High Voltage Tracking Resistance (HVTR)

UL 746A

The High Voltage Tracking Resistance (HVTR) test method is used to assess the susceptibility to tracking of insulating materials that are exposed to high voltages outdoors. Insulators installed in the open are often at the mercy of humidity. Their electrical insulation properties can deteriorate to such an extent as a result that tracking paths are formed on the insulator surface. This test determines the tracking resistance that defines the dielectric strength of the insulating material surface and the maximum allowable leakage current (tracking).

High voltage arc tracking rate is denoted as the rate, in millimeters per minute, that a tracking path can be produced on the surface of the material under standardized test conditions. A note is made if ignition on the material takes place. The results of testing the nominal 3 millimeter thickness are considered representative of the material’s performance in any thickness.