A realistic multistress screening/ranking test for high voltage outdoor polymeric insulators

IEC 1109 specifies a 1000 h salt fog test to evaluate the tracking and erosion of polymeric insulators. A high conductivity of 16000 μS/cm is specified for this purpose. However, in the real world, insulators are exposed to more than one stress and the pollution severity is not always this severe. This necessitates the need for a more meaningful test than the existing one to evaluate various polymeric insulation systems. This work presents the results of 800 h screening/ranking multistress tests. The various stresses applied include UV-A radiation, salt fog and temperature. 28 kV thermoplastic elastomeric (TPE) and silicone rubber (SiR) distribution class, dead-end insulators were used for this purpose. From the series of results it was realized that this kind of multistress testing could effectively be used for screening or ranking various insulators and/or materials used for high voltage outdoor insulators. A reduced period of 500 h or 600 h also seems to suffice to achieve this purpose.