The term “extra high voltage grid” refers to a 1000 kV AC or ±800 kV DC grid. The transmission voltage is generally divided into HV, UHV and UHV. Internationally, high voltage (HV) usually refers to voltages from 35 to 220 kV; ultra-high voltage ( UHV) usually refers to voltages of 330 kV and above and below 1000 kV; extra-high voltage (UHV) refers to voltages of 1000 kV and above.
High voltage direct current (HVDC) usually refers to direct current transmission voltages of 1 600 kV and below, and voltages above ±800 kV are called ultra-high voltage direct current transmission (UHVDC).
For the vast majority of China’s current power grids, high-voltage power grids refer to 110 kV and 220 kV grids; ultra-high voltage grids refer to 330 kV, 500 kV and 750 kV grids. UHV transmission refers to the 1000 kV AC voltage and ±800 kV DC voltage transmission projects and technologies that are being developed.
The UHV grid refers to a modern, stratified, zoned and clearly structured grid with a 1000 kV transmission grid as the backbone, an ultra-high voltage transmission grid and a high-voltage transmission grid as well as an ultra-high voltage DC transmission high-voltage DC transmission and distribution grid.
The basic condition for the formation and development of the UHV grid is the continuous growth of electricity load, as well as the construction and development of large-capacity and extra-large-capacity power plants, whose outstanding feature is the large-capacity and long-distance transmission of electricity.
At present, China’s long-distance transmission and the rest of the world, mainly with 500 kV AC grid, only in Russia, Japan, Italy have a small number of 1000 kV AC lines, and are operating at reduced voltage.
