On line reclamation of aged transformer oils

The reclamation of aged transformer oils by Fuller´s Earth has long been practised by the electrical power industry. Although the major analytical properties of processed oil such as the dissipation factor at 100°C, the interfacial tension (IFT) and the total acid number (TAN) improve to the level of new oils, the quality of reclaimed oil is considered to be doubtful. Consequently, condition-based maintenance planners believe that purified liquid insulation can never regain the performance of new oil. This mistrust is fuelled by the fact that the existing testing procedures are not capable of establishing a quantitative relationship between oxidation stability and gassing tendency under electrical stress determined in laboratory conditions and the performance of oil in real life. Over the past years, the co-operation between certain state of the art instrument manufacturers and enhanced testing procedure developers has provided the electrical power industry with the means of eliminating this deficiency. This paper intends to show that the quality of properly reclaimed aged oils can successfully compete with that of new oils. Thus, in addition to extending the life cycle of a nonrenewable resource, the online reclamation of liquid insulation might also prevent the premature ageing of paper insulation