UHV grid refers to 1000kV AC or 800kV DC grid. Transmission voltage is generally divided into high voltage, ultra-high voltage and ultra-high voltage. Internationally, high voltage (HV) usually refers to the voltage of 35~220kV; extra high voltage (EHV) usually refers to the voltage of 330kV and above and below 1000kV; extra high voltage (UHV) refers to the voltage of 1000kV and above. High voltage direct current (HVDC) usually refers to the direct current transmission voltage of 600kV and below, and the voltage above 800kV is called ultra high voltage direct current transmission (UHVDC).
For the vast majority of power grids in my country, high-voltage power grids refer to 110kV and 220kV power grids; ultra-high-voltage power grids refer to 330kV, 500kV and 750kV power grids. UHV transmission refers to the 1000kV AC voltage and 800kV DC voltage transmission projects and technologies under development. UHV power grid refers to a modern large power grid with 1000kV transmission network as the backbone network, ultra-high voltage transmission network and high-voltage transmission network, as well as UHV DC transmission and HVDC transmission and distribution network.
The basic conditions for the formation and development of UHV power grids are the continuous growth of electricity load, as well as the construction and development of large-capacity and extra-large-capacity power plants, whose prominent features are large-capacity and long-distance power transmission. At present, China's long-distance power transmission, like other countries in the world, mainly uses 500 kV AC power grids. Only in Russia, Japan, and Italy there are a small number of 1,000 kV AC lines, and they all operate at a reduced voltage.