Tests on oil impregnated paper

About 2 years ago a series of researches was started to study the causes of dielectric loss, chemical deterioration, and electrical failure of oil impregnated paper insulation. Miniature technique has been developed so that at moderate cost specimens can be assembled in glass under accurately controlled conditions, subjected to high voltage life tests, tested periodically for electrical properties and finally examined minutely for changes in electrical, physical, and chemical properties. The results obtained in the first part of this program are presented herewith. Hypotheses now held regarding the effects of variations in several different factors on the life of oil impregnated paper insulation are discussed, and a description of the techniques developed for preparing and testing specimens is given. Illustrative examples are given of the results obtained to date from the correlation of life tests with microscopic physical and chemical examination.