Measurement of organic and inorganic ions in cable insulation and shields

It was demonstrated that HPIC (high-performance ion chromatography) can detect inorganic and organic ions in PE (polyethylene) and XLPE (cross-linked PE) insulation and shields in concentrations as low as ~10 μg/L in the extraction solutions. This analytical technique requires liquid extraction of the ions prior to their content evaluation. The limitations of the extraction technique used are discussed. The detected inorganic ions correspond to the elements determined by other analytical techniques, but the ionic fraction is small. The actual ionic fraction could be higher, since the extraction technique used is far from being optimized. Manufacturing and aging lead to increased SO^2-₄ and Cl^- contamination in XLPE cables. Migration from the contaminated shields appears to be one of the causes for this increase. Use of the much cleaner acetylene black should improve the situation. Organic ions were also detected and appear to be essentially by-products of PE oxidation. It is possible that service aging induces the formation of more oxalate ions. Shields made with ethylene vinyl acetate may also generate some acetate ions