ABSTRACT
High-voltage direct current (HVDC) energy transmission was developed in the late 1920s, and the Ÿrst commercial HVDC submarine cable started operation in 1954. is system used mercury-arc valves, which required constant maintenance and rebuilding. With the development of the high-voltage and high-power thyristors in the early 1970s, thyristor valves gradually replaced the mercury-arc valves. yristor valves increased system reliability signiŸcantly with reduced maintenance. is resulted in fast development of the technology and the building of several new HVDC systems worldwide. Today, HVDC is a mature, well-developed technology.
