The Influence of Material Modification and Residues on Space Charge Accumulation in XLPE for DC Cable Application

Effects of cross-linking by-products (residues) of polyethylene on space charge accumulation and decay are investigated in the paper using the pulsed electro-acoustic technique. Space charge profiles have shown a great variation both in the charge initiation over the voltage ramping up process and later on long term stressing and decay (volts off) among the samples subjected to different conditioning, which results in diverse residues content (fresh, 0.5% residue and thoroughly degassed). The results show that by-products of cross-linking or the residual impurities play a key role in the space charge accumulation in cross-linked polyethylene. On the removal of impurities by degassing, small homocharge was built up in the vicinity of the electrode. It is concluded that space charge accumulation is governed by the charge injection through dielectric/electrode interface when sample is thoroughly degassed. Index Terms Space charge; Cross-linking by-products; XLPE and PEA.