A study of correlation between the ect and ehd properties of different aged insulating oil mixtures that can Be an alternative to mineral oil for the insulation and cooling of power transformers

This article presents the hypothetical steps leading to the damage of power transformers in order to examine whether there is a correlation between the electrostatic properties (ECT) and the electro-hydrodynamic properties (EHD) of insulating oils. Vegetable oils such as, olive oil (OO) and sunflower oil (SO) have been tested as alternative oils for the insulation and cooling of transformers and their blends with naphthenic mineral oil (MO) on the basis of well-defined ratios and for a remarkable aging time, which is an original contribution and insight offered by this paper. The results obtained for the different mixtures with regard to the electrostatic properties and the electro-hydrodynamic properties as well as the physico-chemical properties (power factor "tgδ", resistivity, conductivity and viscosity) in terms of the aging time were compared with that of the mineral oil. The study of the physico-chemical properties of insulating oils and their mixtures is carried out according to international standards.