are produced both on A.C. and D.C.
  sides.
• These harmonics cause interference with audio
  frequency signals.
• lack of HVDC circuit breakers hampers
  multi-terminal or network operation
• Filters are required at both ends

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WHEN HVDC IS PREFERED?
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Modern trends in D.C. Transmission

• Power semiconductors and valves.
• Converter control.
• D.C. breakers.
• Conversion of existing A.C. lines.
• Operation with weak A.C. systems.

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CONCLUSION

• HVDC systems remain the best economical and
  environmentally friendly option for the above
  conventional applications.
• It is quite conceivable that with changed
  circumstances in the electricity industry, the
  technological developments, and environmental
  considerations, HVDC would be the preferred
  alternative in many more transmission projects.

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• Thank you !!
• ?
• 
  presented by
• 
  
• 
  ANUSHA BURA
• 
  MAHESH KUMAR.G