From the editor´s desk

This issue contains five articles, the first of which is titled ??Equilibrium Charts for Moisture in Paper and Pressboard Insulations in Mineral and Natural Ester Transformer Oils?? by Valentina Mandic and Jelena Lukic of the Electrical Engineering Institute Nikola Tesla, Belgrade, Serbia, and Christophe Perrier and Mamadou-Lamine Coulibaly of Alstom Grid, Massy, France. The article provides moisture equilibrium charts for Kraft paper and pressboard immersed in mineral insulating oil and natural-ester oil. Direct measurement of moisture in the oil, paper, and pressboard was performed by Karl-Fisher titration, and moisture equilibrium isotherms were created for temperatures from 40 to 120??C and for water content in paper and pressboard from 0.5 to 5%. The developed charts are referred to in this article as the ??Perrier-Lukic?? equilibrium charts. Comparative analyses of the moisture distribution between natural ester and mineral oil, and paper and pressboard insulations are also presented for absolute moisture content.