Preliminary studies on soluble and colloidal decomposition products in ester filled transformers

Esters dielectric fluids are found to be prominent replicate for mineral oil based insulation systems. Explicit studies on aging performance of these new insulating oils improve existing knowledge on the actual performance and degradation process. In this work, degradation of synthetic ester and natural ester has been investigated in comparison to mineral oil. Investigation is aimed at understanding the generation rate of soluble and colloidal particles in different oils with aging. Thermal aging is carried out as per ASTM D 1934 with a controlled aging history at different durations in presence of cellulose. Later, separation of colloidal particles is carried out as per ASTM D 1698 to study the comparative degradation rate of oils. Turbidity of oil and Particle counter measurements are performed before and after centrifuge to identify the growth of decay contents with aging in oils. A significant difference in the evolution of decay contents has been identified between esters fluids and mineral oils. The impact of colloidal particles on degradation of ester fluids is almost negligible whereas the degradation in mineral oils majorly governed by colloidal particles.