Comparative performance of silicone rubber insulators with IEC stipulated test methods

IEC standard 61109/62217 stipulates three alternatives for design tests for polymeric insulators, namely (a) tracking and erosion test(1000 hours), (b) track wheel test (30,000 cycles) and (c) multi- stress ageing test (5000 hours). The minimum requirement for the insulator to comply with the design test is compliance with any one of these tests. However, experience in carrying out these tests in CPRI indicate that the assess the relative merits of the tracking and erosion test and the track wheel test, both the tests were carried out on a 33 kV polymeric insulator. Both the tests were terminated after 1000 hours. The results indicate track wheel test is severe. Analytical tests such as hydrophobicity test, EDX and XRD tests were performed to check the degree of degradation of the insulator material.