The highest operational electricity transmission voltages are in the Ultra-High Voltage (UHV) class, defined as 1,000 kV (1 million volts) and above for alternating current (AC) and ±800 kV and above for direct current (DC).

• UHVDC: The world's highest voltage and longest transmission line is the ±1,100 kV Zhundong–South Anhui UHVDC line in China. It spans over 3,000 km, carrying power from Xinjiang to Anhui. This line is a testament to China's leadership in UHV technology.

• UHVAC: The highest operational AC voltage is 1,150 kV on the Ekibastuz–Kokshetau line in Kazakhstan, which was built during the Soviet era. However, China is a world leader in developing and operating modern 1,000 kV UHVAC lines, which form the backbone of its "West-to-East" power transmission initiative.