Calculation of a Health Index for Oil-Immersed Transformers Rated Under 69 kV Using Fuzzy Logic

This paper presents a new method for calculating a health index for transformers (for operating voltage 69 kV or less) based on diagnostic tests. The method relies on the use of furan analysis, dissolved gas analysis, and other oil analysis results as a means of calculating the health index using fuzzy set theory. Real field data for 90 working transformers were used to test the proposed method. The results were compared with the results calculated for the same set of transformers by an experienced asset management and health assessment consulting company. The comparison shows that the results are highly reliable.