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

DC links are used to connect two different grids with different frequencies. To connect the grid three main types of DC links are used in HVDC Transmission.

The type of dc-links are classified into 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

See also.. 

2) How can test electrical relay | method of relay testing  

Mono polar links have one conductor and ground as a return part. Usually, the 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

A bipolar dc link has two conductors, one is a positive conductor and the other is negative as a return.

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

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

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

If the fault occurs on one of the conductors it can operate with other conductors using the ground as a return path.

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

homo polar dc link

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

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