Water in oil-filled high-voltage equipment part II: water content as physicochemical tools for insulation condition diagnostic

In the first part of this investigations, we examined the current state of knowledge of the effect of water on paper and liquid-insulating materials. Demonstrated that the scientific representation of the states of water in insulating liquids has a direct practical application as a diagnostic tool for electrical equipment, at least for the dielectric properties of the insulation. The work presented in this second part of these investigations is divided into four sections. The first section deals with the influence of water on the electrical characteristics of the oil/paper insulating materials, followed by a critical review of up-to-date water quantification methods. Based on the physicochemical criteria of the limiting state discussed in the third section, this article proposes some analytical expressions that can help electrical engineers monitor and/or diagnose oil-filled, high-voltage equipment. Our investigations show the advantage of diverse methods for measuring humidity in insulating liquids, and a variety of analytical expressions for calculating the condition of liquid/ solid insulation systems.