Analysis of polyethylene cable insulation interior by X-ray photoelectron spectroscopy

Abstract

Over the past several years we studied some of the mechanisms for incipient insulation failure in polyethylene (PE). The previous studies indicated that detectable changes with pure PE can occur on the surface of cavities (artificially produced), as observed by X-ray Photoelectron Spectroscopy (XPS)-a technique that analyzes the first few atomic layers of a solid surface. These studies modeled conditions that could not be measured in routine utility-type test procedures. Production grade PE (usually cross-linked) has voids that range from below one /spl mu/m to under 1 mm. Also, this type of PE contains other species, e.g., antioxidants and impurities often present in commercial products. Since the earlier studies were done with pure PE and cavities made for easy analysis of the surface by XPS, the question remained, would the prior findings be relevant to materials used by the electrical utilities? To answer this question the current investigation was initiated with PE insulation from a series of cables that had undergone long-term testing. Interior surfaces created by fracturing the PE were analyzed by XPS.