With the continuous consumption of fossil energy， increasingly severe climate change and worsening environment pollution， the human being has put forward higher requirements for reliable， environmentally friendly and sustainable energy， bringing global energy interconnection into being. The core of sustainable development is clean development. UHV transmission technology is critical for the reliable and efficient delivery of clean energy， and it is of great significance to promote its global allocation.
　　After a century of development， the transmission technology of power system has made great progress in terms of voltage level， transmission capacity and distance. As for UHV AC power transmission technology， UHV DC transmission technology， flexible AC and VSC DC transmission technology， their respective voltage and transmission capacity have exceeded 1000 kV/5000 MVA， ：tll00 kV/12000 MW and +800 kV/5000 MW. Flexible AC transmission technology has started to be applied in 1000 kV projects. The development of UHV power transmission technology provides a strong support for the world's large-scale energy development and long-distance transmission， facilitates a large-scale optimization of energy allocation， and greatly improves the reliability and economic efficiency of power supply in human society.