Over the past several years we studied some of the mechanisms forincipient insulation failure in polyethylene (PE). The previous studiesindicated that detectable changes with pure PE can occur on the surfaceof cavities (artificially produced), as observed by X-ray PhotoelectronSpectroscopy (XPS)-a technique that analyzes the first few atomic layersof a solid surface. These studies modeled conditions that could not bemeasured in routine utility-type test procedures. Production grade PE(usually cross-linked) has voids that range from below one μm tounder 1 mm. Also, this type of PE contains other species, e.g.,antioxidants and impurities often present in commercial products. Sincethe earlier studies were done with pure PE and cavities made for easyanalysis of the surface by XPS, the question remained, would the priorfindings be relevant to materials used by the electrical utilities? Toanswer this question the current investigation was initiated with PEinsulation from a series of cables that had undergone long-term testing.Interior surfaces created by fracturing the PE were analyzed byXPS
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