Surface degradation on XLPE under PD activity

The paper deals with PD bombardment of polymer surfaces exposed to corona PD. The target is to investigate chemical attack, electron and ion bombardment; this information is fundamental to develop models able to infer lifetimes of insulation systems subjected to PD activity. For this purpose, a needle/plane electrode test cell has been used to expose XLPE surfaces to PD of assigned polarity. By using a unipolar square voltage generator and changing the connections of the circuit, the XLPE specimens were bombarded by PD of single polarity. The effects of unipolar PD on these surfaces were investigated using partial discharge phase resolved patterns, optical and SEM microscopy, as well as the evolution of the surface profile as a function of time under stress.