3. Electrical trees

Electrical arborescences are branched filamentary structures made up of hollow microchannels capable of propagating over distances of several millimeters in volume and on the subsurface of insulators. The internal diameter of the filaments can vary from a micron to several hundred microns, depending on the nature of the insulation and the conditions in which the tree grows. They represent a permanent degradation of materials and are closely associated with breakdown.