Materials, Methods & Technologies, Volume 12, 2018

Abstract: High-voltage power cables, terminations and joints are factory-tested before installation to ensure quality and reliability according to customer requirements and standards. However, cables can be damaged during transportation, laying and during the installation of terminations and joints. These defects may not cause initial failure under voltage but can create partial discharge (PD) in the insulation system. If allowed to continue, partial discharge will erode the insulation, usually forming a tree-shaped pattern of deterioration (electrical tree) and eventually result in complete breakdown and failure of the cable or accessory. Such failures cause unplanned power outages, loss of plant production, equipment damage, and/or personnel injury. Partial discharges may intensify during the operation of electrical equipment due to electrical, thermal or environmental stresses. In this paper, partial discharge parameters defined in the IEC 60270 (apparent charge, inception field and pulse repetition rate), on unaged and thermally aged joint plane models, made of XLPE/EPR, are measured. The results show that the inception field decreases on thermally aged samples. If the ageing time increases the inception field decreases further. On the other hand, the apparent charge and pulse repetition rate increase with the ageing time as well.