Charge injection studies on XLPE surfaces exposed to partial discharges

Metallic electrodes covered by an on-site deposited XLPE films were annealed to release tribologic stresses and then exposed to Partial Discharge (PD) action. After exposure, time evolution of the remaining charge profile was investigated using a high spatial resolution capacitive probe. The results demonstrate a correlation between charge profile and partial discharge by-products formation. Furthermore, homo and hetero charges appear after the by-products were removed from the surface using different solvents. A strong negative charge injection is measured when a spot increases its degradation and evolves into a failure. Alteration of charge profiles changes were investigated using different degradation atmospheres including nitrogen and air. Studies performed on XLPE films allowed to correlate humidity, present during the partial discharge exposition, and PD magnitude, PD repetition rate, by-products formation and charge profile.