Study on process of DC pollution flashover of porcelain insulators of parallel double-strings form at high altitude

Artificial contamination tests of DC porcelain insulator, XZP1-300 were carried out for different forms of strings at high altitude area, Kunming China. The insulator studied were single string, parallel double-strings and different distances between adjacent strings. According to video recording of the flashover process, how the factors (distance between adjacent strings and equivalent salt deposit density (ESDD), etc.) influenced the development of the electric arc was studied. It was found that: the relationship between flashover voltage of insulator (string) and ESDD was a negative power function in the condition of non-soluble deposit density (NSDD) remained constant; the independence of arc developing and degree of arc deviating had some regular pattern because of diffusion of thermal ionization gas. These results would be useful in analysis on flashover characteristics of insulator strings in large-scale domain, and can also be treated as basis for outdoor insulator selection of transmission lines.