Natural Contamination Research of Insulators in AC-DC Multi-Loop Transmission Lines with the Same Tower

The insulation of the multi-loop AC-DC transmission lines with the same tower has been more concerned as the erect of which meets the needs of resource- saving society. The paper analyzed the contamination characteristics and polluted external insulation design of the multi-loop AC-DC transmission lines based on dirt retention data, which obtained from natural pollution deposit contamination tests, and dirt retention characteristics calculated by simulation of electric field calculation. The result shows that there exists differences of the dirt retention characteristic between DC insulator and AC insulator, and the former`s pollution grade is more serious. The surface accumulated pollution of surrounded insulators are greatly affected when they are close to HVDC field. The degree of the dirt retention is determined by the distance between the AC insulator and the DC field in certain ranges.