Condition assessment of oil-paper insulated bushings

Bushings failures are responsible for a large number of costly forced outages of transformers, breakers and reactors. Almost half of the bushing failures are catastrophic in nature and may pose danger to personnel and other equipment in vicinity. Many techniques are available for assessing the dielectric condition of oil-paper insulated power apparatus bushings. However, no single technique seems to work all the time. The Life Cycle Management of Substation Equipment and Apparatus (LCMSEA) Interest Group of CEATI (see www.ceati.com) sponsored a project to undertake a review of available diagnostic techniques for bushings. Under this project a survey of utilities was conducted to identify common practices and available diagnostic techniques, and the experience of utilities with these techniques. This paper presents the results of the survey. There is a large variation among utilities in terms of use of different diagnostic tests, intervals between diagnostic tests, and experience with these tests.