The power transmission and transformation project is a general term for transmission line construction and transformer installation engineering. The higher the voltage level of the power transmission and transformation project, the larger the power delivered and the farther the transmission distance. The power transmission and transformation project with a voltage exceeding 330,000 volts is called "Ultra High Voltage Transmission and Transformation". At present, the highest voltage level of UHV transmission and transformation lines put into operation in China is ±1100kV DC transmission line and 1000kV AC transmission line.