Investigation the effect of environmental factors on the performance of polymeric outdoor insulation

Surface tracking is one of the severe degradation mechanisms observed on polymeric insulators. There are too many factors associated with the degradation process, hence it is not easy to make an estimate about the useful service life of an insulator. However it is possible to reduce the variability observed in the tracking initiation times and tracking patterns by testing the samples in laboratory under predefined conditions (4 kV applied voltage and 36 ml/h flow rate of liquid). In this study, by using the ASTM D 2303 Inclined Plane Tracking Test method the effects of longitudinal compressive and tensile stress, ultraviolet (UV) radiation and wind pressure from different positions with respect to the surface of the sample under test have been investigated in detail. All samples have been prepared by using polyester resin without any accelerator. In all cases tracking initiation times were reduced significantly depending on the external conditions. UV radiation and wind pressure caused bushy type carbonised tracking patterns with wide branches around the high voltage electrode.