Spectrum of polarization phenomena of long time-constant as a diagnostic method of oil-paper insulating systems

A novel test method for the assessment of the bulk dielectric properties of oil-paper insulation has been developed. Specifically, the authors describe a simple on-site DC testing and apparatus for the determination of the polarization spectrum in the polarization time-constant domain of 10/sup -3/ to 10/sup 4/ s. In this range the so-called interface polarization phenomena of long time constant are active, which are highly influenced by the water content of oil-impregnated paper insulation and the adsorption of byproducts of aging. The method can be regarded as a complementary diagnosis method of dissolved gas analysis and other analytical methods and gives information on the general state and dielectric aging of the impregnated paper insulation. The test method and apparatus have been successfully and widely used on high-voltage power transformers of the Hungarian Electricity Board.<
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