A new mathematical model of moisture equilibrium in mineral and vegetable oil-paper insulation

Moisture equilibrium characteristics of oil-paper insulation systems are important for insulation condition evaluation of oil-filled transformers. This paper presents moisture equilibrium curves of mineral and vegetable oil-paper insulation systems obtained by both direct and indirect methods. A new mathematical model is proposed to determine moisture content in oil-paper insulation systems. Experiments on moisture equilibrium in oil-paper insulation systems are conducted. The results estimated through the mathematical model agree with experimental results. The moisture equilibrium curves between vegetable and mineral oil-paper insulation systems are presented and compared. The moisture content in the vegetable oil-impregnated paper is significantly smaller than that in the mineral oil-impregnated paper, when both types of insulating oils have the same moisture content.