Performance of Simple Insulator Shapes under Heavily Contaminated Conditions

Flashover voltage, scintillation current, resistance of a number of simple insulator geometries (rods, disks, and cones) have been measured under contaminated conditions. Results have been compared with porcelain suspension insulators. Tests were made in a high-density conducting mist and correlated with the resistivity of the contaminant solution. With such tests it seems possible to optimize insulator geometries. Flashover voltage of about twice that for conventional 6-in-long porcelain suspension insulators has been demonstrated for small-diameter cones on rods. While maintaining the same clearance distance1 for an insulator design, the effectiveness (per unit length of additional creepage distance) decreases with an increase in creepage distance. This is especially true in the vertical orientation. An increase in insulator diameter decreases effectiveness. Small-diameter rods perform well. Current measurements and photographs of scintillation and partial flashovers provide insight into insulator performance. Scintillation and arcing currents may lead to tracking and erosion of plastic insulators. Optimized design can reduce such currents by as much as 20 times.