Unthresholded Recurrence Plots Analysis for Degradation Assessment of Power Cables Insulation

Abstract

Underground power cables have been widely used in transmission and distribution power systems, especially in urban areas. During their operating conditions, power cables are subjected to thermal, mechanical and electrical stresses. These stresses lead to accelerate the degradation process of the insulation material. In this paper, we present a novel methodology in the field that could be used to detect degradation level of power cables insulation due to thermal aging. In light of this, cross-linked polyethylene (XLPE) and polyvinyl chloride based compound (PVC, class B or PVC/B) were chosen as the studied materials. Thermal aging tests were performed at different aging temperatures (80, 100, 120 and 140 °C). Thereafter, the alternative bulk current through the aged samples was recorded at different aging stages and under AC applied voltage of 12 kV. For the aim to better analyze in-depth the obtained current waveforms, unthresholded recurrence plots (UTRPs) technique is introduced in order to extract features from the AC bulk current and reveal its characteristics. The obtained results show that the proposed method could be used as an assessment tool for current analysis and thermal degradation monitoring of insulation materials used in extruded power cables.