Effects of Non-uniform Pollution on the AC Flashover Performance of Suspension Insulators

Abstract

The non-uniform distribution of contamination on insulator surface has appreciable effects on flashover voltage, and corresponding researches are valuable for the better selection of outdoor insulation. In this paper, two typical types of porcelain and glass insulators which are widely used in ac lines were taken as the research subjects, and their corrections of AC flashover voltage under nonuniform pollution were studied. Besides, their flashover characteristics under different ratio (T/B) of top to bottom surface salt deposit density (SDD) were investigated, including the analysis of flashover voltage, surface pollution layer conductivity and critical leakage current. Test results gave the modified formulas for predicting flashover voltage of the two samples, which can be directly applied in the transmission line design. Also, the analysis delivered that, the basic reason why the flashover voltage increases with the decrease of T/B, is due to the decrease of equivalent surface conductivity of the whole surface and the decrease of critical leakage current. This research will be of certain value in providing references for outdoor insulation selection, as well as in proposing more information for revealing pollution flashover mechanism.