Modern Methods of Analysing the Transformer Oil

From the practice of operation and maintenance of electrical equipment (transformers, motors and generators, etc.) it is known that, in order to ensure a safe operation and functionality, it is necessary to know, among other things, the condition of the insulation system, because about 40% of flaws which occur in operation are due to insulation flaws, in some cases can reach even close to 100% [1], [2]. Electrically insulating oils are used in high-power transformers with multiple functions: electrical insulation and cooling medium. Therefore, knowing the condition of the transformer oil can provide valuable data about its ageing status, the remaining life of the transformer, useful information in the maintenance activity. This paper proposes the presentation of modern methods and equipment for the study and analysis of physical and chemical properties (analysis of water content, density and interfacial tension) and electrical (determination of loss factor tanδ, and relative permittivity εr) of transformer oil. Samples of transformer oil type MOL TO 30.01 uninhibited electrical insulator (non-additive), new StaSo Transformer Oil I (high quality inhibited insulating oil) were studied: two samples collected directly from the original barrel, two samples collected from the transformer tank, after dielectric tests at the transformer’s manufacturer, and two samples of used TR 30 oil, collected from two transformers.