DC High Voltage Transmission Lines
Construction began in early 2007 on the world's first 800kV DC power
transmission lines. They are located in China. Currently, there are
HVDC transmission lines in Italy (200kV), the US (called the Pacific
DC Intertie, from the Pacific Northwest to Los Angeles), Brazil
(600kV) and elsewhere.
DC transmission lines have lower losses than comparable AC
lines. Also, the transmission lines themselves cost less than for
AC. Thus, they are preferable in cases where power generating
stations are far from population centers. Such conditions exist for
large hydroelectric plants in Brazil, India and China.
HVDC converter stations use thyristors to convert the generated power
from AC to DC, and vice versa.