Study on the external insulation performance of ±800 kV DC transmission lines at high altitudes

High altitudes and heavy pollution are special technical problems faced by UHV DC transmission line in China. Much research work of external insulation performance for ±800 kV DC Transmission Lines were carried out at National Engineering Laboratory for Ultra High Voltage (UHV) Engineering Technology (Kunming). For composite insulators, the shed design parameters have great influence on the flashover voltages. It was found that, with the same insulation distance, the flashover voltage had optimized values at a particular value of the radial extent of the shed and of the between-repeat distance. And the suspension patterns also play an important role in the flashover performance for composite insulators. The flashover voltage of the full scale post insulator decreased with the increasing of the SDD. The switching impulse strength of air gap clearance at a full scale conductor-to-tower model of Yunnan-Guangdong ± 800 kV UHVDC project is also studied.