Contribution to the qualitative and quantitative estimation of the PD effect on the surface layer of epoxy resins and composites

Joint application of electron scanning profilometry, optical and scanning microscopy and of measurements of the Rs surface resistance has yielded promising results in investigations into partial discharges (PD) degradation processes of the surface layer of epoxy resins and composites. On the basis of the investigations it was possible, among others, to state that local changes in resistivity are not directly a consequence of changes in the epoxy surface profile. The results suggest instead the possible importance of deposits on the surface in modifying the resistivity. On the example of the Epidian 2 (Ep2) resin and its composite with the Al2O3 filler (Ep2K), this paper draws attention to some conditions which should be taken into account when the behaviour of the surface layer of a dielectric in various types of PD exposure is compared