Erosion — Inclined plane, liquid contaminant tracking test

The electrical failure of contaminated insulation surfaces is caused by surface scintillation — tiny arcs. It is often characterized by progressive carbonization in a number of branching and sometimes interconnected channels often called "tracks." The appearance and nature of tracks is dependent upon the concentration of the contaminant and the voltage stress as well as the composition of the insulating material¹. With some track resistant material formulations, tracking as described above does not occur, particularly at lower voltage stress and higher contaminant concentrations. Instead, a loss of volume — erosion of the insulation — occurs under the influence of the surface electrical scintillation.