Correlation between surface degradation and PD wave shape evolution for spherical voids

The present study reports the recording of partial discharges (PDs) wave shapes using ultra wide band (UWB) techniques and its relation to the surface degradation produced on the surface of a single spherical void. The spherical void was occluded in epoxy resin at the time of molding the sample. The surface degradation was studied by optical and electron scanning microscopy (SEM) showing that the evolution of localized degradation was related to the pulse shape detected on the UWB system. These degradation zones evolved into a tree. This tree is also presented on optical microscopy photographs. Analysis of the wave shape at UWB can therefore correlate directly to ageing and ultimate failure of polymerical insulation