1000 kV EHV transmission lines need to adopt multiple split conductors, such as 8, 12 and 16, and the cross section of each split conductor is mostly over 600 square millimeters, which can reduce the loss caused by corona discharge and the adverse effects such as radio interference, TV interference and audible noise interference. The height of the tower is about 40 ~ 50 meters. The tower of double-circuit parallel transmission line is 90 ~ 97 meters high. Many countries are committed to developing new tower structures to reduce the size of towers and the cost of lines. The former Soviet Union, the United States, Italy, Japan and other countries have begun to plan and construct 1000 kV UHV transmission lines, and the transmission capacity of single-circuit lines is generally 600 ~ 1000 kW. For example, the former Soviet Union is stepping up the construction of large energy bases such as Ekibasitou, Kansk-Achinsk and Tyumen Oilfield. It already has a thermal power plant with an installed capacity of 6.4 million kilowatts, and plans to build a giant hydropower station with an installed capacity of 20 million kilowatts and a nuclear power plant with a large installed capacity. These energy bases are about 1000 ~ 2500 kilometers away from the power load center, and need to use 1 150 kV, 750 kV DC, or even 1800 ~ 2000 kV for transmission. The former Soviet Union has built a 270km long 1 150KV transmission line, which is also used as an industrial test line. The trial operation of 1986 began, and the construction of 1 150KV transmission line will continue, with the line length of 1236 km. By the end of the 20th century, 1638 will be formed. It is estimated that by the end of the 20th century, 60% of thermal power plants will be built in the east of Cascade Mountains, and about 32 million kilowatts of electricity will need to pass through the mountains to send electricity to the western load center. It is planned to adopt 1 100 kV voltage level for transmission. Each line is about 300 kilometers long and the transmission capacity is about100000 kilowatts. Italy plans to use 1000 kV high-voltage lines to transmit electricity from thermal power plants and nuclear power plant bases along the Mediterranean coast to industrial areas such as Milan in the north. Japan chose 1000 kV double-circuit parallel UHV transmission line to transmit the power of Xiabei giant nuclear power plant to Tokyo, with a line length of 600 kilometers and a transmission capacity of100000 kW. These UHV transmission lines are scheduled to be completed in the 1990s.

China has a vast territory, and two-thirds of the exploitable hydropower resources are distributed in the northwest and southwest regions. Most coal resources are located in the northwest and the west of North China, and the load center is mainly concentrated in the eastern coastal areas. Due to the uneven distribution of power resources and load centers, with the development of power system, the research and development of UHV transmission will also be put on the agenda.