Experimental investigation on pollution flashover performance of multiple parallel suspension insulators

In order to meet the requirement of mechanical properties, multiple parallel suspension insulators will be used in UHV lines. In this paper, pollution flashover performance of multiple parallel insulators has been investigated based on artificial contamination tests under both AC and DC voltage. Four types of multiple parallel suspension mode are used in the tests, which has 2 strings, 3 strings, 4 strings and 6 strings, respectively. Experimental results indicated that multiple parallel insulators' pollution flashover voltage was lower than that of single string. Study showed that the result is not only affected by the multiple string leads to reduced pollution flashover probability, but also affected by the ionization of air. When the parallel number was less than 4, pollution flashover voltage of multiple parallel porcelain insulators was about 4% lower than that of a single string. If the parallel number was greater than or equal to 4, the value of flashover voltage was reduced by more than 10%. For composite insulators, the voltage drop of the multiple parallel insulators is not as obvious as that of porcelain insulators. In actual project application of the multiple parallel strings, the number of porcelain insulators and the insulation length of composite insulator was proposed to increase. The conclusion of this work can provide technical reference for the external insulation design and construction of UHV transmission lines.