A New Explanation of Gas Evolution in Electrically Stressed Oil‐Impregnated Paper Insulation

In void‐free oil‐impregnated paper, gas evolution starts at a critical stress which is markedly dependent on the degree of dryness of the paper. The gas first formed arises from decomposition of water in the cellulose, the nature of the impregnant having little effect. Subsequent more rapid gassing resulting from decomposition of the oil is a secondary process depending on ionization within gas bubbles previously formed. Study of the fundamental primary process suggests that water absorbed by the cellulose is ionized by electron bombardment in regions of high stress and is then decomposed electrochemically.