Analysis of deterioration of PET insulation with multiple voids due to electrical stressing

The insulation systems of high-voltage power cables and their accessories are subjected to different kinds of stresses during their service life and thus suffer degradation and deterioration. These can lead to a reduction of life which in turn can lower the reliability of electrical power systems. Therefore, a lot of research activities are being carried out to get a better understanding of the insulation degradation phenomena. Polymeric insulating materials with excellent electrical properties are widely used in electrical power equipment. They are degraded however when they are subjected to partial discharges (PD). Deterioration of polymeric dielectrics by Partial Discharge occurs at defects in an insulation system. The degree and rate of deterioration might vary depending on the type of defect present and also on the number and position of the defect in the insulation. The type of defect studied in this paper is the most common one - air voids present in insulation. The model void is created using layers of polymer, to allow well defined structures. To determine the changes to the surface of the voids as a result of the chemical processes produced by PD, the Fourier Transform Infra-Red (FTIR) spectrum of the polymer specimens subjected to PD were examined.