Different types of HVDC links-Monopolar link,Bipolar link,Homopolar link

DC links are used to connect two different grid with different frequency. To connect grid three main types of dc links are used in HVDC Transmission.

Type of dc-link are classified in 3 different categories. All types of DC links are explained below.

Direct current links classified as given below:

1) Mono polar dc link
2) Bipolar Dc link
3) Homo polar DC link

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Mono polar link have one conductor and ground as a return part. Usually, conductor has a negative polarity. Operating line with negative polarity conductor has advantages like it reduced corona loss in line and radio interference with a neighbor communication line.

Bipolar hvdc link

Bipolar dc link have two conductors, one is a positive conductor and other is negative as a return.

There are two converters of equal voltage and rating are connected in series at each end of dc transmission line.

In bipolar link, converter junction is grounded at one end or at both ends of transmission line,

If a junction is grounded at both ends it provides advantages of both lines can operate independently from each other.

And if the fault occurs on one of conductor it can operate with other conductor using the ground as a return path.

Due to this. reliability of bipolar dc link is equal to double circuit three phase ac line.

homo polar dc link

Homopolar link have one or more conductor mostly negative polarity for a reason of corona loss and radio interference, always operate with the ground as a return path.

Due to more conductor if the fault occurs on one of conductor, remaining healthy conductor carry load more than half of the load power. This is an advantage of Homo polar dc link, but it increases losses in power line due to overloading.