On the testing methods for chemical stability of transformer insulating oils

A brief review of the aging behaviour of oils of different quality under operating conditions is given. Simultaneous tests of numerous samples of oils of various type origin and quality were performed. The testing methods used are briefly described and the interpretation of the experimental results is given in tabular and graphical form. An analysis is given of the aging stability of oils samples towards oxidation. It appears that new testing methods which would be applicable to all types of transformer oil on the market should be developed.