Transmission lines is divided by DC (Direct Current) and AC (Alternate Current). High-voltage Direct Current, called HVDC, is a form of transmission method used for long distance power delivery because of its ability to transmit current over very long distances with fewer losses than AC. For comparison, a thousand-mile HVDC line carrying thousands of megawatts might lose 6 to 8 percent of its power, compared to 12 to 25 percent for a similar AC line. Another advantages of HVDC is that it would require fewer lines along a route, hence it is suitable for places with long distance from power plant to urban areas and for underwater underwater electricity transmission.
HVDC might be higher compare to HVAC in terms of cost of investment, however, for long distance, HVDC is widely used to eliminate the line power losses. Below is the comparison between HVDC and HVAC:
In 2013, the world’s longest transmission lines has been built with the length over 2,375 kilometer (1,550 miles) in southern Brazil in the Amazon area with a total capacity of 6,540 MW, this line had surpassing the Xiangjiaba-Shanghai system in China. It connect between two power plants: “Jirau” and “Santo Antonio” in the southeastern Brazil called Rio Madeira HVDC System.
By using back-to-back system, whereby the two convertor stations at Porto Velho in Rondônia and Araraquara in Sao Paulo, interconnected by two bipolar ±600 kV DC transmission lines with a capacity of 3150 MW each and 28 converter transformers.
“It is a good reference in remembrance of ‘War of Currents’ between Nikola Tesla and Thomas Edison“.
We'll keep you posted!