The Influence of Residue on Space Charge Accumulation in Purposely Modified Thick Plaque XLPE Sample for DC Application

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Description/Abstract

Effects residues (cross-linking by-products and additives) in polyethylene on space charge accumulation and decay have been investigated using the pulsed electro-acoustic technique. Space charge profiles have shown a great variation both in the charge initiation during the voltage ramping-up process and during long term stressing and decay (volts off). Samples were subjected to different conditioning processes, resulting in different proportions of residues (fresh, 0.5% residue and thoroughly degassed). The results show that residual impurities, including the by-products of cross-linking, play a key role in the space charge accumulation in cross-linked polyethylene. On the removal of impurities by degassing, a small homocharge build up was found in the vicinity of the electrode. It is concluded that space charge accumulation is governed by the charge injection through dielectric/electrode interface when the sample is thoroughly degassed.