A novel approach for imaging of electrical trees

Electrical treeing is a long term electrical breakdown process in polymers, and therefore, can be a precursor of power equipment failure. In order to get a better understanding of the phenomenon a considerable effort has been put in imaging and morphological characterisation of electrical trees. However, most of the imaging research has been carried out from a two-dimensional perspective. This work is focused on the three-dimensional (3-D) imaging of electrical trees using X-ray computed tomography, a non-destructive imaging technique. Electrical trees in two polymer materials were scanned using X-ray tomography with phase contrast enhancement. Two cases are presented here: an electrical breakdown through a tree and a bush-type electrical tree. In both cases a 3-D virtual replica has been created, with a spatial resolution of a few microns, through which the electrical tree can be sliced and internally inspected. Electrical treeing characteristics such as length, area, volume and number of branches can be extracted from the model.