Comparative evaluation of aging of insulating, material in natural ester and mineral oil

Aging of transformer insulating material in natural ester insulating oil is compared to that in conventional transformer oil. Aging of insulating paper and insulating oil have been studied by performing accelerated thermal aging test. Sealed aging test vessels containing cooper, laminated core, Kraft paper and insulating oil(natural oil or mineral oil) were aged at 140°C for 500, 1000, 1500 hours. Degradation of insulating paper after aging is determined using mechanical insulating paper after aging is determined using mechanical strength.Also, insulating oils after aging are investigated with total acid number, breakdown voltage and viscosity.Accelerated aging studies demonstrate a slower aging rate for natural ester insulating oil compared to the rate for conventional mineral oil.