New end life criteria for mineral insulating oils

Mineral insulating oil manufacturing processes have changed significantly over the last twenty years. Oil base structures have also changed due to that, furthermore, the use of additives have also been improved. As a result, oil degradation kinetics is currently different, oil properties variation during aging must be re-evaluated. This paper describes mineral oil ageing behavior under mild and heavy oxidative environment. Traditional properties as well as unconventional tests are measured along ageing process and results are compared to determine best criteria to set the point of non-return for corrective maintenance action over the oil.