Water Treeing Phenomena in Humid Air

Water treeing is a phenomenon which causes organic insulating material to degrade under electrical stress when moisture is present. Papers have been published on water treeing, for instance, those on laboratory experiments through acceleration test methods. In all these reports, some part of the specimen was exposed to water. In the experiment described in this paper, specimens were exposed only to water vapor, not water in the liquid state. A part of the experimental results already has been reviewed and presented by Nunes and Shaw [1]. This paper discusses the problem of water treeing in humid air in detail.