ASTM D2303-13

4.1 These test methods differentiate among solid electrical insulating materials on the basis of their resistance to the action of voltage stresses along the surface of the solid when wet with an ionizable, electrically conductive liquid contaminant.

4.2 These test methods quantitatively evaluate, in a relative manner, the effects upon an insulating material resulting from the action of electrical discharges upon a material surface. The effects are similar to those that may occur in service under the influence of dirt combined with moisture condensed from the atmosphere.

4.3 The time-to-track a 1-in. (25-mm) distance at a specified voltage between electrodes separated 2 in. (50 mm) has also been found useful in categorizing insulating materials for indoor and protected outdoor applications, such as metal-clad switchgear.

4.4 The initial tracking voltage has been found useful for evaluating insulating materials to be used at high voltages or outdoors and unprotected, as well as for establishing (see 4.5 In service many types of contamination cause tracking and erosion of different materials to different degrees. This method recognizes the importance of such variability and suggests the use of special test solutions to meet specific service needs. For example, an ionic contaminant containing, in addition, a carbonaceous component such as sugar is substituted to cause tracking on very resistant materials like polymethylmethacrylate. Such contamination is considered representative of some severe industrial environments. In this case, the time-to-track technique is used, since time is required to decompose the contaminant solution and build up conducting residues on the sample surface.

4.6 Very track-resistant materials, such as polymethylmethacrylate, typically erodes rather than track under more usual contaminant conditions in service. The use of this method for measuring erosion is consequently important. For erosion studies, only tests as a function of time at constant voltage are useful.

1.1 These test methods cover the evaluation of the relative tracking and erosion resistance of insulating solids using the liquid-contaminant, inclined-plane test.1.2 Two tracking and one erosion test procedure are described: