Effects of dibenzyl disulfide on pressboard

Pressboard is a hard and rigid board having high with excellent electrical and mechanical properties, is specifically produced for the high voltage and extra high voltage Transformer Industry. Components and insulating sheets of pressboard are used in oil-cooled power transformers and distribution transformers primarily due to their high purity, mechanical strength and optimal oil-impregnability. The components formed of pressboard, such as angle rings, snout segments and end leads, enable an exact adaptation to the electric field conditions prevailing in the transformer. since the 1960´s the main insulation of power transformers has been built up as layered oil/board-insulation. The latter represents a hybrid system, consisting of oil filled gaps subdivided by pressboard barriers. Different new mineral oils have differing values of conductivity (about a factor of 10), whereas the conductivity of solid insulation hardly changes. In this paper, observations are made for break down strength of press board insulation of power transformers under different applied voltages.