Emergence of Polymeric Insulation: Implications for its testing

For many years glass and porcelain have been the dominant insulation materials for our bushes, insulators and circuit breakers. Recently however, the situation has changed and we now see outdoor circuit breakers at very high voltages of the order of hundreds of kilovolts using polymeric insulation. The advantages of polymeric insulation have always been known but their tracking performance in highly polluted environments has been disappointing, until now. As manufacturers engage in fierce competition to produce the new generation of insulators, the question of quality and reliability in performance becomes an overriding one. There several tests that have been prescribed by standardization bodies to assess the quality of insulation among them the IEC Tracking Test, the Inclined Plane Test and the Dust Fog Test. In this the authors will start with a brief description of the chemical structures of polymeric materials. They will then discuss the Inclined Plane test based on the American Standard D2303. Further, it will describe the design and operating performance and future prospects of a test set that is suitable for rapid and reliable testing of insulator samples that may be of interest to a manufacturer.