Structural Performance of Porcelain and Polymer Post Insulators in High Voltage Electrical Switches

Post insulators are key components of most electrical substation equipment, but they are vulnerable during earthquakes. To better understand the seismic response of post insulators, this paper presents an experimental program that involved two types of 230-kV disconnect switches post insulators. Several solid ceramic (porcelain) and hollow-core composite (polymer) insulators were tested. The experiments consisted of static loading and dynamic shaking table tests. The static cyclic-loading, resonance-search, and pull tests - including material characterization - allowed the determination of the insulators lateral stiffness, fundamental frequency, and mode of failure. Moreover, failure loads and corresponding displacements and strains were determined. Additionally, the shaking table tests involved substructured dynamic tests of single porcelain and polymer post insulators. The main objective of the static and dynamic tests was to compare the behavior of porcelain and polymer post insulators under lateral loading. It was found that while the polymer insulators have much lighter mass than the porcelain ones, and in turn are more favorable from a seismic performance perspective; they have a comparable structural response to that of the porcelain insulators.