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Despite alternating current being the dominant mode for electric power transmission, in a number of applications, the advantages of HVDC makes it the preferred option over AC transmission.
Examples include:
· Undersea cables where high capacitance causes additional AC losses (e.g., the 250-km Baltic Cable between Sweden and Germany).
· Endpoint-to-endpoint long-haul bulk powertransmission without intermediate taps, for example, in remote areas.
· Increasing the capacity of an existing power grid in situations where additional wires are difficult or expensive to install.
· Allowing power transmission between unsynchronized AC distribution systems.
· Reducing the profile of wiring and pylons for a given power transmission capacity, as HVDC can carry more power per conductor of a given size.
· Connecting a remote generating plant to the distribution grid; for example, the Nelson River Bipole line in Canada (IEEE 2005).
· Stabilizing a predominantly AC power grid without increasing the maximum prospective short-circuit current.
· Reducing corona losses (due to highervoltage peaks) compared to HVAC transmission lines of similar power.
· Reducing line cost, since HVDC transmission requires fewer conductors; for example, two for a typical bipolar HVDC line compared to three for three-phase HVAC.
HVDC transmission is particularly advantageous in undersea power transmission. Long undersea AC cables have a high capacitance.
