The paper addresses the problem of transformer equipment fault data analysis in application to power system equipment operation data consistency improvement. Fuzzy and indefinite nature of such data is a primary barrier for effective problem solution. Fault data analysis is based on expert ranking results and transformer diagnostics data. Proposed approach integrates fuzzy linguistic estimations and quantitative characteristics of power equipment under consideration, carried out by pair comparison using fundamental Saaty scale, which gives the possibility to reveal the most considerable failure symptoms. The methodology is verified by corresponding calculations results. Transformer failure cause analysis is given in the paper conclusion. Additional discussion about the possibility of proposed methodology application in decision-making systems are provided as well.