Thursday, 16 January 2020

High Voltage DC Transmission System- Advantages, Disadvantages, Applications

High Voltage DC Transmission System

Layout of HVDC Transmission System
Layout of HVDC Transmission System 

Advantages of HVDC Transmission

1) Cheaper in cost
2) Line losses are less.
3) No skin effect due to absence of inductance.
4) Less corona losses.
5) Greater reliability.
6) Greater transmission efficiency. HVDC system requires only one or two conductors and because of absence of skin effect the effect of resist of conductor is less. So due to lower losses it has greater efficiency.
7) Greater voltage regulation. Due to absence of inductive reactance  voltage drop voltage drop in the line is less. Hence voltage regulation is greater.
8) Absence of charging current.
9) There is no limitations of line loading.
10) Lower short circuit current.
11)Independent control is possible.
12) Rapid change of energy flow can be achieved.

Disadvantages of HVDC Transmission

1) Power can not be generated in DC form.
2) Voltage can not be step up or step down.
3) The design of switches or circuit breakers is difficult in DC circuit.
4) The converter station can produce harmonics which affect the stability of system.
5) The cost of high voltage DC system is more below 75km of length.

Applications of High Voltage Transmission System

Long distance high power transmission.

High voltage transmission system is preferred that is above 750km or 500 km or more than 500km.

Underground or under water transmission-
Due to the absence of charging current and lower dielectric losses HVDC cable can be used for underground or under water transmission.

Back to Back connection-   
For back to back connection of AC or DC the generally high voltage transmission system is used.

For conversion of frequency for inter grid connection.

Multi terminal HVDC system is used for inter connecting 3 or more than 3 phase supply. 



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