HVDC Circuit Breakers
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Technologies > HVDC compared to AC transmission
High Voltage Direct Current has been used for decades for transmission of power over long distances. The fact that capacitance in cables doesn't cause losses means that it makes up for drawbacks in the conversion process from AC, since HVDC conversion stations are more expensive than the AC ones. On the other hand, long distance HVDC lines cost in general less than the respective AC lines. As we can see from figure 1, above a certain distance HVDC transmission will have lower costs.
Figure 1: HVDC-HVAC cost comparison [http://www.trec-uk.org.uk/ reports/ larruskain_HVAC_to_HVDC.pdf]
There are many HVDC point to point links in use today, often over international
borders for trade of energy resources between countries. One natural progression
for this industry would be the implementation of a HVDC grid linking multiple AC
grids and transferring power in any direction between these points. A grid such
as this promises huge savings on conversion facilities and the cost of lines. It
would also be beneficial for the economic transmission of energy from areas where
it is cheap, abundant and/or clean to regions where generation is more limited.
Although AC/DC conversion technologies have improved greatly recently, in order to operate a practical HVDC grid, circuit breaker technology still doesn't exist to satisfactorily isolate a single branch line of the grid, meaning that the whole grid would have to be shut down in the event of a malfunction. This means that development of a successful HVDC circuit breaker would be a significant breakthrough for the future of power transmission.