Dry transformer bushings with composite insulators — The obvious combination for increased reliability

This article is aimed at reviewing certain key aspects related to the inner- and outer insulation on dry high voltage condenser bushings fitted with silicone insulators. Some of the subjects covered are how the shed profile design impacts the pollution performance and ageing resistance, and how the selection of manufacturing method and material selection impacts the erosion resistance. Service experience of silicone insulators in South America is presented, as well as comparisons between laboratory testing and field testing in general. Furthermore, two tests on the inner insulation system on dry bushings are detailed. Both on them goes beyond the industry standards and are relevant to verify the performance under certain extreme conditions that may occur.