JR Dennison

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This study investigates the effects of absorbed water introduced via exposure to atmospheric humidity on electrostatic breakdown field strength measurements of polymers. Conducting breakdown tests under sample conditions appropriate for different applications is essential. If the breakdown field strength is overestimated for an application, an insulator may be used inappropriately in high electric fields where they are more likely to break down. Comparisons are made between: sets of pristine samples, samples that underwent a thorough vacuum bake out to remove absorbed water, and samples subject to subsequent incremental prolonged atmospheric exposure. These investigated the effects of absorbed water and determined how quickly samples reverted to an unbaked state. Specifically, we compared: changes in measured electrostatic breakdown field strength, pre-breakdown arcing (DC partial discharge) rate, rates of flashover signatures, and images of the arc damage sites. The polymeric dielectric materials chosen were hydrophobic low density polyethylene (LDPE), intermediate polyether-etherketone (PEEK), and more hydrophilic Nylon 66.

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