Since the implementation of high-voltage DC transmission in the 1950s, high-voltage and ultra-high-voltage DC transmission technology has made significant progress over the course of more than 50 years of development. Two ±600 kV ultra-high-voltage DC transmission projects in Brazil have been operational for over 20 years, while China’s ±500 kV ultra-high-voltage DC transmission projects have been constructed and operating for nearly 20 years. These projects have contributed to a deeper understanding and maturity of DC transmission technology, providing a solid technical foundation for the manufacturing of equipment for ±800 kV UHV DC transmission projects.
In the 1970s and 1980s, the former Soviet Union carried out ±750 kV UHV DC transmission projects, with factory testing of its main equipment and the construction of over 1,000 km of transmission lines. International industry and academia have continuously conducted research on ±600 kV UHV DC transmission technology, with a particular focus on the ±800 kV voltage level. Concurrently, research and development efforts have been devoted to the 1000 kV AC transmission technology. The former Soviet Union and Japan have successfully implemented AC UHV projects, accumulating over 30 years of experience in the operation of 750 kV AC transmission systems. This experience has led to the development and maturity of key equipment design and manufacturing technologies for AC transformers, lightning arresters, and switches. Although not directly transferable, this knowledge and experience can be effectively applied in the development process of ±800 kV UHV DC equipment.
Numerous studies and tests have indicated that the necessary conditions for the engineering application of ±800 kV UHV DC transmission technology have been met, and all the required equipment for ±800 kV UHV DC transmission can be manufactured.