Lifetime prediction of 20 kV field-aged silicone rubber insulators via condition assessment

Abstract

Field investigations of silicone rubber (SiR) insulators provide useful information about their performance. The field performance of SiR insulators depends on many factors, including electrical stress, and environmental and service conditions experienced. This paper provides a condition assessment of the housing material of five different types of 20 kV field-aged SiR insulators from the same manufacturer with different operating years and states. The assessment was performed through mechanical, electrical, and material techniques. The main objective of this paper is to investigate the aging behavior of SiR insulators, in order to predict their lifetimes. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were utilized to quantify the degree of degradation. The mechanisms of the variations in mechanical properties for aged samples were also discussed. In a tensile test, the reduction of strain-to-break to 50% and in other tests the failure of insulators in salt fog chamber were used as the end of life criterion. Finally, the lifetime of the tested insulators was predicted based on the various aforementioned tests.