some advantages and disadvantages of HVDC system

Advantages:-

1. 1. Cost of transmission is less, since only two conductors are used for transmission.
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3. 2. There is no reactive power. So transmission losses are reduced.
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5. 3. Due to high voltage transmission, for the same power current is less. So I²R loss is very less.
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7. 4. 4.Becau of DC transmission, there is no skin effect. So thin conductors can be used. In case of HVAC transmission, the thick conductors must be used to eliminate skin effect.
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9. 5.Two AC systems having different frequencies can be interconnected using HVDC transmission lines. This is not possible in HVAC transmission system.
10. Installation cost is less. Due to only two conductors and smaller towers required for HVDC.
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12. 6. HVDC uses electronic converters. So Protections, fault clearance can be implemented faster than HVAC. Therefore DC transmission system have improved transient stability.
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14. 7. In case of faults, power levels on HVDC system can be controlled electronically (i.e., very fast).
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16. 8. Since HVDC requires no charging current and the reactive power, it is preferred in power transmission through cables.
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18. 9. Unlike HVDC transmission system, HVAC induces body currents in the vicinity of the conductors.
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20. 10.HVDC transmission does not have any dielectric loss heating problems in the insulation of conductors.
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22. 11. H has minimum audible noise as well as minimum radio, TV interference.
23. Due to bipolar transmission the voltage levels are balanced with respect to an earth.
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25. 12 cables used for transmission are cheaper than AC cables.
26. In HVDC, line charging and electric resonance do not present which leads to high-efficiency
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28. 13. biggest advantage is the Bulk Power flow over a long distance. Our project is designed to transmit 6000 MW of Power over 1700 km.
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30. 14.Less Right of Way (ROW) is required i.e. HVAC having 3 phases need a larger tower as compared to HVDC having only 2 conductor
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32. 15.Lesser Line Losses are there. As the transmission voltage in HVDC is very high ( 800 kV in our case ) so for required power level the Load current will be Low & hence the I² R losses will be Low.
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34. 16.Power Flow Control is possible. We can control the magnitude of Power that is to be transmitted, Also we can change/reverse the direction of Power flow by Running Rectifier as Inverter & vice-versa
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36. 18.It act as a Link between two different Power system running at two different frequencies.

Disadvantages:-

1. It has costlier equipment such as thyristors, converter transformers etc.
2. More Research & Development is involved in HVDC System.
3. It’s working is dependent on the various auxiliaries such as Valve Cooling system ( used to cool the Thyristors of Rectifier & Inverter ) , AC FIlters (used to supress the Harmonics generated during AC to DC & DC to AC Conversion).
4. Reactive Power Support is required. Although this criteria is fulfilled by the AC Harmonic filters ( made up of R-L-C).