DC cables can transmit electricity with large capacity over long distances, and are mainly used in submarine cables and underground cables that supply power to large cities. In the past 20 years, the application of DC transmission has been greatly developed. DC cables have been used in many projects. The highest voltage is ±500kV, the transmission capacity is 2800MW, and the longest line is 250km.
In the recent feasibility study report of the Guangdong and Hainan interconnection projects in my country, it is recommended to lay a submarine cable in the Qiongzhou Strait. In the initial stage, 500kV AC transmission should be used. The length of the submarine cable is about 30km, and the maximum depth of the submarine is 80m. The line is 280km and the transmission capacity is 600MW; the long-term use of ±500kV DC transmission, the transmission capacity is 1200MW.
