Investigation of the electrical properties of operationally aged PVC medium-voltage cables to analyse the ageing condition

To ensure the operational safety and production capability of industrial companies in a chemical park, the used PVC medium-voltage cables have been investigated to analyse the ageing condition after operation stress of more than 40 years. For the investigation, dielectric measurements and breakdown tests were carried out and compared to each other taking the operation stress as well as the external appearance of the cables into account. The dielectric measurements were performed at 50 Hz and high voltage and, for a comprehensive overview, with a polarization current measuring system from 100 muHz to 1 kHz at 200 Vpeak. The dielectric results show significant differences between the cable samples, but the breakdown tests reveal a very high electric strength for all cable samples. The operational safety is ensured because the cables still have a very high residual strength despite decades of stress and ageing.