Five-electrode inclined-plane tests of textured silicone rubber samples

The shank region of polluted polymeric insulators is susceptible to thermal damage where high current density and high electric field magnitude occurs. The recently proposed textured design consisting of hemispherical protuberances, aims to reduce the current density and the electric field gradient and increase the longitudinal creepage length without increasing the overall length of the insulator. Moreover, the formation of parallel current paths can lead to less harmful discharges. For the purpose of having a more detailed insight of the formation of these parallel current paths, the IEC-60587 standard that deals with the inclined plane test was modified by replacing the single ground electrode by five smaller separate electrodes. The test results of this modified inclined plane test of textured and conventional untextured rectangular samples are presented along with an analysis of the current distribution and the discharge activity. The improved performance of textured samples, in terms of resistance and tracking, has been excellent.